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Impurity effects on gas tungsten arc welds in V?Cr?Ti alloys
NASA Astrophysics Data System (ADS)
Grossbeck, M. L.; King, J. F.; Hoelzer, D. T.
Plates 6.4 mm thick of V-Cr-Ti alloys, mostly V-4Cr-4Ti, were welded in a glove box argon atmosphere. A hot titanium getter led to excessive hydrogen concentrations. A cold zirconium-aluminum getter was used to reduce both oxygen and hydrogen. It was observed that a major source of hydrogen was dissociation of water vapor by the electric arc of the welding torch. Careful monitoring of atmospheric impurities and successive pumping and backfilling cycles permitted welds of higher quality than previously achieved. Welds were evaluated primarily by the Charpy impact test. A ductile-to-brittle transition temperature (DBTT) of -28¯C was achieved in V-4Cr-4Ti. Previous GTA welds in the same material seldom had a DBTT below room temperature. Electron beam welding can achieve a DBTT of below -90¯C in the V-4Cr-4Ti alloy, indicating a lower limit to the DBTT by impurity control.
CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium
Park, J.H.; Kassner, T.F.
Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. The electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5--85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400--420{degrees}C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was {approx}10{sup 6} {Omega} at 400{degrees}C. Thermal cycling between 300 and 700{degrees}C changed the coating layer resistance. which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes(e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at {ge}360{degrees}C.
CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium system
Park, J.H.; Kassner, T.F.
Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. Electrical resistance of CaO coatings that were produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li containing 0.5-85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420{degrees}C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was {approx}10{sup 6} {Omega} at 400{degrees}C. Thermal cycling between 300 and 700{degrees}C changed the coating layer resistance, which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at {>=}360{degrees}C.
[Fatigue properties of dental alloys. 12% Au-Pd-Ag alloy and type III gold alloy].
Kato, H
Usually the mechanical properties of dental alloys are determined from the values obtained through static tests of their tensile strength, hardness, etc. Generally, high tensile strength and ductility are preferred. However, when small stresses within proportional limits are applied repeatedly (even though not amounting to destructive forces in static tests), they may cause rupture in the alloy or, at least, cause it to lose its original mechanical properties. This phenomenon is called metal fatigue. It is estimated that the intraoral stress loads received by dental restorations during mastication or during insertion and removal of appliances are repeated more than 3 x 10(5) times/year. From this standpoint, it may be more appropriate to estimate the fracture strength of such dental alloys based on the fatigue properties of the restorative materials used for clasps, bars, and fixed bridges. For this reason, it is necessary to obtain data through fatigue tests on the fatigue strength and the fatigue endurance limits of dental alloys, and it is important to find a correlation between these data and the static data on tensile strengths and ductility obtained by tensile tests. Two alloys are used in these experiments. Both wrought specimens and cast specimens of 12% Au-Pd-Ag and Type III gold alloy were prepared for the fatigue tests. The size of the rectangular wrought specimens was 3 x 4 x 110 mm. The 12% Au-Pd-Ag alloy was heated to 800 degrees C for 15 minutes, quenched, and reheated to 400 degrees C for 20 minutes and quenched again according to the manufacturer's instructions for heat treatment. The Type III gold alloy was heated to 700 degrees C for 10 minutes, quenched, and reheated to 350 degrees C for 20 minutes and quenched again. The cylindrical cast specimens were 60 mm long and 2 mm in diameter. They were invested by conventional methods and cast in a centrifugal casting machine, Thermotrol Model 2500. The four point bending test for the wrought specimen was performed with a Universal Fatigue testing machine, Shimazu UF-15 at a stress amplitude rate of 30 Hz. The cylindrical cast specimens were tested in cyclic tension in a Hydraulic IC Servo Machine, Instron Model 8501 at a gauge length of 25 mm and a stress amplitude of 10 Hz. The tensile tests for both wrought and cast specimens were performed with a Universal Testing Machine, Instron Model 1125 and measured at a cross-head speed of 1 mm/min.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2489466
Gas tungsten arc welding of vanadium alloys with impurity control
NASA Astrophysics Data System (ADS)
Grossbeck, M. L.; King, J. F.; Nagasaka, T.; David, S. A.
Gas tungsten arc welding in vanadium alloys is controlled by interstitial impurities. Techniques have been developed to weld V-4Cr-4Ti in a high-purity argon atmosphere resulting in a DBTT of -20 ¯C. The atmosphere was controlled by a Zr-Al getter which is activated at high temperature to obtain a clean surface then cooled and allowed to absorb hydrogen and oxygen impurities. Through the use of low-oxygen base metal and high-purity weld filler wire, a DBTT of -145 ¯C was obtained. Experiments using electron beam welding have shown that grain size also has an important effect on weld ductility. Introduction of nitrogen and yttrium has been used to study their effect on grain size. Using a combination of atmosphere control, alloy purity control, and grain size control, it is anticipated that V-Cr-Ti alloys will be weldable in field conditions.
Development and testing ov danadium alloys for fusion applications
Chung, H.M.; Loomis, B.A.; Smith, D.L.
V base alloys have advantages for fusion reactor first-wall and blanket structure. To screen candidate alloys and optimize a V-base alloy, physical and mechanical properties of V-Ti, V-Cr-Ti, and V-Ti- Si alloys were studied before and after irradiation in Li environment in fast fission reactors. V-4Cr-4Ti containing 500-1000 wppM Si and <1000 wppM O+N+C was investigated as the most promising alloy, and more testing is being done. Major results of the work are presented in this paper. The reference V-4Cr-4Ti had the most attractive combination of the mechanical and physical properties that are prerequisite for first-wall and blanket structures: good thermal creep, good tensile strength/ductility, high impact energy, excellent resistance to swelling, and very low ductile-brittle transition temperature before and after irradiation. The alloy was highly resistant to irradiation-induced embrittlement in Li at 420-600 C, and the effects of dynamically charged He on swelling and mechanical properties were insignificant. However, several important issues remain unresolved: welding, low-temperature irradiation, He effect at high dose and high He concentration, irradiation creep, and irradiation performance in air or He. Initial results of investigation of some of these issues are also given.
INVITED FEATURE PAPERS Growth and transport properties of p-type GaNBi alloys
Wu, Junqiao
INVITED FEATURE PAPERS Growth and transport properties of p-type GaNBi alloys Alejandro X. Levander 2011) Thin films of GaNBi alloys with up to 12.5 at.% Bi were grown on sapphire using low to the midgap position of GaN, whereas the conduction band edge shifted more gradually. I. INTRODUCTION Alloying
The effect of cobalt content in U-700 type alloys on degradation of aluminide coatings
NASA Technical Reports Server (NTRS)
Zaplatynsky, I.
The influence of cobalt content in U-700 type alloys on the behavior of aluminide coatings is studied in burner rig cyclic oxidation tests at 1100C. It is determined that aluminide coatings on alloys with higher cobalt offer better oxidation protection than the same coatings on alloys containing less cobalt.
Beta type Ti-Mo alloys with changeable Young's modulus for spinal fixation applications.
Zhao, Xingfeng; Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko
To develop a novel biomedical titanium alloy with a changeable Young's modulus via deformation-induced ? phase transformation for the spinal rods in spinal fixation devices, a series of metastable ? type binary Ti-(15-18)Mo alloys were prepared. In this study, the microstructures, Young's moduli and tensile properties of the alloys were systemically examined to investigate the effects of deformation-induced ? phase transformation on their mechanical properties. The springback of the optimal alloy was also examined. Ti-(15-18)Mo alloys subjected to solution treatment comprise a ? phase and a small amount of athermal ? phase, and they have low Young's moduli. All the alloys investigated in this study show an increase in the Young's modulus owing to deformation-induced ? phase transformation during cold rolling. The deformation-induced ? phase transformation is accompanied with {332}(?) mechanical twinning. This resulted in the maintenance of acceptable ductility with relatively high strength. Among the examined alloys, the Ti-17Mo alloy shows the lowest Young's modulus and the largest increase in the Young's modulus. This alloy exhibits small springback and could be easily bent to the required shape during operation. Thus, Ti-17Mo alloy is considered to be a potential candidate for the spinal rods in spinal fixation devices. PMID:22326686
Investigation of new type Cu-Hf-Al bulk glassy alloys
NASA Astrophysics Data System (ADS)
Nagy, E.; Rontµ, V.; Sµlyom, J.; Roµsz, A.
In the last years new type Cu-Hf-Al ternary alloys were developed with high glass forming ability and ductility. The addition of Al to Cu-Hf alloys results in improvements in glass formation, thermal stability and mechanical properties of these alloys. We have investigated new Cu-based bulk amorphous alloys in Cu-Hf-Al ternary system. The alloys with Cu49Hf42Al9, Cu46Hf45Al9, Cu50Hf42.5Al7.5 and Cu50Hf45Al5 compositions were prepared by arc melting. The samples were made by centrifugal casting and were investigated by X-ray diffraction method. Thermodynamic properties were examined by differential scanning calorimetry and the structure of the crystallising phases by scanning electron microscopy. The determination of liquidus temperatures of alloys were measured by differential thermal analysis.
Evaluation of tensile properties of 5052 type aluminum-magnesium alloy at warm temperatures
F. Ozturk; S. Toros; S. Kilic
Purpose: The purpose of the paper is to evaluate the tensile properties of 5052 type aluminum-manganese alloy in warm temperatures. Design\\/methodology\\/approach: In this research, uniaxial tensile deformation behavior of 5052-H32 type aluminum magnesium alloy was studied range between room to 300¯C and in the strain rate range of 0.0083-0.16 s-1. Findings: It was observed that the uniaxial tensile elongation of
Formation of F- and P-Type Icosahedral Quasicrystals in the Zn Mg Ho Alloy System*
NASA Astrophysics Data System (ADS)
Shimizu, Takayuki; Ishimasa, Tsutomu
Two types of icosahedral quasicrystals, F- and P-types, formed at 563¯C in the Zn60Mg40-xHox alloy depending on Ho content. In the composition range of 6?x?10, F-type icosahedral quasicrystal formed as a major phase in these alloys. The intensity of superlattice reflections which occurred due to F-type ordering became weaker in the alloys with lower Ho content. At x=5, P-type icosahedral quasicrystal formed, coexisting with MgZn2-type Laves phase at 563¯C and 503¯C. Some electron diffraction patterns of the P-type icosahedral quasicrystal exhibited diffuse scattering intensity at positions corresponding to F-type superlattice reflections. By annealing at 403¯C, a mixture of the P-type icosahedral quasicrystal and the MgZn2-type phase changed to a mixture of the F-type quasicrystal and a decagonal quasicrystal. The former state was reversibly obtained by additional annealing at 503¯C. These experimental results support the interpretation that the three types of quasicrystals form as a thermodynamically stable state in the Zn Mg Ho alloy system.
Journal of Statistical Physics, Vol. 38, Nos. 1/2, 1985 Phase Diagram of Cu-Au-Type Alloys ~
Lebowitz, Joel
Journal of Statistical Physics, Vol. 38, Nos. 1/2, 1985 Phase Diagram of Cu-Au-Type Alloys ~ Joel L phase diagram of an binary alloy on a face centered cubic lattice. In Ising spin language the nearest alloys; phase diagrams; frustration; first-order phase transitions. 1. INTRODUCTION The study of phase
Distributed type of actuators by shape memory alloy and its application to underwater mobile robotic mechanism
Toshio Fukuda; Hidemi Hosokai; Isamu Kikuchi
The basic idea of a new type of actuator based on a shape memory alloy (SMA) and its application to underwater mobile robots are presented. The actuator consists of a multimode SMA, so that any shape can be produced as the synthesized sum of excited modes. Thus, the actuator shows the characteristics of distributed-parameter-type actuators with a specified number of
Strain glass transition in a multifunctional ?-type Ti alloy
Wang, Yu; Gao, Jinghui; Wu, Haijun; Yang, Sen; Ding, Xiangdong; Wang, Dong; Ren, Xiaobing; Wang, Yunzhi; Song, Xiaoping; Gao, Jianrong
Recently, a class of multifunctional Ti alloys called GUM metals attracts tremendous attentions for their superior mechanical behaviors (high strength, high ductility and superelasticity) and novel physical properties (Invar effect, Elinvar effect and low modulus). The Invar and Elinvar effects are known to originate from structural or magnetic transitions, but none of these transitions were found in the GUM metals. This challenges our fundamental understanding of their physical properties. In this study, we show that the typical GUM metal Ti-23Nb-0.7Ta-2Zr-1.2O (at%) alloy undergoes a strain glass transition, where martensitic nano-domains are frozen gradually over a broad temperature range by random point defects. These nano-domains develop strong texture after cold rolling, which causes the lattice elongation in the rolling direction associated with the transition upon cooling and leads to its Invar effect. Moreover, its Elinvar effect and low modulus can also be explained by the nano-domain structure of strain glass. PMID:24500779
Corrosion potential measurements on type 304 SS and alloy 182 in simulated BWR environments
Macdonald, D.D. (Pennsylvania State Univ., University Park (United States)); Song, H. (SRI International, Menlo Park, CA (United States)); Makela, K. (VTT, Espoo (Finland)); Yoshida, K. (Ishikawajima-Harima Heavy Industries Co., Ltd., Yokohama (Japan))
The effects of dissolved oxygen, hydrogen, and hydrogen peroxide on the corrosion (electrochemical) potentials (ECPs) of type 304 SS and alloy 182 in simulated boiling water reactor (BWR) coolant environments under various water chemistry conditions at 288 C are reported. In oxygenated systems, the measured ECP fell within the range +20 to [minus]600 mV (vs SHE) depending on the O[sub 2] concentration. The effect of water flow rate on the ECP was also studied as function of dissolved O[sub 2] concentration. Increasing flow rate at constant oxygen concentration increased the ECPs of type 304 SS and alloy 182. The effect of hydrogen peroxide (H[sub 2]O[sub 2]) on the ECP of type 304 SS and alloy 182 in pure water was also determined. The authors found that the concentration of oxygen and the ECP increased immediately when H[sub 2]O[sub 2] was injected into the cell. The measured corrosion potentials of both alloys were 200 to 400 mV more positive than for dissolved O[sub 2] at similar levels. However, the ECP was lower than that expected theoretically from a mixed potential model (COREPOTENTIAL), which the authors attribute to thermal decomposition of H[sub 2]O[sub 2]. The ECPs of type 304 SS and alloy 182 in water containing various O[sub 2]/H[sub 2]/H[sub 2]O[sub 2] combinations were measured and compared with theoretical data from COREPOTENTIAL. The ECPs were lower than expected due to decomposition of H[sub 2]O[sub 2] in the high-temperature environment. Finally, the difference between the ECP of type 304 SS and alloy 182 was negligible (normally < [plus minus] 20 mV) under all conditions.
NASA Astrophysics Data System (ADS)
Jung, Sung-Jin; Kim, Seong Keun; Park, Hyung-Ho; Hyun, Dow-Bin; Baek, Seung-Hyub; Kim, Jin-Sang
The effects of mechanical deformation and subsequent annealing on the thermoelectric properties and microstructure have been investigated for p-type (Bi0.25Sb0.75)2Te3 alloys prepared by melting followed by quenching. The mechanically deformed pellets were prepared by repetition of cold-pressing of quenched samples at room temperature. Cold-pressed pellets were then annealed at 300¯C in vacuum, and the thermoelectric properties and microstructure were traced through the course of the heat treatment. For the heavily deformed samples, the Seebeck coefficient rapidly increased at the very early stage of annealing and did not change as the annealing time increased, due to recrystallization of a new ?-phase which equilibrated at the annealing temperature of 300¯C (?300-phase). At the initial stage of annealing (recovery stage), the electrical resistivity sharply increased, probably due to the interaction of antistructural defects with vacancies produced during the cold-pressing treatment. However, for the lightly deformed samples, recrystallization occurred only at some portion of the grain boundaries, and the newly generated ?300-phase slowly replaced the original, as-solidified ?ingot-phase.
NixCd1-xO: Semiconducting alloys with extreme type III band offsets
NASA Astrophysics Data System (ADS)
Francis, Christopher A.; Detert, Douglas M.; Chen, Guibin; Dubon, Oscar D.; Yu, Kin M.; Walukiewicz, Wladek
We have synthesized alloys of NiO and CdO that exhibit an extreme type III band offset and have studied the structural, electrical, and optical properties of NixCd1-xO over the entire composition range. The alloys are rocksalt structured and exhibit a monotonic shift of the (220) diffraction peak to higher 2? angles with increasing Ni concentration. The electron mobility and electron concentration decrease with increasing x, and samples become insulating for Ni content x > 0.44. This decrease in n-type conductivity is consistent with the movement of the conduction band minimum from below to above the Fermi stabilization energy with increasing Ni content. The optical absorption edge of the alloys can be tuned continuously from CdO to NiO. The intrinsic gap of the alloys was calculated with the electrical and optical measurements and accounting for Burstein-Moss carrier filling and carrier-induced bandgap renormalization effects. We observe an uncommon composition dependence of the intrinsic bandgap on the alloy composition. The effect is tentatively attributed to an interaction between extended states of the conduction band and localized d-states of Ni.
Effects of SiC Nanodispersion on the Thermoelectric Properties of p-Type and n-Type Bi2Te3-Based Alloys
NASA Astrophysics Data System (ADS)
Liu, Da-Wei; Li, Jing-Feng; Chen, Chen; Zhang, Bo-Ping
Polycrystalline p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.7Se0.3 thermoelectric (TE) alloys containing a small amount (vol.% ?5) of SiC nanoparticles were fabricated by mechanical alloying and spark plasma sintering. It was revealed that the effects of SiC addition on TE properties can be different between p-type and n-type Bi2Te3-based alloys. SiC addition slightly increased the power factor of the p-type materials by decreasing both the electrical resistivity ( ?) and Seebeck coefficient ( ?), but decreased the power factor of n-type materials by increasing both ? and ?. Regardless of the conductivity type, the thermal conductivity was reduced by dispersing SiC nanoparticles in the Bi2Te3-based alloy matrix. As a result, a small amount (0.1 vol.%) of SiC addition increased the maximum dimensionless figure of merit ( ZT max) of the p-type Bi0.5Sb1.5Te3 alloys from 0.88 for the SiC-free sample to 0.97 at 323 K, though no improvement in TE performance was obtained in the case of n-type Bi2Te2.7Se0.3 alloys. Importantly, the SiC-dispersed alloys showed better mechanical properties, which can improve material machinability and device reliability.
Investigation of changes in the type B PLC effect of AlMgCu type alloy for various strain rates
K. Darowicki; J. Orlikowski; A. Zieli?ski
The PortevinLeChatelier (PLC) effect exemplifies itself as continuous stress changes during the tensile deformation of particular alloys. The PLC effect takes several forms, which differ significantly in both the spatial distribution of strain bands and in the shape of the stressstrain curve. The courses corresponding to particular serration types are characterized by different properties of the signal energy distribution, depending
Tensile impact properties of vanadium-base alloys irradiated at <430{degree}C.
Chung, H. M.
Tensile and impact properties were investigated at <430 C on V-Cr-Ti, V-Ti-Si, and V-Ti alloys after irradiation to {approx}2-46 dpa at 205-430 C in lithium or helium in the Fast Flux Test Facility (FFTF), High Flux Isotope Reactor (HFIR), Experimental Breeder Reactor II (EBR-II), and Advanced Test Reactor (ATR). A 500-kg heat of V-4Cr-4Ti exhibited high ductile-brittle transition temperature and minimal uniform elongation as a result of irradiation-induced loss of work-hardening capability. Work-hardening capabilities of 30- and 100-kg heats of V-4Cr-4Ti varied significantly with irradiation conditions, although the 30-kg heat exhibited excellent impact properties after irradiation at {approx}390-430 C. The origin of the significant variations in the work-hardening capability of V-4Cr-4Ti is not understood, although fabrication variables, annealing history, and contamination from the irradiation environment are believed to play important roles. A 15-kg heat of V-3Ti-1Si exhibited good work-hardening capability and excellent impact properties after irradiation at {approx}390-430 C. Helium atoms, either charged dynamically or produced via transmutation of boron in the alloys, promote work-hardening capability in V-4Cr-4Ti and V-3Ti-1Si.
Precipitation of an intermetallic phase with Pt2Mo-type structure in alloy 625
NASA Astrophysics Data System (ADS)
Sundararaman, M.; Kumar, Lalit; Prasad, G. Eswara; Mukhopadhyay, P.; Banerjee, S.
The microstructure of Alloy 625, which has undergone prolonged (70,000 hours) service at temperatures close to but less than 600 ¯C, has been characterized by transmission electron microscopy. The precipitation of an intermetallic phase Ni2(Cr, Mo) with Pt2Mo-type structure has been observed in addition to that of the ?? phase. Six variants of Ni2(Cr, Mo) precipitates have been found to occur in the austenite grains. These particles exhibit a snowflake-like morphology and are uniformly distributed in the matrix. They have been found to dissolve when the alloy is subjected to short heat treatments at 700 ¯C. The occurrence of the Ni2(Cr, Mo) phase has been discussed by taking the alloy chemistry into consideration. Apart from the intermetallic phases, the precipitation of a M6C-type carbide phase within the matrix and the formation of near continuous films, comprising discrete M6C/M23C6 carbide particles, at the austenite grain boundaries have been noticed in the alloy after prolonged service.
A vertical-type twin roll caster for aluminum alloy strips
Toshio Haga; Kenta Takahashi; Masaaki Ikawa; Hisaki Watari
A vertical-type twin roll caster for strip casting of aluminum alloys was devised and its properties were investigated. The strip, which was thinner than 3mm, could be cast at speeds higher than 60m\\/min. Features of the twin roll casters are as below. Copper rolls were used and lubricant was not used in order to increase the casting speed. Heat transfer
Site preference of Mg acceptors and improvement of p-type doping efficiency in nitride alloys.
Park, Ji-Sang; Chang, K J
We perform first-principles density functional calculations to investigate the effect of Al and In on the formation energy and acceptor level of Mg in group-III nitride alloys. Our calculations reveal a tendency for the Mg dopants to prefer to occupy the lattice sites surrounded with Al atoms, whereas hole carriers are generated in In- or Ga-rich sites. The separation of the Mg dopants and hole carriers is energetically more favourable than a random distribution of dopants, being attributed to the local bonding effect of weak In and strong Al potentials in alloys. As a consequence, the Mg acceptor level, which represents the activation energy of Mg, tends to decrease with increasing numbers of Al next-nearest neighbours, whereas it increases as the number of In next-nearest neighbours increases. Based on the results, we suggest that the incorporation of higher Al and lower In compositions will improve the p-type doping efficiency in quaternary alloys, in comparison with GaN or AlGaN ternary alloys with similar band gaps. PMID:23709500
Mechanical properties of L1{sub 2} type Zn{sub 3}Ti-based alloy
Hosoda, Hideki; Hanada, Shuji
An alloy composed of L1{sub 2}-type Zn{sub 3}Ti was investigated in terms of phase stability and mechanical properties. Zn and Ti powders were mixed at a composition of Zn-25mol%Ti using a ball mill in Ar, and an ingot was made by melting the powders. Optical microscopy, X-ray diffraction analysis and thermogravimetry--differential thermal analysis were carried out. Mechanical properties were investigated by Vickers hardness tests at room temperature (RT) and compression tests from RT to 703K in Ar. It is found that (1) the alloy is mainly composed of L1{sub 2}Zn{sub 3}Ti, (2) the alloy has weak positive temperature dependence of strength, and (3) normalized strength by melting point is comparable to that of L1{sub 2}Al{sub 3}Ti-Cr alloys. L1{sub 2}Zn{sub 3}Ti has HV178 and is brittle at RT. Reaction temperatures of Zn-rich portion of the Zn-Ti phase diagram were also reinvestigated and a peritectic-reaction temperature between Zn{sub 3}Ti and liquid + Zn{sub 2}Ti is determined to be at 880K.
Synthesis of NiCoMnX (X = In, Al) Heusler-type Magnetic Shape Memory Alloy Thin Films
Rios, Steven Eli
moderate magnetic field, but their constituents consisting of rare earth metals, Tb and Dy, are expensive. There are numerous types of shape memory alloys (SMAs), including conventional SMAs, magnetic SMAs (MSMAs), or high temperature SMAs (HTSMAs...
Thermoelectric properties of the Heusler-type Fe2VTaxAl1-x alloys
NASA Astrophysics Data System (ADS)
Renard, Krystel; Mori, Arinori; Yamada, Yuichiro; Tanaka, Suguru; Miyazaki, Hidetoshi; Nishino, Yoichi
This study focuses on the thermoelectric properties of the Heusler-type Fe2VTaxAl1-x alloys (0?x?0.12). By means of Rietveld analyses on synchrotron X-ray diffraction patterns, it is shown that the Ta atoms enter sites occupied by V atoms in the stoichiometric Fe2VAl alloy, while the ejected V atoms are transferred to the vacant Al sites. This Ta substitution leads to an improvement of the n-type thermoelectric properties owing to two mechanisms. On the one hand, the atoms position in the structure leads to an off-stoichiometric effect such as already observed in V-rich Fe2V1+yAl1-y compounds: the Seebeck coefficient is increased towards negative absolute values and the electrical resistivity is decreased, with a large shift of their peak temperature towards higher temperature. The maximum power factor is 6.5 æ 10-3 W/mK2 for x = 0.05 at 340 K. On the other hand, the heavy element Ta substitution combined with this off-stoichiometric effect leads to a large decrease of the thermal conductivity, owing to an increase of the scattering events. Consequently, the dimensionless figure of merit is seen to reach higher values than for the Fe2V1+yAl1-y alloys, i.e., 0.21-0.22 around 400-500 K for x = 0.05 and 500 K for x = 0.08.
On the Understanding of Aluminum Grain Refinement by Al-Ti-B Type Master Alloys
NASA Astrophysics Data System (ADS)
Wang, Xiaoming; Liu, Zhiwei; Dai, Wei; Han, Qingyou
Al-Ti-B type master alloys have been widely used in the grain refinement of aluminum since 1940s. The introduction of Al3Ti and TiB2(AlB2) particles reduces the grain sizes down to about 200 micrometer level and makes aluminum alloys castable. However, the mechanism for the grain refinement is still not clear, though it is believed that TiB2 particles in the presence of Al3Ti nucleate ?-Al grains during solidification. This paper presents our finding on the formation of (Ti,Al)B2 solid solution, which leads to a proposed theory on grain refinement by Al-Ti-B type master alloys that upon addition into aluminum melt stable TiB2 particles react with aluminum slowly and release titanium into the melt. The titanium thus released in combination with titanium in the melt through dissolution of Al3Ti particles maintains a dynamic titanium-rich layer on the surface of (Ti,Al)B2. This layer offers a low crystal mismatch with ?-Al and promotes the nucleation of aluminum grains.
P-type InGaN across the entire alloy composition range
NASA Astrophysics Data System (ADS)
Wang, K.; Araki, T.; Yu, K. M.; Katsuki, T.; Mayer, M. A.; Alarcon-Llado, E.; Ager, J. W.; Walukiewicz, W.; Nanishi, Y.
A systematic investigation on Mg doped and undoped InGaN epilayers grown by plasma-assisted molecular beam epitaxy has been conducted. Single phase InGaN alloys across the entire composition range were synthesized and Mg was doped into InxGa1-xN (0.1 ? x ? 0.88) epilayers up to 1020/cm3. Hall effect, thermopower, and electrochemical capacitance voltage experimental results demonstrate the realization of p-type InGaN across the entire alloy composition range for properly Mg doped InGaN. Hole densities have been measured or estimated to be in the lower 1018/cm3 range when the net acceptor concentrations are in the lower 1019/cm3 range across the composition range.
Structure fragmentation in Fe-based alloys by means of cyclic martensitic transformations of different types
The effect of martensite transformations of different types on the misorientation of austenite crystalline lattice, which characterizes the degree of structure fragmentation, was investigated for Fe-Ni and Fe-Mn alloys. As a result of multiple face-centered cubic (f.c.c.)-body-centered cubic (b.c.c.)-f.c.c. transformations, an austenite single-crystalline specimen is transformed in a polycrystalline one due to progressive fragmentation. It was shown that the degree of fragmentation depends on the magnitude of volume change and the density of dislocations generated on martensitic transformations. PMID:24565160
Predominant factor determining wear properties of ?-type and (?+?)-type titanium alloys in metal-to-metal contact for biomedical applications.
Lee, Yoon-Seok; Niinomi, Mitsuo; Nakai, Masaaki; Narita, Kengo; Cho, Ken
The predominant factor determining the wear properties of a new titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ) and a conventional titanium alloy, Ti-6Al-4V extra-low interstitial (Ti64) was investigated for TNTZ and Ti64 combinations in metal-to-metal contacting bio-implant applications. The worn surfaces, wear debris, and subsurface damages were analyzed using a scanning electron microscopy combined with energy-dispersive spectroscopy and electron-back scattered diffraction analysis. The volume loss of TNTZ is found to be larger than that of Ti64, regardless of the mating material. The wear track of TNTZ exhibits the galled regions and severe plastic deformation with large flake-like debris, indicative of delamination wear, which strongly suggests the occurrence of adhesive wear. Whereas, the wear track of Ti64 have a large number of regular grooves and microcuttings with cutting chip-like wear debris and microfragmentation of fine oxide debris, indicative of abrasive wear combined with oxidative wear. This difference in the wear type is caused by severe and mild subsurface deformations of TNTZ and Ti64, respectively. The lower resistance to plastic shearing for TNTZ compared to that of Ti64 induces delamination, resulting in a higher wear rate. PMID:25460417
Effects of alloying additions on corrosion and passivation behaviors of type 304 stainless steel
Hermas, A.A.; Ogura, K.; Takagi, S.; Adachi, T. [Yamaguchi Univ., Ube (Japan). Dept. of Applied Chemistry
The effects of copper, silicon, molybdenum, and nitrogen as alloying elements on the microstructure and corrosion behavior of type 304 (UNS S30400) austenitic stainless steel (SS) in deaerated dilute acidic chloride solutions at 30 C and 60 C was investigated using potentiodynamic, scanning electron microscopy, and energy dispersive X-ray analysis techniques. The addition of 2% Cu decreased the corrosion and critical current densities sharply. Surface analysis showed the presence of insoluble cuprous chloride dispersed on the steel surface in severe conditions. The additive Cu had no measurable effect on the other passivation parameters. The presence of 3% Si promoted the formation of some {delta}-ferrite phase, but the Si-rich film on the surface was sufficient to improve the general and pitting corrosion resistance. A combined beneficial effect was brought about by alloying 0.8% Mo with high-nickel type 304 SS containing 2% Cu + 3% Si. SEM revealed the segregation of N-rich phases in the presence of 0.24% N in these steels. However, N addition shifted the pitting potential in the positive direction, extending the passive range of the steel.
Microstructure and mechanical properties of thermoelectric nanostructured n-type silicon-germanium alloys synthesized employing spark plasma sintering
Bathula, Sivaiah [CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Department of Applied Physics, Delhi Technological University, Delhi (India); Gahtori, Bhasker; Tripathy, S. K.; Tyagi, Kriti; Srivastava, A. K.; Dhar, Ajay, E-mail: email@example.com [CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Jayasimhadri, M. [Department of Applied Physics, Delhi Technological University, Delhi (India)
Owing to their high thermoelectric (TE) figure-of-merit, nanostructured Si{sub 80}Ge{sub 20} alloys are evolving as a potential replacement for their bulk counterparts in designing efficient radio-isotope TE generators. However, as the mechanical properties of these alloys are equally important in order to avoid in-service catastrophic failure of their TE modules, we report the strength, hardness, fracture toughness, and thermal shock resistance of nanostructured n-type Si{sub 80}Ge{sub 20} alloys synthesized employing spark plasma sintering of mechanically alloyed nanopowders of its constituent elements. These mechanical properties show a significant enhancement, which has been correlated with the microstructural features at nano-scale, delineated by transmission electron microscopy.
A new type of Cu-Al-Ta shape memory alloy with high martensitic transformation temperature
NASA Astrophysics Data System (ADS)
Wang, C. P.; Su, Y.; Y Yang, S.; Shi, Z.; Liu, X. J.
In this study, a new type of Cu-Al-Ta (Cu86Al12Ta2 wt%) shape memory alloy with high martensitic transformation temperature is explored. The microstructure, reversible martensitic transformation and shape memory properties are investigated by means of optical microscopy, back-scattered electron, electron probe microanalysis, x-ray diffraction, differential scanning calorimetry and tensile tests. It is proposed that Cu86Al12Ta2 alloy consists of a mixture of primarily {\\beta }_{1}^{\\prime} martensite and a little {\\gamma }_{1}^{\\prime} martensite and some different precipitates. The tiny thin-striped Ta2(Al,Cu)3 precipitate is predominant in the as-quenched condition, whereas the particle-shaped Cu(Al, Ta) precipitate is dominant after hot-rolling. Additionally, the dendritic-shaped ?1(Cu9Al4) phase begins to appear after hot-rolling, but it disappears when the sample is re-quenched. All studied samples have reversible martensitic transformation temperatures higher than 450?¯ C. The results show that two-step martensitic transformation behavior is observed for Cu86Al12Ta2 alloy in all three different conditions due to the transformations between ({\\beta }_{1}^{\\prime}+{\\gamma }_{1}^{\\prime}) martensites and the austenite parent phase. The results further show that the recovery ratios are almost 100% when the pre-strains are ?2.5%, then they gradually decrease with further increase of the pre-strains. The shape memory effects clearly increase as a result of increase of the pre-strains, up to a maximum value of 3.2%.
Comprehensive thermoelectric properties of n- and p-type 78a/o Si - 22a/o Ge alloy
NASA Technical Reports Server (NTRS)
Raag, V.
The time and temperature dependence of the thermoelectric properties on n- and p-type 78 a/o Si - 22 a/o Ge alloy are presented in detail for the range of temperatures of zero to 1000 C and operating times up to twelve years. The mechanisms responsible for the time dependence of the properties are discussed and mathematical models used in the derivation of the property values from experimental data are presented. The thermoelectric properties for each polarity type of the alloy are presented as a function of temperature for various operating times.
Low-temperature electrical transport in Heusler-type Fe2V (AlSi) alloys
NASA Astrophysics Data System (ADS)
Vasundhara, M.; Srinivas, V.; Rao, V. V.
The temperature variation of the electrical resistivity ? and the Seebeck coefficient S of Heusler-type Fe2VAl1-xSix (0<=x<=1) alloys has been investigated. We have shown that the transport parameters are very sensitive to doping. For the x = 0 sample, high values of ? and negative temperature coefficient of resistivity (TCR) have been observed. As the Si concentration increases, ? decreases and the TCR changes its sign, while S shows significant changes in magnitude as well as sign when Al is replaced with Si. These changes appear to be reminiscent of a metal to semiconductor transition. It has been shown that the conventional transport theories proposed for intermetallic alloys or semiconductors cannot explain the transport behaviour in the whole temperature range of the present study. Low-temperature resistivity data of x = 0-0.02 samples could be described with a gapless semiconductor model. The strong composition dependence of S and ? is attributed to the sharp variations in electronic density of states at the Fermi energy. It is also shown that by optimum doping one can achieve very large values of power factor (P). The estimated power factor at room temperature is observed to be highest (2.23 æ 10-3 W mK-2) for x = 0.06 and comparable to that of conventional thermoelectric material. At lower temperatures P is found to be even higher than that of conventional thermoelectric material.
Origin of thickness dependent spin reorientation transition of B2 type FeCo alloy films
Kim, Dongyoo [Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, SE-10044 Stockholm (Sweden); Hong, Jisang [Department of Physics, Pukyong National University, Busan 608-737 (Korea, Republic of)
We have investigated the origin of thickness dependent spin reorientation transition (SRT) of B2 type FeCo alloy using the full potential linearized augmented plane wave method. It has been reported that FeCo alloy films on various substrates show a SRT from perpendicular to in-plane magnetization at an approximate thickness of 15 monolayers (MLs). The enhanced perpendicular magnetic anisotropy in bulk FeCo is attributed to a tetragonal distortion. However, we have found that the tetragonal distortion tends to suppress the magnetocrystalline anisotropy (MCA) energy at increasing film thickness in two-dimensional structure. In contrast, the magnitude of the shape anisotropy energy increases at increasing FeCo film thickness. Interestingly, the shape anisotropy overcomes the MCA and the SRT, from perpendicular anisotropy to in-plane magnetization, which occurs at a thickness of 15 ML. Consequently, we are able to clearly understand the physical mechanism of the thickness dependent SRT in terms of the competing reactions of these two counteracting contributions.
Adhesive strength of medical polymer on anodic oxide nanostructures fabricated on biomedical ?-type titanium alloy.
Hieda, Junko; Niinomi, Mitsuo; Nakai, Masaaki; Cho, Ken; Mohri, Tomoyoshi; Hanawa, Takao
Anodic oxide nanostructures (nanopores and nanotubes) were fabricated on a biomedical ?-type titanium alloy, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), by anodization in order to improve the adhesive strength of a medical polymer, segmented polyurethane (SPU), to TNTZ. TNTZ was anodized in 1.0M H3PO4 solution with 0.5 mass% NaF using a direct-current power supply at a voltage of 20V. A nanoporous structure is formed on TNTZ in the first stage of anodization, and the formation of a nanotube structure occurs subsequently beneath the nanoporous structure. The nanostructures formed on TNTZ by anodization for less than 3,600s exhibit higher adhesive strengths than those formed at longer anodization times. The adhesive strength of the SPU coating on the nanoporous structure formed on top of TNTZ by anodization for 1,200s improves by 144% compared to that of the SPU coating on as-polished TNTZ with a mirror surface. The adhesive strength of the SPU coating on the nanotube structure formed on TNTZ by anodization for 3,600s increases by 50%. These improvements in the adhesive strength of SPU are the result of an anchor effect introduced by the nanostructures formed by anodization. Fracture occurs at the interface of the nanoporous structure and the SPU coating layer. In contrast, in the case that SPU coating has been performed on the nanotube structure, fracture occurs inside the nanotubes. PMID:24433910
Microstructure and electrochemical properties of high entropy alloysa comparison with type-304 stainless steel
Y. Y. Chen; T. Duval; U. D. Hung; J. W. Yeh; H. C. Shih
High entropy alloys (HEAs) are a newly developed family of multi-component glassy alloys composed of several major alloying elements, such as copper, nickel, aluminum, cobalt, chromium, iron, silicon, titanium, etc. The HEA studied had a nearly amorphous structure as proven by X-ray diffraction (XRD), selected area diffraction (SAD), and differential scanning calorimetry (DSC) analysis. The dendritic phase was composed mainly
Corrosion of high Ni-Cr alloys and Type 304L stainless steel in HNO/sub 3/-HF
Ondrejcin, R.S.; McLaughlin, B.D.
Nineteen alloys were evaluated as possible materials of construction for steam heating coils, the dissolver vessel, and the off-gas system of proposed facilities to process thorium and uranium fuels. Commercially available alloys were found that are satisfactory for all applications. With thorium fuel, which requires HNO/sub 3/-HF for dissolution, the best alloy for service at 130/sup 0/C when complexing agents for fluoride are used is Inconel 690; with no complexing agents at 130/sup 0/C, Inconel 671 is best. At 95/sup 0/C, six other alloys tested would be adequate: Haynes 25, Ferralium, Inconel 625, Type 304L stainless steel, Incoloy 825, and Haynes 20 (in order of decreasing preference); based on composition, six untested alloys would also be adequate. The ions most effective in reducing fluoride corrosion were the complexing agents Zr/sup 4 +/ and Th/sup 4 +/; Al/sup 3 +/ was less effective. With uranium fuel, modestly priced Type 304L stainless steel is adequate. Corrosion will be most severe in HNO/sub 3/-HF used occasionally for flushing and in solutions of HNO/sub 3/ and corrosion products (ferric and dichromate ions). HF corrosion can be minimized by complexing the fluoride ion and by passivation of the steel with strong nitric acid. Corrosion caused by corrosion products can be minimized by operating at lower temperatures.
Collagen type-I leads to in vivo matrix mineralization and secondary stabilization of Mg-Zr-Ca alloy implants.
Mushahary, Dolly; Wen, Cuie; Kumar, Jerald Mahesh; Lin, Jixing; Harishankar, Nemani; Hodgson, Peter; Pande, Gopal; Li, Yuncang
Biodegradable magnesium-zirconia-calcium (Mg-Zr-Ca) alloy implants were coated with Collagen type-I (Coll-I) and assessed for their rate and efficacy of bone mineralization and implant stabilization. The phases, microstructure and mechanical properties of these alloys were analyzed using X-ray diffraction (XRD), optical microscopy and compression test, respectively, and the corrosion behavior was established by their hydrogen production rate in simulated body fluid (SBF). Coll-I extracted from rat tail, and characterized using fourier transform infrared (FT-IR) spectroscopy, was used for dip-coating the Mg-based alloys. The coated alloys were implanted into the femur bones of male New Zealand white rabbits. In vivo bone formation around the implants was quantified by measuring the bone mineral content/density (BMC/BMD) using dual-energy X-ray absorptiometry (DXA). Osseointegration of the implant and new bone mineralization was visualized by histological and immunohistochemical analysis. Upon surface coating with Coll-I, these alloys demonstrated high surface energy showing enhanced performance as an implant material that is suitable for rapid and efficient new bone tissue induction with optimal mineral content and cellular properties. The results demonstrate that Coll-I coated Mg-Zr-Ca alloys have a tendency to form superior trabecular bone structure with better osteoinduction around the implants and higher implant secondary stabilization, through the phenomenon of contact osteogenesis, compared to the control and uncoated ones in shorter periods of implantation. Hence, Coll-I surface coating of Mg-Zr-Ca alloys is a promising method for expediting new bone formation in vivo and enhancing osseointegration in load bearing implant applications. PMID:25179112
Reduced thermal conductivity due to scattering centers in p-type SiGe alloys
NASA Technical Reports Server (NTRS)
Beaty, John S.; Rolfe, Jonathon L.; Vandersande, Jan; Fleurial, Jean-Pierre
Spark erosion was used to produce ultra-fine particles of SiGe thermoelectric material and boron nitride, an inert phonon-scattering material. A homogeneous powder was made by mixing the two powders. The mixture was hot pressed to produce a thermoelectric material with uniformity dispersed, ultra-fine, inert, phonon-scattering centers. It is shown that, in samples with inert boron nitride or silicon nitride, thermal conductivity of a SiGe alloy can be reduced by about 25 percent while maintaining the electrical properties of the samples. Annealing of all the samples at 1525 K caused grain growth to over a micron, eliminating the detrimental effect attributable to small grains. Only in the sample with boron nitride the thermal conductivity did remain well below that for standard p-type SiGe (about 25 percent), while the electrical resistivity and Seebeck coefficient were very close to the values for standard p-type 80/20 SiGe.
Synthesis of Zr-based perovskite-type alloy phosphors by polymerized complex method
NASA Astrophysics Data System (ADS)
Komagata, Hiroki; Kato, Riku; Kato, Ariyuki
To demonstrate the fabrication of inorganic electroluminescent (EL) devices using perovskite-type oxide phosphors by electrophoretic deposition (EPD), AZrO3:RE (A = Ca, Sr, Ba; RE = Eu, Tb) were synthesized by the polymerized complex method. AZrO3:Eu showed orange or red emissions and AZrO3:Tb showed blue-green or green emissions depending on their crystal structures. The emission intensity was found to be enhanced by introducing strains to the host matrices by Mg codoping or alloying. Inorganic EL devices prepared by EPD using BaZrO3:Eu and SrZrO3:Eu as the phosphor layers showed orange and blue emissions that were observable under room light, respectively, which is the first observation of EL emission from the devices prepared by EPD to the best of our knowledge. The combination of perovskite-type oxide phosphors and EPD was found to be a promising way to fabricate inorganic EL devices.
Al-Si alloy formation in narrow p-type Si contact areas for rear passivated solar cells
NASA Astrophysics Data System (ADS)
Urrejola, Elias; Peter, Kristian; Plagwitz, Heiko; Schubert, Gunnar
For high efficiency silicon solar cells, the rear surface passivation by a dielectric layer has significant advantages compared to the standard fully covered Al back-contact structure. In this work the rear contact formation of the passivated emitter and rear cell device structure is analyzed. Contrary to expected views, we found that the contact resistivity of fine screen printed Al fingers alloyed on narrow p-type Si areas depends on the geometry of the Al-Si alloy formation below the contacts, and decreases by reducing the contact area, while the contact resistance remains constant. At the solar cell level, the reduction in the contact resistivity leads to a minimization of the fill factor losses. At the same time, narrow Al-Si alloy formations increased the passivated area below the contacts, improving the optical properties of the rear side, reducing the short-circuit current and open-circuit voltage losses. Scanning electron microscopy analysis of the Al-Si alloy geometry is performed, in order to understand its influence on the contact resistivity. The analysis presented in this article has application in Al-Si alloying processes and advanced solar cells concepts, like back-contact and rear passivated solar cells.
Structural studies of secondary crystallization products of the Fe23B6-type in a nanocrystalline FeCoB-based alloy
Laughlin, David E.
Structural studies of secondary crystallization products of the Fe23B6-type in a nanocrystalline Fe crystallization of an amorphous alloy precursor. Current state of the art nanocomposite soft magnetic alloys dispersed in a residual amor- phous matrix. When these nanocomposite soft magnetic ma- terials
Influence of substrate metal alloy type on the properties of hydroxyapatite coatings deposited using a novel ambient temperature deposition technique.
Barry, J N; Cowley, A; McNally, P J; Dowling, D P
Hydroxyapatite (HA) coatings are applied widely to enhance the level of osteointegration onto orthopedic implants. Atmospheric plasma spray (APS) is typically used for the deposition of these coatings; however, HA crystalline changes regularly occur during this high-thermal process. This article reports on the evaluation of a novel low-temperature (<47¯C) HA deposition technique, called CoBlast, for the application of crystalline HA coatings. To-date, reports on the CoBlast technique have been limited to titanium alloy substrates. This study addresses the suitability of the CoBlast technique for the deposition of HA coatings on a number of alternative metal alloys utilized in the fabrication of orthopedic devices. In addition to titanium grade 5, both cobalt chromium and stainless steel 316 were investigated. In this study, HA coatings were deposited using both the CoBlast and the plasma sprayed techniques, and the resultant HA coating and substrate properties were evaluated and compared. The CoBlast-deposited HA coatings were found to present similar surface morphologies, interfacial properties, and composition irrespective of the substrate alloy type. Coating thickness however displayed some variation with the substrate alloy, ranging from 2.0 to 3.0??m. This perhaps is associated with the electronegativity of the metal alloys. The APS-treated samples exhibited evidence of both coating, and significantly, substrate phase alterations for two metal alloys; titanium grade 5 and cobalt chrome. Conversely, the CoBlast-processed samples exhibited no phase changes in the substrates after depositions. The APS alterations were attributed to the brief, but high-intensity temperatures experienced during processing. PMID:23589437
Two different types of age-hardening behaviors in commercial dental gold alloys.
Hisatsune, Kunihiro; Shiraishi, Takanobu; Takuma, Yasuko; Tanaka, Yasuhiro; Luciano, Rhodora H
Age-hardening behavior during continuous heating in commercial dental casting gold alloys was investigated by means of electrical resistivity measurements, hardness tests and X-ray diffraction. Two distinguishable behaviors were detected. It is considered that the difference was attributed to the amount of platinum, and the atomic ratio of gold and copper in each alloy. The phase transformations during continuous heating progressed into two steps (stages I and II). Increase of the platinum addition in gold-based alloys retards the rate of the reaction and decreases remarkably the amount of stage I. PMID:17546416
Determination of damage functions for the pitting of AISI type 403 blade alloy and ASTM A470/471 disk alloy
NASA Astrophysics Data System (ADS)
Zhang, Yancheng
The prediction of pitting accumulation on turbine blades and disks is of particular importance to predict localized corrosion damages in low pressure (LP) steam turbines. Damage Function Analysis (DFA) and Deterministic Extreme Value Statistics (DEVS) have been employed to predict the pitting damage on AISI Type 403 stainless steel (SS) blade alloy and ASTM A470/471 disk steel in simulated LP steam turbine environments within the phase transition zone. The passivity properties of Type 403 SS and A470/471 steel in the passive regions, including defect type, defect concentration in the barrier film, barrier film thickness, and the steady-state current density, agree with the predictions of the Point Defect Model (PDM) for an n-type semiconductor. Optimization of the PDM based impedance model on the experimental electrochemical impedance data has yielded a set of parameter values that can be used to predict the barrier film growth on Type 403 SS in deaerated borate buffer solution ( pH = 8.2) at ambient temperature. Experimental relationships between the breakdown potential and chloride activity, pH, temperature, and potential scan rate have demonstrated the applicability of the PDM for describing passivity breakdown on Type 403 SS and A470/471 steel. The obtained parameter values were used to calculate the breakdown potential, induction time, and their distributions, via the PDM, which represents the first quantitative characterization of the passivity breakdown behavior on Type 403 SS. Pitting damage functions for Type 403 SS have been experimentally determined for the first time. However, low pit density on A470/471 steel led to insufficient pit numbers on the 1.27 cm2 surface for the effective determination of damage functions. DEVS has been demonstrated by predicting the average maximum pit depth for 750 hours from short-term (24 hours and 240 hours) maximum pit depth data on Type 403 SS in deaerated buffer solution with 0.10 M NaCl at an applied potential of 0.090 VSCE and on A470/471 steel in the solution with 0.028 M NaCl at 0.058 VSCE. To the author's knowledge, the work reported in this dissertation represents the first instance in which DEVS has been used to predict the accumulation of pitting damage on LP steam turbine alloys, thereby heralding a new era in the prediction of corrosion damage in these systems.
[New type titan alloy with shape memory for use in dental implantology].
Grigor'ian, A S; Filonov, M R; Arkhipov, A V; Selezneva, I I; Zhukova, Iu S
The paper summarizes the results of in vitro and in vivo studies that have proved biocompatibility and medical safety of Ta and Ti-Nb-Ta-bases alloys. According to some in vitro data Ti-Nb-Ta-based alloy possesses certain advantages when comparing to Ta-based. In particular, it contributes to elevation of viability of cellular elements and to definite increase of their adhesive potential. PMID:23528392
Method of fabricating n-type and p-type microcrystalline semiconductor alloy material including band gap widening elements
Guha, Subhendu (Troy, MI); Ovshinsky, Stanford R. (Bloomfield Hills, MI)
A method of fabricating doped microcrystalline semiconductor alloy material which includes a band gap widening element through a glow discharge deposition process by subjecting a precursor mixture which includes a diluent gas to an a.c. glow discharge in the absence of a magnetic field of sufficient strength to induce electron cyclotron resonance.
Effects of Annealing Temperature on the Electrochemical Hydrogen Storage Behaviors of La-Mg-Ni-Based A2B7-Type Electrode Alloys
NASA Astrophysics Data System (ADS)
Zhang, Yanghuan; Yuan, Zeming; Zhai, Tingting; Yang, Tai; Bu, Wengang; Guo, Shihai
In an attempt to improve the cyclic stability of La-Mg-Ni-based A2B7-type electrode alloys, La0.8Mg0.2Ni3.3Co0.2Si x (x = 0-0.2) electrode alloys were fabricated by casting and annealing, and the effects of annealing temperature on the structures and electrochemical hydrogen storage performances of the alloys were systematically investigated. The results indicate that the as-cast and annealed alloys exhibit multiple structures that contain two major phases, (La,Mg)2Ni7 with a Ce2Ni7-type hexagonal structure and LaNi5 with a CaCu5-type hexagonal structure; and one residual phase, LaNi3. Both the lattice constants and cell volumes of the two major phases increase with the increasing annealing temperature. Instead of altering the phase composition, the annealing treatment causes the abundances of these two major phases to vary. Based on electrochemical measurements, the cycle stabilities of the alloys are found to be considerably improved by annealing, and the alloy's discharge capacity yields a maximum value with the increasing annealing temperature due to the variation in phase abundance and the homogenization of the composition, respectively. The influence of the annealing treatment on the electrochemical kinetics of the alloys is associated with the alloy's composition; the electrochemical kinetics of the Si-free alloy become slower with the increasing annealing temperature, whereas those of the Si-added alloys first mount up and then go down under the same conditions.
Antiferromagnetic half-metals, gapless half-metals, and spin gapless semiconductors: The D0{sub 3}-type Heusler alloys
Gao, G. Y., E-mail: email@example.com; Yao, Kai-Lun, E-mail: firstname.lastname@example.com [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China)] [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China)
High-spin-polarization materials are desired for the realization of high-performance spintronic devices. We combine recent experimental and theoretical findings to theoretically design several high-spin-polarization materials in binary D0{sub 3}-type Heusler alloys: gapless (zero-gap) half-metallic ferrimagnets of V{sub 3}Si and V{sub 3}Ge, half-metallic antiferromagnets of Mn{sub 3}Al and Mn{sub 3}Ga, half-metallic ferrimagnets of Mn{sub 3}Si and Mn{sub 3}Ge, and a spin gapless semiconductor of Cr{sub 3}Al. The high spin polarization, zero net magnetic moment, zero energy gap, and slight disorder compared to the ternary and quaternary Heusler alloys make these binary materials promising candidates for spintronic applications. All results are obtained by the electronic structure calculations from first-principles.
Hydrogen in lanthanum-magnesium-nickel alloys with structures of the L22, D2 d , and L60 types
NASA Astrophysics Data System (ADS)
Zaginaichenko, S. Yu.; Matysina, Z. A.; Shchur, D. V.
A statistical theory of the solubility of hydrogen in alloys with structures of the L22, D2 d , and L60 types and in phase mixtures of these alloys is developed. The isotherms of absorption and desorption have been studied; their dependence on the activity of hydrogen and concentration of magnesium has been established. It is shown that with an increase in the magnesium concentration and a decrease in the activity of hydrogen, a plateau (a horizontal segment) appears and is lengthened in the isotherms. Hysteresis effects have been investigated with allowance for volume effects; the hysteresis coefficients have been estimated. The decrease in the hysteresis coefficient with increasing magnesium concentration is substantiated. The results of the theoretical calculations are compared with experimental data.
Alloying and coating strategies for improved Pb-Li compatibility in DEMO-type fusion reactors
NASA Astrophysics Data System (ADS)
Unocic, K. A.; Pint, B. A.
Two strategies were explored to improve the Pb-16Li compatibility of Fe-base alloys for a fusion energy blanket system. The use of thin (?50 ?m) Al-rich diffusion coatings on Grade 92 (9Cr-2W) substrates significantly reduced the mass loss in static Pb-Li capsule tests for up to 5000 h at 600 ¯C and 700 ¯C. However, significant Al loss was observed at 700 ¯C. Thicker coatings with Fe-Al intermetallic layers partially spalled after exposure at 700 ¯C, suggesting that coating strategies are limited to lower temperatures. To identify compositions for further alloy development, model FeCrAlY alloys with 10-20 wt.%Cr and 3-5%Al were exposed for 1000 h at 700 ¯C. There was little effect on mass change of varying the Cr content, however, alloys with <5% Al showed mass losses in these experiments. For both coatings and FeCrAl alloys, the surface reaction product was LiAlO2 after exposure and cleaning.
Characterization of corrosion products of AB{sub 5}-type hydrogen storage alloys for nickel-metal hydride batteries
Maurel, F.; Knosp, B.; Backhaus-Ricoult, M.
To better understand the decrease in storage capacity of AB{sub 5}-type alloys in rechargeable Ni/MH batteries undergoing repeated charge/discharge cycles, the corrosion of a MnNi{sub 3.55}Co{sub 0.75}Mn{sub 0.4}Al{sub 0.3} alloy in aqueous KOH electrolyte was studied. The crystal structure, chemical composition, and distribution of corrosion products were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Hollow and filed needles of a mixed rare earth hydroxide Mn(OH){sub 3} were found to cover a continuous nanocrystalline corrosion scale composed of metal (Ni, Co) solid solution, oxide (Ni,Co)O solid solution and rare earth hydroxide, and a Mn-depleted alloy subscale. Corrosion kinetics were measured for three different temperatures. Growth kinetics of the continuous corrosion scale and of the Mm(OH){sub 3} needles obeyed linear and parabolic rate laws, respectively. Models for the corrosion mechanism were developed on the basis of diffusional transport of Mn and OH through the hydroxide needles and subsequent diffusion along grain boundaries through the nanocrystalline scale.
Mechanical properties of modified low cobalt powder metallurgy Udimet 700 type alloys
NASA Technical Reports Server (NTRS)
Harf, Fredric H.
Eight superalloys derived from Udimet 700 were prepared by powder metallurgy, hot isostatically pressed, heat treated and their tensile and creep rupture properties determined. Several of these alloys displayed properties superior to those of Udimet 700 similarly prepared, in one case exceeding the creep rupture life tenfold. Filter clogging by extracted gamma prime, its measurement and significance are discussed in an appendix.
Thermoelectric properties of fine-grained FeVSb half-Heusler alloys tuned to p-type by substituting vanadium with titanium
Zou, Minmin [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)] [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Li, Jing-Feng, E-mail: email@example.com [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)] [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Kita, Takuji [Advanced Material Engineering Division, Vehicle Engineering Group, Higashifuji Technical Center, Toyota Motor Corporation, 1200, Mishuku, Susono, Shizuoka 410-1193 (Japan)] [Advanced Material Engineering Division, Vehicle Engineering Group, Higashifuji Technical Center, Toyota Motor Corporation, 1200, Mishuku, Susono, Shizuoka 410-1193 (Japan)
Fine-grained Ti-doped FeVSb half-Heusler alloys were synthesized by combining mechanical alloying and spark plasma sintering and their thermoelectric properties were investigated with an emphasis on the influences of Ti doping and phase purity. It was found that substituting V with Ti can change the electrical transport behavior from n-type to p-type due to one less valence electron of Ti than V, and the sample with nominal composition FeV{sub 0.8}Ti{sub 0.4}Sb exhibits the largest Seebeck coefficient and the maximum power factor. By optimizing the sintering temperature and applying annealing treatment, the power factor is significantly improved and the thermal conductivity is reduced simultaneously, resulting in a ZT value of 0.43 at 500 Degree-Sign C, which is relatively high as for p-type half-Heusler alloys containing earth-abundant elements. - Graphical abstract: Fine-grained Ti-doped FeVSb alloys were prepared by the MA-SPS method. The maximum ZT value reaches 0.43 at 500 Degree-Sign C, which is relatively high for p-type half-Heusler alloys. Highlights: Black-Right-Pointing-Pointer Ti-doped FeVSb half-Heusler alloys were synthesized by combining MA and SPS. Black-Right-Pointing-Pointer Substituting V with Ti changes the electrical behavior from n-type to p-type. Black-Right-Pointing-Pointer Thermoelectric properties are improved by optimizing sintering temperature. Black-Right-Pointing-Pointer Thermoelectric properties are further improved by applying annealing treatment. Black-Right-Pointing-Pointer A high ZT value of 0.43 is obtained at 500 Degree-Sign C for p-type Ti-doped FeVSb alloys.
Effect of alloy type and surface conditioning on roughness and bond strength of metal brackets.
Nergiz, Ibrahim; Schmage, Petra; Herrmann, Wolfram; Ozcan, Mutlu
The effect of 5 different surface conditioning methods on bonding of metal brackets to cast dental alloys was examined. The surface conditioning methods were fine (30-microm) or rough (125-microm) diamond bur, sandblasting (50-microm or 110-microm aluminum oxide [Al2O3]), and silica coating (30-microm silica). Fifty disc-shaped specimens of 5 different alloys (gold-silver, palladium-silver, nickel-chromium, cobalt-chromium, and titanium) were ground with 1200-grit silicone carbide abrasive and polished before being reused for each conditioning method. Polished surfaces were used as negative controls. After measuring surface roughness (RZ), metal brackets were bonded to the conditioned alloys with a self-curing resin composite. Specimens were thermocycled (5000 times, 5 degrees-55 degrees C, 30 seconds), and shear bond tests were performed. Significantly higher (P<.001) surface roughnesses were observed with use of the rough diamond bur (RZ approximately 33 microm), 110-microm Al2O3 (RZ approximately 14 microm), and fine diamond bur (RZ approximately 10 microm), compared with the controls (RZ approximately 1 microm). Silica coating (RZ approximately 4 microm) and 50-microm Al2O3 (RZ approximately 4 microm) demonstrated no significant difference (P>.001) in roughness when compared with the controls. The control group showed no resistance to shear forces (0 MPa). Bond values were greater (19 MPa) when silica coating was used, compared with 50-microm Al2O3 (7 MPa) and 110-microm Al2O3 (8 MPa) for all alloys tested. However, interaction between alloys and conditioning methods exhibited significant differences (P<.0001). PMID:14718878
Heterogeneous nucleation of ?-type precipitates on nanoscale Zr-rich particles in a Mg-6Zn-0.5Cu-0.6Zr alloy
Zirconium (Zr) is an important alloying element to Mg-Zn-based alloy system. In this paper, we report the formation of the ?-type precipitates on the nanoscale Zr-rich particles in a Mg-6Zn-0.5Cu-0.6Zr alloy during ageing at 180¯C. Scanning transmission electron microscopy examinations revealed that the nanoscale Zr-rich [0001]? rods/laths are dominant in the Zr-rich core regions of the as-quenched sample after a solution treatment at 430¯C. More significantly, these Zr-rich particles served as favourable sites for heterogeneous nucleation of the Zn-rich ?-type phase during subsequent isothermal ageing at 180¯C. This research provides a potential route to engineer precipitate microstructure for better strengthening effect in the Zr-containing Mg alloys. PMID:22682092
Characterization of core shell type and alloy Ag/Au bimetallic clusters by using extended X-ray absorption fine structure spectroscopy
NASA Astrophysics Data System (ADS)
Chen, H. M.; Liu, R. S.; Jang, L.-Y.; Lee, J.-F.; Hu, S. F.
Bimetallic silver and gold nanoparticles, a core-shell type structure, have been prepared by NaBH 4 reduction method. The optical absorption spectra are recorded and compared with various ratios of Ag/Au alloy nanoparticles. The absorption spectra of bimetallic nanoparticles suggested the formation of core-shell structure. On the other hand, the high resolution transmission electron microscopy image of the nanoparticles confirmed the core-shell type configuration directly. Moreover, we studied the surrounding environment of core-shell type and alloy nanoparticles around gold atoms by using extended X-ray absorption fine structure spectroscopy.
Direct synthesis of BiCuChO-type oxychalcogenides by mechanical alloying
Pele, Vincent; Barreteau, Celine [Institut de Chimie MolÕculaire et des MatÕriaux dOrsay, Univ. Paris-Sud, UMR 8182, Orsay F-91405 (France); CNRS, Orsay F-91405 (France); Berardan, David, E-mail: email@example.com [Institut de Chimie MolÕculaire et des MatÕriaux dOrsay, Univ. Paris-Sud, UMR 8182, Orsay F-91405 (France); CNRS, Orsay F-91405 (France); Zhao, Lidong; Dragoe, Nita [Institut de Chimie MolÕculaire et des MatÕriaux dOrsay, Univ. Paris-Sud, UMR 8182, Orsay F-91405 (France); CNRS, Orsay F-91405 (France)
We report on the direct synthesis of BiCuChO based materials by mechanical alloying (Ch=Se, Te). We show that contrary to the synthesis paths used in the previous reports dealing with this family of materials, which use costly annealings in closed silica tubes under controlled atmosphere, this new synthesis route enables the synthesis of pure phase materials at room temperature under air, with reasonable milling time. This synthesis procedure is easily scalable for large scale applications. - Highlights: Phase pure BiCuSeO doped and undoped prepared by mechanical alloying. Synthesis performed under air at room temperature. Electrical properties similar to that of samples synthesized by a classical path.
Use of titanium alloy swarf for the production of TK type hard metals
S. S. Kiparisov; Yu. V. Levinskii; A. P. Petrov; I. P. Deulina
In the present work a trial batch (200 kg) of titanium carbide of nonstoichiometric composition made under industrial conditions was employed for the production of TK grade hard metals. The starting material for carbidization was a mixture of VT-3,1 titanium alloy milling chips (size 50 20 0.5 mm) and PM-15TS carbon black (GOST 3815-31--71). Carbidization was performed in
Crevice Repassivation Potential of Alloy 22 in High-Nitrate Dust Deliquescence Type Environments
Lian, T; Gdowski, G E; Hailey, P D; Rebak, R B
The nitrate ion (NO{sub 3}{sup -}) is an inhibitor for crevice corrosion of Alloy 22 (N06022) in chloride (Cl{sup -}) aqueous solutions. Naturally formed electrolytes may contain both chloride and nitrate ions. The higher the ratio R = [NO{sub 3}{sup -}]/[Cl{sup -}] in the solution the stronger the inhibition of crevice corrosion. Atmospheric desert dust contains both chloride and nitrate salts, generally based on sodium (Na{sup +}) and potassium (K{sup +}). Some of these salts may deliquescence at relatively low humidity at temperatures on the order of 150 C and higher. The resulting deliquescent brines are highly concentrated and especially rich in nitrate. Electrochemical tests have been performed to explore the anodic behavior of Alloy 22 in high chloride high nitrate electrolytes at temperatures as high as 150 C at ambient atmospheres. Naturally formed brines at temperatures higher than 120 C do not induce crevice corrosion in Alloy 22 because they contain high levels of nitrate. The inhibitive effect of nitrate on crevice corrosion is still active for temperatures higher than 100 C.
Invar and Elinvar type amorphous Fe-Cr-B alloys with high corrosion resistance
NASA Technical Reports Server (NTRS)
Kikuci, M.; Fukamichi, K.; Masumoto, T.
Amorphous (Fe(1-x)Cr(x))85B15 alloys (x = 0 to 0.15) were prepared from the melts by rapid quenching using a single roller techinque, and their Invar and Elinvar characteristics and corrosion resistance were investigated. With an increase in chromium content the Curie temperature and the saturation magnetic moment per iron atom decreased monotonically, while the crystallization temperature incresed gradually. The thermal expansion coefficient alpha around room temperature became slightly larger with increasing chromium content. Nevertheless, these amorphous alloys exhibited excellent Invar characteristics below the Curie temperature. The value of Young's modulus increased remarkably in a relatively low magnetic field and then saturated at a field of about 80 kA/m, showing a large delta E effect. Its value as well as a longitudinal linear magnetostriction became smaller with an increase in chromium content. The temperature coefficient of Young's modulus changed from postive to negative, and the temperature range showing the Elinvar characteristics became narrower with chromium content. The temperature coefficient of delay time determined from the values of alpha and e was very small. The corrosion resistance of these alloys was extremely improved by chromium addition.
Effect of Sn Doping on the Thermoelectric Properties of n-type Bi2(Te,Se)3 Alloys
NASA Astrophysics Data System (ADS)
Lee, Jae-Uk; Lee, Deuk-Hee; Kwon, Beomjin; Hyun, Dow-Bin; Nahm, Sahn; Baek, Seung-Hyub; Kim, Jin-Sang
In the present work, 0.01-0.05wt.% Sn-doped Bi2(Te0.9Se0.1)3 alloys were prepared by mechanical deformation followed by hot pressing, and their thermoelectric properties were studied. We observed that the Sn element is a very effective dopant as an acceptor to control the carrier concentration in the n-type Bi2(Te0.9Se0.1)3 alloys to optimize their thermoelectric property. The n-type carrier concentration can be controlled from 4.2 æ 1019/cm3 to 2.4 æ 1019/cm3 by 0.05wt.% Sn-doping. While the Seebeck coefficient and the electrical resistivity are both increased with doping, the power factor remains the same. Therefore, we found that the thermoelectric figure-of-merit becomes maximized at 0.75 when the thermal conductivity has a minimum value for the 0.03wt.% Sn-doped sample.
Magnetic studies of Fe-doped martensitic Ni2Mn1.44Sn0.56-type Heusler alloy
NASA Astrophysics Data System (ADS)
Passamani, E. C.; Cµrdova, C.; Alves, A. L.; Moscon, P. S.; Larica, C.; Takeuchi, A. Y.; Biondo, A.
Localization and magnetism of Fe replacing either Mn or Ni in the Ni2Mn1.44Sn0.56-type Heusler alloy have been systematically investigated using magnetization, scanning electron microscopy and M—ssbauer spectroscopy. It has been shown that the addition of Fe either in Mn or in Ni sites reduces the fraction of the Mn-rich NiMnSn-type Heusler alloys that has short-range antiferromagnetic interactions; consequently it reduces the martensitic-austenitic transition temperature and increases the thermal hysteresis width due to an increase in atomic disorder caused by Fe replacements. The Fe atoms in Mn sites have two magnetic configurations with magnetic moments of 0.8?B/Fe and 1.4?B/Fe in the martensitic orthorhombic structure, while Fe in Ni sites have magnetic moments smaller than 0.1?B/Fe. These results indicate that the Fe atoms are distinctly substituting either Mn or Ni and the decrease in the martensitic phase transition temperature for increasing Fe content can be mainly attributed to the Fe atoms in the Mn sites in both cases.
Microstructure, elastic deformation behavior and mechanical properties of biomedical ?-type titanium alloy thin-tube used for stents.
Tian, Yuxing; Yu, Zhentao; Ong, Chun Yee Aaron; Kent, Damon; Wang, Gui
Cold-deformability and mechanical compatibility of the biomedical ?-type titanium alloy are the foremost considerations for their application in stents, because the lower ductility restricts the cold-forming of thin-tube and unsatisfactory mechanical performance causes a failed tissue repair. In this paper, ?-type titanium alloy (Ti-25Nb-3Zr-3Mo-2Sn, wt%) thin-tube fabricated by routine cold rolling is reported for the first time, and its elastic behavior and mechanical properties are discussed for the various microstructures. The as cold-rolled tube exhibits nonlinear elastic behavior with large recoverable strain of 2.3%. After annealing and aging, a nonlinear elasticity, considered as the intermediate stage between "double yielding" and normal linear elasticity, is attributable to a moderate precipitation of ? phase. Quantitive relationships are established between volume fraction of ? phase (V?) and elastic modulus, strength as well as maximal recoverable strain (?max-R), where the ?max-R of above 2.0% corresponds to the V? range of 3-10%. It is considered that the "mechanical" stabilization of the (?+?) microstructure is a possible elastic mechanism for explaining the nonlinear elastic behavior. PMID:25706668
A model for the high-temperature transport properties of heavily doped n-type silicon-germanium alloys
NASA Technical Reports Server (NTRS)
Vining, Cronin B.
A model is presented for the high-temperature transport properties of large-grain-size, heavily doped n-type silicon-germanium alloys. Electron and phonon transport coefficients are calculated using standard Boltzmann equation expressions in the relaxation time approximation. Good agreement with experiment is found by considering acoustic phonon and ionized impurity scattering for electrons, and phonon-phonon, point defect, and electron-phonon scattering for phonons. The parameters describing electron transport in heavily doped and lightly doped materials are significantly different and suggest that most carriers in heavily doped materials are in a band formed largely from impurity states. The maximum dimensionless thermoelectric figure of merit for single-crystal, n-type Si(0.8)Ge(0.2) at 1300 K is estimated at ZT about 1.13 with an optimum carrier concentration of n about 2.9 x 10 to the 20th/cu cm.
High-velocity-oxidation performance of metal-chromium-aluminum (MCrAl), cermet, and modified aluminide coatings on IN-100 and type VIA alloys at 1093 C
NASA Technical Reports Server (NTRS)
Deadmore, D. L.
Cermet, MCrAl, and modified aluminide types of coatings applied to IN-100 and NASA-TRW-VIA alloy specimens were cyclically oxidation tested in a high velocity (Mach 1) gas flame at 1093 C. Several coating compositions of each type were evaluated for oxidation resistance. The modified aluminide coating, Pt-Al, applied to alloy 6A proved to be the best, providing oxidation protection to approximately 750 hours based on weight change measurements. The second best, a CoCrAlY coating applied to 6A, provided protection to 450 hours. The third best was a cermet + aluminide coating on 6A with a protection time to 385 hours.
Irradiation Performance of U-Mo Alloy Based Monolithic Plate-Type Fuel Design Selection
A. B. Robinson; G. S. Chang; D. D. Keiser, Jr.; D. M. Wachs; D. L. Porter
A down-selection process has been applied to the U-Mo fuel alloy based monolithic plate fuel design, supported by irradiation testing of small fuel plates containing various design parameters. The irradiation testing provided data on fuel performance issues such as swelling, fuel-cladding interaction (interdiffusion), blister formation at elevated temperatures, and fuel/cladding bond quality and effectiveness. U-10Mo (wt%) was selected as the fuel alloy of choice, accepting a somewhat lower uranium density for the benefits of phase stability. U-7Mo could be used, with a barrier, where the trade-off for uranium density is critical to nuclear performance. A zirconium foil barrier between fuel and cladding was chosen to provide a predictable, well-bonded, fuel-cladding interface, allowing little or no fuel-cladding interaction. The fuel plate testing conducted to inform this selection was based on the use of U-10Mo foils fabricated by hot co-rolling with a Zr foil. The foils were subsequently bonded to Al-6061 cladding by hot isostatic pressing or friction stir bonding.
Investigation of early cellsurface interactions of human mesenchymal stem cells on nanopatterned ?-type titaniumniobium alloy surfaces
Medda, Rebecca; Helth, Arne; Herre, Patrick; Pohl, Darius; Rellinghaus, Bernd; Perschmann, Nadine; Neubauer, Stefanie; Kessler, Horst; Oswald, Steffen; Eckert, J■rgen; Spatz, Joachim P.; Gebert, Annett; Cavalcanti-Adam, Elisabetta A.
Multi-potent adult mesenchymal stem cells (MSCs) derived from bone marrow have therapeutic potential for bone diseases and regenerative medicine. However, an intrinsic heterogeneity in their phenotype, which in turn results in various differentiation potentials, makes it difficult to predict the response of these cells. The aim of this study is to investigate initial cellsurface interactions of human MSCs on modified titanium alloys. Gold nanoparticles deposited on ?-type Ti40Nb alloys by block copolymer micelle nanolithography served as nanotopographical cues as well as specific binding sites for the immobilization of thiolated peptides present in several extracellular matrix proteins. MSC heterogeneity persists on polished and nanopatterned Ti40Nb samples. However, cell heterogeneity and donor variability decreased upon functionalization of the gold nanoparticles with cyclic RGD peptides. In particular, the number of large cells significantly decreased after 24 h owing to the arrangement of cell anchorage sites, rather than peptide specificity. However, the size and number of integrin-mediated adhesion clusters increased in the presence of the integrin-binding peptide (cRGDfK) compared with the control peptide (cRADfK). These results suggest that the use of integrin ligands in defined patterns could improve MSC-material interactions, not only by regulating cell adhesion locally, but also by reducing population heterogeneity. PMID:24501674
The characterization of shape memory effect for low elastic modulus biomedical {beta}-type titanium alloy
Wang Liqiang [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China); Lu Weijie, E-mail: firstname.lastname@example.com [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China); Qin Jining; Zhang Fan; Zhang Di [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China)
This work investigates the textures of biomedical TiNbTaZr alloy rolled by 99% cold reduction ratios in thickness. The relationship between textures and superelasticity of the specimens treated at 873 K and 1223 K for 1.2 ks is studied. The microstructure of tensile specimen is investigated by transmission electron microscopy. Textures of cold-rolled and heat-treated specimens are studied. During unloading, the anisotropy of superelastic strain and pure elastic strain in the heat-treated specimens is observed. Superelastic strain along rolling direction and transverse direction is larger than those along 45 deg. from rolling direction while pure elastic strain shows the highest value along 45 deg. from rolling direction in the specimen treated at 873 K. For the specimen treated at 1223 K, higher pure elastic strain is obtained along rolling direction. The maximum recovered strain around 2.11% is obtained along rolling direction.
Field ion microscopy of cascades of atomic displacements in metals and alloys after various types of irradiation
NASA Astrophysics Data System (ADS)
Ivchenko, V. A.
Experimental results on atomic-spatial investigation of radiative defect formation in surface layers of materials, initiated by neutron bombardment (of Pt, E > 0.1 MeV) and ion implantation (in Cu3Au: E = 40 keV, F = 1016 ion/m2, j = 10-3 A/cm2), are considered. Quantitative estimates are obtained for the size, shape, and volume fraction of cascades of atomic displacements formed under various types of irradiation in the surface layers of the materials. It is shown that the average size of radiation clusters after irradiation of platinum to a fast neutron fluence of 6.7 æ 1022 m-2 ( E > 0.1 MeV) is about 3.8 nm. The experimentally established average size of a radiation cluster (disordered zone) in the alloy after ion bombardment is 4 æ 4 æ 1.5 nm.
Thermal gradient mass transfer of type 316L stainless steel and alloy 718 in flowing mercury
NASA Astrophysics Data System (ADS)
Pawel, S. J.; DiStefano, J. R.; Manneschmidt, E. T.
Thermal convection loops (TCLs) fabricated from 316L stainless steel (SS) and containing mercury and a variety of 316L coupons representing variable surface conditions and heat treatments have been operated continuously for periods up to 5000 h. In each case, the maximum TCL temperature was about 305¯C, the minimum temperature about 240¯C, and the Hg velocity was constant at either 1.2 m/min or 5 m/min, depending on the TCL cross-section diameter. Wetting of 316L by Hg was somewhat sporadic and inconsistent, and was generally encouraged by steam cleaning and/or gold-coating of specimens prior to testing as well as relatively high exposure temperatures. Interaction of 316L and Hg was observed to generate a porous surface layer substantially depleted of Ni and Cr which resulted in transformation to ferrite, but the maximum penetration detected for all of the test conditions corresponded to only about 60-70 ?m/yr, with far less penetration for most exposures. In limited testing, alloy 718 was found more resistant to wetting/attack than 316L.
Bandgap bowing and p-type doping of (Zn, Mg, Be)O wide-gapsemiconductor alloys: a first-principles study
Hongliang Shi; Yifeng Duan
Using a first-principles band-structure method and a\\u000a special quasirandom structure (SQS) approach, we systematically\\u000a calculate the band gap bowing parameters and p-type doping\\u000a properties of (Zn, Mg, Be)O related random ternary and quaternary\\u000a alloys. We show that the bowing parameters for ZnBeO and MgBeO\\u000a alloys are large and dependent on composition. This is due to the\\u000a size difference and chemical
Development of One-Body Type Water- and Air-Cooling Fixed Masks Made of Forged 0.2% Beryllium Copper Alloy
NASA Astrophysics Data System (ADS)
Mase, Kazuhiko; Kikuchi, Takashi; Tanaka, Hirokazu; Toyoshima, Akio; Watanabe, Fumio
One-body type water- and air-cooling fixed masks made of forged 0.2% beryllium copper alloy have been developed, and successfully applied for the front end of a new undulator beamline, BL-13A, at the Photon Factory in Tsukuba, Japan. Advantages of the masks are a simple structure, no welding, low cost, high duration, and an extremely low out-gassing rate. Forged 0.2% beryllium copper alloy is demonstrated to be a valuable material for synchrotron radiation instruments.
Low-cycle fatigue of Type 347 stainless steel and Hastelloy alloy X in hydrogen gas and in air at elevated temperatures
NASA Technical Reports Server (NTRS)
Jaske, C. E.; Rice, R. C.; Buchheit, R. D.; Roach, D. B.; Porfilio, T. L.
An investigation was conducted to assess the low-cycle fatigue resistance of two alloys, Type 347 stainless steel and Hastelloy Alloy X, that were under consideration for use in nuclear-powered rocket vehicles. Constant-amplitude, strain-controlled fatigue tests were conducted under compressive strain cycling at a constant strain rate of 0.001/sec and at total axial strain ranges of 1.5, 3.0, and 5.0 %, in both laboratory-air and low-pressure hydrogen-gas environments at temperatures from 538 to 871 C. Specimens were obtained from three heats of Type 347 stainless steel bar and two heats of Hastelloy Alloy X. The tensile properties of each heat were determined at 21, 538, 649, and 760 C. The continuous cycling fatigue resistance was determined for each heat at temperatures of 538, 760, and 871 C. The Type 347 stainless steel exhibited equal or superior fatigue resistance to the Hastelloy Alloy X at all conditions of this study.
Fabrication of a maxillary posterior fixed partial denture with a type 4 gold alloy and a dual-polymerizing indirect composite.
Matsumura, Hideo; Mori, Shuichi; Tanoue, Naomi
The aim of the present study was to design and fabricate a maxillary posterior fixed partial denture (FPD) made of a type 4 gold alloy and an indirect composite. Unlike the conventional framework design of a resin veneered restoration, cut-back was extended approximately 1/4 to 1/3 width in the occlusal table of the buccal cusp. Multiple retentive beads 150-200 mum in diameter were placed on the metal surface to be veneered. The gold alloy was cast in a cristobalite mold using a centrifugal casting machine. The cut surface with the retentive beads was air-abraded with alumina, and a priming agent (Alloy Primer) that contained triazine dithione monomer (VTD) was applied. A tooth-colored veneer was then fabricated with a highly loaded light- and heat-cured composite material (Estenia). This design and procedure can be applied as a standardized laboratory technique for fabrication of maxillary posterior restorations and FPDs. PMID:18403895
Determination of thermal conductivities of Sn-Zn lead-free solder alloys with radial heat flow and Bridgman-type apparatus
NASA Astrophysics Data System (ADS)
Meydaneri, Fatma; SaatÓi, Buket; G■nd■z, Mehmet; øzdemir, Mehmet
The variations of thermal conductivities of solid phases versus temperature for pure Sn, pure Zn and Sn-9 wt.% Zn, Sn-14 wt.% Zn, Sn-50 wt.% Zn, Sn-80 wt.% Zn binary alloys were measured with a radial heat flow apparatus. The thermal conductivity ratios of liquid phase to solid phase for the pure Sn, pure Zn and eutectic Sn-9 wt.% Zn alloy at their melting temperature are found with a Bridgman-type directional solidification apparatus. Thus, the thermal conductivities of liquid phases for pure Sn, pure Zn and eutectic Sn-9 wt.% Zn binary alloy at their melting temperature were evaluated by using the values of solid phase thermal conductivities and the thermal conductivity ratios of liquid phase to solid phase.
Band-gap bowing and p-type doping of (Zn, Mg, Be)O wide-gap semiconductor alloys: a first-principles study
NASA Astrophysics Data System (ADS)
Shi, H.-L.; Duan, Y.
Using a first-principles band-structure method and a special quasirandom structure (SQS) approach, we systematically calculate the band gap bowing parameters and p-type doping properties of (Zn, Mg, Be)O related random ternary and quaternary alloys. We show that the bowing parameters for ZnBeO and MgBeO alloys are large and dependent on composition. This is due to the size difference and chemical mismatch between Be and Zn(Mg) atoms. We also demonstrate that adding a small amount of Be into MgO reduces the band gap indicating that the bowing parameter is larger than the band-gap difference. We select an ideal N atom with lower p atomic energy level as dopant to perform p-type doping of ZnBeO and ZnMgBeO alloys. For N doped in ZnBeO alloy, we show that the acceptor transition energies become shallower as the number of the nearest neighbor Be atoms increases. This is thought to be because of the reduction of p- d repulsion. The NO acceptor transition energies are deep in the ZnMgBeO quaternary alloy lattice-matched to GaN substrate due to the lower valence band maximum. These decrease slightly as there are more nearest neighbor Mg atoms surrounding the N dopant. The important natural valence band alignment between ZnO, MgO, BeO, ZnBeO, and ZnMgBeO quaternary alloy is also investigated.
Cluster packing geometry for Al-based F-type icosahedral alloys
Nobuhisa Fujita; Hikari Takano; Akiji Yamamoto; An-Pang Tsai
This paper presents a new highly stable periodic approximant to the Al-based F-type icosahedral quasicrystals, i-Al-Pd-TM (TM=transition metals). The structure of this intermetallic Al-Pd-Cr-Fe compound is determined ab initio using single-crystal X-ray diffraction, where the space group is identified to be Pa-3 and the lattice constant 40.5 angstrom. The structure is well described as a dense packing of clusters of two kinds, which are known in the literature as the pseudo-Mackay type and the Bergman type clusters. The clusters are centered at the vertices of a canonical cell tiling, in which the parity of each vertex determines the kind of the associated cluster. Adjacent clusters can be markedly interpenetrated, while the structure requires no glue atoms to fill in the gaps between the clusters. It is shown that the crystal can be designated as a 2x2x2 superstructure of the ordinary cubic 3/2 rational approximant. The superlattice ordering is shown to be of a different kind from the P-type superlattice ordering previously reported in i-Al-Pd-Mn. The present results will greatly improve the understanding of atomic structures of F-type icosahedral quasicrystals and their approximants.
Properties of a new type Al/Pb-0.3%Ag alloy composite anode for zinc electrowinning
NASA Astrophysics Data System (ADS)
Yang, Hai-tao; Liu, Huan-rong; Zhang, Yong-chun; Chen, Bu-ming; Guo, Zhong-cheng; Xu, Rui-dong
An Al/Pb-0.3%Ag alloy composite anode was produced via composite casting. Its electrocatalytic activity for the oxygen evolution reaction and corrosion resistance was evaluated by anodic polarization curves and accelerated corrosion test, respectively. The microscopic morphologies of the anode section and anodic oxidation layer during accelerated corrosion test were obtained by scanning electron microscopy. It is found that the composite anode (hard anodizing) displays a more compact interfacial combination and a better adhesive strength than plating tin. Compared with industrial Pb-0.3%Ag anodes, the oxygen evolution overpotentials of Al/Pb-0.3%Ag alloy (hard anodizing) and Al/Pb-0.3%Ag alloy (plating tin) at 500 Añm-2 were lower by 57 and 14 mV, respectively. Furthermore, the corrosion rates of Pb-0.3%Ag alloy, Al/Pb-0.3%Ag alloy (hard anodizing), and Al/Pb-0.3%Ag alloy (plating tin) were 13.977, 9.487, and 11.824 gñm-2ñh-1, respectively, in accelerated corrosion test for 8 h at 2000 Añm-2. The anodic oxidation layer of Al/Pb-0.3%Ag alloy (hard anodizing) is more compact than Pb-0.3%Ag alloy and Al/Pb-0.3%Ag alloy (plating tin) after the test.
Annihilation momentum density of positrons trapped at vacancy-type defects in metals and alloys
A. Bansil; R. Prasad; R. Benedek
Positron annihilation, especially the angular correlation of annihilation radiation, is a powerful tool for investigating the electronic spectra of ordered as well as defected materials. The tendency of positrons to trap at vacancy-type defects should enable this technique to study the local environment of such defects. However, we need to develop a theoretical basis for calculating the two-photon annihilation momentum
N-type Doped PbTe and PbSe Alloys for Thermoelectric Applications
NASA Technical Reports Server (NTRS)
Snyder, G. Jeffrey (Inventor); LaLonde, Aaron (Inventor); Pei, Yanzhong (Inventor); Wang, Heng (Inventor)
The present invention demonstrates that weak scattering of carriers leads to a high mobility and therefore helps achieve low electric resistivity with high Seebeck coefficient for a thermoelectric material. The inventors demonstrate this effect by obtaining a thermoelectric figure of merit, zT, higher than 1.3 at high temperatures in n-type PbSe, because of the weak scattering of carriers in the conduction band as compared with that in the valence band. The invention further demonstrates favorable thermoelectric transport properties of n-type PbTe.sub.1-xI.sub.x with carrier concentrations ranging from 5.8.times.10.sup.18-1.4.times.10.sup.20 cm.sup.-3.
Optimization of Cr content of metastable ?-type Ti-Cr alloys with changeable Young's modulus for spinal fixation applications.
Zhao, Xingfeng; Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko; Ishimoto, Takuya; Nakano, Takayoshi
Metallic implant rods used in spinal fixtures should have a Young's modulus that is sufficiently low to prevent stress shielding for the patient and sufficiently high to suppress springback for the surgeon. Therefore, we propose a new concept: novel biomedical titanium alloys with a changeable Young's modulus via deformation-induced ? phase transformation. In this study, the Cr content in the range of 10-14 mass% was optimized to produce deformation-induced ? phase transformation, resulting in a large increase in the Young's modulus of binary Ti-Cr alloys. The springback and cytotoxicity of the optimized alloys were also examined. Ti-(10-12)Cr alloys exhibit an increase in Young's modulus owing to deformation-induced ? phase transformation. In this case, such deformation-induced ? phase transformation occurs along with {332}(?) mechanical twinning, resulting in the maintenance of acceptable ductility with relatively high strength. Among the examined alloys, the lowest Young's modulus and largest increase in Young's modulus are obtained from the Ti-12Cr alloy. This alloy exhibits smaller springback than and comparable cytocompatibility to the biomedical Ti alloy Ti-29Nb-13Ta-4.6Zr. PMID:22342893
Thermoelectric Properties of Si2Ti-Type Al-(Mn,Cr,Fe)-Si Alloys
NASA Astrophysics Data System (ADS)
Toyama, Yasuhiro; Hazama, Hirofumi; Asahi, Ryoji; Takeuchi, Tsunehiro
To optimize the thermoelectric properties of Si2Ti-type Al32Mn34Si34 ( C54-phase), which possesses a large absolute Seebeck coefficient | S| exceeding 300 ?V/K with negative sign, we partially substituted Cr and Fe for Mn, and succeeded in decreasing the number of valence electrons (in the case of Cr) without observing precipitation of secondary phases. A large, positive Seebeck coefficient exceeding 200 ?V/K was observed for Al32Cr x Mn34- x Si34 (1 ? x ? 2.5), which consists almost solely of the C54-phase. The increase of hole concentration caused by Cr substitution for Mn was confirmed by both the reduction in electrical resistivity and the sign reversal of the Seebeck coefficient. The largest ZT-value for positive Seebeck coefficient ( p-type behavior) was obtained for Al32Cr2.5Mn31.5Si34, with the resulting ZT-value reaching a magnitude twice as large as the largest ZT-value of the ternary compound Al33Mn34Si33 possessing p-type behavior.
Germanium- and tellurium-doped GaAs for non-alloyed p-type and n-type ohmic contacts
NASA Astrophysics Data System (ADS)
Park, Joongseo; Barnes, Peter A.; Lovejoy, Michael L.
Epitaxial ohmic contacts to GaAs were grown by liquid phase epitaxy. Heavily Ge-doped GaAs was grown to prepare ohmic contacts to p-GaAs while Te was used for the n-type contacts. Hall measurements were carried out for the samples grown from melts in which the mole fraction of Ge was varied between 1.55 atomic % and 52.2 atomic %, while the Te mole fractions varied between 0.03% and 0.5%. Specific contact resistance, rc, as low as rcp=2.9æ10-6 ohm-cm 2 for Ge doping of p=(Na-Nd)=6.0æ1019 holes/cm3 was measured for p-contacts and rcn=9.6æ10-5 ohm-cm2 was measured for Te doping of n=(Nd-Na)=8.9æ1018 electrons/cm3 for GaAs metallized with non-alloyed contacts of Ti/Al.
Deformation-induced changeable Young's modulus with high strength in ?-type Ti-Cr-O alloys for spinal fixture.
Liu, Huihong; Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko; Cho, Ken
In order to meet the requirements of the patients and surgeons simultaneously for spinal fixation applications, a novel biomedical alloy with a changeable Young's modulus, that is, with a low Young's modulus to prevent the stress-shielding effect for patients and a high Young's modulus to suppress springback for surgeons, was developed. In this study, the chromium and oxygen contents in ternary Ti(11, 12 mass%)Cr-(0.2, 0.4, 0.6 mass%)O alloys were optimized in order to achieve a changeable Young's modulus via deformation-induced ?-phase transformation with good mechanical properties. The Young's moduli of all the examined alloys increase after cold rolling, which is attributed to the deformation-induced ?-phase transformation. This transformation is suppressed by oxygen but enhanced with lower chromium content, which is related to the ?(bcc)-lattice stability. Among the examined alloys, the Ti-11Cr-0.2O alloy shows a low Young's modulus of less than 80GPa in the solution-treated (ST) condition and a high Young's modulus of more than 90GPa in the cold rolled (CR) condition. The Ti-11Cr-0.2O alloy also exhibits a high tensile strength, above 1000MPa, with an acceptable elongation of ~12% in the ST condition. Furthermore, the Ti-11Cr-0.2O alloy exhibits minimal springback. This value of springback is the closest to that of Ti64 ELI alloy among the compared alloys. Therefore, the Ti-11Cr-0.2O alloy, which has a good balance between large changeable Young's modulus, high tensile strength, good plasticity, and minimal springback, is considered to be a potential candidate for spinal fixation applications. PMID:24317494
Effect of Ternary Alloying Elements Addition on the Order-Disorder Transformation Temperatures of B2-Type Ordered Fe-Al-X Intermetallics
NASA Astrophysics Data System (ADS)
Yildirim, Mehmet; Vedat Akdeniz, M.; Mekhrabov, Amdulla O.
The effect of alloying element additions on B2?A2 order-disorder phase transformation temperatures of B2-type ordered Fe0.5(Al1- n X n )0.5 intermetallics (X = Cr, Ni, Mo, Ta, Mn, Ti, and W) that readily form single-phase solid solution for X = 1 at. pct were investigated experimentally. It was shown that the type of the ternary substitutional alloying elements have a profound effect on the variation of order-disorder transition temperature of Fe0.5(Al1- n X n )0.5 alloys. Based on the magnitude of partial ordering energies of the Al-X and Fe-X atomic pairs, predicted normalized transition temperatures, ? T/ T o , were verified experimentally. Besides the normalized transition temperature, the relative partial ordering energy (RPOE) parameter, ?, was also defined to estimate the extent of variation in B2?A2 order-disorder phase transformation temperatures upon ternary alloying additions. The RPOE parameter, ?, takes into account both the effects of magnitude of partial ordering energies of Al-X and Fe-X atomic pairs and also the lattice site occupation preferences of X element atoms over B2-type ordered Fe-Al sublattices. The alloying elements, which are preferentially distributed Fe sublattice sites, ? > 0, and owing to ? >> 1, are more effective in increasing order-disorder transformation temperature in Fe-Al (B2) intermetallics. On the contrary, alloying elements having ? < 1 tend to decrease the transition temperature slightly relative to the binary FeAl intermetallic. The experimentally determined B2?A2 order-disorder transition temperatures are in good qualitative or semiquantitative agreement with theoretical predictions for all X ternary alloying elements. Accordingly, the present experimental results confirm the validity of the theoretical model and calculations proposed in our previous study on the B2?A2 order-disorder transition temperatures of single-phase Fe0.5(Al1- n X n )0.5 intermetallics.
Effects of cycle type and coating on the TMF lives of a single crystal nickel based gas turbine blade alloy
Bressers, J.; Timm, J. [Joint Research Centre, Petten (Netherlands). Inst. for Advanced Materials; Williams, S.J.; Bennett, A. [Rolls-Royce plc, Derby (United Kingdom); Affeldt, E.E. [Motoren und Turbinen Union Muenchen (Germany)
Strain controlled thermo-mechanical fatigue cycles simulating the temperature-strain-time history at critical locations of blades of advanced aero gas turbines are applied to the single crystal nickel based alloy SRR99 in the uncoated and aluminide coated conditions. The TMF cycle selection includes a {minus}135{degree} lag cycle and an in-phase cycle, with various R-ratios, T{sub min} = 300 C, and T{sub max} = 1,050 C and 850 C, respectively. The cycle-specific stress response is analyzed and discussed in terms of the accumulation of inelastic strain during the TMF tests, and the inelastic strain build-up is correlated with the cyclic hardening/softening behavior. The number of cycles for initiating microcracks is measured by means of a computer vision system. Various modes of crack initiation and crack growth are observed and correlated with the TMF cycle type, with the strain range imposed, and with the ductile/brittle behavior of the coating. The differences in TMF lives are discussed in terms of the material and TMF parameters.
Atomic states, potential energies, volumes, stability and brittleness of ordered FCC TiAl 2 type alloys
NASA Astrophysics Data System (ADS)
Xie, Y. Q.; Tao, H. J.; Peng, H. J.; Li, X. B.; Liu, X. B.; Peng, K.
In this paper, the framework of the systematic science of alloys (SSA) is presented. It has been proved that according to the basic information of sequences of characteristic crystals in the FCC Ti-Al system, not only the states, potential energies and volumes of atoms at various lattice points, and average atomic states, average atomic potential energies, average atomic volumes and lattice constants of the cells, as well as cohesive energies, heats of formation, bulk moduli and Debye temperatures for h- and ?-TiAl 2 compounds can be calculated, but also the compositional variations of the atomic states, atomic potential energies, atomic volumes, lattice constants, cohesive energies, heat of formation, bulk moduli and Debye temperatures of the ordered FCC TiAl 2 type alloys and their Ti- and Al-components can be calculated by the SSA framework. The average atomic states of h- and ?-TiAl 2 compounds are, respectively, ?(h-TiAl)=1/6?10,1Ti+1/6?10,2Ti+1/2?8,4Al+1/6?6,6Al and ?(?-TiAl)=1/3?10,1Ti+1/3?8,6Al+1/3?6,6Al. At low temperature, the h-TiAl 2 compound with lower potential energy and smaller volume is more stable than the ?-TiAl 2 compound, because the ?10,2Ti and the ?8,4Al atoms have lower potential energies and smaller volumes than the corresponding ?10,1Ti and ?8,6Al atoms. But at high temperature, the ?-TiAl 2 compound with larger vibrational entropy and larger mixing entropy due to containing ?8,6Al- and more the same state ?10,1Ti-atoms with higher potential energy may be more stable than h-TiAl 2 compound. The calculated lattice constants of ?-TiAl 2 compounds are in good agreement with experimental ones. The relationships of brittleness with atomic states and potential energy wave planes for FCC TiAl 2 compounds have been analysed.
Electrical properties and stability of p-type ZnO film enhanced by alloying with S and heavy doping of Cu
Pan, H. L.; Yang, T.; Xu, Y. [Department of Physics, State Key Laboratory Superhard Material, Jilin University, Changchun 130023 (China); Yao, B. [Department of Physics, State Key Laboratory Superhard Material, Jilin University, Changchun 130023 (China); Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Zhang, B. Y.; Liu, W. W.; Shen, D. Z. [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)
Single wurtzite p-type Zn{sub 1-y}Cu{sub y}O{sub 1-x}S{sub x} alloy films with 0.081{<=}x{<=}0.186 and 0.09{<=}y{<=}0.159 were grown on quartz reproducibly by magnetron sputtering. The alloys show very stable p-type conductivity with a hole concentration of 4.31-5.78x10{sup 19} cm{sup -3}, a resistivity of 0.29-0.34 {Omega} cm and a mobility of 0.32-0.49 cm{sup 2} V{sup -1} s{sup -1}. The p-type conductivity is attributed to substitution of Cu{sup +1} for the Zn site, and the ionization energy of the Cu{sup +1} acceptor is measured to be 53 meV, much less than that of Cu-doped ZnO reported previously. The small ionization energy is due to Cu heavy doping and increase in valence band maximum of ZnO induced by alloying with S.
Atomic states, potential energies, volumes, stability and brittleness of ordered FCC Ti 3Al-type alloys
NASA Astrophysics Data System (ADS)
Xie, Y. Q.; Peng, H. J.; Liu, X. B.; Peng, K.
According to the basic information of sequences of characteristic atoms in the FCC Ti-Al system, the compositional variations of the atomic states, atomic potential energies, atomic volumes, lattice constants and cohesive energies of the ordered FCC Ti 3Al-type alloys have been calculated. Without considering the influence of the second nearest neighbouring atoms, the D0 22- and L1 2-Ti 3Al compounds have the same atomic state, same atomic volume, same lattice constant and same cohesive energy. Their average atomic state is 0.75[Ar](3d n) 0.229(3d c) 2.5669(4s c) 0.5448(4s f) 0.6593 +0.25[Ne](3s c) 1.772(3p c) 1.008(3s f) 0.22. Considering the influence of second neighbouring atoms, the calculated atomic potential energies, formation energies and lattice constants of the D0 22- and L1 2-Ti 3Al compounds are, respectively, ?a=-4.8158 eV/atom, ? H=-0.3378 eV/atom, a=0.39131 nm, c=0.44108 nm, c/a=1.1272; and ? a=-4.7952 eV/atom, ? H=-0.3172 eV/atom, a=0.41091 nm. The D0 22-Ti 3Al compound is slightly more stable than the L1 2- Ti 3Al compound. The correctness of these results has been proved indirectly by the calculated results of the D0 22- and L1 2-TiAl 3 as well as HfGa 2- and ZrGa 2-type TiAl 2 compounds with the same basic information and the same method. Between 0 and 40 at.%Al, the HCP lattice is more stable than the FCC lattice, for which the atomic state factor may play determining action. The brittleness order of these compounds is L1 2-Ti 3Al
Wang, R.; Merz, M.D.
Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.
A Comparative Study on Improved Arrhenius-Type and Artificial Neural Network Models to Predict High-Temperature Flow Behaviors in 20MnNiMo Alloy
Yu, Chun-tang; Liu, Ying-ying; Xia, Yu-feng
The stress-strain data of 20MnNiMo alloy were collected from a series of hot compressions on Gleeble-1500 thermal-mechanical simulator in the temperature range of 1173?1473?K and strain rate range of 0.01?10?s?1. Based on the experimental data, the improved Arrhenius-type constitutive model and the artificial neural network (ANN) model were established to predict the high temperature flow stress of as-cast 20MnNiMo alloy. The accuracy and reliability of the improved Arrhenius-type model and the trained ANN model were further evaluated in terms of the correlation coefficient (R), the average absolute relative error (AARE), and the relative error (?). For the former, R and AARE were found to be 0.9954 and 5.26%, respectively, while, for the latter, 0.9997 and 1.02%, respectively. The relative errors (?) of the improved Arrhenius-type model and the ANN model were, respectively, in the range of ?39.99%?35.05% and ?3.77%?16.74%. As for the former, only 16.3% of the test data set possesses ?-values within Ý1%, while, as for the latter, more than 79% possesses. The results indicate that the ANN model presents a higher predictable ability than the improved Arrhenius-type constitutive model. PMID:24688358
Properties of the quaternary half-metal-type Heusler alloy CoãMn{sub 1-x}FeãSi
Benjamin Balke; Gerhard H. Fecher; Hem C. Kandpal; Claudia Felser; Keisuke Kobayashi; Eiji Ikenaga; Jung-Jin Kim; Shigenori Ueda
This paper reports on the bulk properties of the quaternary Heusler alloy CoãMn{sub 1-x}FeãSi with the Fe concentration x=0,1\\/2,1. All samples, which were prepared by arc melting, exhibit L2ã long-range order over the complete range of Fe concentration. The structural and magnetic properties of the CoãMn{sub 1-x}FeãSi Heusler alloys were investigated by means of x-ray diffraction, high- and low-temperature magnetometry,
Properties of the quaternary half-metal-type Heusler alloy Co2Mn1-xFexSi
Benjamin Balke; Gerhard H. Fecher; Hem C. Kandpal; Claudia Felser; Keisuke Kobayashi; Eiji Ikenaga; Jung-Jin Kim; Shigenori Ueda
This paper reports on the bulk properties of the quaternary Heusler alloy Co2Mn1-xFexSi with the Fe concentration x=0,1\\/2,1 . All samples, which were prepared by arc melting, exhibit L21 long-range order over the complete range of Fe concentration. The structural and magnetic properties of the Co2Mn1-xFexSi Heusler alloys were investigated by means of x-ray diffraction, high- and low-temperature magnetometry, M—ssbauer
Optical anisotropy and domain structure of multiferroic Ni-Mn-Ga and Co-Ni-Ga Heusler-type alloys
NASA Astrophysics Data System (ADS)
Ivanova, A. I.; Gasanov, O. V.; Kaplunova, E. I.; Kalimullina, E. T.; Zalyotov, A. B.; Grechishkin, R. M.
A study is made of the reflectance anisotropy of martensitic and magnetic domains in ferromagnetic shape memory alloys (FSMA) Ni-Mn-Ga and Co-Ni-Ga. The reflectance of metallographic sections of these alloys was measured in the visible with the aid of standard inverted polarized light microscope with a 360¯ rotatable specimen stage. Calculations are presented for the estimation of image contrast values between neighboring martensite twins. Qualitative and quantitative observations and angular measurements in reflected polarized light proved to be useful for the analysis of specific features of the martensite microstructure of multiferroic materials.
Effects of micro- and nano-scale wave-like structures on fatigue strength of a beta-type titanium alloy developed as a biomaterial.
Narita, Kengo; Niinomi, Mitsuo; Nakai, Masaaki
Some newly developed ?-type titanium alloys for biomedical applications exhibit distinctive heterogeneous structures. The formation mechanisms for these structures have not been completely revealed; however, understanding these mechanisms could lead to improving their properties. In this study, the heterogeneous structures of a Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), which is a candidate for next-generation metallic biomaterials, were analyzed. Furthermore, the effects of such heterogeneous structures on the mechanical strength of this alloy, including fatigue strength, were revealed by comparing its strength to that of homogenous TNTZ. The heterogeneous structures were characterized micro-, submicro- and nano-scale wave-like structures. The formation mechanisms of these wave-like structures are found to be different from each other even though their morphologies are similar. It is revealed that the micro-, submicro- and nano-scale wave-like structures are caused by elemental segregation, crystal distortion related to kink band and phase separation into ? and ?', respectively. However, these structures have no significant effect on both tensile properties and fatigue strength comparison with homogeneous structure in this study. PMID:24184863
The effect of disorder on electronic and magnetic properties of quaternary Heusler alloy CoFeMnSi with LiMgPbSb-type structure
NASA Astrophysics Data System (ADS)
Feng, Yu; Chen, Hong; Yuan, Hongkuan; Zhou, Ying; Chen, Xiaorui
Thin films based on Heusler alloy often lost their theoretical predicted ultra-high spin polarization owing to the appearance of disorder. Using the first-principles calculations within density functional theory (DFT), we investigate the effect of disorder including antisite and swap on electronic and magnetic properties of quaternary Heusler alloy CoFeMnSi with LiMgPbSb-type structure. Twelve kinds of antisites and six kinds of swap disorders are proposed and studied comprehensively. In our calculations, Co(Fe)-, Mn(Fe)-, Si(Mn)-antisite and Co-Fe swap disorders are most favorable due to their lowest formation energies. Moreover, the positive binding energies of Co-Fe, Co-Si, Fe-Si and Mn-Si swap disorders with respect to their corresponding antisite disorders indicate that these complex swap disorders are more stable compared with their corresponding isolated antisite disorders. The investigations on density of states (DOS) show that the spin down energy gap of disordered structures suffers contraction and their DOS entirely move towards lower zone. Besides, the 100% spin polarization is maintained in all structures with antisite and swap disorders except for those with Co(Mn)-, Co(Si)-antisite and Co-Mn, Co-Si swap disorders. Therefore, the half-metallicity of quaternary Heusler alloy CoFeMnSi is quite robust against interfering effects such as Si(Mn), Co(Fe) and Co-Fe disorders most possibly formed in the growth.
Development and validation of capabilities to measure thermal properties of layered monolithic U-Mo alloy plate-type fuel
Burkes, Douglas; Casella, Andrew M.; Buck, Edgar C.; Casella, Amanda J.; Edwards, Matthew K.; MacFarlan, Paul J.; Pool, Karl N.; Smith, Frances N.; Steen, Franciska H.
The uranium-molybdenum (U-Mo) alloy in a monolithic form has been proposed as one fuel design capable of converting some of the worlds highest power research reactors from the use of high enriched uranium (HEU) to low enriched uranium (LEU). One aspect of the fuel development and qualification process is to demonstrate appropriate understanding of thermal conductivity behavior of the fuel system as a function of temperature and expected irradiation conditions. The purpose of this paper is to verify and validate the functionality of equipment methods installed in hot cells for eventual measurements on irradiated uranium-molybdenum (U-Mo) monolithic fuel specimens, procedures to operate the equipment, and models to extract the desired thermal properties. The results presented here demonstrate the adequacy of the equipment, procedures and models that have been developed for this purpose based on measurements conducted on surrogate depleted uranium-molybdenum (DU-Mo) alloy samples containing a zirconium diffusion barrier and clad in aluminum alloy 6061 (AA6061). The results are in excellent agreement with thermal property data reported in the literature for similar U-Mo alloys as a function of temperature.
Effect of Ti substitution on the microstructure and properties of ZrMnVNi AB2 type hydride electrode alloys
Song, Xueyan
-substituted alloy of Zr0.5Ti0.5(Mn0.1V0.3Ni0.6)2: C14 Laves phase and Ti-containing "premartensite" R phase of Ti00.2Ni R-phase, and disappearance of ZrÙNi binaries. I. INTRODUCTION The AB2 (A Zr, Ti; B V, Cr, Mn
Correlation between Mechanical Behavior and Actuator-type Performance of Ni-Ti-Pd High-temperature Shape Memory Alloys
NASA Technical Reports Server (NTRS)
Bigelow, Glen S.; Padula, Santo A., II; Garg, Anita; Noebe, Ronald D.
High-temperature shape memory alloys in the NiTiPd system are being investigated as lower cost alternatives to NiTiPt alloys for use in compact solid-state actuators for the aerospace, automotive, and power generation industries. A range of ternary NiTiPd alloys containing 15 to 46 at.% Pd has been processed and actuator mimicking tests (thermal cycling under load) were used to measure transformation temperatures, work behavior, and dimensional stability. With increasing Pd content, the work output of the material decreased, while the amount of permanent strain resulting from each load-biased thermal cycle increased. Monotonic isothermal tension testing of the high-temperature austenite and low temperature martensite phases was used to partially explain these behaviors, where a mismatch in yield strength between the austenite and martensite phases was observed at high Pd levels. Moreover, to further understand the source of the permanent strain at lower Pd levels, strain recovery tests were conducted to determine the onset of plastic deformation in the martensite phase. Consequently, the work behavior and dimensional stability during thermal cycling under load of the various NiTiPd alloys is discussed in relation to the deformation behavior of the materials as revealed by the strain recovery and monotonic tension tests.
Thermoelectric properties of the Heusler-type Fe{sub 2}VTa{sub x}Al{sub 1?x} alloys
Renard, Krystel, E-mail: email@example.com; Mori, Arinori; Yamada, Yuichiro; Tanaka, Suguru; Nishino, Yoichi [Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Miyazaki, Hidetoshi [Center for Fostering Young and Innovative Researchers, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)
This study focuses on the thermoelectric properties of the Heusler-type Fe{sub 2}VTa{sub x}Al{sub 1?x} alloys (0?x?0.12). By means of Rietveld analyses on synchrotron X-ray diffraction patterns, it is shown that the Ta atoms enter sites occupied by V atoms in the stoichiometric Fe{sub 2}VAl alloy, while the ejected V atoms are transferred to the vacant Al sites. This Ta substitution leads to an improvement of the n-type thermoelectric properties owing to two mechanisms. On the one hand, the atoms position in the structure leads to an off-stoichiometric effect such as already observed in V-rich Fe{sub 2}V{sub 1+y}Al{sub 1?y} compounds: the Seebeck coefficient is increased towards negative absolute values and the electrical resistivity is decreased, with a large shift of their peak temperature towards higher temperature. The maximum power factor is 6.5?æ?10{sup ?3} W/mK{sup 2} for x?=?0.05 at 340?K. On the other hand, the heavy element Ta substitution combined with this off-stoichiometric effect leads to a large decrease of the thermal conductivity, owing to an increase of the scattering events. Consequently, the dimensionless figure of merit is seen to reach higher values than for the Fe{sub 2}V{sub 1+y}Al{sub 1?y} alloys, i.e., 0.210.22 around 400500?K for x?=?0.05 and 500?K for x?=?0.08.
The structural, electronic and dynamic properties of the L1{sub 2}- type Co{sub 3}Ti alloy
Arikan, Nihat [Ahi Evran Éniversitesi E?itim Fak■ltesi, ?lk—?retim B—l■m■, K?r?ehir (Turkey); øzduran, Mustafa [Ahi Evran Éniversitesi, Fen Edebiyat Fak■ltesi, Fizik B—l■m■, K?r?ehir (Turkey)
The structural, electronic and dynamic properties of the cubic Co{sub 3}Ti alloy in L1{sub 2} structure have been investigated using a pseudopotential plane wave (PP-PW) method within the generalized gradient approximation proposed by PerdewBurkeErnzerhof (GGA-PBE). The structural properties, including the lattice constant, the bulk modulus and its pressure derivative agree reasonably with the previous results. The density of state (DOS), projected density of state (PDOS) and electronic band structure are also reported. The DOS shows that Co{sub 3}Ti alloy has a metallic character since the energy bands cross the Fermi level. The density of states at Fermi level mainly comes from the Co-3d states. Phonon dispersion curves and their corresponding total densities of states were obtained using a linear response in the framework of the density functional perturbation theory. All computed phonon frequencies are no imaginer and thus, Co{sub 3}Ti alloy is dynamically stable. The zone center phonon modes have been founded to be 9.307, 9.626 and 13.891 THz for Co{sub 3}Ti.
Microstructural studies on Alloy 693
NASA Astrophysics Data System (ADS)
Halder, R.; Dutta, R. S.; Sengupta, P.; Samajdar, I.; Dey, G. K.
Superalloy 693, is a newly identified high-temperature corrosion resistant alloy. Present study focuses on microstructure and mechanical properties of the alloy prepared by double vacuum melting route. In general, the alloy contains ordered Ni3Al precipitates distributed within austenitic matrix. M6C primary carbide, M23C6 type secondary carbide and NbC particles are also found to be present. Heat treatment of the alloy at 1373 K for 30 min followed by water quenching (WQ) brings about a microstructure that is free from secondary carbides and Ni3Al type precipitates but contains primary carbides. Tensile property of Alloy 693 materials was measured with as received and solution annealed (1323 K, 60 min, WQ) and (1373 K, 30 min, WQ) conditions. Yield strength, ultimate tensile strength (UTS) and hardness of the alloy are found to drop with annealing. It is noted that in annealed condition, considerable cold working of the alloy can be performed.
Hans Thieme, Cornelis Leo (Westborough, MA); Thompson, Elliott D. (Coventry, RI); Fritzemeier, Leslie G. (Acton, MA); Cameron, Robert D. (Franklin, MA); Siegal, Edward J. (Malden, MA)
An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.
Platinum-group minerals from placers related to the Nizhni Tagil (Middle Urals, Russia) Uralian-Alaskan-type ultramafic complex: ore-mineralogy and study of silicate inclusions in (Pt, Fe) alloys
NASA Astrophysics Data System (ADS)
Johan, Z.
The study of platinum-group minerals (PGM) concentrates from the Nizhni Tagil placers related to the Soloviev Mountain (Gora Solovieva) Uralian-Alaskan-type intrusion revealed a predominance of (Pt, Fe) alloys over Ir-, and Os-bearing alloys. (Pt, Fe) alloys (isoferroplatinum-type) are interstitial with respect to chromite and show important variations in their chemical compositions, which are, however, falling within the experimentally determined stability field of isoferroplatinum. Tetraferroplatinum, enriched in Cu and Ni and tulameenite represent low-temperature mineral phases replacing (Pt, Fe) alloys. Alloys belonging to the Os-Ir-Ru ternary system have compositions corresponding to native osmium, iridium and ruthenium, respectively, and to rutheniridosmine. Osmium exsolutions appear in Ir-, and (Pt, Fe) alloys, and iridium exsolutions in (Pt, Fe) alloys. Laurite is a high-temperature phase included in native iridium and (Pt, Fe) alloys. Low-temperature PGM association comprises Ir-bearing sulpharsenides, including a phase (Ir, Os, Fe, Pt, Ru, Ni)3(As, Sb)0.85S, and a palladium antimonide Pd20Sb7. These two phases were previously unknown in nature. Furthermore, native palladium occurs in the studied concentrates. This low-temperature paragenesis indicates an interaction of Pt-, Os-, Ir- and Ru-bearing alloys with late fluids enriched in volatiles, As and Sb. The chromite composition is characterized by the predominance of Cr3+ ? Fe3+ substitution like in other Uralian-Alaskan-type intrusions; that indicates a fO2 variation during the chromite precipitation. Monomineralic inclusions of euhedral clinopyroxene and chromite crystals in (Pt, Fe) alloys were observed. Furthermore, (Pt, Fe) alloys contain polyphase silicate inclusions, which occupy the alloy negative crystals. Two types of silicate inclusions were recognized: (1) Low-pressure inclusions composed of amphibole, biotite, Jd-poor clinopyroxene, magnetite, apatite and glass; (2) High-pressure inclusions include: omphacitic clinopyroxene (up to 56 mol.% Jd), tremolite, muscovite, apatite, titanite and glass. In this case, the clinopyroxene is strongly zoned, revealing a pressure drop from about 25 to 5 kbar. The chemical composition of glass is corundum-normative and its H2O content varies from about 12 to 15 wt.%. The composition of magmatic melts, from which the silicate inclusions have originated was estimated using EPMA and image analysis interpreted by stereology. Their compositions are close to those obtained experimentally by hydrous partial melting of upper mantle rocks. The interpretation of analytical data shows that magmatic melts entrapped by (Pt, Fe) alloys crystallized from about 1100 to 700 ¯C. The (Pt, Fe) alloys formed after the crystallization of chromite, clinopyroxene and albite. Consequently, the precipitation temperature of (Pt, Fe) alloys is estimated at about 900 ¯C. The significant pressure drop implies a decrease of volatile concentrations in the magmatic melt and the possible formation of a fluid phase, which might have generated, the precipitation of chromite and PGM.
Influences of xTi/ xAl on atomic states, lattice constants and potential-energy planes of ordered FCC TiAl-type alloys
NASA Astrophysics Data System (ADS)
Xie, Y. Q.; Peng, K.; Liu, X. B.
Based on the framework of systematic science of alloys, the basic information about states, volumes and potential energies of characteristic atoms in FCC Ti-Al system has been determined. For ordered FCC TiAl type alloys, the functions of the atomic states, atomic potential energies, cohesive energies, atomic volumes, the lattice constants and axis ratio c/ a? varying with concentrations have also been established. The extreme points of curves v? xAl, a? xAl and c/ a?? xAl are all at the xAl=70%. When xTi/ xAl=1, ? (FCC TiAl) =? 8Ti+? 4Al= [Ar](3d n) 0.125(3d c) 2.7125(4s c) 0.55(4s f) 0.6125+ [Ne](3s c) 1.789(3p c) 0.75(3s f+3p f) 0.454, calculated lattice constants a?=0.39954 nm, c=0.40777 nm, c/ a?=1.0206, which are in good agreement with experimental values. When xTi/ xAl>1, ?8Ti atoms decrease and ? 7Ti, ? 6Ti atoms appear in succession with the increase of xTi; ?4Al atoms decrease and ? 3Al, ? 2Al atoms appear one after another. Because the influence of the change of Ti atomic states exceeds that of the change of Al atomic states, rich Ti-FCC TiAl alloys have larger atomic volumes, larger lattice constants, c/ a? much closer to unity and comparatively good ductility, though the stability of FCC lattice is reduced. When xTi/ xAl<1, with the increase of xAl, the atomic states ?8Ti and ?4Al changes in the direction opposite to the case with xTi/ xAl>1. Thus, ordered rich Al-FCC TiAl alloys have smaller atomic volumes, smaller lattice constants, larger c/ a? which depart further from unity and poorer ductility, and there is an increase of stability for the FCC lattice.
In vivo corrosion, tumor outcome, and microarray gene expression for two types of muscle-implanted tungsten alloys
Schuster, B.E. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States)] [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States); Roszell, L.E. [U.S. Army Institute of Public Health, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010?5403 (United States)] [U.S. Army Institute of Public Health, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010?5403 (United States); Murr, L.E.; Ramirez, D.A. [Department of Metallurgical and Materials Engineering, University of Texas, El Paso, TX 79968 (United States)] [Department of Metallurgical and Materials Engineering, University of Texas, El Paso, TX 79968 (United States); Demaree, J.D. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States)] [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, B434 Mulberry Road, Aberdeen Proving Ground, MD 21005-5609 (United States); Klotz, B.R. [Dynamic Science Inc., Aberdeen Proving Ground, MD 21005?5609 (United States)] [Dynamic Science Inc., Aberdeen Proving Ground, MD 21005?5609 (United States); Rosencrance, A.B.; Dennis, W.E. [U.S. Army Center for Environmental Health Research, Department of Chemistry, Ft. Detrick, MD 21702?5010 (United States)] [U.S. Army Center for Environmental Health Research, Department of Chemistry, Ft. Detrick, MD 21702?5010 (United States); Bao, W. [SAS Institute, Inc. SAS Campus Drive, Cary, NC 27513 (United States)] [SAS Institute, Inc. SAS Campus Drive, Cary, NC 27513 (United States); Perkins, E.J. [U.S. Army Engineer Research and Development Center, 3909 Hall Ferry Road, Vicksburg MS 39180 (United States)] [U.S. Army Engineer Research and Development Center, 3909 Hall Ferry Road, Vicksburg MS 39180 (United States); Dillman, J.F. [U.S. Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010?5400 (United States)] [U.S. Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010?5400 (United States); Bannon, D.I., E-mail: email@example.com [U.S. Army Institute of Public Health, 5158 Blackhawk Road, Aberdeen Proving Ground, MD 21010?5403 (United States)
Tungsten alloys are composed of tungsten microparticles embedded in a solid matrix of transition metals such as nickel, cobalt, or iron. To understand the toxicology of these alloys, male F344 rats were intramuscularly implanted with pellets of tungsten/nickel/cobalt, tungsten/nickel/iron, or pure tungsten, with tantalum pellets as a negative control. Between 6 and 12 months, aggressive rhabdomyosarcomas formed around tungsten/nickel/cobalt pellets, while those of tungsten/nickel/iron or pure tungsten did not cause cancers. Electron microscopy showed a progressive corrosion of the matrix phase of tungsten/nickel/cobalt pellets over 6 months, accompanied by high urinary concentrations of nickel and cobalt. In contrast, non-carcinogenic tungsten/nickel/iron pellets were minimally corroded and urinary metals were low; these pellets having developed a surface oxide layer in vivo that may have restricted the mobilization of carcinogenic nickel. Microarray analysis of tumors revealed large changes in gene expression compared with normal muscle, with biological processes involving the cell cycle significantly up?regulated and those involved with muscle development and differentiation significantly down?regulated. Top KEGG pathways disrupted were adherens junction, p53 signaling, and the cell cycle. Chromosomal enrichment analysis of genes showed a highly significant impact at cytoband 7q22 (chromosome 7) which included mouse double minute (MDM2) and cyclin?dependant kinase (CDK4) as well as other genes associated with human sarcomas. In conclusion, the tumorigenic potential of implanted tungsten alloys is related to mobilization of carcinogenic metals nickel and cobalt from corroding pellets, while gene expression changes in the consequent tumors are similar to radiation induced animal sarcomas as well as sporadic human sarcomas. -- Highlights: ? Tungsten/nickel/cobalt, tungsten/nickel/iron, and pure tungsten were studied. ? Male Fischer rats implanted with pellets in gastrocnemius muscle of each hind leg. ? Aggressive rhabdomyosarcomas developed from tungsten/nickel/cobalt pellets only. ? Microarray gene expression analysis was carried out on selected tumors. ? Pellet degradation, urinary metal concentration, and sarcoma were correlated.
Ohmic Contact Formation on p-type GaN Using Pd/Mo Electrode without Alloying Process
NASA Astrophysics Data System (ADS)
Kurimoto, Eiji; Hangyo, Masanori; Harima, Hiroshi; Takatani, Kunihiro; Ishida, Masaya; Taneya, Masataka; Kisoda, Kenji
Ohmic contact formation on a p-GaN layer with a specific contact resistance of ?c=5æ 10-4 ?cm2 has been achieved using a Pd/Mo electrode without the use of an alloying process. ?c was reduced to 2æ 10-4 ?cm2 by annealing in vacuum at 500¯C. The Pd/Mo electrode showed much improved ohmic-contact characteristics than the Ni/Mo electrode. Characterization by micro-Raman scattering revealed that the hole concentration increased in the p-GaN layer just under the Pd/Mo electrode with increasing annealing temperature. This cannot be explained by the removal of hydrogen. A decrease in the density of hole traps and an increase in the density of active acceptors, such as Ga vacancies, are considered to be the most significant contributing factors.
Influence of shooting angle of polishing particle on surface roughness of a cobalt-chromium alloy using a centrifugal shooting type polishing machine.
Ono, Takahiro; Ishikawa, Kaori; Yamaba, Osamu; Nokubi, Takashi
The centrifugal shooting type polishing machine is a recently developed apparatus that seeks to improve the efficiency and environment of polishing removable prostheses. In an attempt to optimize the effectiveness of this apparatus, this study examined the influence of the shooting angle of polishing particle on the surface roughness of cobalt-chromium alloy casting specimens. Polishing was performed for three minutes under five shooting angle conditions: 90 degrees, 60 degrees, 45 degrees, 30 degrees, and 15 degrees. Surface roughness (Ra, Sm) was measured after each polishing stage. There were significant differences (p < 0.01) in Ra between shooting angle of 90 degrees (0.95 microm) and shooting angles of 45 degrees (0.62 microm) or less, and in Sm between 90 degrees (207 microm), 60 degrees (350 microm), and shooting angles of 45 degrees (868 microm) or less. These findings indicated that excellent surface texture was produced when shooting angle was 45 degrees or less. PMID:15688732
Improving the structure, magnetic properties and thermal stability of rapidly quenched TbCu7-type SmCo6.4Si0.3Zr0.3 alloy by carbon addition
NASA Astrophysics Data System (ADS)
Feng, D. Y.; Liu, Z. W.; Zheng, Z. G.; Zeng, D. C.; Zhang, G. Q.
The effects of carbon addition on the structure and magnetic properties of rapidly quenched TbCu7-type SmCo6.4Si0.3Zr0.3 alloy have been investigated. The alloys with a small amount of C addition (x?0.2) showed single Sm(Co,M)7 phase, while ZrC phase appeared in the alloys with x=0.3 and 0.4. With the increase of C content, the grain size decreased from approximately 850 nm for x=0.1 to approximately 300 nm for x=0.4. The coercivity Hc and maximum magnetic energy product (BH)max increased with the C content from x=0 to 0.2 and then decreased with excessive C addition. The optimal magnetic properties of Hc=1577 kA/m, Jr=0.53 T and (BH)max=52.1 kJ/m3 were achieved for SmCo6.4Si0.3Zr0.3C0.2 alloy with a grain size of 600-700 nm, which is close to the single domain size of TbCu7-type Sm(Co,Zr)7 alloy. Furthermore, C addition also improved the thermal stability by reducing the absolute values of temperature coefficients of remanence and coercivity.
Amorphous metal alloy and composite
Wang, Rong (Richland, WA); Merz, Martin D. (Richland, WA)
Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.
Thermodynamic Aspects of Homogeneous Nucleation Enhanced by Icosahedral Short Range Order in Liquid Fcc-Type Alloys
NASA Astrophysics Data System (ADS)
Rappaz, Michel; Kurtuldu, G■ven
We have recently shown that minute solute element additions to liquid metallic alloys can strongly influence the nucleation of the fcc phase and act as a grain refinement method. Electron back-scattered diffraction observations revealed a concomitant increase in the percentage of nearest neighbor (nn) grains that are in a twin relationship. Furthermore, multiple-twinned (MT) nn grain configurations with a fivefold symmetry around a common < 110rangle direction have been identified, an occurrence that can be explained when the symmetry of the icosahedron is accounted for. It was then conjectured that a new nucleation mechanism occurs in two steps: first, the formation of small icosahedral quasicrystals in the melt, followed by heteroepitaxy of the fcc phase on facets of these quasicrystals. In the present contribution, based on thermodynamics arguments, it is proposed that the first step occurs by spinodal decomposition of the liquid, in a manner similar to Guinier-Preston zones formation in solid state precipitation, while the second step is a transformation of these quasicrystal precursors into MT-fcc nanocrystals once the driving force for this transformation is sufficient to overcome the fcc-liquid interfacial energy and the elastic strains associated with MT-fcc nanoparticles. This explanation sets up guidelines for finding solute elements and composition ranges that favor this grain refinement mechanism.
Osmium isotope systematics of Os-rich alloys and Ru-Os sulfides from oceanic mantle: evidence from Proterozoic and Paleozoic ophiolite-type complexes
NASA Astrophysics Data System (ADS)
Badanina, Inna Yu.; Malitch, Kreshimir N.; Belousova, Elena A.; Lord, Richard A.; Meisel, Thomas C.; Murzin, Valery V.; Pearson, Norman J.
This study presents a substantial data set of Os-isotope compositions of Os-rich alloys and Ru-Os sulfides from deep portions of ophiolite sections from oceanic mantle. These are represented by samples from different in age ophiolite-type massifs (i.e., Neoproterozoic Kunar in Northern Taimyr, Russia, and Hochgrossen in Eastern Alps, Austria, Paleozoic Verkh-Neivinsk in Middle Urals, Russia, and Shetland in northern Scotland). The investigation employed a number of analytical techniques, including electron microprobe analysis, ID ICP-MS after high pressure acid digestion, and laser ablation attached to multiple collector-inductively coupled plasma mass-spectrometry (LA MC-ICP-MS). Two distinct platinum-group mineral (PGM) assemblages have been recognized at the Shetland and Verkh-Neivinsk localities: a 'primary' euhedral PGM assemblage, which occur as inclusions in chromite, and a modified 'secondary' subeuhedral to anhedral PGM assemblage observed in cracks filled by chlorite or serpentine, interstitially to chromite grains [1]. A 'primary' PGM assemblage at Shetland is represented by solitary grains of laurite or iridian osmium and composite grains of laurite + osmian iridium Ý iridian osmium that display well defined phase boundaries between two or three distinct PGMs. A 'primary' PGM assemblage at Verkh-Neivinsk is represented by Ru-Os-Ir alloy grains that frequently mantled by 'secondary' Ru-Os sulfide and/or Ru-Os sulfarsenide overgrowths. The osmium isotope results identify (1) a restricted range of 'unradiogenic' 187Os/188Os values for coexisting laurite and Os-rich alloy pairs that form 'primary' PGM assemblages at Hochgrossen and Shetland (0.11860-0.11866 and 0.12473-0.12488, respectively); (2) similar 'unradiogenic' 187Os/188Os values for both 'primary' and 'secondary' PGM assemblages at Shetland (with mean 187Os/188Os 0.12419 and 0.12464, respectively) and Verkh-Neivinsk (with distinct mean 187Os/188Os values), and (3) a wide scatter of subchondritic 187Os/188Os values for 'primary' PGM assemblages at Kunar (i.e., 187Os/188Os 0.11848-0.11239), Verkh-Neivinsk (0.11619-0.12565), and Hochgrossen (0.11860-0.12450). The whole-rock Os-isotope budget of chromitite at Shetland (0.1240Ý0.0006) is largely controlled by laurite-dominant assemblages. In this case, the 'secondary' PGM assemblage inherited the 'unradiogenic' Os-isotope signature of the 'primary' PGMs. No evidence for other source contributions during later thermal events has been observed here. However, the wide range of subchondritic 187Os/188Os values has been found in the 'primary' PGM assemblages (e.g., laurite and Os-rich alloys) from the ophiolite-type complexes worldwide [2 and references cited therein]. This wide range would be consistent with a model, in which a prolonged history of melting events of parent ultramafic source rocks took place in the mantle. This variability is in agreement with the conclusion that the Os-isotope system of PGMs records multiple events during the chemical differentiation history of the mantle [3] and could have been controlled by deep-geodynamic processes [4]. On the other hand, the observed Os-isotope heterogeneity may be also attributed to the presence of subcontinental lithospheric mantle (SCLM), characterized by highly unradiogenic 187Os/188Os values (i.e.,
Effects of Microstructure and Alloy Contents on the L■ders Line Formation in Al-Mg Alloys
Ildong Choi; Sunhwa Jin; Sukbong Kang
There have been several efforts to replace steel with aluminum for automobile weight reduction. Main efforts have been on the development of 5000 series Al alloys (Al-Mg alloys) because of their good formability. However, Al-Mg alloys suffer from the formation of various types of Lueders line. Particularly, type A Lueders lines formed under 1% elongation make a surface completely unacceptable
Structural and transport properties in alloyed Ti/Al Ohmic contacts formed on p-type Al-implanted 4H-SiC annealed at high temperature
NASA Astrophysics Data System (ADS)
Frazzetto, A.; Giannazzo, F.; Lo Nigro, R.; Raineri, V.; Roccaforte, F.
In this paper, the transport properties of alloyed Ti/Al Ohmic contacts formed on p-type Al-implanted silicon carbide (4H-SiC) were studied. The morphology of p-type implanted 4H-SiC was controlled using a capping layer during post-implantation activation annealing at 1700 ¯C. The different morphological conditions do not affect the macroscopic electrical properties of the implanted SiC (such as the sheet resistance or the mobility). On the other hand, the improved morphology of implanted SiC allows us to achieve a flatter Ti/Al surface and a lower specific contact resistance. The temperature dependence of the specific resistance of the contacts was studied to obtain physical insights into the carrier transport mechanism at the metal/SiC interface. The fit comparing several models shows that thermionic field emission is the dominant transport mechanism through the metal/SiC interface, and that a reduction in the barrier height from 0.51 to 0.46 eV is associated with the improvement of the Ohmic properties. Transmission electron microscopy analysis showed the presence of a laterally inhomogeneous microstructure of the metal/SiC interface. The reduction in the barrier height could be correlated with the different microstructures of the interfacial region.
Influence of Fluidized Bed Quenching on the Mechanical Properties and Quality Index of T6 Tempered B319.2-Type Aluminum Alloys
NASA Astrophysics Data System (ADS)
Ragab, Kh. A.; Samuel, A. M.; Al-Ahmari, A. M. A.; Samuel, F. H.; Doty, H. W.
The current study aimed to investigate the effect of fluidized sand bed (FB) quenching on the mechanical performance of B319.2 aluminum cast alloys. Traditional water and conventional hot air (CF) quenching media were used to establish a relevant comparison with FB quenching. Quality charts were generated using two models of quality indices to support the selection of material conditions on the basis of the proposed quality indices. The use of an FB for the direct quenching-aging treatment of B319.2 casting alloys yields greater UTS and YS values compared to conventional furnace quenched alloys. The strength values of T6 tempered B319 alloys are greater when quenched in water compared with those quenched in an FB or CF. For the same aging conditions (170¯C/4h), the fluidized bed quenched-aged 319 alloys show nearly the same or better strength values than those quenched in water and then aged in a CF or an FB. Based on the quality charts developed for alloys subjected to different quenching media, higher quality index values are obtained by conventional furnace quenched-aged T6-tempered B319 alloys. The modification factor has the most significant effect on the quality results of the alloys investigated, for all heat treatment cycles, as compared to other metallurgical parameters. The results of alloys subjected to multi-temperature aging cycles reveal that the optimum strength properties of B319.2 alloys, however, is obtained by applying multi-temperature aging cycles such as, for example, 240 ¯C/2 h followed by 170 ¯C/8 h, rather than T6 aging treatments. The regression models indicate that the mean quality values of B319 alloys are highly quench sensitive due to the formation of a larger percent of clusters in Al-Si-Cu-Mg alloys. These clusters act as heterogeneous nucleation sites for precipitation and enhance the aging process.
Effects of Stoichiometry on Transformation Temperatures and Actuator-Type Performance of NiTiPd and NiTiPdX High-Temperature Shape Memory Alloys
NASA Technical Reports Server (NTRS)
Bigelow, Glen S.; Gaydosh, Darrell; Garg, Anita; Padula, Santo A., II; Noebe, Ronald D.
High-temperature shape memory NiTiPd and NiTiPdX (X=Au, Pt, Hf) alloys were produced with titanium equivalent (Ti+Hf) compositions of 50.5, 50.0, 49.5, and 49.0 at.%. Thermo-mechanical testing in compression was used to evaluate the transformation temperatures, transformation strain, work output, and permanent deformation behavior of each alloy to study the effects of quaternary alloying and stoichiometry on high-temperature shape memory alloy behavior. Microstructural evaluation showed the presence of second phases for all alloy compositions. No load transformation temperatures in the stoichiometric alloys were relatively unchanged by Au and Pt substitutions, while the substitution of Hf for Ti causes a drop in transformation temperatures. The NiTiPd, NiTiPdAu and NiTiPdHf alloys exhibited transformation temperatures that were highest in the Ti-rich compositions, slightly lower at stoichiometry, and significantly reduced when the Ti equivalent composition was less than 50 at.%. For the NiTiPdPt alloy, transformation temperatures were highest for the Ti-rich compositions, lowest at stoichiometry, and slightly higher in the Ni-rich composition. When thermally cycled under constant stresses of up to 300 MPa, all of the alloys had transformation strains, and therefore work outputs, which increased with increasing stress. In each series of alloys, the transformation strain and thus work output was highest for stoichiometric or Ti-rich compositions while permanent strain associated with the constant-load thermal cycling was lowest for alloys with Ni-equivalent-rich compositions. Based on these results, basic rules for optimizing the composition of NiTiPd alloys for actuator performance will be discussed.
Identification of a new pseudo-binary hydroxide during calendar corrosion of (La, Mg)2Ni7-type hydrogen storage alloys for Nickel-Metal Hydride batteries
Boyer, Edmond
hydrogen storage alloys for Nickel-Metal Hydride batteries J. Monnier 1 , H. Chen 1 , S. Joiret2,3 , J hydrogen storage capacity and higher discharge capacity, eg. 356mAh/g for LaCaMgNi9 [4] compared to the AB5 market of hybrid electric vehicles (HEV) and Emergency Light Units (ELU). Hydrogen-absorbing alloys based
Improvement in Fatigue Strength of Biomedical ?-type Ti-Nb-Ta-Zr Alloy While Maintaining Low Young's Modulus Through Optimizing ?-Phase Precipitation
NASA Astrophysics Data System (ADS)
Nakai, Masaaki; Niinomi, Mitsuo; Oneda, Takahiro
The improvement in fatigue strength, with maintenance of a low Young's modulus, in a biomedical ?-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), by thermomechanical treatment was investigated. A short aging time at an ?-phase-forming temperature combined with severe cold rolling was employed. A fine ? phase is observed in TNTZ subjected to this thermomechanical treatment. Because the rolling texture of ? phase is formed by cold rolling, such as the ? phase may be preferentially oriented to a direction that is effective for inhibiting the increase in Young's modulus. The samples aged at 573 K (300 ¯C) for 3.6 ks and 10.8 ks after cold rolling exhibit a good balance between a high tensile strength and low Young's modulus. In the case of the sample aged for 3.6 ks, the tensile strength is improved, although the fatigue strength is not improved significantly. Both the tensile strength and the fatigue strength of the sample aged for 10.8 ks are improved. This fatigue strength is the highest among the TNTZ samples used in the current and in previous studies with Young's moduli less than 80 GPa.
Characterization of Newly Developed Semisolid Stir Joining Method for Cast Cu Base Alloy (Cu-Al-Si-Fe) and Effect of Stirrer Type on Uniformity of Microstructure
NASA Astrophysics Data System (ADS)
Ferasat, Keyvan; Aashuri, Hossein; Kokabi, Amir Hossein; Nikzad, Siamak; Shafizadeh, Mahdi
In this research, the semisolid stir joining method was used to overcome the problem of hot cracking in welding aluminum and silicon bronzes. Moreover, the effects of grooved and cylindrical tools on the microstructure and mechanical properties of samples were examined. After welding specimens, mechanical tests were carried out to find differences between the cast and welded samples. Optical microscopy and scanning electron microscopy were used to study microstructure. X-ray diffraction was used to investigate compounds formed during casting and welding. The solidus and liquidus temperatures of the alloy were measured by differential scanning calorimetry. In this study, the temperature of the work pieces was raised to 1203 K (930 ¯C) that is in the semisolid region, and the weld seams were stirred by two different types of tools at the speed of 1600 rpm. Macro and micro-structural analyses show uniformity in the phase distribution for specimens welded by cylindrical tool. Desirable and uniform mechanical properties obtained when the cylindrical tool was used.
Synthesis and structure determination of a new series of hydrogen storage alloys; RMg 2Ni 9 (R=La, Ce, Pr, Nd, Sm and Gd) built from MgNi 2 Laves-type layers alternating with AB 5 layers
K. Kadir; T. Sakai; I. Uehara
A number of new ternary magnesium based alloys, RMg2Ni9 (where R=La, Ce, Pr, Nd, Sm and Gd), have been synthesized by reacting a mixture of MgNi2 with RNi5 intermetallic compounds or by direct combination of the elements in the atomic ratio R:Mg:Ni=1:2:9. The crystal structure, determined by Guinier-Hðgg X-ray powder diffraction, is related to the hexagonal PuNi3 type. All interatomic
Use of n-type semiconductor silicon as substrate material for electrodeposition of Zn1-xFex alloy thin films
NASA Astrophysics Data System (ADS)
?limbey, ?smail; Yurdal, Ka?an; Bakkalo?lu, ømer Faruk; Karahan, ?smail Hakk?; Bedir, Metin
Zn1-xFex alloys were electrochemically deposited on semiconductor silicon substrates from sulfate bath. Effect of bath composition on phase formation, chemical composition, crystallite shape, electrical resistivity and magnetoresistance were investigated using appropriate characterization tools. It was shown that Zn-Fe alloys can be successfully deposited directly on semiconductor silicon substrate using electrodeposition technique. Iron content in films influences crystallite size, resistivity and magnetoresistance of films.
Effect of chromium content on stress corrosion cracking susceptibility of shielded metal arc weld metals for 600 type alloy in high-temperature pressurised pure water
Satoru Nishikawa; Yukihiko Horii; Kenji Ikeuchi
The stress corrosion cracking (SCC) susceptibility of SMAW metals for Inconel alloy 600 to which Cr was added to 14.821.4 mass% has been investigated on the basis of a creviced bent beam test in pressurized hot water (corresponding to the service condition of boiling water reactor nuclear power plant), since the TIG weld metal of alloy 82 involving 1822 mass%
J. S. Benjamin
A new technique of combining metals has been developed which overcomes many of the limitations of conventional alloying. Ball mills that generate higher energies than conventional ball mills are used to tumble a mixture of powders, such as WC and Co, in order to form a composite. Ni-base alloys can be dispersion-hardened in this way with an oxide such as
NASA Technical Reports Server (NTRS)
Blackburn, Linda B. (inventor); Starke, Edgar A., Jr. (inventor)
This invention relates to aluminum alloys, particularly to aluminum-copper-lithium alloys containing at least about 0.1 percent by weight of indium as an essential component, which are suitable for applications in aircraft and aerospace vehicles. At least about 0.1 percent by weight of indium is added as an essential component to an alloy which precipitates a T1 phase (Al2CuLi). This addition enhances the nucleation of the precipitate T1 phase, producing a microstructure which provides excellent strength as indicated by Rockwell hardness values and confirmed by standard tensile tests.
Theoretical investigation of new type of ternary magnesium alloys AMgNi 4 (A=Y, La, Ce, Pr and Nd)
NASA Astrophysics Data System (ADS)
Wang, Ji-Wei; Yang, Fang; Fan, Tou-Wen; Tang, Bi-Yu; Peng, Li-Ming; Ding, Wen-Jiang
New ternary magnesium alloys AMgNi 4 (A=Y, La, Ce, Pr and Nd) have been studied by First-Principles calculations within the generalized gradient approximation. The optimized structural parameters were in good agreement with the available experimental data. The calculated cohesive energies and formation enthalpies showed that these alloys had strong structural stability. Then the elastic constants Cij of these AMgNi 4 alloys were calculated, and the bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio ? and anisotropy value A of polycrystalline materials were derived from the elastic constants, the related mechanical properties were further discussed. The electronic structures were also calculated to reveal the underlying mechanism for the structural stability and the elastic property.
Method of producing superplastic alloys and superplastic alloys produced by the method
NASA Technical Reports Server (NTRS)
Troeger, Lillianne P. (Inventor); Starke, Jr., Edgar A. (Inventor); Crooks, Roy (Inventor)
A method for producing new superplastic alloys by inducing in an alloy the formation of precipitates having a sufficient size and homogeneous distribution that a sufficiently refined grain structure to produce superplasticity is obtained after subsequent PSN processing. An age-hardenable alloy having at least one dispersoid phase is selected for processing. The alloy is solution heat-treated and cooled to form a supersaturated solid solution. The alloy is plastically deformed sufficiently to form a high-energy defect structure useful for the subsequent heterogeneous nucleation of precipitates. The alloy is then aged, preferably by a multi-stage low and high temperature process, and precipitates are formed at the defect sites. The alloy then is subjected to a PSN process comprising plastically deforming the alloy to provide sufficient strain energy in the alloy to ensure recrystallization, and statically recrystallizing the alloy. A grain structure exhibiting new, fine, equiaxed and uniform grains is produced in the alloy. An exemplary 6xxx alloy of the type capable of being produced by the present invention, and which is useful for aerospace, automotive and other applications, is disclosed and claimed. The process is also suitable for processing any age-hardenable aluminum or other alloy.
Precipitates in Biomedical Co-Cr Alloys
NASA Astrophysics Data System (ADS)
Narushima, Takayuki; Mineta, Shingo; Kurihara, Yuto; Ueda, Kyosuke
Herein, precipitates in biomedical Co-Cr-Mo and Co-Cr-W-Ni alloys are reviewed with a focus on their phase, chemical composition, morphology, and formation/dissolution during heat treatment. The effects of the heat-treatment conditions and the addition of minor alloying elements such as carbon, nitrogen, Si, and Mn on the precipitates are also discussed. Mostly, the precipitates in the alloys are of the ?-phase, M23X6-type phase, ?-phase (M6X-M12X type), ?-phase (M2T3X type), ?-phase, M7X3-type phase, or M2X-type phase (M and T refer to metallic elements, and X refers to carbon and/or nitrogen); the ?- and ?-phases are intermetallic compounds, and the others are carbides, nitrides, and carbonitrides. The dissolution of the precipitates during solution treatment is delayed by the formation of the ?-phase at temperatures where partial melting occurs in the alloys. In addition, the stability of the precipitates depends on the content of minor alloying elements. For example, the addition of carbon enhances the formation of M23X6-type and M7X3-type precipitates. Nitrogen stabilizes the M2X-type, ?-phase, and ?-phase precipitates, and Si stabilizes the ?-phase and ?-phase precipitates. The balance between the minor alloying element abundances also affects the constitution of the precipitates in Co-Cr alloys.
Ab Initio Study of the 57Fe Electric Field Gradient in (FeAl)1-xTx (T = 3d Element) Dilute Alloys with B2-Type Structure
NASA Astrophysics Data System (ADS)
Michalecki, T.; Hanc, A.; Deniszczyk, J.; Borgie?, W.
We present an ab initio study of the electric field gradient at Fe nuclei in the series of (FeAl)1-xTx dilute alloys with B2-type crystal structure. The ternary additions T, of concentration x ? 0.06, from the group of 3d-type transition metals (Ti, V, Cr, Mn, Co, Ni, Cu) are considered. Lattice, local valence electron (3d, 4p) and weakly bound 3p core electron contributions to electric field gradient are separated out and discussed in the context of the T-atom site preference and changes of the electronic structure upon alloying. Contrary to earlier reports, we found that for most Fe nuclei the dominant contribution comes from the d-type valence electrons cancelled partially by the 3p and 4p electric field gradients which are both of opposite sign to that of the 3d one. The shielding effect of 3p semicore electrons is found and related to the electric field gradient contributed by the local valence electrons.
Effects of Li concentration and a Mg addition on serrated flow in Al-Li alloys
S. J. Zambo; J. A. Wert
Serrated flow phenomena have been reported in a variety of precipitation-strengthened aluminum alloys. In the particular case of precipitation-strengthened Al-Li alloys, serrated flow effects of similar character have been reported in binary Al-Li alloys and in commercial-type Al-Li alloys containing multiple alloying elements. Observations of serrated flow in binary Al-Li alloys indicate that the presence of Li alone is sufficient
Bond Strength of Gold Alloys Laser Welded to Cobalt-Chromium Alloy
Watanabe, Ikuya; Wallace, Cameron
The objective of this study was to investigate the joint properties between cast gold alloys and Co-Cr alloy laser-welded by Nd:YAG laser. Cast plates were fabricated from three types of gold alloys (Type IV, Type II and low-gold) and a Co-Cr alloy. Each gold alloy was laser-welded to Co-Cr using a dental laser-welding machine. Homogeneously-welded and non-welded control specimens were also prepared. Tensile testing was conducted and data were statistically analyzed using ANOVA. The homogeneously-welded groups showed inferior fracture load compared to corresponding control groups, except for Co-Cr. In the specimens welded heterogeneously to Co-Cr, Type IV was the greatest, followed by low-gold and Type II. There was no statistical difference (P<0.05) in fracture load between Type II control and that welded to Co-Cr. Higher elongations were obtained for Type II in all conditions, whereas the lowest elongation occurred for low-gold welded to Co-Cr. This study indicated that, of the three gold alloys tested, the Type IV gold alloy was the most suitable alloy for laser-welding to Co-Cr. PMID:19088892
Elevated temperature aluminum alloys
NASA Technical Reports Server (NTRS)
Meschter, Peter (Inventor); Lederich, Richard J. (Inventor); O'Neal, James E. (Inventor)
Three aluminum-lithium alloys are provided for high performance aircraft structures and engines. All three alloys contain 3 wt % copper, 2 wt % lithium, 1 wt % magnesium, and 0.2 wt % zirconium. Alloy 1 has no further alloying elements. Alloy 2 has the addition of 1 wt % iron and 1 wt % nickel. Alloy 3 has the addition of 1.6 wt % chromium to the shared alloy composition of the three alloys. The balance of the three alloys, except for incidentql impurities, is aluminum. These alloys have low densities and improved strengths at temperatures up to 260.degree. C. for long periods of time.
NASA Astrophysics Data System (ADS)
Mikami, M.; Mizoshiri, M.; Ozaki, K.; Takazawa, H.; Yamamoto, A.; Terazawa, Y.; Takeuchi, T.
Power generation performance of a thermoelectric module consisting of the Heusler Fe2VAl alloy was evaluated. For construction of the module, W-doped Fe2VAl alloys were prepared using powder metallurgy process. Power generation tests of the module consisting of 18 pairs of p- n junctions were conducted on a heat source of 373-673 K in vacuum. The reduction of thermal conductivity and improvement of thermoelectric figure of merit by W-doping enhanced the conversion efficiency and the output power. High output power density of 0.7 W/cm2 was obtained by virtue of the high thermoelectric power factor of the Heusler alloy. The module exhibited good durability, and the relatively high output power was maintained after temperature cycling test in air.
Comparison of Three Primary Surface Recuperator Alloys
Matthews, Wendy [Capstone Turbines; More, Karren Leslie [ORNL; Walker, Larry R [ORNL
Extensive work performed by Capstone Turbine Corporation, Oak Ridge National Laboratory, and various others has shown that the traditional primary surface recuperator alloy, type 347 stainless steel, is unsuitable for applications above 650 C ({approx}1200 F). Numerous studies have shown that the presence of water vapor greatly accelerates the oxidation rate of type 347 stainless steel at temperatures above 650 C ({approx}1200 F). Water vapor is present as a product of combustion in the microturbine exhaust, making it necessary to find replacement alloys for type 347 stainless steel that will meet the long life requirements of microturbine primary surface recuperators. It has been well established over the past few years that alloys with higher chromium and nickel contents than type 347 stainless steel have much greater oxidation resistance in the microturbine environment. One such alloy that has replaced type 347 stainless steel in primary surface recuperators is Haynes Alloy HR-120 (Haynes and HR-120 are trademarks of Haynes International, Inc.), a solid-solution-strengthened alloy with nominally 33 wt % Fe, 37 wt % Ni and 25 wt % Cr. Unfortunately, while HR-120 is significantly more oxidation resistant in the microturbine environment, it is also a much more expensive alloy. In the interest of cost reduction, other candidate primary surface recuperator alloys are being investigated as possible alternatives to type 347 stainless steel. An initial rainbow recuperator test has been performed at Capstone to compare the oxidation resistance of type 347 stainless steel, HR-120, and the Allegheny Ludlum austenitic alloy AL 20-25+Nb (AL 20-25+Nb is a trademark of ATI Properties, Inc. and is licensed to Allegheny Ludlum Corporation). Evaluation of surface oxide scale formation and associated alloy depletion and other compositional changes has been carried out at Oak Ridge National Laboratory. The results of this initial rainbow test will be presented and discussed in this paper.
First-principle investigation of electronic structure, magnetism and phase stability of Heusler-type Pt2-xMn1+xGa alloys
NASA Astrophysics Data System (ADS)
Feng, L.; Liu, E. K.; Zhang, W. X.; Wang, W. H.; Wu, G. H.
The electronic structure, magnetism and phase stability of Pt2-xMn1+xGa (x=0, 0.25, 0.5, 0.75, 1) alloys are studied by first-principle calculations. The calculations reveal that a potential magnetic martensitic transformation can be expected in all the series. In addition, a large magnetic-field-induced strain is likely to appear in Pt2-xMn1+xGa (x=0, 0.25, 0.75, 1) alloys. The electronic structure calculations indicate that the tetragonal phase is stabilized upon the distortion because of the pseudogap formation at the Fermi Level. The magnetic structure is also investigated and the total magnetic moment of the tetragonal phase is a little larger than that of the cubic austenite phase in all the series.
The qualitative effects of various types of hygiene instrumentation on commercially pure titanium and titanium alloy implant abutments: an in vitro and scanning electron microscope study
Frieda Von Giese Brookshire; William W. Nagy; Virendra B. Dhuru; Gerald J. Ziebert; Srinivas Chada
Statement of problem. Implant survival depends on proper and timely oral hygiene maintenance, and a wide variety of oral prophylaxis procedures have been recommended and used on implant abutments.Purpose. This in vitro study compared the surface quality of both commercially pure titanium and titanium-alloy implant abutments, subjected to various hygiene methods and instruments with a standardized, clinically applicable scaling force.Material
First-principles investigation of the binary AB 2 type Laves phase in Mg-Al-Ca alloy: Electronic structure and elastic properties
NASA Astrophysics Data System (ADS)
Yu, Wei-Yang; Wang, Na; Xiao, Xiao-Bing; Tang, Bi-Yu; Peng, Li-Ming; Ding, Wen-Jiang
First-principles calculations have been carried out to investigate the electronic structure and mechanical properties of the main binary Laves phase CaMg 2, CaAl 2 and MgAl 2 with C14, C15 and C36 structures in Mg-Al-Ca alloy, respectively. The optimized structural parameters were in very good agreement with the experimental values. The calculated heat of formation and cohesive energy showed that the C15-CaAl 2 Laves phase was of the strongest alloying ability and structural stability. The electronic density of states (DOS) and charge density distribution were given. The elastic parameters C ij were calculated, then the bulk modulus, shear modulus, Young's modulus, Possion's ratio and anisotropy value were derived. The ductility and plasticity were discussed in comparison with the previous experimental and theoretical data. The results showed that C14-MgAl 2 is of the best ductility and C15-MgAl 2 is of the best plasticity in the investigated binary alloys.
Properties of the quaternary half-metal-type Heusler alloy Co{sub 2}Mn{sub 1-x}Fe{sub x}Si
Balke, Benjamin; Fecher, Gerhard H.; Kandpal, Hem C.; Felser, Claudia; Kobayashi, Keisuke; Ikenaga, Eiji; Kim, Jung-Jin; Ueda, Shigenori [Institut fuer Anorganische und Analytische Chemie, Johannes Gutenberg Universitaet, D-55099 Mainz (Germany); Japan Synchrotron Radiation Research Institute (SPring-8/JASRI), Kouto 1-1-1, Mikaduki-cho, Sayou-gun, Hyogo, 679-5198 (Japan)
This paper reports on the bulk properties of the quaternary Heusler alloy Co{sub 2}Mn{sub 1-x}Fe{sub x}Si with the Fe concentration x=0,1/2,1. All samples, which were prepared by arc melting, exhibit L2{sub 1} long-range order over the complete range of Fe concentration. The structural and magnetic properties of the Co{sub 2}Mn{sub 1-x}Fe{sub x}Si Heusler alloys were investigated by means of x-ray diffraction, high- and low-temperature magnetometry, Moessbauer spectroscopy, and differential scanning calorimetry. The electronic structure was explored by means of high-energy photoemission spectroscopy at about 8 keV photon energy. This ensures true bulk sensitivity of the measurements. The magnetization of the Fe-doped Heusler alloys is in agreement with the values of the magnetic moments expected for a Slater-Pauling-like behavior of half-metallic ferromagnets. The experimental findings are discussed on the basis of self-consistent calculations of the electronic and magnetic structure. To achieve good agreement with experiment, the calculations indicate that on-site electron-electron correlation must be taken into account, even at low Fe concentration. The present investigation focuses on searching for the quaternary compound where the half-metallic behavior is stable against outside influences. Overall, the results suggest that the best candidate may be found at an iron concentration of about 50%.
Production of Aluminum Alloys: Status and Prospects
G. S. Makarov
Due to their physico-mechanical properties, aluminum alloys are one of the most important structural materials presently in use. Aluminum alloys are second only to steel in terms of volume of production and substantially outstrip other nonferrous metals in this regard. For example, the worldwide production of different types of metals at the end of the last century broke down as
Alloys of clathrate allotropes for rechargeable batteries
Chan, Candace K; Miller, Michael A; Chan, Kwai S
The present disclosure is directed at an electrode for a battery wherein the electrode comprises clathrate alloys of silicon, germanium or tin. In method form, the present disclosure is directed at methods of forming clathrate alloys of silicon, germanium or tin which methods lead to the formation of empty cage structures suitable for use as electrodes in rechargeable type batteries.
Tantalum modified ferritic iron base alloys
NASA Technical Reports Server (NTRS)
Oldrieve, R. E.; Blankenship, C. P. (inventors)
Strong ferritic alloys of the Fe-CR-Al type containing 0.4% to 2% tantalum were developed. These alloys have improved fabricability without sacrificing high temperature strength and oxidation resistance in the 800 C (1475 F) to 1040 C (1900 F) range.
Wear behavior of alloyed hypereutectic gray cast iron
Aravind Vadiraj; G. Balachandran; M. Kamaraj; B. Gopalakrishna; D. Venkateshwara Rao
Alloyed gray cast iron of varying compositions was studied for their wear behavior. In general, the alloyed gray irons studied have higher graphite volume fraction (?20%) with Type-A graphite flake morphology. Base cast iron showed two to three times higher wear rates than the alloyed gray irons. Tensile strength and wear rates show decreasing trend with increase in graphite and
Effect of toothbrushing on the toxicity of casting alloys
John C. Wataha; Petra E. Lockwood; Mamoru Noda; Steven K. Nelson; Donald J. Mettenburg
Statement of Problem. The biological properties of casting alloys have been assessed largely under passive conditions. The effect of common intraoral stresses such as brushing, toothpastes, and low pH on alloy toxicity are not known. Purpose. This study assessed the toxicity of 5 types of casting alloys commonly used in prosthodontics after toothbrushing, brushing in an acidic environment, or brushing
New alloys to conserve critical elements
NASA Technical Reports Server (NTRS)
Stephens, J. R.
Based on availability of domestic reserves, chromium is one of the most critical elements within the U.S. metal industry. New alloys having reduced chromium contents which offer potential as substitutes for higher chromium containing alloys currently in use are being investigated. This paper focuses primarily on modified Type 304 stainless steels having one-third less chromium, but maintaining comparable oxidation and corrosion properties to that of type 304 stainless steel, the largest single use of chromium. Substitutes for chromium in these modified Type 304 stainless steel alloys include silicon and aluminum plus molybdenum.
Advanced cutting conditions for the milling of aeronautical alloys
L. N Lµpez de lacalle; J PÕrez; J. I Llorente; J. A SÃnchez
This paper deals with possible improvement aspects on the chip cutting milling of two alloys that are used frequently in the aerospace industry, in particular the titanium alphabeta-based alloy Ti6Al4V and the nickel alloy usually known as type 718. Both alloys are used widely in the manufacture of different turbo-engine parts, considering their excellent mechanic features, and their resistance to
The Development of the Low-Cost Titanium Alloy Containing Cr and Mn Alloying Elements
NASA Astrophysics Data System (ADS)
Zhu, Kailiang; Gui, Na; Jiang, Tao; Zhu, Ming; Lu, Xionggang; Zhang, Jieyu; Li, Chonghe
The ? + ?-type Ti-4.5Al-6.9Cr-2.3Mn alloy has been theoretically designed on the basis of assessment of the Ti-Al-Cr-Mn thermodynamic system and the relationship between the molybdenum equivalent and mechanical properties of titanium alloys. The alloy is successfully prepared by the split water-cooled copper crucible, and its microstructures and mechanical properties at room temperature are investigated using the OM, SEM, and the universal testing machine. The results show that the Ti-4.5Al-6.9Cr-2.3Mn alloy is an ? + ?-type alloy which is consistent with the expectation, and its fracture strength, yield strength, and elongation reach 1191.3, 928.4 MPa, and 10.7 pct, respectively. Although there is no strong segregation of alloying elements under the condition of as-cast, the segregation of Cr and Mn is obvious at the grain boundary after thermomechanical treatment.
Environmental Cracking of Corrosion Resistant Alloys in the Chemical Process Industry - A Review
Rebak, R B
A large variety of corrosion resistant alloys are used regularly in the chemical process industry (CPI). The most common family of alloys include the iron (Fe)-based stainless steels, nickel (Ni) alloys and titanium (Ti) alloys. There also other corrosion resistant alloys but their family of alloys is not as large as for the three groups mentioned above. All ranges of corrosive environments can be found in the CPI, from caustic solutions to hot acidic environments, from highly reducing to highly oxidizing. Stainless steels are ubiquitous since numerous types of stainless steels exist, each type tailored for specific applications. In general, stainless steels suffer stress corrosion cracking (SCC) in hot chloride environments while high Ni alloys are practically immune to this type of attack. High nickel alloys are also resistant to caustic cracking. Ti alloys find application in highly oxidizing solutions. Solutions containing fluoride ions, especially acid, seem to be aggressive to almost all corrosion resistant alloys.
R. F. Voitovich; R. V. Makarova
The little-known corrosion-resisting properties of Ti-- Zr and Ta- Zr ; alloys were investigated by following the oxidation of the alloys using a ; continuous weighing method. The Ti-- Zr system consists of a continuous series ; of solid solutions while Ta forms eutectic type limited-solubility alloys with Zr. ; Ti alloys containing 30, 70, and 90% Zr and Ta
Relations between the modulus of elasticity of binary alloys and their structure
NASA Technical Reports Server (NTRS)
Koster, Werner; Rauscher, Walter
A comprehensive survey of the elastic modulus of binary alloys as a function of the concentration is presented. Alloys that form continuous solid solutions, limited solid solutions, eutectic alloys, and alloys with intermetallic phases are investigated. Systems having the most important structures have been examined to obtain criteria for the relation between lattice structure, type of binding, and elastic behavior.
Amorphous metal alloys produced by mechanical alloying
Tiainen, T.J.; Schwarz, R.B.
Mechanical alloying is a powder metallurgy method used in commercial production of high temperature superalloys. Under specific conditions, mechanical alloying allows the synthesis of amorphous metal alloys from mixtures of pure metal powders or from the powders of intermetallic compounds. Because the amorphizing transformation during mechanical alloying is a solid state reaction, most of the difficulties related to the amorphization by rapid solidification of melts can be avoided. Mechanical alloying allows the synthesis of amorphous alloys from metals with high melting temperatures and the resulting alloys have interesting properties such as high hardness and high crystallization temperatures. We used mechanical alloying for the synthesis of amorphous alloys in the binary alloy systems Nl-Sn, Nb-Si and Al-Hf. The amorphous alloy powders were characterized by x-ray diffraction, differential scanning calorimetry, scanning and transmission electron microscopy and hardness measurements. Produced alloys were compacted by hot pressing and the obtained compacts were characterized by x-ray diffraction, density and hardness measurements and by optical and scanning electron microscopy. The results of the amorphization and compaction studies are presented and discussed together with the characteristics of the mechanical alloying process. 15 refs., 5 figs.
A New Ion-coating Surface Treatment of Alloys for Dental Adhesive Resins
T. Tanaka; M. Hirano; M. Kawahara; H. Matsumura; M. Atsuta
4-META and new phosphate-methacrylate resins adhere strongly to dental alloys. However, for strengthening the water durability of the adhesive interface, the oxidation of the alloy surface is indispensable. A new oxidation method using ion-sputtering was developed, and the effectiveness of this surface treatment on two dental alloys-a type IV gold alloy and Ni-Cr-Be alloy-was investigated. As an endurance test, thermocycling
Cutting efficiency of air-turbine burs on cast titanium and dental casting alloys
I Watanabe; C Ohkubo; J. P Ford; M Atsuta; T Okabe
Objective: The purpose of this study was to investigate the cutting efficiency of air-turbine burs on cast free-machining titanium alloy (DT2F) and to compare the results with those for cast commercially pure (CP) Ti, Ti6Al4V alloy, and dental casting alloys.Methods: The cast metal (DT2F, CP Ti, Ti6Al4V, Type IV gold alloy and CoCr alloy) specimens were cut with air-turbine burs
Riley, William D. (Avondale, MD); Brown, Jr., Robert D. (Avondale, MD)
To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.
Oxidation Behavior of Glassy Alloys
NASA Technical Reports Server (NTRS)
Yurek, G.
The oxidation behavior of high temperature glassy alloys produced by rapid solidification processing is investigated and the effects of processing and composition on oxidation behavior is studied. Glassy Ta-44.5at%Ir, Ta-40at%Ir-10at%B and Nb-45at%Ir oxidized rapidly at 700 to 800 C at an oxygen partial pressure of .001 atm. The alloys were embrittled during the oxidation process. No apparent oxidation or embrittlement of the Ta-Ir alloy occurred after oxidation for 4h at 500 C at an oxygen partial pressure of .001 atm. Embrittlement occurred, however, after 100h of exposure under the latter conditions. Alloy embrittlement is associated with the partial or full conversion of the metallic glass to a mixture of crystalline beta-Ta2O5 and metallic iridium. Hot compaction of glassy alloys of this type must be limited to relatively low temperatures (approx. 500 C) and short times at the low temperatures unless extremely low oxygen partial pressures can be achieved during the compaction process.
Simulation of Sinusoidal Diffuse Scattering Loci in the Nonstoichiometric B8-Type Alloy Phases A1+ xB, A=(Co, Ni), B=(Ge, Sn)
NASA Astrophysics Data System (ADS)
Christy, Andrew G.; Larsson, Ann-Kristin
The alloys (Co, Ni) 1+ x(Ge, Sn) form a range of superstructures in which one [1 overline10] repeat of the hexagonal B8 substructure is preserved. Less well-ordered phases also occur in which continuous sinusoidal loci of diffuse scattering are observed trending parallel to c *. The curves can be modeled as cosine waves with maximum kat l=even and minimum kat l=odd. The shape of the curves vary with composition and annealing temperature. Computer simulation was used to generate two-dimensional projections of real-space occupancy patterns that produced similar diffraction patterns. The synthesized real-space arrays were characterized by sets of correlation coefficients. A Monte Carlo algorithm was then used to find sets of two-body interaction energies for which these structures lay at an energy minimum. Good fits between calculated and experimental diffraction patterns were found in all cases. The fitted interaction energies were mainly positive, implying that most two-body interactions were repulsive between sites of like occupancy. Magnitudes were significant out to third-nearest neighboring interstitial sites. The magnitudes tended to be largest near x=0.5. Additional variations of both interaction energies and resulting correlations with composition and annealing temperature are discussed. It is shown that the double-locus diffraction pattern observed for the Ni-Ge system is not necessarily produced by a mechanical mixture of two structures, but can correspond to a single phase. Interactions Eijout to nth nearest neighbors include a larger number of symmetrically distinct < i, j> terms than the corresponding < u, v, w> terms in three dimensions, implying that only approximate three-dimensional energies can be obtained by fitting from the energies of this study. Mutual frustration of repulsive interactions on the interstitial sublattice, which has a large number of triangularly connected neighbors, is responsible for both breaking the hexagonal symmetry of the sublattice and the failure to form structures giving conventional "spot" diffraction patterns.
Study of nontoxic aluminum and vanadium-free titanium alloys for biomedical applications
H. M. Silva; S. G. Schneider; C. Moura Neto
Pure titanium and its alloys are the most attractive materials for biomedical applications. Studies have shown that ?-type titanium alloys, containing the elements Mo, Zr, Nb, Ta and Fe, can exhibit an elastic modulus lower than Ti6Al4V alloy. This work describes the microstructures and mechanical properties of two ?-type titanium alloys, Ti8Nb13Zr and Ti18Nb13Zr (wt.%), which were produced by furnace
Twin roll casting of aluminum alloy strips
Toshio Haga; Kenta Tkahashi; Masaaki Ikawaand; Hisaki Watari
Two kinds of twin roll caster for aluminum alloys were devised in the present study. Vertical type was adopted. The strip, which was thinner than 3mm, could be cast at speeds higher than 60m\\/min. Aluminum alloy, which freezing zone is very wide like A5182, could be cast using the twin roll caster of the present study at speeds up to
Corrosion Testing of Ni Alloy HVOF Coatings in High Temperature Environments for Biomass Applications
NASA Astrophysics Data System (ADS)
Paul, S.; Harvey, M. D. F.
This paper reports the corrosion behavior of Ni alloy coatings deposited by high velocity oxyfuel spraying, and representative boiler substrate alloys in simulated high temperature biomass combustion conditions. Four commercially available oxidation resistant Ni alloy coating materials were selected: NiCrBSiFe, alloy 718, alloy 625, and alloy C-276. These were sprayed onto P91 substrates using a JP5000 spray system. The corrosion performance of the coatings varied when tested at ~525, 625, and 725 ¯C in K2SO4-KCl mixture and gaseous HCl-H2O-O2 containing environments. Alloy 625, NiCrBSiFe, and alloy 718 coatings performed better than alloy C-276 coating at 725 ¯C, which had very little corrosion resistance resulting in degradation similar to uncoated P91. Alloy 625 coatings provided good protection from corrosion at 725 ¯C, with the performance being comparable to wrought alloy 625, with significantly less attack of the substrate than uncoated P91. Alloy 625 performs best of these coating materials, with an overall ranking at 725 ¯C as follows: alloy 625 > NiCrBSiFe > alloy 718 ? alloy C-276. Although alloy C-276 coatings performed poorly in the corrosion test environment at 725 ¯C, at lower temperatures (i.e., below the eutectic temperature of the salt mixture) it outperformed the other coating types studied.
NASA Technical Reports Server (NTRS)
MacKay, Rebecca
The High Speed Research Airfoil Alloy Program developed a fourth-generation alloy with up to an +85 F increase in creep rupture capability over current production airfoil alloys. Since improved strength is typically obtained when the limits of microstructural stability are exceeded slightly, it is not surprising that this alloy has a tendency to exhibit microstructural instabilities after high temperature exposures. This presentation will discuss recent results obtained on coated fourth-generation alloys for subsonic turbine blade applications under the NASA Ultra-Efficient Engine Technology (UEET) Program. Progress made in reducing microstructural instabilities in these alloys will be presented. In addition, plans will be presented for advanced alloy development and for computational modeling, which will aid future alloy development efforts.
Thermal and transport properties of the Heusler-type Fe2VAl1-xGex(0?x?0.20) alloys: Effect of doping on lattice thermal conductivity, electrical resistivity, and Seebeck coefficient
NASA Astrophysics Data System (ADS)
Nishino, Y.; Deguchi, S.; Mizutani, U.
We report on the thermoelectric properties of the Heusler-type Fe2VAl1-xGex alloys with compositions 0?x?0.20 . While Fe2VAl(x=0) exhibits a semiconductorlike behavior in electrical resistivity, a slight substitution of Ge for Al causes a significant decrease in the low-temperature resistivity and a large enhancement in the Seebeck coefficient, reaching -130?V/K for x=0.05 at around room temperature. Comparison with the Fe2VAl1-xSix system demonstrates that the compositional variation of the Seebeck coefficient falls on a universal curve irrespective of the doping elements (Ge and Si), both of which are isoelectronic elements. The net effect of doping is most likely to cause a rigid-bandlike shift of the Fermi level from the central region in the pseudogap. In spite of a similar decrease in the electrical resistivity with composition of Ge and Si, the thermal conductivity decreases more rapidly for the Ge substitution. It is concluded that doping of heavier atoms such as Ge reduces more effectively the lattice thermal conductivity while retaining the low electrical resistivity as well as the large Seebeck coefficient.
Conduction mechanisms in p-type Pb{sub 1-x}Eu{sub x}Te alloys in the insulator regime
Peres, M. L.; Rubinger, R. M.; Ribeiro, L. H.; Rubinger, C. P. L. [Departamento de Fisica e Quimica, Instituto de Ciencias Exatas, Universidade Federal de Itajuba, Itajuba, PB 50, MG CEP 37500-903 (Brazil); Ribeiro, G. M. [Departamento de Fisica, ICEx, Universidade Federal de Minas Gerais, Belo Horizonte, PB 702, MG CEP 30123-970 (Brazil); Chitta, V. A. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, PB 66318, SP CEP 05315-970 (Brazil); Rappl, P. H. O.; Abramof, E. [Laboratorio Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, PB 515, SP CEP 12201-970 (Brazil)
Electrical resistivity measurements were performed on p-type Pb{sub 1-x}Eu{sub x}Te films with Eu content x = 4%, 5%, 6%, 8%, and 9%. The well-known metal-insulator transition that occurs around 5% at room temperature due to the introduction of Eu is observed, and we used the differential activation energy method to study the conduction mechanisms present in these samples. In the insulator regime (x > 6%), we found that band conduction is the dominating conduction mechanism for high temperatures with carriers excitation between the valence band and the 4f levels originated from the Eu atoms. We also verified that mix conduction dominates the low temperatures region. Samples with x = 4% and 5% present a temperature dependent metal insulator transition and we found that this dependence can be related to the relation between the thermal energy k{sub B}T and the activation energy {Delta}{epsilon}{sub a}. The physical description obtained through the activation energy analysis gives a new insight about the conduction mechanisms in insulating p-type Pb{sub 1-x}Eu{sub x}Te films and also shed some light over the influence of the 4f levels on the transport process in the insulator region.
Sheppard, T.
In recent years the importance of extruded alloys has increased due to the decline in copper extrusion, increased use in structural applications, environmental impact and reduced energy consumption. There have also been huge technical advances. This text provides comprehensive coverage of the metallurgical, mathematical and practical features of the process. The contents include: continuum principles; metallurgical features affecting the extrusion of Al-alloys; extrusion processing; homogenization and extrusion conditions for specific alloys; processing of 6XXX alloys; plant utilization; Appendix A: specification of AA alloys and DIN equivalents; Appendix B: chemical compositions; and Appendix C: typical properties.
Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX
High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.
Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub
High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.
High temperature mechanical properties of a zirconium-modified, precipitation- strengthened nickel, 30 percent copper alloy
NASA Technical Reports Server (NTRS)
Whittenberger, J. D.
A precipitation-strengthened Monel-type alloy has been developed through minor alloying additions of zirconium to a base Ni-30Cu alloy. The results of this exploratory study indicate that thermomechanical processing of a solution-treated Ni-30Cu-0.2Zr alloy produced a dispersion of precipitates. The precipitates have been tentatively identified as a Ni5Zr compound. A comparison of the mechanical properties, as determined by testing in air, of the zirconium-modified alloy to those of a Ni-30Cu alloy reveals that the precipitation-strengthened alloy has improved tensile properties to 1200 K and improved stress-rupture properties to 1100 K. The oxidation characteristics of the modified alloy appeared to be equivalent to those of the base Ni-30Cu alloy.
Development of new metallic alloys for biomedical applications.
Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko
New low modulus ?-type titanium alloys for biomedical applications are still currently being developed. Strong and enduring ?-type titanium alloy with a low Young's modulus are being investigated. A low modulus has been proved to be effective in inhibiting bone atrophy, leading to good bone remodeling in a bone fracture model in the rabbit tibia. Very recently ?-type titanium alloys with a self-tunable modulus have been proposed for the construction of removable implants. Nickel-free low modulus ?-type titanium alloys showing shape memory and super elastic behavior are also currently being developed. Nickel-free stainless steel and cobalt-chromium alloys for biomedical applications are receiving attention as well. Newly developed zirconium-based alloys for biomedical applications are proving very interesting. Magnesium-based or iron-based biodegradable biomaterials are under development. Further, tantalum, and niobium and its alloys are being investigated for biomedical applications. The development of new metallic alloys for biomedical applications is described in this paper. PMID:22765961
Wear behaviour of cast hypereutectic aluminium silicon alloys
Dheerendra Kumar Dwivedi
In the present paper, influence of alloying elements on wear behaviour of binary (Al17%Si) and multi-component (Al17Si0.8Ni0.6Mg1.2Cu0.6Fe) cast hypereutectic aluminium alloys has been reported. Experimental alloys were prepared via foundry technique. Wear behaviour of Al17Si and Al17SiX {X=Ni, Cu, Mg, Fe} alloys was studied using pin on disc (ASTM: G99) type of friction and wear testing machine. Dry sliding wear
Analysis of thermoelectric properties of high-temperature complex alloys of nickel-base, iron-base and cobalt-base groups
NASA Technical Reports Server (NTRS)
Holanda, R.
The thermoelectric properties alloys of the nickel-base, iron-base, and cobalt-base groups containing from 1% to 25% 106 chromium were compared and correlated with the following material characteristics: atomic percent of the principle alloy constituent; ratio of concentration of two constituents; alloy physical property (electrical resistivity); alloy phase structure (percent precipitate or percent hardener content); alloy electronic structure (electron concentration). For solid-solution-type alloys the most consistent correlation was obtained with electron concentration, for precipitation-hardenable alloys of the nickel-base superalloy group, the thermoelectric potential correlated with hardener content in the alloy structure. For solid-solution-type alloys, no problems were found with thermoelectric stability to 1000; for precipitation-hardenable alloys, thermoelectric stability was dependent on phase stability. The effects of the compositional range of alloy constituents on temperature measurement uncertainty are discussed.
Surface Alloying Using High-Power Continuous Lasers
NASA Astrophysics Data System (ADS)
Moore, Peter G.; Weinman, Leslie S.
High power continuous lasers can be used to modify the chemical composition of alloy surfaces to depths ranging from 0.01 to 1 mm. Such coatings exhibit potential advantages over more conventional coating techiliques in terms of the integrity of the coating, the character of the interface between the surface alloy and the substrate, and an increased control over the composition of the coating. The processing conditions used in laser surface alloy ing are selected in order to facilitate the mixing of the alloying material with molten substrate material. The manufacture of chromium steel suiface alloys on low carbon steel substrates is described in terms of this mixing and the extension of these results to other systems is discussed. Auger and electron microprobe analyses of chromium steel surface alloys have been performed and indicate that a high degree of compositional uniformity can be obtained with proper control of the processing. The various types of metallurgical and morphological structures are described.
Oxidation and sulfidation resistant alloys with silicon additions
Dunning, John S.; Alman, David E.; Poston, J.A., Jr. (NETL); Siriwardane, R. (NETL)
The Albany Research Center (ARC) has considerable experience in developing lean chromium, austenitic stainless steels with improved high temperature oxidation resistance. Using basic alloy design principles, a baseline composition of Fe-16Cr-16Ni-2Mn-1Mo alloys with Si and Al addition at a maximum of 5 weight percent was selected for potential application at temperatures above 700¤C for supercritical and ultra-supercritical power plant application. The alloys were fully austenitic. Cyclic oxidation tests in air for 1000 hours were carried out on alloys with Si only or combined Si and Al additions in the temperature range 700¤C to 800¤C. Oxidation resistances of alloys with Si only additions were outstanding, particularly at 800¤C (i.e., these alloys possessed weight gains 4 times less than a standard type-304 alloy). In addition, Si alloys pre-oxidized at 800¤C, showed a zero weight gain in subsequent testing for 1000 hours at 700¤C. Similar improvements were observed for Si only alloy after H2S exposure at 700¤C compared with type 304 stainless steel. SEM and ESCA analysis of the oxide films and base material at the oxide/base metal interface were conducted to study potential rate controlling mechanisms at ARC. Depth profile analysis and element concentration profiles (argon ion etching/x-ray photoelectron spectroscopy) were conducted on oxidized specimens and base material at the National Energy Technology Laboratory.
The influence of heat treatment and role of boron on sliding wear behaviour of ?-type Ti-35Nb-7.2Zr-5.7Ta alloy in dry condition and in simulated body fluids.
Majumdar, P; Singh, S B; Chakraborty, M
The wear behaviour of heat-treated Ti-35Nb-7.2Zr-5.7Ta (TNZT) and Ti-35Nb-7.2Zr-5.7Ta-0.5B (TNZTB) alloys (all compositions are in wt%) was investigated in dry condition and in simulated body fluids. It has been found that there is no straightforward relationship between the wear rate and the microstructure. The hardness has no appreciable effect on the wear behaviour of these alloys. The presence of boron in the TNZT alloy deteriorates its wear properties. The wear rate of TNZT and TNZTB alloys in various media increases in the following sequence: dry condition < Hank's solution < bovine serum. PMID:21316616
NASA Technical Reports Server (NTRS)
Gayda, John
Gas turbine engines for future subsonic transports will probably have higher pressure ratios which will require nickel-base superalloy disks with 13000 to 1400 F temperature capability. Several advanced disk alloys are being developed to fill this need. One of these, Allied Signal's Alloy 10, is a promising candidate for gas turbine engines to be used on smaller, regional aircraft. For this application, compressor/turbine disks must withstand temperatures of 1300 F for several hundred hours over the life of the engine. In this paper, three key properties of Alloy 10--tensile, 0.2% creep, and fatigue crack growth--will be assessed at 1300 F.
Aluminum Alloys for High Temperatures
NASA Technical Reports Server (NTRS)
Meschter, Peter J.; Lederich, Richard J.; O'Neal, James E.
New Al/Li alloys processed by rapid solidification show greatly improved strength-to-density ratios. Alloys suitable substitutes for heavier titanium alloys and weaker aluminum alloys in high-performance aircraft, bombers, and transports. Also suitable for use in high-performance-aircraft structures heated by engines and normally constructed from titanium alloys.
Photoelectron spectroscopic study on the electronic structures of the dental gold alloys and their interaction with L-cysteine
Ogawa, Koji; Takahashi, Kazutoshi; Azuma, Junpei; Kamada, Masao [Synchrotron Light Application Center, Saga University, 1 Honjo, Saga, Saga 840-8502 (Japan); Tsujibayashi, Toru; Ichimiya, Masayoshi [Department of Physics, Osaka Dental University, 8-1 Kuzuha-hanazono, Hirakata, Osaka 573-1121 (Japan); Fujimoto, Hitoshi [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto, Kumamoto 860-8555 (Japan); Sumimoto, Michinori [Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611 (Japan)
The valence electronic structures of the dental gold alloys, type 1, type 3, and K14, and their interaction with L-cysteine have been studied by ultraviolet photoelectron spectroscopy with synchrotron radiation. It was found that the electronic structures of the type-1 and type-3 dental alloys are similar to that of polycrystalline Au, while that of the K14 dental alloy is much affected by Cu. The peak shift and the change in shape due to alloying are observed in all the dental alloys. It is suggested that the new peak observed around 2 eV for the L-cysteine thin films on all the dental alloys may be due to the bonding of S 3sp orbitals with the dental alloy surfaces, and the Cu-S bond, as well as the Au-S and Au-O bonds, may cause the change in the electronic structure of the L-cysteine on the alloys.
Photoelectron spectroscopic study on the electronic structures of the dental gold alloys and their interaction with L-cysteine
NASA Astrophysics Data System (ADS)
Ogawa, Koji; Tsujibayashi, Toru; Takahashi, Kazutoshi; Azuma, Junpei; Ichimiya, Masayoshi; Fujimoto, Hitoshi; Sumimoto, Michinori; Kamada, Masao
The valence electronic structures of the dental gold alloys, type 1, type 3, and K14, and their interaction with L-cysteine have been studied by ultraviolet photoelectron spectroscopy with synchrotron radiation. It was found that the electronic structures of the type-1 and type-3 dental alloys are similar to that of polycrystalline Au, while that of the K14 dental alloy is much affected by Cu. The peak shift and the change in shape due to alloying are observed in all the dental alloys. It is suggested that the new peak observed around 2 eV for the L-cysteine thin films on all the dental alloys may be due to the bonding of S 3sp orbitals with the dental alloy surfaces, and the Cu-S bond, as well as the Au-S and Au-O bonds, may cause the change in the electronic structure of the L-cysteine on the alloys.
Ordered iron aluminide alloys having an improved room-temperature ductility and method thereof
Sikka, Vinod K. (Clinton, TN)
A process is disclosed for improving the room temperature ductility and strength of iron aluminide intermetallic alloys. The process involves thermomechanically working an iron aluminide alloy by means which produce an elongated grain structure. The worked alloy is then heated at a temperature in the range of about 650.degree. C. to about 800.degree. C. to produce a B2-type crystal structure. The alloy is rapidly cooled in a moisture free atmosphere to retain the B2-type crystal structure at room temperature, thus providing an alloy having improved room temperature ductility and strength.
Corrosion Embrittlement of Duralumin II Accelerated Corrosion Tests and the Behavior of High-Strength Aluminum Alloys of Different Compositions
NASA Technical Reports Server (NTRS)
Rawdon, Henry S
The permanence, with respect to corrosion, of light aluminum alloy sheets of the duralumin type, that is, heat-treatable alloys containing Cu, Mg, Mn, and Si is discussed. Alloys of this type are subject to surface corrosion and corrosion of the interior by intercrystalline paths. Results are given of accelerated corrosion tests, tensile tests, the effect on corrosion of various alloying elements and heat treatments, electrical resistance measurements, and X-ray examinations.
The Mg impurity in nitride alloys
Zvanut, M. E.; Willoughby, W. R.; Sunay, U. R. [Department of Physics, University of Alabama at Birmingham, Birmingham AL (United States); Koleske, D. D.; Allerman, A. A. [Sandia National Laboratory, Albuquerque NM (United States); Wang, Ke; Araki, Tsutomu [Department of Photonics, Ritsumeikan University, Kusatsu, Shiga (Japan); Nanishi, Yasushi [Department of Photonics, Ritsumeikan University, Kusatsu, Shiga, Japan and WCU Program, Department of Materials Science and Engineering, Seoul National University, Seoul (Korea, Republic of)
Although several magnetic resonance studies address the Mg acceptor in GaN, there are few reports on Mg doping in the alloys, where hole production depends strongly on the Al or In content. Our electron paramagnetic resonance (EPR) measurements of the p-type alloys suggest that the Mg impurity retains the axial symmetry, characteristic of a p-type dopant in both alloys; however, In and Al produce additional, different characteristics of the acceptor. In InGaN, the behavior is consistent with a lowering of the acceptor level and increasing hole density as In concentration increases. For AlGaN, the amount of neutral Mg decreases with increasing Al content, which is attributed to different kinetics of hydrogen diffusion thought to occur in samples with higher Al mole fraction.
NASA Astrophysics Data System (ADS)
Tan, Xincai
Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.
Low activation ferritic alloys
Gelles, David S. (West Richland, WA); Ghoniem, Nasr M. (Granada Hills, CA); Powell, Roger W. (Pasco, WA)
Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.
Low activation ferritic alloys
Gelles, D.S.; Ghoniem, N.M.; Powell, R.W.
Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.
Ferromagnetic bulk amorphous alloys
Akihisa Inoue; Akira Takeuchi; Tao Zhang
This article reviews our recent results on the development of ferromagnetic bulk amorphous alloys prepared by casting processes.\\u000a The multicomponent Fe-(Al,Ga)-(P,C,B,Si) alloys are amorphized in the bulk form with diameters up to 2 mm, and the temperature\\u000a interval of the supercooled liquid region before crystallization is in the range of 50 to 67 K. These bulk amorphous alloys\\u000a exhibit good
The oxidation of metals and alloys
NASA Technical Reports Server (NTRS)
Scheil, Erich
This paper reviews the various types of oxidation processes occurring with pure metals and gives explanations for the varying time-temperature-oxidation rate relations that exist for copper, tungsten, zinc, cadmium, and tantalum. The effect of shape and crystal structure on oxidation is discussed. Principles derived are applied to the oxidation of alloys.
Thompson, D.S.; Scott, D.H.
Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.
Thompson, David S. (Richmond, VA); Scott, Darwin H. (Mechanicsville, VA)
Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.
Abhijit Bhattacharyya; Dimitris C Lagoudas
This special issue on shape memory alloys (SMA) is an encore to a special issue on the same topic edited by us six years ago (Smart Mater. Struct.9 (5) October 2000). A total of 19 papers is offered in this issue, organized into the three broad categories of modeling, characterization and applications. In addition to thermally activated shape memory alloys,
Ductile transplutonium metal alloys
Conner, W.V.
Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as souces of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.
Kim, H.E.; Moorhead, A.J.
A transparent, strong CsI alloy is described having additions of monovalent iodides. Although the preferred iodide is AgI, RbI and CuI additions also contribute to an improved polycrystalline CsI alloy with outstanding multispectral infrared transmittance properties. 6 figs.
Schmidt, Frederick A. (Ames, IA); Verhoeven, John D. (Ames, IA); Gibson, Edwin D. (Ames, IA)
A tantalum-copper alloy can be made by preparing a consumable electrode consisting of an elongated copper billet containing at least two spaced apart tantalum rods extending longitudinally the length of the billet. The electrode is placed in a dc arc furnace and melted under conditions which co-melt the copper and tantalum to form the alloy.
Ductile transplutonium metal alloys
Conner, William V. (Boulder, CO)
Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.
Mizia, Ronald E. (Idaho Falls, ID); Shaber, Eric L. (Idaho Falls, ID); DuPont, John N. (Whitehall, PA); Robino, Charles V. (Albuquerque, NM); Williams, David B. (Bethlehem, PA)
The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.
Tuominen, S.; Wojcik, C. [Teledyne Wah Chang, Albany, OR (United States)
Aerospace industries require special allows with many properties tailored to meet specific needs. Prerequisites include clean melting techniques to maintain low impurity levels, tight control of alloy chemistry, and the analytical capability to characterize the product. Teledyne Wah Chang (TWC) produces specially refractory metals, including zirconium, hafnium, titanium, niobium and vanadium, which are essential components of many aerospace alloys. Alloys are prepared by vacuum-arc-remelting (VAR) or electron beam (EB) melting, and ingots are processed to products ranging from bar and tube stock to wire and foil. Chemical, mechanical, and microstructural tests are all conducted at TWC`s in-house laboratory facilities. Of the alloys described here, Ti-3Al-2.5V, Tiadyne 3515 (Alloy C), NiTiFe, and C-103 are produced commercially, while orthorhombic titanium aluminides are promising candidates for future light-weight composite matrices.
Dual alloy interface stability
NASA Technical Reports Server (NTRS)
Harf, F. H.
Powder metallurgy dual alloy fabrication is applied to combinations of superalloys having a high iron, and low strategic metal content, with standard nickel base superalloys, containing the strategic metals chromium, cobalt, and columbium. The possibility of combining Alloy 901 (12 percent Cr, 36 percent Fe, 0 percent Co, and 0 percent Cb) with turbine disk alloys Rene 95 (13 percent Cr, 8 percent Co, and 4 percent Cb) or low carbon astroloy (L.C.A.; 15 percent Cr, 17 percent Co, and 0 percent Cb) is investigated. Preliminary results for combinations show that a strong interface with rapid diffusion is obtained between alloys and that the standard heat treatments for either alloy may be satisfactory.
Synthesis and Characterization of Magnesium-Alloyed Hematite Thin Films
NASA Astrophysics Data System (ADS)
Tang, Houwen; Matin, M. A.; Wang, Heli; Al-Jassim, Mowafak; Turner, John; Yan, Yanfa
We have synthesized pure and Mg-alloyed hematite thin films on F-doped, SnO2-coated glass substrates by radiofrequency magnetron cosputtering of iron oxide with and without MgO sources in mixed Ar/O2 and mixed N2/O2 ambient. We found that hematite films deposited in N2/O2 ambient exhibited much poorer crystallinity than those deposited in Ar/O2 ambient. We determined that Mg alloying led to increased crystallinity and bandgap. Furthermore, we found that Mg alloying inverted the type of conductivity of the thin films: pure hematite thin films exhibited n-type conductivity, whereas Mg-alloyed hematite thin films exhibited p-type conductivity.
Hydrogen pickup mechanism of zirconium alloys
NASA Astrophysics Data System (ADS)
Couet, Adrien
Although the optimization of zirconium based alloys has led to significant improvements in hydrogen pickup and corrosion resistance, the mechanisms by which such alloy improvements occur are still not well understood. In an effort to understand such mechanisms, a systematic study of the alloy effect on hydrogen pickup is conducted, using advanced characterization techniques to rationalize precise measurements of hydrogen pickup. The hydrogen pick-up fraction is accurately measured for a specially designed set of commercial and model alloys to investigate the effects of alloying elements, microstructure and corrosion kinetics on hydrogen uptake. Two different techniques to measure hydrogen concentrations were used: a destructive technique, Vacuum Hot Extraction, and a non-destructive one, Cold Neutron Prompt Gamma Activation Analysis. The results indicate that hydrogen pickup varies not only from alloy to alloy but also during the corrosion process for a given alloy. For instance Zircaloy type alloys show high hydrogen pickup fraction and sub-parabolic oxidation kinetics whereas ZrNb alloys show lower hydrogen pickup fraction and close to parabolic oxidation kinetics. Hypothesis is made that hydrogen pickup result from the need to balance charge during the corrosion reaction, such that the pickup of hydrogen is directly related to (and indivisible of) the corrosion mechanism and decreases when the rate of electron transport or oxide electronic conductivity sigmao xe through the protective oxide increases. According to this hypothesis, alloying elements (either in solid solution or in precipitates) embedded in the oxide as well as space charge variations in the oxide would impact the hydrogen pick-up fraction by modifying sigmaox e, which drives oxidation and hydriding kinetics. Dedicated experiments and modelling were performed to assess and validate these hypotheses. In-situ electrochemical impedance spectroscopy (EIS) experiments were performed on Zircaloy-4 tubes to directly measure the evolution of sigma oxe as function of exposure time. The results show that sigmao xe decreases as function of exposure time and that its variations are directly correlated to the instantaneous hydrogen pickup fraction variations. The electron transport through the oxide layer is thus altered as the oxide grows, reasons for which are yet to be exactly determined. Preliminary results also show that sigma oxe of ZrNb alloys would be much higher compared with Zircaloy-4. Thus, it is confirmed that sigmaox e is a key parameter in the hydrogen and oxidation mechanism. Because the mechanism whereby alloying elements are incorporated into the oxide layer is critical to changing sigmao xe, the evolution of the oxidation state of two common alloying elements, Fe and Nb, when incorporated into the growing oxide layers is investigated using X-Ray Absorption Near-Edge Spectroscopy (XANES) using micro-beam synchrotron radiation on cross sectional oxide samples. The results show that the oxidation of both Fe and Nb is delayed in the oxide layer compared to that of Zr, and that this oxidation delay is related to the variations of the instantaneous hydrogen pick-up fraction with exposure time. The evolution of Nb oxidation as function of oxide depth is also compatible with space charge compensation in the oxide and with an increase in sigmaox e of ZrNb alloys compared to Zircaloys. Finally, various successively complex models from the well-known Wagner oxidation theory to the more complex effect of space charge on oxidation kinetics have been developed. The general purpose of the modeling effort is to provide a rationale for the sub-parabolic oxidation kinetics and demonstrate the correlation with hydrogen pickup fraction. It is directly demonstrated that parabolic oxidation kinetics is associated with high sigmao xe and low space charges in the oxide whereas sub-parabolic oxidation kinetics is associated with lower sigmaox e and higher space charge in the oxide. All these observations helped us to propose a general corrosion mechanism of zirconium allo
Micro stepping of Shape Memory Alloy based Poly Phase motor
S. V. Sharma; M. M. Nayak; N. S. Dinesh; L. Umanand
In literature we find broadly two types of shape memory alloy based motors namely limited rotation motor and unlimited rotation motor. The unlimited rotation type SMA based motor reported in literature uses SMA springs for actuation. An attempt has been made in this paper to develop an unlimited rotation type balanced poly phase motor based on SMA wire in series
Metallographic characterization of four alternative alloys intended for fixed prostheses.
Bessing, C; Bergman, M
Four dental casting alloys intended as alternatives for type III gold alloys were studied with regard to their metallographic appearance. The structures of two low-gold and two silver-palladium alloys were evaluated in the as-cast and hardened conditions and in the condition achieved after annealing for 1 h at 100 degrees C below the solidus temperature. The microstructure was studied by light optical microscopy, scanning electron microscopy, electron microprobe analysis, and X-ray diffraction analysis. In addition, the hardness and the grain size of the alloys were determined. The presence of concentration gradients and dissimilar phases is discussed. It was concluded that to obtain the optimum properties of these alloys, strict and detailed instructions about the various heat treatments are needed. PMID:3460302
Electrochemical corrosion behavior of biomedical Ti22Nb and Ti22Nb6Zr alloys in saline medium
Zheng, Yufeng
. All these observations suggested a nobler electrochemical behavior of the titanium alloys with the addition of Zr element and after polarization. 1 Introduction Titanium and its alloys are one of the most that the recent metallic biomaterials research has focused on the b-type titanium alloys with excellent
Cluster model studies on the electronic and magnetic properties of LaCo13 and La(Fe,Al, ,,),,.alloys
Gong, Xingao
(Fe,Al, ,,),,.alloys G. W. Zhang, X. G. Gong,aj and Q. Q. Zheng,a)sb) Institute of Solid State Physics, Academia Sinica(FeXAl,-xjls is discussed. The cubic NaZn,,-type alloys havelong beenthe subject of much research.Recently, the successfulfabrication of LaCo,,, La(Fe,Al,& alloys haveenrichedthis family and attractedmuch experimentaland
The time and temperature dependence of the thermoelectric properties of silicon-germanium alloy
NASA Technical Reports Server (NTRS)
Raag, V.
Experimental data on the electrical resistivity and Seebeck coefficient of n-type and p-type silicon-germanium alloys are analyzed in terms of a solid-state dopant precipitation model proposed by Lifshitz and Slyozov (1961). Experimental findings on the time and temperature dependence of the thermal conductivity of these two types of alloy indicate that the thermal conductivity of silicon-germanium alloys changes with time, contrary to previous hypothesis. A preliminary model is presented which stipulates that the observed thermal conductivity decrease in silicon-germanium alloys is due partly to dopant precipitation underlying the electrical property changes and partly to enhanced alloying of the material. It is significant that all three properties asymptotically approach equilibrium values with time. Total characterization of these properties will enable the time change to be fully compensated in the design of a thermoelectric device employing silicon-germanium alloys.
Alloy development of FeAl aluminide alloys for structural use in corrosive environments
Liu, C.T.; Sikka, V.K.; McKamey, C.G.
Objectives include adequate ductilities ([ge]10%) at ambient temperature, high-temperature strength better than stainless steels (types 304 and 316), and fabricability and weldability by conventional techniques (gas tungsten arc). The alloys should be capable of being corrosion resistant in molten nitrate salts with rates lower than other iron-base structural alloys and coating materials (such as Fe-Cr-Al alloys). Such corrosion rates should be less than 0.3 mm per year. The FeAl aluminide containing 35.8 at. % Al was selected as base composition. Preliminary studies indicate that additions of B and Zr, increase the room-temperature ductility of FeAl. Further alloying with 0.2% Mo, and/or 5% Cr, improves the creep. Our preliminary alloying effort has led to identification of the following aluminide composition with promising properties: Fe - (35 [plus minus] 2)Al - (0.3 [plus minus] 0.2)Mo - (0.2 [plus minus] 0.15)Zr - (0.3 [plus minus] 0.2)B- up to 5Cr, at. %. However, this composition is likely to be modified in future work to improve the weldability of the alloy. The FeAl alloy FA-362 (Fe-35.8% Al-0.2% Mo-0.05% Zr-0.24% B) produced by hot extrusion at 900C showed a tensile ductility of more than 10% at room temperature and a creep rupture life longer than unalloyed FeAl by more than an order of magnitude at 593C at 138 MPa. Melting and processing of scaled-up heats of selected FeAl alloys are described. Forging, extruding, and hot-rolling processes for the scale-up heats are also described.
Alloy development of FeAl aluminide alloys for structural use in corrosive environments
Liu, C.T.; Sikka, V.K.; McKamey, C.G.
Objectives include adequate ductilities ({ge}10%) at ambient temperature, high-temperature strength better than stainless steels (types 304 and 316), and fabricability and weldability by conventional techniques (gas tungsten arc). The alloys should be capable of being corrosion resistant in molten nitrate salts with rates lower than other iron-base structural alloys and coating materials (such as Fe-Cr-Al alloys). Such corrosion rates should be less than 0.3 mm per year. The FeAl aluminide containing 35.8 at. % Al was selected as base composition. Preliminary studies indicate that additions of B and Zr, increase the room-temperature ductility of FeAl. Further alloying with 0.2% Mo, and/or 5% Cr, improves the creep. Our preliminary alloying effort has led to identification of the following aluminide composition with promising properties: Fe - (35 {plus_minus} 2)Al - (0.3 {plus_minus} 0.2)Mo - (0.2 {plus_minus} 0.15)Zr - (0.3 {plus_minus} 0.2)B- up to 5Cr, at. %. However, this composition is likely to be modified in future work to improve the weldability of the alloy. The FeAl alloy FA-362 (Fe-35.8% Al-0.2% Mo-0.05% Zr-0.24% B) produced by hot extrusion at 900C showed a tensile ductility of more than 10% at room temperature and a creep rupture life longer than unalloyed FeAl by more than an order of magnitude at 593C at 138 MPa. Melting and processing of scaled-up heats of selected FeAl alloys are described. Forging, extruding, and hot-rolling processes for the scale-up heats are also described.
A comparative study on the bond strength of porcelain to the millingable Pd-Ag alloy
Hong, Jun-Tae
PURPOSE The porcelain fused to gold has been widely used as a restoration both with the natural esthetics of the porcelain and durability and marginal fit of metal casting. However, recently, due to the continuous rise in the price of gold, an interest towards materials to replace gold alloy is getting higher. This study compared the bond strength of porcelain to millingable palladium-silver (Pd-Ag) alloy, with that of 3 conventionally used metal-ceramic alloys. MATERIALS AND METHODS Four types of metal-ceramic alloys, castable nonprecious nickel-chrome alloy, castable precious metal alloys containing 83% and 32% of gold, and millingable Pd-Ag alloy were used to make metal specimens (n=40). And porcelain was applied on the center area of metal specimen. Three-point bending test was performed with universal testing machine. The bond strength data were analyzed with a one-way ANOVA and post hoc Scheffe's tests (?=.05). RESULTS The 3-point bending test showed the strongest (40.42 Ý 5.72 MPa) metal-ceramic bond in the nonprecious Ni-Cr alloy, followed by millingable Pd-Ag alloy (37.71 Ý 2.46 MPa), precious metal alloy containing 83% of gold (35.89 Ý 1.93 MPa), and precious metal alloy containing 32% of gold (34.59 Ý 2.63 MPa). Nonprecious Ni-Cr alloy and precious metal alloy containing 32% of gold showed significant difference (P<.05). CONCLUSION The type of metal-ceramic alloys affects the bond strength of porcelain. Every metal-ceramic alloy used in this study showed clinically applicable bond strength with porcelain (25 MPa). PMID:25352959
Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2
NASA Technical Reports Server (NTRS)
Ray, Ranjan; Jha, Sunil C.
Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.
Mechanical and corrosion resistance of a new nanostructured Ti-Zr-Ta-Nb alloy.
Raducanu, D; Vasilescu, E; Cojocaru, V D; Cinca, I; Drob, P; Vasilescu, C; Drob, S I
In this work, a multi-elementary Ti-10Zr-5Nb-5Ta alloy, with non-toxic alloying elements, was used to develop an accumulative roll bonding, ARB-type procedure in order to improve its structural and mechanical properties. The alloy was obtained by cold crucible semi-levitation melting technique and then was ARB deformed following a special route. After three ARB cycles, the total deformation degree per layer is about 86%; the calculated medium layer thickness is about 13 ?m. The ARB processed alloy has a low Young's modulus of 46 GPa, a value very close to the value of the natural cortical bone (about 20 GPa). Data concerning ultimate tensile strength obtained for ARB processed alloy is rather high, suitable to be used as a material for bone substitute. Hardness of the ARB processed alloy is higher than that of the as-cast alloy, ensuring a better behaviour as a implant material. The tensile curve for the as-cast alloy shows an elastoplastic behaviour with a quite linear elastic behaviour and the tensile curve for the ARB processed alloy is quite similar with a strain-hardening elastoplastic body. Corrosion behaviour of the studied alloy revealed the improvement of the main electrochemical parameters, as a result of the positive influence of ARB processing. Lower corrosion and ion release rates for the ARB processed alloy than for the as-cast alloy, due to the favourable effect of ARB thermo-mechanical processing were obtained. PMID:21783152
Structure, castability and mechanical properties of commercially pure and alloyed titanium cast in graphite mould.
Cheng, W W; Ju, C P; Lin, J H Chern
This report is a study of structure, castability, mechanical properties as well as corrosion behaviour of titanium doped with up to 5 weight percentage (wt%) of a series of alloy elements, including Ta, Mo, Nb, Hf, Zr, Sn, Bi and Ag. The results indicate that, with addition of 1 wt% alloy element, Bi and Mo were most effective in enhancing the castability of titanium. With more alloy elements added, the castability values of most alloys more or less decreased. Except Ti-Mo system, all Ti alloys with a fine acicular morphology had the same crystal structure (hcp) as that of c.p. Ti with a typical lath type morphology. When 3 wt% or more Mo was added, a finer orthorhombic alpha'' phase was formed. The microhardness and bending strength values of Ti alloys were all higher than those of c.p. Ti. Among all alloys, Ti-Mo system exhibited the highest hardness and strength level. For a certain alloy, the bending strength did not necessarily increase with its alloy content. Except Ti-5Zr and Ti-Mo alloys, the bending moduli of most alloy systems were not much different from that of c.p. Ti. All alloys showed an excellent resistance to corrosion in Hanks' solution at 37 degrees C. PMID:17559621
Ductile ordered intermetallic alloys.
Liu, C T; Stiegler, J O
Many ordered intermetallic alloys have attractive high-temperature properties; however, low ductility and brittle fracture limit their use for structural applications. The embrittlement in these alloys is mainly caused by an insufficient number of slip systems (bulk brittleness) and poor grain-boundary cohesion. Recent studies have shown that the ductility and fabricability of ordered intermetallics can be substantially improved by alloying processes and control of microstructural features through rapid solidification and thermomechanical treatments. These results demonstrate that the brittleness problem associated with ordered intermetallics can be overcome by using physical metallurgical principles. Application of these principles will be illustrated by results on Ni(3)Al and Ni(3)V-Co(3)V-Fe(3)V. The potential for developing these alloys as a new class of high-temperature structural materials is discussed. PMID:17774926
Electroplating on titanium alloy
NASA Technical Reports Server (NTRS)
Lowery, J. R.
Activation process forms adherent electrodeposits of copper, nickel, and chromium on titanium alloy. Good adhesion of electroplated deposits is obtained by using acetic-hydrofluoric acid anodic activation process.
Electrochemical corrosion of titanium and titanium-based alloys
Chotiros Kuphasuk; Yoshiki Oshida; Carl J. Andres; Suteera T. Hovijitra; Martin T. Barco; David T. Brown
Statement of problem. Two varieties of unalloyed titanium, Ti-6Al-4V and NiTi, commonly are used in medical and dental fields. Several other types of alloys for potential use in these fields have been developed, including Ti-4.5Al-3V-2Mo-2Fe and vanadium-free alloys (Ti-5Al-2.5Fe and Ti-5Al-3Mo-4Zr). The corrosion of these alloys under simulated physiologic conditions is not known. Purpose. This study compared the corrosion behaviors
High Thermoelectric Power Factor Near Room Temperature in Full-Heusler Alloys
NASA Astrophysics Data System (ADS)
Skoug, Eric J.; Zhou, Chen; Pei, Yanzhong; Morelli, Donald T.
We present results on the electrical resistivity, Seebeck coefficient, and thermal conductivity for the Heusler alloys Fe2VAl1- x Si x and Fe2VAl1- x Sn x synthesized using standard arc-melting techniques. While alloys with x = 0 are p-type, upon substitution of Si or Sn for Al the alloys can be made n-type with optimized sample compositions exhibiting thermoelectric power factors in excess of that of bismuth telluride near room temperature. The lattice thermal conductivity ? L of these alloys is too large to produce a high figure of merit; the prospects for and initial attempts at lowering ? L are discussed.
Mechanical alloying and milling
C. Suryanarayana
Mechanical alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from
Ultrahigh temperature intermetallic alloys
Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.
A new family of Cr-Cr{sub 2}Ta intermetallic alloys based on Cr-(6--10)Ta (at.%) is under development for structural use in oxidizing environments in the 1,000-1,300 C (1,832--2,372 F) temperature range. Development objectives relate to high temperature strength and oxidation resistance and room temperature fracture toughness. The 1,200 C (2,192 F) strength goals have been met: yield and fracture strengths of 275 MPa (40 ksi) and 345 MPa (50 ksi), respectively, were achieved. Progress in attaining reasonable fracture toughness of Cr-Cr{sub 2}Ta alloys has been made; current alloys exhibit room-temperature values of about 10--12 MPa{radical}m (1.1 MPa{radical}m = 1 ksi{radical}in.). Oxidation rates of these alloys at 950 C (1,742 F) in air are in the range of those reported for chromia-forming alloys. At 1,100 C (2,012 F) in air, chromia volatility was significant but, nevertheless, no scale spallation and positive weight gains of 1--5 mg/cm{sup 2} have been observed during 120-h, 6-cycle oxidation screening tests. These mechanical and oxidative properties represent substantial improvement over Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr alloys previously developed.
Electron beam surface remelting and alloying of aluminium alloys
P Petrov
This paper reports results of a study of structural and mechanical changes in layers of hypereutectic cast Al? Si alloys as results electron beam remelting and alloying with Fe?Cr powders and followed by electron beam remelting.
Formation of single-walled bimetallic coinage alloy nanotubes in confined carbon nanotubes: molecular dynamics simulations.
Han, Yang; Zhou, Jian; Dong, Jinming; Yoshiyuki, Kawazoe
The growth of single-walled bimetallic Au-Ag, Au-Cu and Ag-Cu alloy nanotubes (NTs) and nanowires (NWs) in confined carbon nanotubes (CNTs) has been investigated by using the classical molecular dynamics (MD) method. It is found that three kinds of single-walled gold-silver, gold-copper and silver-copper alloy NTs could indeed be formed in confined CNTs at any alloy concentration, whose geometric structures are less sensitive to the alloy concentration. And an extra nearly pure Au (Cu) chain will exist at the center of Au-Ag (Au-Cu and Ag-Cu) NTs when the diameters of the outside CNTs are big enough, thus producing a new type of tube-like alloy NWs. The bonding energy differences between the mono- and hetero-elements of the coinage metal atoms and the quasi-one-dimensional confinement from the CNT play important roles in suppressing effectively the "self-purification" effects, leading to formation of these coinage alloy NTs. In addition, the fluid-solid phase transition temperatures of the bimetallic alloy NTs are found to locate between those of the corresponding pure metal tubes. Finally, the dependences of the radial breathing mode (RBM) frequencies and the tube diameters of the alloy NTs on the alloying concentration were obtained, which will be very helpful for identifying both the alloying concentration and the alloy tube diameters in future experiments. PMID:24013729
Nickel-Titanium Alloys: Corrosion "Proof" Alloys for Space Bearing, Components and Mechanism Applications
NASA Technical Reports Server (NTRS)
DellaCorte, Christopher
An intermetallic nickel-titanium alloy, 60NiTi (60 wt% Ni, 40 wt% Ti), is shown to be a promising candidate tribological material for space mechanisms. 60NiTi offers a broad combination of physical properties that make it unique among bearing materials. 60NiTi is hard, electrically conductive, highly corrosion resistant, readily machined prior to final heat treatment, and is non-magnetic. Despite its high Ti content, 60NiTi is non-galling even under dry sliding. No other bearing alloy, metallic or ceramic, encompasses all of these attributes. Since 60NiTi contains such a high proportion of Ti and possesses many metallic properties, it was expected to exhibit poor tribological performance typical of Ti alloys, namely galling type behavior and rapid lubricant degradation. In this poster-paper, the oil-lubricated behavior of 60NiTi is presented.
Nickel-Titanium Alloys: Corrosion "Proof" Alloys for Space Bearing, Components and Mechanism Applications
NASA Technical Reports Server (NTRS)
DellaCorte, Christopher
An intermetallic nickel-titanium alloy, 60NiTi (60wt%Ni, 40wt%Ti), is shown to be a promising candidate tribological material for space mechanisms. 60NiTi offers a broad combination of physical properties that make it unique among bearing materials. 60NiTi is hard, electrically conductive, highly corrosion resistant, readily machined prior to final heat treatment, and is non-magnetic. Despite its high titanium content, 60NiTi is non-galling even under dry sliding. No other bearing alloy, metallic or ceramic, encompasses all of these attributes. Since 60NiTi contains such a high proportion of titanium and possesses many metallic properties, it was expected to exhibit poor tribological performance typical of titanium alloys, namely galling type behavior and rapid lubricant degradation. In this poster-paper, the oil-lubricated behavior of 60NiTi is studied.
Some features of the transgranular embrittlement of ?-titanium alloys under the influence of the environment
A. I. Igolkin
Some common features of the transgranular embrittlement of a-titanium alloys in chloride solutions, hot salts, liquid metals, and air are established. These types of brittle fracture are typical symptoms of trans-granular embrittlement along the basal (near-basal) cleavage planes of metals (alloys) with hcp crystal lattices with various values of the ratioc\\/a. In this connection, the role of alloying elements and
Structural and M—ssbauer spectroscopic study of Fe-Ni alloy nanoparticles
Kumar, Asheesh; Banerjee, S., E-mail: email@example.com; Sudarsan, V., E-mail: email@example.com [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085 (India); Meena, S. S. [Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085 (India)
Nano-crystalline Fe-Ni alloys have been synthesized in ethylene glycol medium. Based on XRD studies it is confirmed that, in these alloys Fe atoms are incorporated at Ni site to form Ni-Fe solid solutions. M—ssbauer studies have established that for alloy particles having smaller size there is significant concentration of two different types of paramagnetic Fe species and their relative concentration decreased with increase in particle size.
Nanocrystalline FeNb(B,Ge) alloys from ball milling: Microstructure, thermal stability and magnetic properties
J. S. BlÃzquez; V. Franco; C. F. Conde; A. Conde
Fe75B20Nb5, Fe75Ge10B10Nb5 and Fe75Ge20Nb5 alloys were prepared by ball milling from pure powders and their microstructure and magnetic properties were studied. A nanocrystalline solid solution of ?-Fe type is the main phase formed, although traces of some intermetallics were found in the FeBNb alloy. The local arrangements of Fe atoms in Ge containing alloys continuously evolve with milling time. The
Translating alloy using Boolean circuits
Daitch, Samuel Isaac
Alloy is a automatically analyzable modelling language based on first-order logic. An Alloy model can be translated into a Boolean formula whose satisfying assignments correspond to instances in the model. Currently, the ...
Oxidation of tantalum carbide alloys
è. I. Golovko; L. F. Ochkas; M. S. Koval'chenko; A. F. Nikityuk
1.A study was made of the oxidation of hot-pressed specimens of tantalum carbide, alloys of tantalum carbide with 5, 10, and 15% Ni and 10% (Ni, W), and VK8 alloy in air at temperatures of 500, 600, and 700¯C.2.It was established that in the temperature range investigated tantalum carbide and its alloys are superior in oxidation resistance to VK8 alloy.
Utilization of titanium alloy equipment
N. M. Shmakov; V. S. Mikheev
Alloys AT-3 and AT-6 have wide application in practice in contrast to many series containing titanium alloyed with cheap obtainable elements such as aluminum, chromium, iron, silicon, and boron. Alloys AT-3 and AT-6 are processable. Extruded electrodes consisting of magnesio-thermic titanium and added alloying elements were fused twice in a vacuum arc furnace in an argon atmosphere. After machining to
A study of surface tension driven segregation in monotectic alloy systems
NASA Technical Reports Server (NTRS)
Andrews, J. Barry; Andrews, Rosalia N.; Gowens, Terrell F.
The compatibilities of various monotectic alloy systems with several different crucible materials were evaluated. The study was carried out using small candidate alloy samples of compositions that produced fifty volume percent of each liquid phase at the monotectic temperature. Compatibility was based on the evaluation of the wetting tendency of the two immiscible phases with the crucible material in a one-g solidified sample. Three types of wetting phenomena were observed during the evaluation. Type 1 indicates an alloy-crucible combination where the L2 phase preferentially wets the crucible material. Since L2 is usually the minority phase in desirable alloys, this material combination would be difficult to process and is therefore considered incompatible. Type 2 behavior indicates an alloy-crucible combination where the L1 phase preferentially wets the crucible material. This type of combination is considered compatible since surface tension effects should aid in processing the alloy to a useful form. Type 3 indicates any combination that leads to major reactions between the alloy and crucible material, gas entrapment, or separation of the metal from the crucible wall. Additional compatibility evaluations would have to be carried out on combinations of this category. The five alloy systems studied included aluminum-bismuth, copper-lead, aluminum-indium, aluminum-lead and cadmium-gallium. The systems were combined with crucibles of alumina, boron nitride, mullite, quartz, silicon carbide and zirconia.
Utilization of Copper Alloys for Marine Applications
NASA Astrophysics Data System (ADS)
Drach, Andrew
Utilization of copper alloy components in systems deployed in marine environment presents potential improvements by reducing maintenance costs, prolonging service life, and increasing reliability. However, integration of these materials faces technological challenges, which are discussed and addressed in this work, including characterization of material performance in seawater environment, hydrodynamics of copper alloy components, and design procedures for systems with copper alloys. To characterize the hydrodynamic behavior of copper alloy nets, mesh geometry of the major types of copper nets currently used in the marine aquaculture are analyzed and formulae for the solidity and strand length are proposed. Experimental studies of drag forces on copper alloy net panels are described. Based on these studies, empirical values for normal drag coefficients are proposed for various types of copper netting. These findings are compared to the previously published data on polymer nets. It is shown that copper nets exhibit significantly lower resistance to normal currents, which corresponds to lower values of normal drag coefficient. The seawater performance (corrosion and biofouling) of copper alloys is studied through the field trials of tensioned and untensioned specimens in a one-year deployment in the North Atlantic Ocean. The corrosion behavior is characterized by weight loss, optical microscopy, and SEM/EDX analyses. The biofouling performance is quantified in terms of the biomass accumulation. To estimate the effects of stray electrical currents on the seawater corrosion measurements, a low cost three-axis stray electric current monitoring device is designed and tested both in the lab and in the 30-day field deployment. The system consists of a remotely operated PC with a set of pseudo-electrodes and a digital compass. The collected data is processed to determine magnitudes of AC and DC components of electric field and dominant AC frequencies. Mechanical behavior of copper alloys is investigated through a series of uniaxial tension tests on virgin and weathered (after one-year deployment in the ocean) specimens. The changes in mechanical properties are quantified in terms of differences in Young's modulus, Poisson's ratio, ultimate strength, and ultimate strain. The obtained stress-strain data is used for numerical modeling of the mechanical behavior of chain-link nets. The simulations are compared with the experimental data on stiffness and strength of the nets. The available information on seawater performance of copper alloys (corrosion, biofouling, mechanics) and copper alloy nets (hydrodynamics) is used to develop engineering procedures for marine aquaculture fish cage systems with copper alloy netting. The design, analysis, and fabrication procedures are illustrated on a commercial size gravity-type offshore fish cage deployed in the Pacific Ocean near Isla Italia (Patagonia, Chile). The funding for this work was provided by the International Copper Association. This work was also supported through two UNH Fellowships: CEPS UNH Graduate Fellowship to Outstanding PhD Program Applicants and Dissertation Year Fellowship.
De-alloyed platinum nanoparticles
Strasser, Peter (Houston, TX); Koh, Shirlaine (Houston, TX); Mani, Prasanna (Houston, TX); Ratndeep, Srivastava (Houston, TX)
A method of producing de-alloyed nanoparticles. In an embodiment, the method comprises admixing metal precursors, freeze-drying, annealing, and de-alloying the nanoparticles in situ. Further, in an embodiment de-alloyed nanoparticle formed by the method, wherein the nanoparticle further comprises a core-shell arrangement. The nanoparticle is suitable for electrocatalytic processes and devices.
Semiconductor alloys - Structural property engineering
NASA Technical Reports Server (NTRS)
Sher, A.; Van Schilfgaarde, M.; Berding, M.; Chen, A.-B.
Semiconductor alloys have been used for years to tune band gaps and average bond lengths to specific applications. Other selection criteria for alloy composition, and a growth technique designed to modify their structural properties, are presently considered. The alloys Zn(1-y)Cd(y)Te and CdSe(y)Te(1-y) are treated as examples.
Atomistic Method Applied to Computational Modeling of Surface Alloys
NASA Technical Reports Server (NTRS)
Bozzolo, Guillermo H.; Abel, Phillip B.
The formation of surface alloys is a growing research field that, in terms of the surface structure of multicomponent systems, defines the frontier both for experimental and theoretical techniques. Because of the impact that the formation of surface alloys has on surface properties, researchers need reliable methods to predict new surface alloys and to help interpret unknown structures. The structure of surface alloys and when, and even if, they form are largely unpredictable from the known properties of the participating elements. No unified theory or model to date can infer surface alloy structures from the constituents properties or their bulk alloy characteristics. In spite of these severe limitations, a growing catalogue of such systems has been developed during the last decade, and only recently are global theories being advanced to fully understand the phenomenon. None of the methods used in other areas of surface science can properly model even the already known cases. Aware of these limitations, the Computational Materials Group at the NASA Glenn Research Center at Lewis Field has developed a useful, computationally economical, and physically sound methodology to enable the systematic study of surface alloy formation in metals. This tool has been tested successfully on several known systems for which hard experimental evidence exists and has been used to predict ternary surface alloy formation (results to be published: Garces, J.E.; Bozzolo, G.; and Mosca, H.: Atomistic Modeling of Pd/Cu(100) Surface Alloy Formation. Surf. Sci., 2000 (in press); Mosca, H.; Garces J.E.; and Bozzolo, G.: Surface Ternary Alloys of (Cu,Au)/Ni(110). (Accepted for publication in Surf. Sci., 2000.); and Garces, J.E.; Bozzolo, G.; Mosca, H.; and Abel, P.: A New Approach for Atomistic Modeling of Pd/Cu(110) Surface Alloy Formation. (Submitted to Appl. Surf. Sci.)). Ternary alloy formation is a field yet to be fully explored experimentally. The computational tool, which is based on the BFS (Bozzolo, Ferrante, and Smith) method for the calculation of the energetics, consists of a small number of simple PCbased computer codes that deal with the different aspects of surface alloy formation. Two analysis modes are available within this package. The first mode provides an atom-by-atom description of real and virtual stages 1. during the process of surface alloying, based on the construction of catalogues of configurations where each configuration describes one possible atomic distribution. BFS analysis of this catalogue provides information on accessible states, possible ordering patterns, and details of island formation or film growth. More importantly, it provides insight into the evolution of the system. Software developed by the Computational Materials Group allows for the study of an arbitrary number of elements forming surface alloys, including an arbitrary number of surface atomic layers. The second mode involves large-scale temperature-dependent computer 2. simulations that use the BFS method for the energetics and provide information on the dynamic processes during surface alloying. These simulations require the implementation of Monte-Carlo-based codes with high efficiency within current workstation environments. This methodology capitalizes on the advantages of the BFS method: there are no restrictions on the number or type of elements or on the type of crystallographic structure considered. This removes any restrictions in the definition of the configuration catalogues used in the analytical calculations, thus allowing for the study of arbitrary ordering patterns, ultimately leading to the actual surface alloy structure. Moreover, the Monte Carlo numerical technique used for the large-scale simulations allows for a detailed visualization of the simulated process, the main advantage of this type of analysis being the ability to understand the underlying features that drive these processes. Because of the simplicity of the BFS method for e energetics used in these calculations, a detailed atom-by-atom analysis can be performed at any
Data mining for structure type prediction
Tibbetts, Kevin (Kevin Joseph)
Determining the stable structure types of an alloy is critical to determining many properties of that material. This can be done through experiment or computation. Both methods can be expensive and time consuming. Computational ...
Iron aluminide alloys with improved properties for high temperature applications
McKamey, C.G.; Liu, C.T.
An improved iron aluminide alloy of the DO[sub 3] type is described that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy conversion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26--30 at. % aluminum, 0.5--10 at. % chromium, 0.02--0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron. 3 figs.
Iron aluminide alloys with improved properties for high temperature applications
McKamey, Claudette G. (Knoxville, TN); Liu, Chain T. (Oak Ridge, TN)
An improved iron aluminide alloy of the DO.sub.3 type that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy corrosion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26-30 at. % aluminum, 0.5-10 at. % chromium, 0.02-0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron.
Laser assisted high entropy alloy coating on aluminum: Microstructural evolution
NASA Astrophysics Data System (ADS)
Katakam, Shravana; Joshi, Sameehan S.; Mridha, Sanghita; Mukherjee, Sundeep; Dahotre, Narendra B.
High entropy alloy (Al-Fe-Co-Cr-Ni) coatings were synthesized using laser surface engineering on aluminum substrate. Electron diffraction analysis confirmed the formation of solid solution of body centered cubic high entropy alloy phase along with phases with long range periodic structures within the coating. Evolution of such type of microstructure was a result of kinetics associated with laser process, which generates higher temperatures and rapid cooling resulting in retention of high entropy alloy phase followed by reheating and/or annealing in subsequent passes of the laser track giving rise to partial decomposition. The partial decomposition resulted in formation of precipitates having layered morphology with a mixture of high entropy alloy rich phases, compounds, and long range ordered phases.
Characteristics of alumina particles in dispersion-strengthened copper alloys
NASA Astrophysics Data System (ADS)
Zhang, Xue-hui; Li, Xiao-xian
Two types of alumina dispersion-strengthened copper (ADSC) alloys were fabricated by a novel in-situ reactive synthesis (IRS) and a traditional internal oxidation (IO) process. The features of alumina dispersoids in these ADSC alloys were investigated by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. It is found that nano-sized ?-Al2O3 particles of approximately 10 nm in diameter are homogeneously distributed in the IRS-ADSC composites. Meanwhile, larger-sized, mixed crystal structure alumina with rod-shaped morphology is embedded in the IO-ADSC alloy. The IRS-ADSC composites can obtain better mechanical and physical properties than the IO-ADSC composites; the tensile strength of the IRS-ADSC alloy can reach 570 MPa at room temperature, its electrical conductivity is 85% IACS, and the Rockwell hardness can reach 86 HRB.
Laser assisted high entropy alloy coating on aluminum: Microstructural evolution
Katakam, Shravana; Joshi, Sameehan S.; Mridha, Sanghita; Mukherjee, Sundeep; Dahotre, Narendra B., E-mail: email@example.com [Department of Materials Science and Engineering, University of North Texas, 1150 Union Circle, 305310 Denton, Texas 76203-5017 (United States)
High entropy alloy (Al-Fe-Co-Cr-Ni) coatings were synthesized using laser surface engineering on aluminum substrate. Electron diffraction analysis confirmed the formation of solid solution of body centered cubic high entropy alloy phase along with phases with long range periodic structures within the coating. Evolution of such type of microstructure was a result of kinetics associated with laser process, which generates higher temperatures and rapid cooling resulting in retention of high entropy alloy phase followed by reheating and/or annealing in subsequent passes of the laser track giving rise to partial decomposition. The partial decomposition resulted in formation of precipitates having layered morphology with a mixture of high entropy alloy rich phases, compounds, and long range ordered phases.
Surface modification of high temperature iron alloys
Park, Jong-Hee (Clarendon Hills, IL)
A method and article of manufacture of a coated iron based alloy. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700.degree. C.-1200.degree. C. to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy.
Modeling of Substitutional Site Preference in Ordered Intermetallic Alloys
NASA Technical Reports Server (NTRS)
Bozzolo, Guillermo; Noebe, Ronald D.; Honecy, Frank
We investigate the site substitution scheme of specific alloying elements in ordered compounds and the dependence of site occupancy on compound stoichiometry, alloy concentration. This basic knowledge, and the interactions with other alloying additions are necessary in order to predict and understand the effect of various alloying schemes on the physical properties of a material, its response to various temperature treatments, and the resulting mechanical properties. Many theoretical methods can provide useful but limited insight in this area, since most techniques suffer from constraints in the type of elements and the crystallographic structures that can be modeled. With this in mind, the Bozzolo-Ferrante-Smith (BFS) method for alloys was designed to overcome these limitations, with the intent of providing an useful tool for the theoretical prediction of fundamental properties and structure of complex systems. After a brief description of the BFS method, its use for the determination of site substitution schemes for individual as well as collective alloying additions to intermetallic systems is described, including results for the concentration dependence of the lattice parameter. Focusing on B2 NiAl, FeAl and CoAl alloys, the energetics of Si, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Hf, Ta and W alloying additions are surveyed. The effect of single additions as well as the result of two simultaneous additions, discussing the interaction between additions and their influence on site preference schemes is considered. Finally, the BFS analysis is extended to ternary L1(sub 2) (Heusler phase) alloys. A comparison between experimental and theoretical results for the limited number of cases for which experimental data is available is also included.
Structure and Properties of High-Carbon High-Vanadium Iron-Base Alloys for Surfacing
E. F. Perepletchikov; I. A. Ryabtsev; V. G. Vasil'ev; H. Heinze
Results of a study of the structure, hardness, and wear resistance of iron-base alloys bearing up to 4.5% C and 15% V are presented. The dependence of the structure and the type of carbides on the chemical composition of the alloys is studied. The effect of the structure on the abrasive strength of surfaced metal close in composition to the
Modifying the properties of the Inconel 625 nickel alloy by glow discharge assisted nitriding
Tomasz Borowski; Agnieszka Brojanowska; Marcin Kost; Halina Garbacz; Tadeusz Wierzcho?
The nickel alloys of the Inconel type (containing above 15wt% of chromium), used in many industrial applications including the manufacture of aircraft, chemistry, power generation, and material processing, have advantageous mechanical properties, high plasticity and good corrosion resistance, but their frictional wear resistance is poor. This drawback can be obviated by subjecting the alloys to various surface treatments.The paper describes
Alloyed coatings for dispersion strengthened alloys
NASA Technical Reports Server (NTRS)
Wermuth, F. R.; Stetson, A. R.
Processing techniques were developed for applying several diffusion barriers to TD-Ni and TD-NiCr. Barrier coated specimens of both substrates were clad with Ni-Cr-Al and Fe-Cr-Al alloys and diffusion annealed in argon. Measurement of the aluminum distribution after annealing showed that, of the readily applicable diffusion barriers, a slurry applied tungsten barrier most effectively inhibited the diffusion of aluminum from the Ni-Cr-Al clad into the TD-alloy substrates. No barrier effectively limited interdiffusion of the Fe-Cr-Al clad with the substrates. A duplex process was then developed for applying Ni-Cr-Al coating compositions to the tungsten barrier coated substrates. A Ni-(16 to 32)Cr-3Si modifier was applied by slurry spraying and firing in vacuum, and was then aluminized by a fusion slurry process. Cyclic oxidation tests at 2300 F resulted in early coating failure due to inadequate edge coverage and areas of coating porosity. EMP analysis showed that oxidation had consumed 70 to 80 percent of the aluminum in the coating in less than 50 hours.
Positron-annihilation 2D-ACAR studies of disordered and defected alloys
Bansil, A.; Prasad, R.; Smedskjaer, L.C.; Benedek, R.; Mijnarends, P.E.
Theoretical and experimental progess in connection with 2D-ACAR positron annihilation studies of ordered, disordered, and defected alloys is discussed. We present, in particular, some of the recent developments concerning the electronic structure of disordered alloys, and the work in the area of annihilation from positrons trapped at vacancy-type defects in metals and alloys. The electronic structure and properties of a number of compounds are also discussed briefly; we comment specifically on high T/sub c/ ceramic superconductors, Heusler alloys, and transition-metal aluminides. 58 refs., 116 figs.
Rapid solidification of copper alloys with high strength and high conductivity
Lopez, F.; Reyes, J.; Campillo, B.; Aguilar-Sahagun, G.; Juarez-Islas, J.A. [Univ. Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Investigaciones en Materiales
Rapid solidification has been employed to develop high-strength/high-conductivity copper alloys, because it offers advantages not achievable by conventional ingot metallurgy practice. The effect of rapid solidification on mechanical properties and electrical conductivity on copper alloys (with and without heat treatment) has been studied. Results indicated that alloys of the Cu-Cr-Zr type, rapidly solidified and aged, show a good combination of electrical conductivity [45.82 {times} 10{sup 6} (1/{Omega} {center_dot} m)] and microhardness Vickers (24.46 {times} 10{sup 6} Pa) values. These values are superior to those of optimally aged conventional copper alloys for resistance welding electrode applications.
Thermal coatings for titanium-aluminum alloys
NASA Technical Reports Server (NTRS)
Cunnington, George R.; Clark, Ronald K.; Robinson, John C.
Titanium aluminides and titanium alloys are candidate materials for use in hot structure and heat-shield components of hypersonic vehicles because of their good strength-to-weight characteristics at elevated temperature. However, in order to utilize their maximum temperature capability, they must be coated to resist oxidation and to have a high total remittance. Also, surface catalysis for recombination of dissociated species in the aerodynamic boundary layer must be minimized. Very thin chemical vapor deposition (CVD) coatings are attractive candidates for this application because of durability and very light weight. To demonstrate this concept, coatings of boron-silicon and aluminum-boron-silicon compositions were applied to the titanium-aluminides alpha2 (Ti-14Al-21Nb), super-alpha2 (Ti-14Al-23-Nb-2V), and gamma (Ti-33Al-6Nb-1Ta) and to the titanium alloy beta-21S (Ti-15Mo-3Al-3Nb-0.2Si). Coated specimens of each alloy were subjected to a set of simulated hypersonic vehicle environmental tests to determine their properties of oxidation resistance, surface catalysis, radiative emittance, and thermal shock resistance. Surface catalysis results should be viewed as relative performance only of the several coating-alloy combinations tested under the specific environmental conditions of the LaRC Hypersonic Materials Environmental Test System (HYMETS) arc-plasma-heated hypersonic wind tunnel. Tests were also conducted to evaluate the hydrogen transport properties of the coatings and any effects of the coating processing itself on fatigue life of the base alloys. Results are presented for three types of coatings, which are as follows: (1) a single layer boron silicon coating, (2) a single layer aluminum-boron-silicon coating, and (3) a multilayer coating consisting of an aluminum-boron-silicon sublayer with a boron-silicon outer layer.
Koizumi, H.; Ishihara, H.; Kawakita, K.; Matsumoto, T.
A molybdenum-based alloy improved in mechanical strength and hot workability, which consists of 0.01 to 5.0% by weight of vanadium, 10 to 100 ppm of boron, 10 to 1,000 ppm of carbon, and the balance of molybdenum.
Lin, X.; Johnson, W.L.
At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10{sup 3}K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf){sub a}(Al,Zn){sub b}(Ti,Nb){sub c}(Cu{sub x}Fe{sub y}(Ni,Co){sub z}){sub d} wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d{hor_ellipsis}y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.
Lin, Xianghong (Pasadena, CA); Johnson, William L. (Pasadena, CA)
At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf).sub.a (Al,Zn).sub.b (Ti,Nb).sub.c (Cu.sub.x Fe.sub.y (Ni,Co).sub.z).sub.d wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d.multidot.y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.
Theoretical Studies of Hydrogen Storage Alloys.
Jonsson, Hannes
Theoretical calculations were carried out to search for lightweight alloys that can be used to reversibly store hydrogen in mobile applications, such as automobiles. Our primary focus was on magnesium based alloys. While MgH{sub 2} is in many respects a promising hydrogen storage material, there are two serious problems which need to be solved in order to make it useful: (i) the binding energy of the hydrogen atoms in the hydride is too large, causing the release temperature to be too high, and (ii) the diffusion of hydrogen through the hydride is so slow that loading of hydrogen into the metal takes much too long. In the first year of the project, we found that the addition of ca. 15% of aluminum decreases the binding energy to the hydrogen to the target value of 0.25 eV which corresponds to release of 1 bar hydrogen gas at 100 degrees C. Also, the addition of ca. 15% of transition metal atoms, such as Ti or V, reduces the formation energy of interstitial H-atoms making the diffusion of H-atoms through the hydride more than ten orders of magnitude faster at room temperature. In the second year of the project, several calculations of alloys of magnesium with various other transition metals were carried out and systematic trends in stability, hydrogen binding energy and diffusivity established. Some calculations of ternary alloys and their hydrides were also carried out, for example of Mg{sub 6}AlTiH{sub 16}. It was found that the binding energy reduction due to the addition of aluminum and increased diffusivity due to the addition of a transition metal are both effective at the same time. This material would in principle work well for hydrogen storage but it is, unfortunately, unstable with respect to phase separation. A search was made for a ternary alloy of this type where both the alloy and the corresponding hydride are stable. Promising results were obtained by including Zn in the alloy.
Correlation of atomic packing with the boson peak in amorphous alloys
Yang, W. M. [State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Liu, H. S., E-mail: firstname.lastname@example.com, E-mail: email@example.com, E-mail: email@example.com, E-mail: email@example.com; Zhao, Y. C. [State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Liu, X. J. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Chen, G. X.; Man, Q. K.; Chang, C. T.; Li, R. W., E-mail: firstname.lastname@example.com, E-mail: email@example.com, E-mail: email@example.com, E-mail: email@example.com [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Dun, C. C. [Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109 (United States); Shen, B. L., E-mail: firstname.lastname@example.com, E-mail: email@example.com, E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Inoue, A. [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); and others
Boson peaks (BP) have been observed from phonon specific heats in 10 studied amorphous alloys. Two Einstein-type vibration modes were proposed in this work and all data can be fitted well. By measuring and analyzing local atomic structures of studied amorphous alloys and 56 reported amorphous alloys, it is found that (a) the BP originates from local harmonic vibration modes associated with the lengths of short-range order (SRO) and medium-range order (MRO) in amorphous alloys, and (b) the atomic packing in amorphous alloys follows a universal scaling law, i.e., the ratios of SRO and MRO lengths to solvent atomic diameter are 3 and 7, respectively, which exact match with length ratios of BP vibration frequencies to Debye frequency for the studied amorphous alloys. This finding provides a new perspective for atomic packing in amorphous materials, and has significant implications for quantitative description of the local atomic orders and understanding the structure-property relationship.
Environmental protection to 922K (1200 F) for titanium alloys
NASA Technical Reports Server (NTRS)
Groves, M. T.
Evaluations are presented of potential coating systems for protection of titanium alloys from hot-salt stress-corrosion up to temperatures of 755 K (900 F) and from oxidation embrittlement up to temperature of 922 K (1200 F). Diffusion type coatings containing Si, Al, Cr, Ni or Fe as single coating elements or in various combinations were evaluated for oxidation protection, hot-salt stress-corrosion (HSSC) resistance, effects on tensile properties, fatigue properties, erosion resistance and ballistic impact resistance on an alpha and beta phase titanium alloy (Ti-6Al-2Sn-4Zr-2Mo). All of the coatings investigated demonstrated excellent oxidation protectiveness, but none of the coatings provided protection from hot-salt stress-corrosion. Experimental results indicated that both the aluminide and silicide types of coatings actually decreased the HSSC resistance of the substrate alloy. The types of coatings which have typically been used for oxidation protection of refractory metals and nickel base superalloys are not suitable for titanium alloys because they increase the susceptibility to hot-salt stress-corrosion, and that entirely new coating concepts must be developed for titanium alloy protection in advanced turbine engines.
A study on the development and wear characteristics of rheocast Al5Cu2Pb alloy and Al5Cu\\/Pb18Sn wire composites
V Agarwala; K. G Satyanarayana; R. C Agarwala; Rajnish Garg
With renewed search for a low cost material for bearing application in place of conventional and expensive AlSn alloy, this paper describes development of an aluminium alloy Al5wt.%Cu2wt.%Pb alloy and Al5wt.%Cu\\/Pb18wt.% Sn wire composite by different types of casting routes. Wear characteristics and microstructural analysis of both alloy and composites have been determined. It is found that rheocast Al5Cu2Pb has
Alloys for hydrogen storage in nickel/hydrogen and nickel/metal hydride batteries
NASA Technical Reports Server (NTRS)
Anani, Anaba; Visintin, Arnaldo; Petrov, Konstantin; Srinivasan, Supramaniam; Reilly, James J.; Johnson, John R.; Schwarz, Ricardo B.; Desch, Paul B.
Since 1990, there has been an ongoing collaboration among the authors in the three laboratories to (1) prepare alloys of the AB(sub 5) and AB(sub 2) types, using arc-melting/annealing and mechanical alloying/annealing techniques; (2) examine their physico-chemical characteristics (morphology, composition); (3) determine the hydrogen absorption/desorption behavior (pressure-composition isotherms as a function of temperature); and (4) evaluate their performance characteristics as hydride electrodes (charge/discharge, capacity retention, cycle life, high rate capability). The work carried out on representative AB(sub 5) and AB(sub 2) type modified alloys (by partial substitution or with small additives of other elements) is presented. The purpose of the modification was to optimize the thermodynamics and kinetics of the hydriding/dehydriding reactions and enhance the stabilities of the alloys for the desired battery applications. The results of our collaboration, to date, demonstrate that (1) alloys prepared by arc melting/annealing and mechanical alloying/annealing techniques exhibit similar morphology, composition and hydriding/dehydriding characteristics; (2) alloys with the appropriate small amounts of substituent or additive elements: (1) retain the single phase structure, (2) improve the hydriding/dehydriding reactions for the battery applications, and (3) enhance the stability in the battery environment; and (3) the AB(sub 2) type alloys exhibit higher energy densities than the AB(sub 5) type alloys but the state-of-the-art, commercialized batteries are predominantly manufactured using Ab(sub 5) type alloys.
Vortex motion and resistivity of type-ll superconductors in a magnetic field
L. P. Gorkov; N. B. Kopnin
The review analyzes the physical mechanisms of energy dissipation in type-II superconducting alloys in the mixed state. A very simple microscopic theory is presented for the dissipative processes in alloys with paramagnetic impurities. The main premises of the microscopic theory are described and its results are presented for the resistivity in the case of ordinary alloys (without paramagnetic impurities) in
Corrosion performance of structural alloys.
Natesan, K.
Component reliability and long-term trouble-free performance of structural materials are essential in power-generating and gasification processes that utilize coal as a feedstock. During combustion and conversion of coal, the environments encompass a wide range of oxygen partial pressures, from excess-air conditions in conventional boilers to air-deficient conditions in 10W-NO{sub x} and gasification systems. Apart from the environmental aspects of the effluent from coal combustion and conversion, one concern from the systems standpoint is the aggressiveness of the gaseous/deposit environment toward structural components such as waterwall tubes, steam superheaters, syngas coolers, and hot-gas filters. The corrosion tests in the program described in this paper address the individual and combined effects of oxygen, sulfur, and chlorine on the corrosion response of several ASME-coded and noncoded structural alloys that were exposed to air-deficient and excess-air environments typical of coal-combustion and gasification processes. Data in this paper address the effects of preoxidation on the subsequent corrosion performance of structural materials such as 9Cr-1Mo ferritic steel, Type 347 austenitic stainless steel, Alloys 800, 825, 625, 214, Hastelloy X, and iron aluminide when exposed at 650 C to various mixed-gas environments with and without HCI. Results are presented for scaling kinetics, microstructural characteristics of corrosion products, detailed evaluations of near-surface regions of the exposed specimens, gains in our mechanistic understanding of the roles of S and Cl in the corrosion process, and the effect of preoxidation on subsequent corrosion.
Casting behavior of titanium alloys in a centrifugal casting machine.
Watanabe, K; Miyakawa, O; Takada, Y; Okuno, O; Okabe, T
Since dental casting requires replication of complex shapes with great accuracy, this study examined how well some commercial titanium alloys and experimental titanium-copper alloys filled a mold cavity. The metals examined were three types of commercial dental titanium [commercially pure titanium (hereinafter noted as CP-Ti), Ti-6Al-4V (T64) and Ti-6Al-7Nb (T67)], and experimental titanium-copper alloys [3%, 5% and 10% Cu (mass %)]. The volume percentage filling the cavity was evaluated in castings prepared in a very thin perforated sheet pattern and cast in a centrifugal casting machine. The flow behavior of the molten metal was also examined using a so-called "tracer element technique." The amounts of CP-Ti and all the Ti-Cu alloys filling the cavity were similar; less T64 and T67 filled the cavity. However, the Ti-Cu alloys failed to reach the end of the cavities due to a lower fluidity compared to the other metals. A mold prepared with specially designed perforated sheets was effective at differentiating the flow behavior of the metals tested. The present technique also revealed that the more viscous Ti-Cu alloys with a wide freezing range failed to sequentially flow to the end of the cavity. PMID:12593955
Hydrogen tolerance of a Ti3Al-based alloy
NASA Technical Reports Server (NTRS)
Chan, Kwai S.
The Ti-24Al-11Nb (Ti-24-11) alloy heat-treated to the fine basketweave microstructure was shown previously to be hydrogen-tolerant. In order to assess its limit of hydrogen tolerance, the tensile, creep, fracture toughness, and sustained-load crack growth behaviors of this alloy were studied as a function of hydrogen content. The mechanical test results indicated that the fine basketweave microstructure was tolerant to hydride embrittlement for hydrogen contents up to about 1500 wppm. On the other hand, hydrogen charging experiments indicated that the Ti-24-11 alloy was severely cracked and pulverized under zero load when the hydrogen content exceeded 3000 wppm. X-ray diffraction results revealed that the dichotomous behaviors might be due to the formation of face-centered cubic (fcc) delta-type hydrides at higher hydrogen contents but face-centered tetragonal (fct) gamma-type hydrides at lower hydrogen contents.
Filler metal alloy for welding cast nickel aluminide alloys
Santella, Michael L. (Knoxville, TN); Sikka, Vinod K. (Oak Ridge, TN)
A filler metal alloy used as a filler for welding east nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and east in copper chill molds.
Filler metal alloy for welding cast nickel aluminide alloys
Santella, M.L.; Sikka, V.K.
A filler metal alloy used as a filler for welding cast nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and cast in copper chill molds. 3 figs.
The effect of tensile stress on hydrogen diffusion in metal alloys
NASA Technical Reports Server (NTRS)
Danford, M. D.
The effect of tensile stress on hydrogen diffusion has been determined for Type 303 stainless steel, A286 CRES, and Waspaloy and IN100 nickel-base alloys. It was found that hydrogen diffusion coefficients are not significantly affected by stress, while the hydrogen permeabilities are greatly affected in Type 303 stainless steel and A286 CRES (iron-based alloys), but are affected little in Waspaloy (nickel-base) and not affected in all in IN100 (nickel base). These observations might be taken as an indication that hydrogen permeabilities are affected by stress in iron-based alloys, but only slightly affected in nickel-based alloys. However, it is too early to make such a generalization based on the study of only these four alloys.
Two phase titanium aluminide alloy
Deevi, Seetharama C. (Midlothian, VA); Liu, C. T. (Oak Ridge, TN)
A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.
Magnesium-lithium casting alloys
NASA Technical Reports Server (NTRS)
Latenko, V. P.; Silchenko, T. V.; Tikhonov, V. A.; Maltsev, V. P.; Korablin, V. P.
The strength properties of magnesium-lithium alloys at room, low, and high temperatures are investigated. It is found that the alloys may have practical application at ambient temperatures up to 100 C, that negative temperatures have a favorable influence on the alloy strength, and that cyclic temperature variations have practically no effect on the strength characteristics. The influence of chemical coatings on corrosion resistance of the MgLi alloys is examined. Several facilities based on pressure casting machines, low-pressure casting machines, and magnetodynamic pumps were designed for producing MgLi alloy castings. Results were obtained for MgLi alloys reinforced with fibers having a volumetric content of 15%.
Alchemy: Transmuting Base Alloy Specifications into Implementations
Krishnamurthi, Shriram
Alchemy: Transmuting Base Alloy Specifications into Implementations Shriram Krishnamurthi Brown to define lightweight models of systems. We present Alchemy, which compiles Alloy specifi- cations into implementations that execute against persistent databases. Alchemy translates a subset of Alloy predicates
Materials data handbook, aluminum alloy 7075
NASA Technical Reports Server (NTRS)
Sessler, J.; Weiss, V.
Materials data handbook on aluminum alloy 7075 includes data on the properties of the alloy at cryogenic, ambient, and elevated temperatures, and other pertinent engineering information required for the design and fabrication of components and equipment utilizing this alloy.
Alloy Interface Interdiffusion Modeled
NASA Technical Reports Server (NTRS)
Bozzolo, Guillermo H.; Garces, Jorge E.; Abel, Phillip B.
With renewed interest in developing nuclear-powered deep space probes, attention will return to improving the metallurgical processing of potential nuclear fuels so that they remain dimensionally stable over the years required for a successful mission. Previous work on fuel alloys at the NASA Glenn Research Center was primarily empirical, with virtually no continuing research. Even when empirical studies are exacting, they often fail to provide enough insight to guide future research efforts. In addition, from a fundamental theoretical standpoint, the actinide metals (which include materials used for nuclear fuels) pose a severe challenge to modern electronic-structure theory. Recent advances in quantum approximate atomistic modeling, coupled with first-principles derivation of needed input parameters, can help researchers develop new alloys for nuclear propulsion.
NSDL National Science Digital Library
This experiment, presented by the National Nanotechnology Infrastructure Network, covers Shape Memory Alloys or Smart Materials. A Smart Material or Shape Memory Alloys belongs to a class of materials which displays the shape memory effect (SME); they possess the ability to radically change crystal structure or phase at a distinct temperature. The lab will "explore how smart materials work and what applications these materials are used in." Additionally, students will be provided with a brief history lesson about the origins of smart material. The experiment is quite fun, students will observe how smart materials can "think and do amazing things." A student and teacher guide is provided with the lab. Overall, this is a great exercise for any science classroom interested in the workings of nanotechnology.
Using the method of positron annihilation for detecting defects in structural alloys caused by fatigue
Arefev, K.P.; Boev, O.V.; Chernitsyn, A.I.; Polukhin, Y.E.; Vordb'ev, S.A.
This paper examines the possibilities of using the method ofpositron annihilation for detecting fatigue defects in structural alloys with various types of crystal structure. The parameter of the positron annihilation process most suitable for the inspection was determined.
Surface Segregation in Ternary Alloys
NASA Technical Reports Server (NTRS)
Good, Brian; Bozzolo, Guillermo H.; Abel, Phillip B.
Surface segregation profiles of binary (Cu-Ni, Au-Ni, Cu-Au) and ternary (Cu-Au-Ni) alloys are determined via Monte Carlo-Metropolis computer simulations using the BFS method for alloys for the calculation of the energetics. The behavior of Cu or Au in Ni is contrasted with their behavior when both are present. The interaction between Cu and Au and its effect on the segregation profiles for Cu-Au-Ni alloys is discussed.
Titanium-tantalum alloy development
Cotton, J.D.; Bingert, J.F.; Dunn, P.S.; Butt, D.P.; Margevicius, R.W. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.
Research has been underway at Los Alamos National Laboratory for several years to develop an alloy capable of containing toxic materials in the event of a fire involving a nuclear weapon. Due to their high melting point, good oxidation resistance, and low solubility in molten plutonium, alloys based on the Ti-Ta binary system have been developed for this purpose. The course of the alloy development to-date, along with processing and property data, are presented in this overview.
Shape memory alloys characterization techniques
Jayagopal Uchil
Shape memory alloys are the generic class of alloys that show both thermal and mechanical memory. The basic physics involved\\u000a in the shape memory effect is the reversible thermoelastic martensitic transformation. In general, there exists two phases\\u000a in shape memory alloys, viz., a high-temperature phase or austenitic phase (A) and a low-temperature phase or martensitic\\u000a phase (M). In addition, an
Nanocrystal dispersed amorphous alloys
NASA Technical Reports Server (NTRS)
Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)
Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.
Varma, Venugopal K. (Knoxville, TN)
An actuator for cycling between first and second positions includes a first shaped memory alloy (SMA) leg, a second SMA leg. At least one heating/cooling device is thermally connected to at least one of the legs, each heating/cooling device capable of simultaneously heating one leg while cooling the other leg. The heating/cooling devices can include thermoelectric and/or thermoionic elements.
Weldability of Fe[sub 3]Al-type Aluminide
S. A. David; T. Zacharia
An investigation was carried out to determine the weldability of a series of Fe[sub 3]Al-type alloys. Autogenous welds were made on thin sheets of iron aluminide alloys using gas tungsten arc (GTA) and electron beam (EB) welding processes at different travel speeds and power levels. The results indicate that although these alloys can be successfully welded using the EB welding
Alloy Design Data Generated for B2-Ordered Compounds
NASA Technical Reports Server (NTRS)
Noebe, Ronald D.; Bozzolo, Guillermo; Abel, Phillip B.
Developing alloys based on ordered compounds is significantly more complicated than developing designs based on disordered materials. In ordered compounds, the major constituent elements reside on particular sublattices. Therefore, the addition of a ternary element to a binary-ordered compound is complicated by the manner in which the ternary addition is made (at the expense of which binary component). When ternary additions are substituted for the wrong constituent, the physical and mechanical properties usually degrade. In some cases the resulting degradation in properties can be quite severe. For example, adding alloying additions to NiAl in the wrong combination (i.e., alloying additions that prefer the Al sublattice but are added at the expense of Ni) will severely embrittle the alloy to the point that it can literally fall apart during processing on cooling from the molten state. Consequently, alloying additions that strongly prefer one sublattice over another should always be added at the expense of that component during alloy development. Elements that have a very weak preference for a sublattice can usually be safely added at the expense of either element and will accommodate any deviation from stoichiometry by filling in for the deficient component. Unfortunately, this type of information is not known beforehand for most ordered systems. Therefore, a computational survey study, using a recently developed quantum approximate method, was undertaken at the NASA Glenn Research Center to determine the preferred site occupancy of ternary alloying additions to 12 different B2-ordered compounds including NiAl, FeAl, CoAl, CoFe, CoHf, CoTi, FeTi, RuAl, RuSi, RuHf, RuTi, and RuZr. Some of these compounds are potential high temperature structural alloys; others are used in thin-film magnetic and other electronic applications. The results are summarized. The italicized elements represent the previous sum total alloying information known and verify the computational method used to establish the table. Details of the computational procedures used to determine the preferred site occupancy can be found in reference 2. As further substantiation of the validity of the technique, and its extension to even more complicated systems, it was applied to two simultaneous alloying additions in an ordered alloy.
Cold rolling textures of Fe-Ni soft magnetic alloys
Park, Y.B. [Sunchon National Univ. (Korea, Republic of). Dept. of Materials Science and Metallurgical Engineering] [Sunchon National Univ. (Korea, Republic of). Dept. of Materials Science and Metallurgical Engineering; Raabe, D. [RWTH, Aachen (Germany). Inst. fuer Metallkunde und Metallphysik] [RWTH, Aachen (Germany). Inst. fuer Metallkunde und Metallphysik; Yim, T.H. [Korea Academy of Industrial Technology, Inchon (Korea, Republic of). Production Technology Center] [Korea Academy of Industrial Technology, Inchon (Korea, Republic of). Production Technology Center
Cold rolling textures of f.c.c. materials can be classified into three different types depending on stacking fault energy (SFE). In low SFE materials such as {alpha}-brass, only the brass (B) component, {l_brace}110{r_brace}<112>, develops strongly. In high SFE materials such as pure aluminum, the S component, {l_brace}123{r_brace}<634>, and the copper (C) component, {l_brace}112{r_brace}<111>, dominate the cold rolling textures. In medium SFE materials such as pure copper, similar intensities of the C, S and B components are commonly observed. Since Fe-Ni alloys may be considered to have medium SFEs, their cold rolling textures are expected to be of the copper-type. However, the texture development of Fe-Ni alloys has been only weakly considered in the last decades although extensive texture research has been carried out over the years with the aid of orientation distribution function (ODF) analysis. Fe-Ni alloys have been widely used for soft magnetic materials. Due to the direct relevance of magnetic properties to the crystallographic texture, a better understanding of the texture development of Fe-Ni alloys will hence be technically beneficial and serve as a basis for practical applications. Thus, the aim of the present work is to systematically investigate the texture development and to elucidate the plastic behavior during cold rolling of Fe base Fe-Ni alloys.
Evaluation of a hydrogen resistant titanium aluminide alloy
NASA Technical Reports Server (NTRS)
Chan, K. S.
The Ti-24Al-11Nb (Ti-24-11) alloy heat treated to the fine basketweave microstructure was shown previously to be hydrogen tolerant. In order to assess its limit of hydrogen tolerance, the tensile, creep, fracture toughness, and sustained load crack growth behaviors of this alloy were studied as a function of hydrogen content. All test specimens were thermally charged with internal hydrogen and tested at 25 and 600 C. Coupon specimens were used for developing the hydrogen charging procedures and for studying compatibility of the alloy with high temperature, high pressure gaseous hydrogen. The mechanical test results indicated that the fine basketweave microstructure was tolerant to hydride embrittlement for hydrogen contents up to approximately 1500 wt. ppm, providing that the hydride formed was of the TiH2 type. On the other hand, hydrogen charging experiments indicated that the Ti-24-11 alloy was severely cracked and pulverized under zero load when the hydrogen content exceeded 3000 wt. ppm. X-ray diffraction results revealed that the dichotomous behaviors might be due to the formation of TiH(1.924) type hydrides at higher hydrogen contents. Thus, hydrogen embrittlement in the Ti-24-11 alloy with the fine basketweave microstructure depends on hydrogen content and the nature of the hydrides formed.
Effect of hydrogen on notch and crack sensitivity of titanium alloy ot4
B. A. Kolachev; A. A. Bukhanova; V. I. Sedov
1.The most sensitive methods of evaluating the tendency of alloy OT4 to first-type hydrogen embrittlement are fracture-toughness tests of specimens with a preinduced fatigue crack and impact-toughness tests of specimens with a notch of 0.5 mm radius.2.The critical stress intensity factor approaches a certain lower limit with an increase in hydrogen content.3.Under the conditions of second-type hydrogen embrittlement of alloy
Fatigue strength of welded joints in 6N01 aluminium alloy extrusions
K. Matsuoka; S. Chiaki; T. Uemura; K. Kamata
In this paper, the fatigue strength of welded joints in 6N01 aluminium alloy extrusions is discussed. Low copper content (?0.02%) alloys were chosen, considering corrosion resistance in sea water. Two series of specimens were prepared. One had two longitudinal stiffeners welded on both sides of the main plate (L?TYPE), and the other a non?load carrying fillet welded cruciform joint (T?TYPE).
Loss of Alloy in Cast Restorations Fabricated by Dental Students.
ERIC Educational Resources Information Center
Soh, George
A study investigated the quantity of alloy lost in the fabrication of three types of cast restoration by dental students, and identified the proportion of loss at each of the four principal stages of the fabrication process. Suggestions for reducing metal loss and related costs in dental schools are offered. (MSE)
Aluminum Alloy and Article Cast Therefrom
NASA Technical Reports Server (NTRS)
Lee, Jonathan A. (Inventor); Chen, Po-Shou (Inventor)
A cast article from an aluminum alloy, which has improved mechanical properties at elevated temperatures, has the following composition in weight percent: Silicon 14 - 25.0, Copper 5.5 - 8.0, Iron 0.05 - 1.2, Magnesium 0.5 - 1.5, Nickel 0.05 - 0.9, Manganese 0.05 - 1.0, Titanium 0.05 - 1.2, Zirconium 0.05 - 1.2, Vanadium 0.05 - 1.2, Zinc 0.05 - 0.9, Phosphorus 0.001 - 0.1, and the balance is Aluminum, wherein the silicon-to-magnesium ratio is 10 - 25, and the copper-to-magnesium ratio is 4 - 15. The aluminum alloy contains a simultaneous dispersion of three types of Al3X compound particles (X=Ti, V, Zr) having a LI2, crystal structure, and their lattice parameters are coherent to the aluminum matrix lattice. A process for producing this cast article is also disclosed, as well as a metal matrix composite, which includes the aluminum alloy serving as a matrix and containing up to about 60% by volume of a secondary filler material.
Tensile and fatigue properties of two titanium alloys as candidate materials for fusion reactors
NASA Astrophysics Data System (ADS)
Marmy, P.; Leguey, T.; Belianov, I.; Victoria, M.
Titanium alloys have been identified as candidate structural materials for the first wall, the blanket and the magnetic coil structures of fusion reactors. Titanium alloys are interesting materials because of their high specific strength and low elastic modulus, their low swelling tendency and their fast induced radioactivity decay. Other attractive properties are an excellent resistance to corrosion and good weldability, even in thick sections. Furthermore titanium alloys are suitable for components exposed to heat loads since they have a low thermal stress parameter. Titanium alloys with an ? structure are believed to have a good resistance against radiation embrittlement and ?+? alloys should possess the best tolerance to hydrogen embrittlement. Two classical industrially available alloys in the two families, the Ti5Al2.4Sn and the Ti6Al4V alloys have been used in this study. The tensile properties between room temperature and 450¯C are reported. A low cycle fatigue analysis has been performed under strain control at total strain ranges between 0.8% and 2% and at a temperature of 350¯C. The microstructure of both alloys was investigated before and after both types of deformation. Both alloys exhibit excellent mechanical properties comparable to or better than those of ferritic martensitic steels.
Welding Metallurgy of Alloy HR-160
DuPont, J.N.; Michael, J.R.; Newbury, B.D.
The solidification behavior and resultant solidification cracking susceptibility of autogenous gas tungsten arc fusion welds in alloy HR-160 was investigated by Varestraint testing, differential thermal analysis, and various microstructural characterization techniques. The alloy exhibited a liquidus temperature of 1387 {deg}C and initiated solidification by a primary L - {gamma} reaction in which Ni, Si, and Ti segregated to the interdendritic liquid and Co segregated to the {gamma} dendrite cores. Chromium exhibited no preference for segregation to the solid or liquid phase during solidification. Solidification terminated at {approx} 1162 {deg}C by a eutectic-type L - [{gamma}+ (Ni,Co){sub 16}(Ti,Cr){sub 6}Si{sub 7}] reaction. The (Ni,Co){sub 16}(Ti,Cr){sub 6}Si{sub 7} phase is found to be analogous to the G phase which forms in the Ni-Ti-Si and Co-Ti-Si ternary systems, and similarities are found to exist between the solidification behavior of this commercial multicomponent alloy and the simple Ni-Si and Ni-Ti binary systems. Reasonable agreement is obtained between the calculated and measured volume percent of the [{gamma} +(Ni,Co){sub l6}(Ti,Cr){sub 6}Si{sub 7}] eutectic-typr constituent with the Scheil equation using experimentally determined k values for Si and Ti from electron microprobe data. The alloy exhibited a very high susceptibility to solidification cracking in the Varestraint test. This is attributed to a large solidification temperature range of 225 {deg}C and the presence of 2 to 5 vol% solute rich interdendritic liquid which preferentially wets the grain boundaries and interdendritic regions.
Anode performance of lithium-silicon alloy prepared by mechanical alloying for use in all-solid-state lithium secondary batteries
NASA Astrophysics Data System (ADS)
Park, Hye Won; Song, Jung-Hoon; Choi, Heekyu; Jin, Joo Sung; Lim, Hyung-Tae
Li22Si5 alloy powder was synthesized by mechanical alloying and its electrochemical performance was investigated for use in solid-state battery anodes. Two types of anode powder were prepared: 1) Li-Si alloy powder after mechanical alloying with Li-granules and Si-powder, and 2) Li-Si alloy powder from the first process followed by additional ball milling for reduction of particle size. Using these anode materials, all-solid-state lithium batteries were assembled with Li4Ti5O12 (LTO) as cathode and Li2S-P2S5 as electrolyte. Impedance spectra of the two types of cells were measured, and the results showed that the non-ohmic resistance was less in the case of the cell with the secondary ball-milled, fine anode powder. Galvanostatic charge/discharge tests were also performed, and capacity was increased about two times by the additional powder milling process; which is consistent with the impedance results. Thus, the results from the present work indicate that using the secondary milling process to refine the electrode powder is an effective way to increase the kinetics of alloying and de-alloying with improvement in interfacial properties in all-solid-state lithium secondary batteries.
Palladium alloys for biomedical devices.
Wataha, John C; Shor, Kavita
In the biomedical field, palladium has primarily been used as a component of alloys for dental prostheses. However, recent research has shown the utility of palladium alloys for devices such as vascular stents that do not distort magnetic resonance images. Dental palladium alloys may contain minor or major percentages of palladium. As a minor constituent, palladium hardens, strengthens and increases the melting range of alloys. Alloys that contain palladium as the major component also contain copper, gallium and sometimes tin to produce strong alloys with high stiffness and relatively low corrosion rates. All current evidence suggests that palladium alloys are safe, despite fears about harmful effects of low-level corrosion products during biomedical use. Recent evidence suggests that palladium poses fewer biological risks than other elements, such as nickel or silver. Hypersensitivity to palladium alone is rare, but accompanies nickel hypersensitivity 90-100% of the time. The unstable price of palladium continues to influence the use of palladium alloys in biomedicine. PMID:20583886
Titanium-tantalum alloy development
J. D. Cotton; J. F. Bingert; P. S. Dunn; D. P. Butt; R. W. Margevicius
Research has been underway at Los Alamos National Laboratory for several years to develop an alloy capable of containing toxic materials in the event of a fire involving a nuclear weapon. Due to their high melting point, good oxidation resistance, and low solubility in molten plutonium, alloys based on the Ti-Ta binary system have been developed for this purpose. The
NASA Technical Reports Server (NTRS)
Merica, Paul D
Report is a summary of research work which has been done here and abroad on the constitution and mechanical properties of the various alloy systems with aluminum. The mechanical properties and compositions of commercial light alloys for casting, forging, or rolling, obtainable in this country are described.
Heat storage in alloy transformations
NASA Technical Reports Server (NTRS)
Birchenall, C. E.; Gueceri, S. I.; Farkas, D.; Labdon, M. B.; Nagaswami, N.; Pregger, B.
The feasibility of using metal alloys as thermal energy storage media was determined. The following major elements were studied: (1) identification of congruently transforming alloys and thermochemical property measurements; (2) development of a precise and convenient method for measuring volume change during phase transformation and thermal expansion coefficients; (3) development of a numerical modeling routine for calculating heat flow in cylindrical heat exchangers containing phase change materials; and (4) identification of materials that could be used to contain the metal alloys. Several eutectic alloys and ternary intermetallic phases were determined. A method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation from data obtained during one continuous experimental test. The method and apparatus are discussed and the experimental results are presented. The development of the numerical modeling method is presented and results are discussed for both salt and metal alloy phase change media.
Thermomechanical treatment of alloys
Bates, John F. (Ogden, UT); Brager, Howard R. (Richland, WA); Paxton, Michael M. (Gaithersburg, MD)
An article of an alloy of AISI 316 stainless steel is reduced in size to predetermined dimensions by cold working in repeated steps. Before the last reduction step the article is annealed by heating within a temperature range, specifically between 1010.degree. C. and 1038.degree. C. for a time interval between 90 and 60 seconds depending on the actual temperature. By this treatment the swelling under neutron bombardment by epithermal neutrons is reduced while substantial recrystallization does not occur in actual use for a time interval of at least of the order of 5000 hours.
Wedlable nickel aluminide alloy
Santella, Michael L. (Knoxville, TN); Sikka, Vinod K. (Oak Ridge, TN)
A Ni.sub.3 Al alloy with improved weldability is described. It contains about 6-12 wt % Al, about 6-12 wt % Cr, about 0-3 wt % Mo, about 1.5-6 wt % Zr, about 0-0.02 wt % B and at least one of about 0-0.15 wt % C, about 0-0.20 wt % Si, about 0-0.01 wt % S and about 0-0.30 wt % Fe with the balance being Ni.
Ohmic contact to p-type indium phosphide
NASA Technical Reports Server (NTRS)
Hawrylo, F. Z.
Low-Series-resistance ohmic contact to p-type InP semiconductor material is achieved in technique utilizing Au-Ge-Zn eutectic alloy. Alloy sets and adheres well to semiconductor surface with higher acceptor concentration at metal semiconductor interface. Technique has provided satisfactory for pn junction LED's and lasers.
Silicon Solar Cells with Front Hetero-Contact and Aluminum Alloy Back Junction: Preprint
Yuan, H.-C.; Page, M. R.; Iwaniczko, E.; Xu, Y.; Roybal, L.; Wang, Q.; Branz, H. M.; Meier, D. L.
We prototype an alternative n-type monocrystalline silicon (c-Si) solar cell structure that utilizes an n/i-type hydrogenated amorphous silicon (a-Si:H) front hetero-contact and a back p-n junction formed by alloying aluminum (Al) with the n-type Si wafer.
Microstructures and mechanical properties of Ti-Mo alloys cold-rolled and heat treated
Zhou Yinglong, E-mail: firstname.lastname@example.com [Department of Mechatronics Engineering, Foshan University, 18 Jiangwan Yi Rd, Foshan 528000, Guangdong Province (China); Luo Dongmei [Department of Civil Engineering, Foshan University, 18 Jiangwan Yi Rd, Foshan 528000, Guangdong Province (China)
In this study, the microstructures and mechanical properties of Ti-10Mo and Ti-20Mo alloys (mass%) are investigated to assess the potential use in biomedical applications. The microstructures are examined by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The mechanical properties are determined from uniaxial tensile tests. The experimental results indicate that the microstructures and mechanical properties of Ti-Mo alloys are dependent upon the cold rolling, solution heat treatment, and Mo content. The Ti-10Mo alloy exhibits ({alpha}'' + {beta}) and ({beta} + {omega}) phases under the cold rolling (CR) and solution treatment (ST), respectively. By contrast, the Ti-20Mo alloy comprises only {beta} phase under such conditions. The quenched Ti-20Mo alloy has the lowest elastic modulus and CR Ti-20Mo alloy has the highest tensile strength. The quenched Ti-10Mo alloy exhibits the excellent ductility and two-stage yielding from stress-strain curves due to the stress-induced martensite transformation from {beta} to {alpha}'' during tensile deformation. These Ti-Mo alloys exhibit low yield strength and good ductility, and they are more suitable for biomedical applications than the conventional metallic biomaterials from the viewpoint of better mechanical compatibility. The quenched Ti-10Mo alloy has some advantages over the other {beta} binary Ti-Mo alloys for biomedical applications. {beta} type Ti-Mo-Sn alloys are expected to be promising candidates for novel metallic biomaterials. - Highlights: {yields} The microstructures and mechanical properties of Ti-Mo alloys are dependent upon the cold rolling, solution heat treatment, and Mo content. {yields} The quenched Ti-10Mo alloy exhibits the excellent ductility and two-stage yielding due to stress-induced martensite transformation from beta to alpha double prime during tensile deformation. {yields} The Ti-Mo alloys are more suitable for biomedical applications than the conventional metallic biomaterials from the viewpoint of better mechanical compatibility. {yields} The quenched Ti-10Mo alloy has more advantages over the other beta binary Ti-Mo alloys for biomedical applications.
SCC Initiation in Alloy 600 Heat Affected Zones Exposed to High Temperature Water
E Richey; DS Morton; RA Etien; GA Young; RB Bucinell
Studies have shown that grain boundary chromium carbides improve the stress corrosion cracking (SCC) resistance of nickel based alloys exposed to high temperature, high purity water. However, thermal cycles from welding can significantly alter the microstructure of the base material near the fusion line. In particular, the heat of welding can solutionize grain boundary carbides and produce locally high residual stresses and strains, reducing the SCC resistance of the Alloy 600 type material in the heat affected zone (HAZ). Testing has shown that the SCC growth rate in Alloy 600 heat affected zone samples can be {approx}30x faster than observed in the Alloy 600 base material under identical testing conditions due to fewer intergranular chromium rich carbides and increased plastic strain in the HAZ [1, 2]. Stress corrosion crack initiation tests were conducted on Alloy 600 HAZ samples at 360 C in hydrogenated, deaerated water to determine if these microstructural differences significantly affect the SCC initiation resistance of Alloy 600 heat affected zones compared to the Alloy 600 base material. Alloy 600 to EN82H to Alloy 600 heat-affected-zone (HAZ) specimens where fabricated from an Alloy 600 to Alloy 600 narrow groove weld with EN82H filler metal. The approximate middle third of the specimen gauge region was EN82H such that each specimen had two HAZ regions. Tests were conducted with in-situ monitored smooth tensile specimens under a constant load, and a direct current electric potential drop was used for in-situ detection of SCC. Test results suggest that the SCC initiation resistance of Alloy 600 and its weld metal follows the following order: EN82H > Alloy 600 HAZ > Alloy 600. The high SCC initiation resistance observed to date in Alloy 600 heat affected zones compared to wrought Alloy 600 is unexpected based on the microstructure of HAZ versus wrought material and based on prior SCC growth rate studies. The observed behavior for the HAZ specimens is likely not related to differences in the environment, differences in surface stress/strain between the various specimen regions (weld, HAZ, wrought), differences in surface residual stress, or differences in the microstructure of the various specimen regions (weld, HAZ, wrought). The behavior may be related to differences in the creep behavior of the various weld regions or differences in the surface area of the various materials (weld, HAZ, wrought) exposed to high temperature water.
The influence of containerless undercooling and rapid solid-state quenching on the superconductive and magnetic properties of some clustering alloy systems
NASA Technical Reports Server (NTRS)
Collings, E. W.
The properties of clustering alloy systems and the manner in which they are influenced by rapid quenching from a containerless undercooled melt are discussed. It was postulated that rapid quenching under such conditions would result in highly disordered metastable alloys, and furthermore, that alloys in such conditions would possess physical properties characteristically different from those of alloys in the annealed equilibrium state. The scope of the program is essentially to gauge the influence of containerless undercooling on the submicrostructure of clustering-type alloys, using certain physical properties as diagnostic tools. Microstructures and macrostructures were to be examined using optical- and scanning-electron microscopy.
Sander, Evelyn
NUCLEATION IN A TWO COMPONENT METAL ALLOY Kalea Sebesta Department of Applied Mathematics, known as nucleation, in a two component metal alloy. The motivation behind this study is to use component metal alloys. These alloys are seen in material sciences; therefore, understanding
Liquid metal ion source and alloy
Clark Jr. William M; Mark W. Utlaut; Robert G. Behrens; Eugene G. Szklarz; Edmund K. Storms; Robert P. Santandrea; Lynwood W. Swanson
A liquid metal ion source and alloy, wherein the species to be emitted from the ion source is contained in a congruently vaporizing alloy. In one embodiment, the liquid metal ion source acts as a source of arsenic, and in a source alloy the arsenic is combined with palladium, preferably in a liquid alloy having a range of compositions from
High-temperature oxidation of alloys
Graham C. Wood
Some recent developments in the understanding of the oxidation of alloys at elevated temperatures are reviewed, with special reference to binary and ternary alloys upon which many commercial materials are based. Following an initial classification of alloy systems, certain basic principles and their limitations are considered, including factors determining whether an alloy displays surface scaling only, internal oxidation only, or
Thermoelectric Properties of (Pb,Sn,Ge)Te-Based Alloys
NASA Astrophysics Data System (ADS)
Gelbstein, Y.; Ben-Yehuda, O.; Pinhas, E.; Edrei, T.; Sadia, Y.; Dashevsky, Z.; Dariel, M. P.
The search for alternative energy sources is presently at the forefront of applied research. In this context, thermoelectricity for direct energy conversion from thermal to electrical energy plays an important role. This paper is concerned with the development of highly efficient p-type [(PbTe)(SnTe)(Bi2Te3)] x (GeTe)1- x alloys for thermoelectric applications using spark plasma sintering (SPS). Varying the carrier concentration of GeTe was achieved by alloying of PbTe, SnTe, and/or Bi2Te3. The rhombohedral to cubic phase transition temperature, T c, was found to be sensitive to the degree of alloying. Highest power factor values ( P ? 33 ?W/cm K2) were obtained for (GeTe)0.95(Bi2Te3)0.05 composition.
Recrystallization behavior of cold-rolled Zr-1Nb alloy
NASA Astrophysics Data System (ADS)
Tian, Hang; Wang, Xitao; Gong, Weijia; Zhou, Jun; Zhang, Hailong
The recrystallization behavior of cold-rolled Zr-1Nb alloy was investigated by measuring the micro-Vickers hardness of the specimens annealed for various times. Different deformation reductions and annealing temperatures were coupled to study the effects of deformation and temperature on the recrystallization behavior of Zr-1Nb alloy. The results show that both large deformation reduction and high annealing temperature accelerate the recrystallization process. The microstructural evolution during recrystallization was characterized by optical microscope (OM) and transmission electron microscope (TEM) to correlate with the variation of Vickers hardness. The TEM observation also revealed the distribution of different types of Nb-containing precipitates during recrystallization. The Vickers hardness data were fitted by using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation to derive the activation energies for recrystallization, giving the corresponding recrystallization maps. This study provides useful guidelines for the processing of a broad family of zirconium alloys based on Zr-1Nb.
Dissimilar metal crevice corrosion of highly alloyed stainless steel
Salamat, G.; Kelly, R.G. [Univ. of Virginia, Charlottesville, VA (United States)
Highly alloyed stainless steels can suffer from dissimilar metal crevice corrosion when creviced with certain other stainless alloys. In order to understand this phenomenon better, the solution which forms inside such crevices was collected and analyzed with ion chromatography and capillary electrophoresis for its metal ion content. These analyses provided the data required to design bulk solutions for electrochemical measurements. Electrochemical measurements in these simulated crevice solutions were made and compared to measurements made in simple acidified chloride solutions. The simulated crevice solutions were found to be much more aggressive. These results are used to rationalize the observations of dissimilar metal crevice corrosion of Alloy S44735 when it is creviced with Type 316 and the failure of electrochemical measurements in simple acidified chloride solutions to predict this attack. The roles of ohmic drop and chloride ion concentration are considered.
Thermodynamic modelling of growth-restriction effects in aluminium alloys
Quested, T.E. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)]. E-mail: firstname.lastname@example.com; Dinsdale, A.T. [National Physical Laboratory, Queens Road, Teddington, Middlesex TW11 0LW (United Kingdom); Greer, A.L. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)
The amount and type of alloying elements in aluminium affect the as-cast microstructure through the dependence of solidified fraction on undercooling. This can be quantified by the growth-restriction parameter Q. Phase-diagram calculations using the CALPHAD method show the effects of thermodynamic parameters on Q. In binary systems, the deviation from linear dependence of Q on solute concentration is assessed. In ternary alloys, model systems elucidate the role of solute interaction in the liquid and solid, and can be used to interpret the behaviour in actual systems. Growth restriction is discussed in relation to solidification modelling and the attainment of a fine, equiaxed microstructure in wrought and shape-casting alloys.
Industrial Experience on the Caustic Cracking of Stainless Steels and Nickel Alloys - A Review
Rebak, R B
Caustic environments are present in several industries, from nuclear power generation to the fabrication of alkalis and alumina. The most common material of construction is carbon steel but its application is limited to a maximum temperature of approximately 80 C. The use of Nickel (Ni) alloys is recommended at higher temperatures. Commercially pure Ni is the most resistant material for caustic applications both from the general corrosion and the stress corrosion cracking (SCC) perspectives. Nickel rich alloys also offer a good performance. The most important alloying elements are Ni and chromium (Cr). Molybdenum (Mo) is not a beneficial alloying element and it dissolves preferentially from the alloy in presence of caustic environments. Austenitic stainless steels such as type 304 and 316 seem less resistant to caustic conditions than even plain carbon steel. Experimental evidence shows that the most likely mechanism for SCC is anodic dissolution.
Oxidation resistant alloys, method for producing oxidation resistant alloys
Dunning, John S.; Alman, David E.
A method for producing oxidation-resistant austenitic alloys for use at temperatures below 800 C. comprising of: providing an alloy comprising, by weight %: 14-18% chromium, 15-18% nickel, 1-3% manganese, 1-2% molybdenum, 2-4% silicon, 0% aluminum and the balance being iron; heating the alloy to 800 C. for between 175-250 hours prior to use in order to form a continuous silicon oxide film and another oxide film. The method provides a means of producing stainless steels with superior oxidation resistance at temperatures above 700 C. at a low cost
Oxidation resistant alloys, method for producing oxidation resistant alloys
Dunning, John S. (Corvallis, OR); Alman, David E. (Salem, OR)
A method for producing oxidation-resistant austenitic alloys for use at temperatures below 800.degree. C. comprising of: providing an alloy comprising, by weight %: 14-18% chromium, 15-18% nickel, 1-3% manganese, 1-2% molybdenum, 2-4% silicon, 0% aluminum and the balance being iron; heating the alloy to 800.degree. C. for between 175-250 hours prior to use in order to form a continuous silicon oxide film and another oxide film. The method provides a means of producing stainless steels with superior oxidation resistance at temperatures above 700.degree. C. at a low cost
High performance alloy electroforming
NASA Technical Reports Server (NTRS)
Malone, G. A.; Winkelman, D. M.
Electroformed copper and nickel are used in structural applications for advanced propellant combustion chambers. An improved process has been developed by Bell Aerospace Textron, Inc. wherein electroformed nickel-manganese alloy has demonstrated superior mechanical and thermal stability when compared to previously reported deposits from known nickel plating processes. Solution chemistry and parametric operating procedures are now established and material property data is established for deposition of thick, large complex shapes such as the Space Shuttle Main Engine. The critical operating variables are those governing the ratio of codeposited nickel and manganese. The deposition uniformity which in turn affects the manganese concentration distribution is affected by solution resistance and geometric effects as well as solution agitation. The manganese concentration in the deposit must be between 2000 and 3000 ppm for optimum physical properties to be realized. The study also includes data regarding deposition procedures for achieving excellent bond strength at an interface with copper, nickel-manganese or INCONEL 718. Applications for this electroformed material include fabrication of complex or re-entry shapes which would be difficult or impossible to form from high strength alloys such as INCONEL 718.
A short-term clinical follow-up study of superplastic titanium alloy for major connectors of removable partial dentures
Noriyuki Wakabayashi; Minoru Ai
Statement of problem . Superplastic forming of Ti-6Al-4V alloy has been used in the fabrication of a removable denture framework. The method provides the titanium alloy denture framework with excellent physical properties not seen in cast titanium prostheses.Purpose . This study describes the technical procedure for fabricating removable dentures with this type of framework and evaluates clinical applications of the
AES study of passive films formed on a type 316 austenitic stainless-steels in a stress field
F. Navaÿ; O. Debbouz
The type AISI 316 stainless steel, in addition to the principal alloying elements chromium and nickel, contains 2.53.5% of molybdenum. This element is added to improve the mechanical properties and the pitting resistance of austenitic alloys. Concerning the Stress Corrosion Cracking (SCC) resistance of austenitic stainless steels, molybdenum additions to alloys have a variable effect: the effect is detrimental for
Directly smelted lead-tin alloys: A historical perspective
NASA Astrophysics Data System (ADS)
Dube, R. K.
This paper discusses evidence related to the genesis and occurrence of mixed lead-tin ore deposit consisting of cassiterite and the secondary minerals formed from galena. These evidences belong to a very long time period ranging from pre-historic to as late as the nineteenth century a.d. This type of mixed ore deposits was smelted to prepare lead-tin alloys. The composition of the alloy depended on the composition of the starting ore mixture. A nineteenth century evidence for the production of directly smelted lead-tin alloys in southern Thailand is discussed. A unique and rather uncommon metallurgical terminology in Sanskrit language N?gajawas introduced in India for the tin recovered from impure lead. This suggests that Indians developed a process for recovering tin from lead-tin alloys, which in all probability was based on the general principle of fire refining. It has been shown that in the context of India the possibility of connection between the word N?gaja and the directly smelted lead-tin alloys cannot be ruled out.
Functionally Graded Al Alloy Matrix In-Situ Composites
NASA Astrophysics Data System (ADS)
Kumar, S.; Subramaniya Sarma, V.; Murty, B. S.
In the present work, functionally graded (FG) aluminum alloy matrix in-situ composites (FG-AMCs) with TiB2 and TiC reinforcements were synthesized using the horizontal centrifugal casting process. A commercial Al-Si alloy (A356) and an Al-Cu alloy were used as matrices in the present study. The material parameters (such as matrix and reinforcement type) and process parameters (such as mold temperature, mold speed, and melt stirring) were found to influence the gradient in the FG-AMCs. Detailed microstructural analysis of the composites in different processing conditions revealed that the gradients in the reinforcement modify the microstructure and hardness of the Al alloy. The segregated in-situ formed TiB2 and TiC particles change the morphology of Si particles during the solidification of Al-Si alloy. A maximum of 20 vol pct of reinforcement at the surface was achieved by this process in the Al-4Cu-TiB2 system. The stirring of the melt before pouring causes the reinforcement particles to segregate at the periphery of the casting, while in the absence of such stirring, the particles are segregated at the interior of the casting.
Preparation of particle-dispersion alloys (M-6)
NASA Technical Reports Server (NTRS)
Muramatsu, Yuji
A particle dispersion alloy is one type of metal-ceramic composite material, and is used as heat resistance material, wear resistance material, and electrical material. This material consists of a metal matrix and dispersed particles, and for its unique structure it has both tenacity as a metal and hardness as a ceramic. Its properties improve when the particles become finer and disperse more uniformly. Most of the particle dispersion alloys are produced by the powder metallurgical process. This process is favorable for uniform dispersion of particles, but it consists of complicated techniques such as mechanical alloying and hot extrusion, and has the following drawbacks: (1) it is difficult to fabricate large-sized products; (2) the amount of particles is limited to a few percent; and (3) the process is complicated and expensive. To overcome these drawbacks, recently special attention has been paid to conventional melting process. However, under terrestrial conditions, dispersions separate immediately due to the different specific gravities of the metal matrix and the particles and thermal convection effects. The microgravity environment is, therefore, considered to be an attractive place for fabricating the dispersion alloy. This space experiment is carried out to clarify the influence of microgravity on the properties of the particle dispersion alloy and to obtain a deeper understanding of the experiment under the microgravity environment.
High-temperature ordered intermetallic alloys II; Proceedings of the Second Symposium, Boston, MA, Dec. 2-4, 1986
NASA Technical Reports Server (NTRS)
Stoloff, N. S. (editor); Koch, C. C. (editor); Liu, C. T. (editor); Izumi, O. (editor)
The papers presented in this volume provide on overview of recent theoretical and experimental research in the field of high-temperature ordered intermetallic alloys. The papers are gouped under the following headings: ordering behavior and theory, microstructures, mechanical behavior, alloy design and microstructural control, and metallurgical properties. Specific topics discussed include antiphase domains, disordered films and the ductility of ordered alloys based on Ni3Al; kinetics and mechanics of formation of Al-Ni intermetallics; deformability improvements of L1(2)-type intermetallic compounds; B2 aluminides for high-temperature applications; and rapidly solidified binary TiAl alloys.
New Amorphous Silicon Alloy Systems
NASA Astrophysics Data System (ADS)
Kapur, Mridula N.
The properties of hydrogenated amorphous silicon (a-Si:H) have been modified by alloying with Al, Ga and S respectively. The Al and Ga alloys are in effect quaternary alloys as they were fabricated in a carbon-rich discharge. The alloys were prepared by the plasma assisted chemical vapor deposition (PACVD) method. This method has several advantages, the major one being the relatively low defect densities of the resulting materials. The PACVD system used to grow the alloy films was designed and constructed in the laboratory. It was first tested with known (a-Si:H and a-Si:As:H) materials. Thus, it was established that device quality alloy films could be grown with the home-made PACVD setup. The chemical composition of the alloys was characterized by secondary ion mass spectrometry (SIMS), and electron probe microanalysis (EPMA). The homogeneous nature of hydrogen distribution in the alloys was established by SIMS depth profile analysis. A quantitative analysis of the bulk elemental content was carried out by EPMA. The analysis indicated that the alloying element was incorporated in the films more efficiently at low input gas concentrations than at the higher concentrations. A topological model was proposed to explain the observed behavior. The optical energy gap of the alloys could be varied in the 0.90 to 1.92 eV range. The Al and Ga alloys were low band gap materials, whereas alloying with S had the effect of widening the energy gap. It was observed that although the Si-Al and Si-Ga alloys contained significant amounts of C and H, the magnitude of the energy gap was determined by the metallic component. The various trends in optical properties could be related to the binding characteristics of the respective alloy systems. A quantitative explanation of the results was provided by White's tight binding model. The dark conductivity-temperature dependence of the alloys was examined. A linear dependence was observed for the Al and Ga systems. Electronic conduction in the S-alloys appeared to proceed by a two step mechanism. The thermal activation energies for the high Al content and S-alloys were close to half the band gap value. The photoresponse of the films was determined from the light to dark conductivity ratio. The best photoresponse (sigma_ {L}/sigma_{D} = 4 times 10^2) was obtained for the Si-S alloys showing that they are promising electrode materials for solar cell application. A single unit photovoltaic electrolyzer was constructed by combining a-Si:H solar cells with an electrolysis cell. Several different configurations ((PIN), (PIN)^2 , and (PIN)^3) of the solar cells were tested. Both electric power and chemical energy (H_2) could be simultaneously drawn from the electrolyzer.
Heat storage in alloy transformations
NASA Technical Reports Server (NTRS)
Birchenall, C. E.
The feasibility of using metal alloys as thermal energy storage media was investigated. The elements selected as candidate media were limited to aluminum, copper, magnesium, silicon, zinc, calcium, and phosphorus on the basis of low cost and latent heat of transformation. Several new eutectic alloys and ternary intermetallic phases were determined. A new method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation. The method and apparatus are discussed and the experimental results are presented for aluminum and two aluminum-eutectic alloys. Candidate materials were evaluated to determine suitable materials for containment of the metal alloys. Graphite was used to contain the alloys during the volume change measurements. Silicon carbide was identified as a promising containment material and surface-coated iron alloys were also evaluated. System considerations that are pertinent if alloy eutectics are used as thermal energy storage media are discussed. Potential applications to solar receivers and industrial furnaces are illustrated schematically.
Heat storage in alloy transformations
NASA Astrophysics Data System (ADS)
Birchenall, C. E.
The feasibility of using metal alloys as thermal energy storage media was investigated. The elements selected as candidate media were limited to aluminum, copper, magnesium, silicon, zinc, calcium, and phosphorus on the basis of low cost and latent heat of transformation. Several new eutectic alloys and ternary intermetallic phases were determined. A new method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation. The method and apparatus are discussed and the experimental results are presented for aluminum and two aluminum-eutectic alloys. Candidate materials were evaluated to determine suitable materials for containment of the metal alloys. Graphite was used to contain the alloys during the volume change measurements. Silicon carbide was identified as a promising containment material and surface-coated iron alloys were also evaluated. System considerations that are pertinent if alloy eutectics are used as thermal energy storage media are discussed. Potential applications to solar receivers and industrial furnaces are illustrated schematically.
Fatigue performance and cyto-toxicity of low rigidity titanium alloy, Ti-29Nb-13Ta-4.6Zr.
Niinomi, Mitsuo
A beta type titanium alloy, Ti-29Nb-13Ta-4.6Zr, was newly designed and developed for biomedical applications. The new alloy contains non-toxic elements such as Nb, Ta, and Zr. In the present study, phases that appeared in the new alloy through various aging treatments were characterized by hardness tests and microstructural observations in order to identify the phase transformation. Fatigue properties of the new alloy were investigated. Young's modulus and cyto-toxicity of the new alloy were also evaluated. Precipitated phases distribute homogeneously over the whole specimen, and they are alpha phase, a small amount of omega phase, and beta phase when the new alloys are subjected to aging treatment at 673K for 259.2ks after solution treatment at 1063K for 3.6ks. The fatigue strength of the new alloy subjected to aging at 673K for 259.2ks after solution treatment at 1063K for 3.6ks is much better than when subjected to other aging treatments. In this case, the fatigue limit is around 700MPa. Young's modulus of the new alloy is much smaller than that of Ti-6Al-4V ELI. The cyto-toxicity of the new alloy is equivalent to that of pure Ti. Therefore, it is proposed that the new alloy, Ti-29Nb-13Ta-4.6Zr, will be of considerable use in biomedical applications. PMID:12711513
The effect of copper, chromium, and zirconium on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloys
NASA Technical Reports Server (NTRS)
Wagner, John A.; Shenoy, R. N.
The present study evaluates the effect of the systematic variation of copper, chromium, and zirconium contents on the microstructure and mechanical properties of a 7000-type aluminum alloy. Fracture toughness and tensile properties are evaluated for each alloy in both the peak aging, T8, and the overaging, T73, conditions. Results show that dimpled rupture essentially characterize the fracture process in these alloys. In the T8 condition, a significant loss of toughness is observed for alloys containing 2.5 pct Cu due to the increase in the quantity of Al-Cu-Mg-rich S-phase particles. An examination of T8 alloys at constant Cu levels shows that Zr-bearing alloys exhibit higher strength and toughness than the Cr-bearing alloys. In the T73 condition, Cr-bearing alloys are inherently tougher than Zr-bearing alloys. A void nucleation and growth mechanism accounts for the loss of toughness in these alloys with increasing copper content.
Nucleation of shear bands in amorphous alloys.
Perepezko, John H; Imhoff, Seth D; Chen, Ming-Wei; Wang, Jun-Qiang; Gonzalez, Sergio
The initiation and propagation of shear bands is an important mode of localized inhomogeneous deformation that occurs in a wide range of materials. In metallic glasses, shear band development is considered to center on a structural heterogeneity, a shear transformation zone that evolves into a rapidly propagating shear band under a shear stress above a threshold. Deformation by shear bands is a nucleation-controlled process, but the initiation process is unclear. Here we use nanoindentation to probe shear band nucleation during loading by measuring the first pop-in event in the load-depth curve which is demonstrated to be associated with shear band formation. We analyze a large number of independent measurements on four different bulk metallic glasses (BMGs) alloys and reveal the operation of a bimodal distribution of the first pop-in loads that are associated with different shear band nucleation sites that operate at different stress levels below the glass transition temperature, Tg. The nucleation kinetics, the nucleation barriers, and the density for each site type have been determined. The discovery of multiple shear band nucleation sites challenges the current view of nucleation at a single type of site and offers opportunities for controlling the ductility of BMG alloys. PMID:24594599
Martin, P.L.; Williams, J.C.
This paper discusses some of the problems associated with attempts to use first principles in alloy design. We briefly summarize the role of microstructure on the properties of high temperature alloys and illustrate some of the microstructural features of conventional superalloys. We also describe how theory and experiment are converging toward some predictive capabilities for relating microstructure and composition using Ni-Al-Mo-X alloys as an example. Finally, this paper suggests that progress is being made in combining the results of condensed matter theory and experimental research.
Modeling dissolution in aluminum alloys
NASA Astrophysics Data System (ADS)
Durbin, Tracie Lee
Aluminum and its alloys are used in many aspects of modern life, from soda cans and household foil to the automobiles and aircraft in which we travel. Aluminum alloy systems are characterized by good workability that enables these alloys to be economically rolled, extruded, or forged into useful shapes. Mechanical properties such as strength are altered significantly with cold working, annealing, precipitation-hardening, and/or heat-treatments. Heat-treatable aluminum alloys contain one or more soluble constituents such as copper, lithium, magnesium, silicon and zinc that individually, or with other elements, can form phases that strengthen the alloy. Microstructure development is highly dependent on all of the processing steps the alloy experiences. Ultimately, the macroscopic properties of the alloy depend strongly on the microstructure. Therefore, a quantitative understanding of the microstructural changes that occur during thermal and mechanical processing is fundamental to predicting alloy properties. In particular, the microstructure becomes more homogeneous and secondary phases are dissolved during thermal treatments. Robust physical models for the kinetics of particle dissolution are necessary to predict the most efficient thermal treatment. A general dissolution model for multi-component alloys has been developed using the front-tracking method to study the dissolution of precipitates in an aluminum alloy matrix. This technique is applicable to any alloy system, provided thermodynamic and diffusion data are available. Treatment of the precipitate interface is explored using two techniques: the immersed-boundary method and a new technique, termed here the "sharp-interface" method. The sharp-interface technique is based on a variation of the ghost fluid method and eliminates the need for corrective source terms in the characteristic equations. In addition, the sharp-interface method is shown to predict the dissolution behavior of precipitates in aluminum alloys when compared with published experimental results. The influence of inter-particle spacing is examined and shown to have a significant effect on dissolution kinetics. Finally, the impact of multiple particles of various sizes interacting in an aluminum matrix is investigated. It is shown that smaller particles dissolve faster, as expected, but influence the dissolution of larger particles through soft-impingement, even after the smaller particles have disappeared.
Microstructural characterization of low and high carbon CoCrMo alloy nanoparticles produced by mechanical milling
NASA Astrophysics Data System (ADS)
Simoes, T. A.; Goode, A. E.; Porter, A. E.; Ryan, M. P.; Milne, S. J.; Brown, A. P.; Brydson, R. M. D.
CoCrMo alloys are utilised as the main material in hip prostheses. The link between this type of hip prosthesis and chronic pain remains unclear. Studies suggest that wear debris generated in-vivo may be related to post-operative complications such as inflammation. These alloys can contain different amounts of carbon, which improves the mechanical properties of the alloy. However, the formation of carbides could become sites that initiate corrosion, releasing ions and/or particles into the human body. This study analysed the mechanical milling of alloys containing both high and low carbon levels in relevant biological media, as an alternative route to generate wear debris. The results show that low carbon alloys produce significantly more nanoparticles than high carbon alloys. During the milling process, strain induces an fcc to hcp phase transformation. Evidence for cobalt and molybdenum dissolution in the presence of serum was confirmed by ICP-MS and TEM EDX techniques.
Microstructure development and helium behavior in nickel and vanadium base alloys
NASA Astrophysics Data System (ADS)
Kalashnikov, A. N.; Chernov, I. I.; Kalin, B. A.; Binyukova, S. Yu
Transmission electron microscopy and thermal helium desorption spectrometry (TDS) have been used to investigate the influence of alloying elements on helium behavior and bubble microstructure evolution in FCC (Ni+1 7.5 wt%Al) and BCC (V+10 40 wt%Ti) metals. The samples were irradiated by 40-keV He + ions at room temperature up to a fluence of 5æ10 20 m -2. Post-irradiation annealings were performed at 1023 K (Ni-Al) and 1075 K (V-Ti) for 1 h. It was shown that alloying elements reduced the bubble size ( d₤b) and increased their density ( ?b) in both types of alloys. In the Ni-Al alloys the TDS peaks are displaced to higher temperatures with increasing Al concentration in contrast to V-Ti alloys where the TDS peaks are displaced to lower temperatures with increasing Ti content. However in both systems of alloys the effective activation energy for helium desorption grows with alloying element concentration. The results are discussed in terms of alloying element influence on the mechanisms of bubble growth and migration.
Novel Ti-base superelastic alloys with large recovery strain and excellent biocompatibility.
Fu, Jie; Yamamoto, Akiko; Kim, Hee Young; Hosoda, Hideki; Miyazaki, Shuichi
In this study, a new Ti-Zr-Nb-Sn alloy system was developed as Ni-free biomedical superelastic alloys with a large recovery strain and excellent biocompatibility. Ti-18Zr-(9-16)Nb-(0-4)Sn alloys were prepared by an Ar arc melting method and the effect of composition on the crystal structure and superelastic properties was investigated. A large superelastic recovery strain of 6.0% was observed in Ti-18Zr-12.5Nb-2Sn, Ti-18Zr-11Nb-3Sn, and Ti-18Zr-9.5Nb-4Sn alloys subjected to cold-rolling and solution treatment. XRD results showed that the large recovery strain of Sn-added alloys is due to a combination effect of a large transformation strain and a strong recrystallization texture. The Ti-18Zr-11Nb-3Sn alloy exhibited excellent cyclic stability with an extremely narrow stress hysteresis about 20MPa. Cytocompatibility was also examined using three types of cell lines, murine fibroblast L929, human osteosarcoma SaOS-2, and human umbilical vein endothelial cell HUVEC and the results showed that the Ti-18Zr-11Nb-3Sn alloy exhibited larger cell covering ratios when compared with those of the Ti-50.5Ni alloy for all kinds of cells. PMID:25676584
Dynamic compressive behavior of Pr-Nd alloy at high strain rates and temperatures
NASA Astrophysics Data System (ADS)
Wang, Huanran; Cai, Canyuan; Chen, Danian; Ma, Dongfang
Based on compressive tests, static on 810 material test system and dynamic on the first compressive loading in split Hopkinson pressure bar (SHPB) tests for Pr-Nd alloy cylinder specimens at high strain rates and temperatures, this study determined a J-C type [G. R. Johnson and W. H. Cook, in Proceedings of Seventh International Symposium on Ballistics (The Hague, The Netherlands, 1983), pp. 541-547] compressive constitutive equation of Pr-Nd alloy. It was recorded by a high speed camera that the Pr-Nd alloy cylinder specimens fractured during the first compressive loading in SHPB tests at high strain rates and temperatures. From high speed camera images, the critical strains of the dynamic shearing instability for Pr-Nd alloy in SHPB tests were determined, which were consistent with that estimated by using Batra and Wei's dynamic shearing instability criterion [R. C. Batra and Z. G. Wei, Int. J. Impact Eng. 34, 448 (2007)] and the determined compressive constitutive equation of Pr-Nd alloy. The transmitted and reflected pulses of SHPB tests for Pr-Nd alloy cylinder specimens computed with the determined compressive constitutive equation of Pr-Nd alloy and Batra and Wei's dynamic shearing instability criterion could be consistent with the experimental data. The fractured Pr-Nd alloy cylinder specimens of compressive tests were investigated by using 3D supper depth digital microscope and scanning electron microscope.
Development of nano-structure CuZr alloys by the mechanical alloying process
M. Azimi; G. H. Akbari
CuZr alloys have many applications in electrical and welding industries for their high strength and high electrical and thermal conductivities. These alloys are among age-hardenable alloys with capability of having nano-structure with high solute contents obtainable by the mechanical alloying process. In the present work, CuZr alloys have been developed by the mechanical alloying process. Pure copper powders with different
NASA Astrophysics Data System (ADS)
Reedlunn, Benjamin; Shaw, John A.
Conventional structural cables (or wire ropes) are composed of steel wires helically wound into strands, which, in turn, are wound around a core. Cables made from shape memory alloy (SMA) wires are a new structural element with promising properties for a broad range of new applications. Among the many potential advantages of this form are increased bending flexibility for spooling/packaging, better fatigue performance, energy absorption and damping, reduced thermal lag, redundancy, and signicant design flexibility. Currently there are no known studies of SMA cables in the literature, so exploratory thermo-mechanical experiments were performed on two commercially available cable designs as part of an ongoing research program to systematically characterize their thermomechanical behavior and demonstrate their potential utility as adaptive or resilient tension elements.
Metallic alloy stability studies
NASA Technical Reports Server (NTRS)
Firth, G. C.
The dimensional stability of candidate cryogenic wind tunnel model materials was investigated. Flat specimens of candidate materials were fabricated and cryo-cycled to assess relative dimensional stability. Existing 2-dimensional airfoil models as well as models in various stages of manufacture were also cryo-cycled. The tests indicate that 18 Ni maraging steel offers the greatest dimensional stability and that PH 13-8 Mo stainless steel is the most stable of the stainless steels. Dimensional stability is influenced primarily by metallurgical transformations (austenitic to martensitic) and manufacturing-induced stresses. These factors can be minimized by utilization of stable alloys, refinement of existing manufacturing techniques, and incorporation of new manufacturing technologies.
Alloyed steel wastes utilization
Sokol, I.V. [Russian Academy of Sciences, Khabarovsk (Russian Federation). Inst. of Materials
Alloyed steel chips and swarf formed during metal processing are looked upon as additional raw materials in metallurgical production. This paper presents some new methods for steel waste chips and swarf cleaning. One of them is swarf and steel chips cleaning in tetrachloroethylene with ultrasonic assistance and solvent regeneration. Thermal cleaning of waste chips and swarf provides off gas products utilization. The catalyst influence of the metal surface on the thermal decomposition of liquid hydrocarbons during the cleaning process has been studied. It has been determined that the efficiency of this metal waste cleaning technique depends on the storage time of the swarf. The waste chips and swarf cleaning procedures have been proven to be economically advantageous and environmentally appropriate.
A theoretical investigation of the band alignment of type-I direct band gap dilute nitride phosphide alloy of GaNxAsyP1-x-y/GaP quantum wells on GaP substrates
NASA Astrophysics Data System (ADS)
ø, L. Énsal; B, G—n■l; M, Temiz
The GaP-based dilute nitride direct band gap material Ga(NAsP) is gaining importance due to the monolithic integration of laser diodes on Si microprocessors. The major advantage of this newly proposed laser material system is the small lattice mismatch between GaP and Si. However, the large threshold current density of these promising laser diodes on Si substrates shows that the carrier leakage plays an important role in Ga(NAsP)/GaP QW lasers. Therefore, it is necessary to investigate the band alignment in this laser material system. In this paper, we present a theoretical investigation to optimize the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs on GaP substrates. We examine the effect of nitrogen (N) concentration on the band offset ratios and band offset energies. We also provide a comparison of the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs with that of the GaNxAsyP1-x-y/AlzGa1-zP QWs on GaP substrates. Our theoretical calculations indicate that the incorporations of N into the well and Al into the barrier improve the band alignment compared to that of the GaAsP/GaP QW laser heterostructures.
Oxide Film Aging on Alloy 22 in Halide Containing Solutions
Rodriguez, Martin A.; Carranza, Ricardo M. [Dept. Materiales, Comision Nacional de Energia Atomica, Av. Gral. Paz 1499, Villa Maipu, 1650 (Argentina); Rebak, Raul B. [Lawrence Livermore National Laboratory, 7000 East Ave, L-631, Livermore, CA, 94550-9698 (United States)
Passive and corrosion behaviors of Alloy 22 in chloride and fluoride containing solutions, changing the heat treatment of the alloy, the halide concentration and the pH of the solutions at 90 deg. C, was investigated. The study was implemented using electrochemical techniques, which included open circuit potential monitoring over time, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements carried out at open circuit and at passivity potentials. Corrosion rates obtained by EIS measurements after 24 h immersion in naturally aerated solutions were below 0.5 {mu}m/year. The corrosion rates were practically independent of solution pH, alloy heat treatment and halide ion nature and concentration. EIS low frequency resistance values increased with applied potential in the passive domain and with polarization time in pH 6 - 1 M NaCl at 90 deg. C. This effect was attributed to an increase in the oxide film thickness and oxide film aging. High frequency capacitance measurements indicated that passive oxide on Alloy 22 presented a double n-type/p-type semiconductor behavior in the passive potential range. (authors)
Erosion of iron-chromium alloys by glass particles
NASA Technical Reports Server (NTRS)
Salik, J.; Buckley, D. H.
The material loss upon erosion was measured for several iron-chromium alloys. Two types of erodent material were used: spherical glass beads and sharp particles of crushed glass. For erosion with glass beads the erosion resistance (defined as the reciprocal of material loss rate) was linearly dependent on hardness. This is in accordance with the erosion behavior of pure metals, but contrary to the erosion behavior of alloys of constant composition that were subjected to different heat treatments. For erosion with crushed glass, however, no correlation existed between hardness and erosion resistance. Instead, the erosion resistance depended on alloy composition rather than on hardness and increased with the chromium content of the alloy. The difference in erosion behavior for the two types of erodent particles suggested that two different material removal mechanisms were involved. This was confirmed by SEM micrographs of the eroded surfaces, which showed that for erosion with glass beads the mechanism of material removal was deformation-induced flaking of surface layers, or peening, whereas for erosion with crushed glass it was cutting or chopping.
Design of Stable Nanocrystalline Alloys
Chookajorn, Tongjai
Nanostructured metals are generally unstable; their grains grow rapidly even at low temperatures, rendering them difficult to process and often unsuitable for usage. Alloying has been found to improve stability, but only ...
Microfissuring in Alloys During Welding
NASA Technical Reports Server (NTRS)
Evaluating cause of intergranular cracking (microfissuring) in high-temperature alloys during welding done by measuring number of microcracks as function of temperature and plastic strain. Two mechanisms of microfissuring in heat-affected zones suggested.
Phase stability of laves intermetallics in stainless steel-zirconium alloys.
Abraham, D. P.
Phase transformations occurring in a stainless steel-15 wt% zirconium (SS-15Zr) alloy were studied by in situ neutron diffraction. Neutron diffraction patterns as a function of time were obtained on alloys that were held at various elevated temperatures (1084-1275 C). As-cast SS-15Zr alloys contain ferrite, austenite, ZrFe{sub 2}-type Laves polytypes C36 and C15, and small amounts of a Fe{sub 23}Zr{sub 6}-type intermetallic. Annealing at high temperatures resulted in an increase of the Fe{sub 23}Zr{sub 6}, intermetallic content. The C15 Laves polytype is the equilibrium phase for T {le} 1230 C; C36 is the stable polytype at higher temperatures ({approximately}1275 C). Phase changes were slow for temperatures <1100 C.These findings have important implications for use of the SS-15Zr alloy as a nuclear waste form.
A new amorphous alloy deposit with high corrosion resistance
Yao, S.; Zhao, S. Guo, H. [Tianjin Univ. (China). Dept. of Applied Chemistry; Kowaka, M.
The corrosion behavior of electrodeposited Ni-P, Ni-W, Ni-W-P, and Fe-W alloys was tested, and the effects of the additive elements W and P on the corrosion resistance of amorphous deposits were studied. Corrosion rates of the alloys were compared to those of stainless steel. Results showed the W content in electrodeposited Ni-W-P amorphous alloy was as high as 55.2 wt%. The hardness (Vickers [HV]) of the alloy was from 700 HV to 800 HV and 1,300 HV to 1,400 HV after heat treatment at 550 C. The hardness, wear resistance, and corrosion resistance of the deposit were shown to be superior to those of Ni-P amorphous deposit. The corrosion potential was moved to noble by adding P to the deposit, and the passive current density dropped remarkably with the addition of W. Amorphous Ni-W, Ni-W-P, and Fe-W alloy deposits showed high corrosion resistance in acid solutions. Immersion tests in 1 mol/L hydrochloric acid solution t 30 C showed the corrosion rate of type 304 stainless steel was 10 times that of Ni-W-P amorphous deposit, 40 times that of Ni-W amorphous deposit, and 15 to 20 times that of Fe-W amorphous deposit. In 0.5 mol/L sulfuric acid solution at 30 C, the corrosion resistance of the amorphous deposit was poorer than that of type 304 SS, but at 60 C, the corrosion rate of type 304 SS increased dramatically, to 180 times that of Fe-W amorphous deposit and 100 to 700 times that of the Ni-based amorphous deposit.
Electron Transport in Ga-Rich InxGa1-xN Alloys
A. Yildiz; S. Lisesivdin B; S. Acar; M. Kasap; M. Bosi
Resistivity and Hall effect measurements on n-type undoped Ga-rich InxGa1-xN (0.06<=x<=0.135) alloys grown by metal-organic vapour phase epitaxy (MOVPE) technique are carried out as a function of temperature (15-350 K). Within the experimental error, the electron concentration in InxGa1-xN alloys is independent of temperature while the resistivity decreases as the temperature increases. Therefore, InxGa1-xN (0.06<=x<=0.135) alloys are considered in the
Glassy solidification criterion of Zr50Cu40Al10 alloy
NASA Astrophysics Data System (ADS)
Yokoyama, Yoshihiko; Fredriksson, Hasse; Yasuda, Hideyuki; Nishijima, Masahiko; Inoue, Akihisa
We examined the solidification morphology and structure of arc-melted Zr50Cu40Al10 glass-forming alloys. Since the crystal growth rate is much lower than the velocity of isothermal plane of glass transition temperature (Tg), arc-melted Zr50Cu40Al10 alloy sometimes reveals glassy phase at finally solidified region (top-side) after crystal growth (bottom side). Vitrification in front of the crystalline solidification interface of arc-melted Zr50Cu40Al10 alloy Zr can be seen when the crystal phase is an Al-supersaturated B2-type ZrCu phase.
Corrosion analysis of AlZnInMgTiMn sacrificial anode alloy
Jingling Ma; Jiuba Wen
The corrosion behaviour of Al5Zn0.02In1Mg0.05Ti0.5Mn (wt%) alloy was investigated by SEM, EDX and TEM. The results show that there exist different corrosion types of the alloy in 3.5% NaCl solution with immersion time. At the initial stage of immersion, pitting predominate the corrosion around precipitates. The major precipitates of the alloy are MgZn2 and Al6Mn particles. The corrosion potential of
Electrochemical test for predicting microbiologically influenced corrosion of aluminum and AA 7005 alloy
Ayllon, E.S. (Ceicor-Citefa/Conicet, Buenos Aires (Argentina)); Rosales, B.M. (Consejo Nacional de Investigaciones Cientificas y Tecnicas, Buenos Aires (Argentina))
The susceptibility of pure aluminum (Al) and Aluminum Association (AA) 7005 alloy (UNS A97005) to pitting by microbiologically influenced corrosion (MIC) in an integral jet fuel tank was determined through polarization measurements. Usually, the most corrosive reported species is the fungus Hormonconis resinae. The effect of its proliferation on pure Al and AA 7005-T6 alloy was studied through anodic and cathodic potentiodynamic polarization. The type and relative amount of corrosion damage to the metal were determined. Morphology of the attack was analyzed by scanning electron microscopy (SEM). Distribution of the alloying elements was determined using energy dispersive x-ray analysis (EDXA).
Wright, Jill; Carroll, Laura; Wright, Richard
The Very High Temperature Reactor (VHTR) Intermediate Heat Exchanger (IHX) may be joined to piping or other components by welding. Creep-fatigue deformation is expected to be a predominant failure mechanism of the IHX1 and thus weldments used in its fabrication will experience varying cyclic stresses interrupted by periods of elevated temperature deformation. These periods of elevated temperature deformation are greatly influenced by a materials creep behavior. The nickel-base solid solution strengthened alloy, Alloy 617, is the primary material candidate for a VHTR-type IHX, and it is expected that Alloy 617 filler metal will be used for welds. Alloy 617 is not yet been integrated into Section III of the Boiler and Pressure Vessel Code, however, nuclear component design with Alloy 617 requires ASME (American Society of Mechanical Engineers) Code qualification. The Code will dictate design for welded construction through significant performance reductions. Despite the similar compositions of the weldment and base material, significantly different microstructures and mechanical properties are inevitable. Experience of nickel alloy welds in structural applications suggests that most high temperature failures occur at the weldments or in the heat-affected zone. Reliably guarding against this type of failure is particularly challenging at high temperatures due to the variations in the inelastic response of the constituent parts of the weldment (i.e., weld metal, heat-affected zone, and base metal) [ref]. This work focuses on the creep-fatigue behavior of nickel-based weldments, a need noted during the development of the draft Alloy 617 ASME Code Case. An understanding of Alloy 617 weldments when subjected to this important deformation mode will enable determination of the appropriate design parameters associated with their use. Specifically, the three main areas emphasized are the performance reduction due to a weld discontinuity in terms of the reduced number of the cycles to failure and whether a saturation in reduced cycle life with increased hold times is observed, the microstructural stability over long cycle times, and finally, the location of the generated weldment data on a creep-fatigue damage diagram (D-diagram).
Effects of Ta content on the phase stability and elastic properties of ? Ti-Ta alloys from first-principles calculations
NASA Astrophysics Data System (ADS)
Wu, C. Y.; Xin, Y. H.; Wang, X. F.; Lin, J. G.
The effects of Ta content on the phase stability, the elastic property and the electronic structure of ? type Ti-Ta alloys were studied from first-principles calculations based on the density functional theory. It is found that the phase stability, tetragonal shear constant C', bulk modulus, elastic modulus and shear modulus of ? type Ti-Ta alloys increase with the Ta content increasing monotonously. The lowest elastic modulus of the alloys is realized when the valence electron number ( e/ a) is around 4.25. Moreover, the phase stability of the alloys was discussed based on the calculated density of state (DOS).
Casting Characteristics of Aluminum Die Casting Alloys
Makhlouf M. Makhlouf; Diran Apelian
The research program investigates the casting characteristics of selected aluminum die casting alloys. Specifically, the alloys' tendencies towards die soldering and sludge formation, and the alloys' fluidity and machinability are evaluated. It was found that: When the Fe and Mn contents of the alloy are low; caution has to be taken against possible die soldering. When the alloy has a high sludge factor, particularly a high level of Fe, measures must be taken to prevent the formation of large hardspots. For this kind of alloy, the Fe content should be kept at its lowest allowable level and the Mn content should be at its highest possible level. If there are problems in die filling, measures other than changing the alloy chemistry need to be considered first. In terms of alloy chemistry, the elements that form high temperature compounds must be kept at their lowest allowable levels. The alloys should not have machining problems when appropriate machining techniques and machining parameters are used.
The mechanism of mechanical alloying
J. S. Benjamin; T. E. Volin
The mechanical alloying process is a new method for producing composite metal powders with controlled microstructures. It\\u000a is unique in that it is an entirely solid state process, permitting dispersion of insoluble phases such as refractory oxides\\u000a and addition of reactive alloying elements such as aluminum and titanium. Interdispersion of the ingredients occurs by repeated\\u000a cold welding and fracture of
Zirconium alloys in nuclear technology
R. Krishnan; M. K. Asundi
This paper describes the historical development of zirconium and its alloys as structural materials for nuclear reactors.\\u000a The various problems encountered in the early stages of the development of zircaloys and their performance in reactors operating\\u000a presently are described in detail. The development of Zr-2.5 % Nb alloys for pressure tube applications is discussed. The\\u000a paper concludes with a detailed
Sintered titanium carbide hard alloys
G. V. Samsonov; N. N. Sergeev; G. T. Dzodziev; V. K. Vitryanyuk; L. V. Latyaeva
1.A study was made of the preparation of titanium carbide hard alloys with a nickel binder. It is shown that satisfactory mechanical properties (bend strength 107115 kg\\/mm2, hardness 9090.5 HRA) are exhibited by 80% TiC-20% Ni alloys produced from fine-milled mixtures by sintering in a vacuum of 5ñ10-3 mm Hg at a temperature of 1300C and an isothermal holding time
Alloy dissolution in argon stirred steel
NASA Astrophysics Data System (ADS)
Webber, Darryl Scott
Alloying is required for the production of all steel products from small castings to large beams. Addition of large quantities of bulk alloys can result in alloy segregation and inconsistent alloy recovery. The objective of this research was to better understand alloy dissolution in liquid steel especially as it relates to Missouri S&Ts' patented continuous steelmaking process. A 45-kilogram capacity ladle with a single porous plug was used to evaluate the effect of four experimental factors on alloy dissolution: alloy species, alloy size or form, argon flow rate, and furnace tap temperature. Four alloys were tested experimentally including Class I low carbon ferromanganese, nickel and tin (as a surrogate for low melting alloys) and Class II ferroniobium. The alloys ranged in size and form from granular to 30 mm diameter lumps. Experimental results were evaluated using a theoretically based numerical model for the steel shell period, alloy mixing (Class I) and alloy dissolution (Class II). A CFD model of the experimental ladle was used to understand steel motion in the ladle and to provide steel velocity magnitudes for the numerical steel shell model. Experiments and modeling confirmed that smaller sized alloys have shorter steel shell periods and homogenize faster than larger particles. Increasing the argon flow rate shortened mixing times and reduced the delay between alloy addition and the first appearance of alloy in the melt. In addition, for every five degree increase in steel bath temperature the steel shell period was shortened by approximately four percent. Class II ferroniobium alloy dissolution was an order of magnitude slower than Class I alloy mixing.
Chemical analysis of uranium-niobium alloys by wavelength dispersive spectroscopy at the sigma complex
Papin, Pallas A.
Uranium-niobium alloys play an important role in the nation's nuclear stockpile. It is possible to chemically quantify this alloy at a micron scale by using a technique know as wavelength dispersive spectroscopy. This report documents how this technique was used and how it is possible to reproduce measurements of this type. Discussion regarding the accuracy and precision of the measurements, the development of standards, and the comparison of different ways to model the matrices are all presented.
High-Thermoelectric Performance of Nanostructured Bismuth Antimony Telluride Bulk Alloys
Bed Poudel; Qing Hao; Yi Ma; Yucheng Lan; Austin Minnich; Xiao Yan; Dezhi Wang; Andrew Muto; Daryoosh Vashaee; Xiaoyuan Chen; M. S. Dresselhaus; Mildred S. Dresselhaus; Gang Chen; Zhifeng Ren
The dimensionless thermoelectric figure of merit (ZT) in bismuth antimony telluride (BiSbTe) bulk alloys has remained around 1 for more than 50 years. We show that a peak ZT of 1.4 at 100¯C can be achieved in a p-type nanocrystalline BiSbTe bulk alloy. These nanocrystalline bulk materials were made by hot pressing nanopowders that were ball-milled from crystalline ingots under
Forging of liquid and partially solid Sn15 Pct Pb and aluminum alloys
S. D. E. Ramati; G. J. Abbaschian; D. G. Backman; R. Mehrabian
The possibility of producing simple shaped components from a liquid and partially solid initial charge material in a forging\\u000a type operation was investigated. Ingots of Sn-15 Pct Pb alloy and aluminum alloys 6061 and A356 were heated to temperatures\\u000a above the liquidus and in the liquid-solid range. The partially solidified charge materials were previously made in a continuous\\u000a slurry producer.
X-ray diffraction study of ?-stabilized plutonium alloys under pressure
Ph Faure; C. Genestier
Previous extensive studies of the ????-phase transformation induced by temperature and\\/or by pressure in ?-stabilized plutonium alloys indicate strong dependence on parameters such as solute type, solute distribution, chemical impurities, kinetics, thermodynamic path .The present paper reports results obtained on two Pu2.3at.%Ga binary alloys differing by solute homogenization treatment and studied under pressure by in situ by X-ray diffraction in diamond
Forming characteristics of austenitic stainless steel sheet alloys under warm hydroforming conditions
Muammer KoÓ; Sasawat Mahabunphachai; Eren Billur
Stainless steel sheet alloys have been increasingly used in heating, ventilating, and air conditioning; appliance; sanitary\\u000a and medical devices; as well as several structural and transportation applications, due to their high strength-to-weight ratio,\\u000a corrosion resistance, biomedical compatibility, and esthetic appearance. Among various stainless steel alloys, austenitic\\u000a stainless steels are the most commonly used type. Due to the forming limitations into
Sensitization Behavior of Alloy 800H as Characterized by the Electrochemical Potentiokinetic Reactivation (EPR) Technique
G. L. Edgemon; D. F. Wilson; G. E. C. Bell; M. L. Marek
The need for a nondestructive test to evaluate levels of sensitization in alloy 800H (UNS N08810) led to modification of the electrochemical potentiokinetic reactivation (EPR) test technique previously developed for type 304 (UNS S30400) stainless steel (SS). Results of testing on alloy 800H specimens aged at temperatures between 450 C and 700 C for 0 h to 5,000 h indicated
Magnetic Moments and Unpaired Spin Densities in the Fe-Rh Alloys
G. Shirane; R. Nathans; C. W. Chen
The distribution of magnetic moments in the Fe-Rh system has been investigated by the neutron diffraction technique in the composition range between 35 and 50 at.%Rh. These alloys have chemical order of CsCl type; the body-corner positions are occupied by FeI atoms and the body centers by Rh and FeII atoms. The magnetic moments in ferromagnetic alloys containing 35, 40,
Studies on a combined reactive plasma sprayed\\/arc deposited duplex coating for titanium alloys
F. Casadei; R. Pileggi; R. Valle; A. Matthews
A new type of duplex layered coating especially developed for titanium alloys is described in this paper. This coating comprises a combination of a graded thick TixNy-based coating and a thin TiN top coat. The graded coating was obtained by reactive plasma spray (RPS) deposition of a Ti4,5Al3V2Mo2Fe powder onto a Ti6Al4V alloy substrate under an N2 atmosphere. Such a
Effect of hydrogen on the phasestructure transformations in ZrCrNi alloy
I. I. Bulyk; Yu. B. Basaraba; A. M. Trostianchyn
The effect of hydrogenHydrogenation, Disproportionation, Desorption, Recombination (HDDR) processfor the ZrCrNi alloy on its phasestructure transformations was investigated by means of differential thermal analysis (DTA) and X-ray diffraction (XRD) at the initial hydrogen pressure ?5.0MPa and the temperature range from room temperature to 970¯C. The hexagonal C14 (MgZn2) type Laves phase is the main phase of the alloy. Besides the
The abrasive corrosion behavior of plasma-nitrided alloy steels in chloride environments
C. K. Lee; H. C. Shih
Both corrosion and abrasive corrosion behavior of plama-nitrided type 304 and 410 stainless steels and 4140 low alloy steel were investigated in 3% NaCl solution (pH = 6.8) by electrochemical corrosion measurements. Surface morphology and alloying elements after corrosion and abrasion corrosion tests were examined by scanning electron microscopy and energy dispersive analysis of X-rays. The results indicated that the
Strip casting of A5182 alloy using a melt drag twin-roll caster
T Haga; T Nishiyama; S Suzuki
The melt drag twin-roll caster (MDTRC) was devised for the high-speed strip casting of mushy solidification type aluminium alloys. The MDTRC enables A5182 aluminium alloy to be cast at a speed of up to 60m\\/min. The MDTRC combines a low separating force, semi-solid forming at the upper side of the strip and the use of copper rolls and requires no
Elastic and microplastic properties of AlSi\\/Ge alloys obtained from levitated melts
S. P. Nikanorov; Yu. A. Burenkov; M. P. Volkov; V. N. Gurin; L. I. Derkachenko; B. K. Kardashev; L. L. Regel
Structure, density, Young's modulus temperature dependencies as well as Young's modulus and ultrasound damping as a function of vibration strain were studied for AlSi and AlGe hypo- and hyper-alloys. Samples were obtained by fast cooling of a levitated melt. Aging of AlSi alloy and recovery of AlGe properties were observed. These phenomena were explained by a transformation of bond type
Choosing An Alloy For Automotive Stirling Engines
NASA Technical Reports Server (NTRS)
Stephens, Joseph R.
Report describes study of chemical compositions and microstructures of alloys for automotive Stirling engines. Engines offer advantages of high efficiency, low pollution, low noise, and ability to use variety of fuels. Twenty alloys evaluated for resistance to corrosion permeation by hydrogen, and high temperature. Iron-based alloys considered primary candidates because of low cost. Nickel-based alloys second choice in case suitable iron-based alloy could not be found. Cobalt-based alloy included for comparison but not candidate, because it is expensive strategic material.
Liu, C.T.
This paper provides a brief review of the recent progress in research and development of Ni{sub 3}Al and its alloys. Emphasis has been placed on understanding low ductility and brittle fracture of Ni{sub 3}Al alloys at ambient and elevated temperatures. Recent studies have resulted in identifying both intrinsic and extrinsic factors governing the fracture behavior of Ni{sub 3}Al alloys. Parallel efforts on alloy design using physical metallurgy principles have led to properties for structural use. Industrial interest in these alloys is high, and examples of industrial involvement in processing and utilization of these alloys are briefly mentioned.
Zinc Alloys for the Fabrication of Semiconductor Devices
NASA Technical Reports Server (NTRS)
Ryu, Yungryel; Lee, Tae S.
ZnBeO and ZnCdSeO alloys have been disclosed as materials for the improvement in performance, function, and capability of semiconductor devices. The alloys can be used alone or in combination to form active photonic layers that can emit over a range of wavelength values. Materials with both larger and smaller band gaps would allow for the fabrication of semiconductor heterostructures that have increased function in the ultraviolet (UV) region of the spectrum. ZnO is a wide band-gap material possessing good radiation-resistance properties. It is desirable to modify the energy band gap of ZnO to smaller values than that for ZnO and to larger values than that for ZnO for use in semiconductor devices. A material with band gap energy larger than that of ZnO would allow for the emission at shorter wavelengths for LED (light emitting diode) and LD (laser diode) devices, while a material with band gap energy smaller than that of ZnO would allow for emission at longer wavelengths for LED and LD devices. The amount of Be in the ZnBeO alloy system can be varied to increase the energy bandgap of ZnO to values larger than that of ZnO. The amount of Cd and Se in the ZnCdSeO alloy system can be varied to decrease the energy band gap of ZnO to values smaller than that of ZnO. Each alloy formed can be undoped or can be p-type doped using selected dopant elements, or can be n-type doped using selected dopant elements. The layers and structures formed with both the ZnBeO and ZnCdSeO semiconductor alloys - including undoped, p-type-doped, and n-type-doped types - can be used for fabricating photonic and electronic semiconductor devices for use in photonic and electronic applications. These devices can be used in LEDs, LDs, FETs (field effect transistors), PN junctions, PIN junctions, Schottky barrier diodes, UV detectors and transmitters, and transistors and transparent transistors. They also can be used in applications for lightemitting display, backlighting for displays, UV and visible transmitters and detectors, high-frequency radar, biomedical imaging, chemical compound identification, molecular identification and structure, gas sensors, imaging systems, and for the fundamental studies of atoms, molecules, gases, vapors, and solids.
Testing of general and localized corrosion of magnesium alloys: A critical review
NASA Astrophysics Data System (ADS)
Ghali, Edward; Dietzel, Wolfgang; Kainer, Karl-Ulrich
The degradation of materials generally occurs via corrosion, fatigue, and wear. Once a magnesium (Mg) alloy is chosen for a certain application, corrosion testing is generally required as a function of the expected service environment, the type of corrosion expected in service, and the type of surface protection, depending on the material and its use in the intended surface. In the absence of appropriate standards for the testing of magnesium alloys, a brief summary of the various procedures of accelerated electrochemical and corrosion testing of Mg alloys that have been adopted by different schools is given, accompanied by some critical comments for future work. Hydroxide, hydroxide-chloride, and corrosive water formulated according to American Society for Testing Materials (ASTM) standard 1384-96 are considered to evaluate general corrosion, localized corrosion, and corrosion influenced by metallurgical parameters. The influence of agitation, oxygenation, pH, and temperature are discussed. Surface cleaning, superficial microstructure, and surface preparation for testing are discussed. Appropriate electrochemical methods that can be applied to this relatively new and electrochemically active structural material are described. Corrosion potential measurements, polarization, impedance, noise electrochemistry, and surface reference electrode technique are recommended as valuable methods for evaluating the resistance of existing or experimental alloys to these types of corrosion. Corrosion kinetics and varying properties of the solution at the alloy/solution interface are examined. A critical description of the relevance and importance of these methods to corrosion testing of Mg alloys is given.
Pack cementation diffusion coatings for Fe-base and refractory alloys. Final report
Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering
With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels and refractory metal alloys. A new comprehensive theory to treat the multi-component thermodynamic equilibria in the gas phase for several coexisting solid phases was developed and used. Many different processes to deposit various types of coatings on several types of steels were developed: Cr-Si codeposition for low- or medium-carbon steels, Cr-Al codeposition on low-carbon steels to yield either a Kanthal-type composition (Fe-25Cr-4Al in wt.%) or else a (Fe, Cr){sub 3}Al surface composition. An Fe{sub 3}Al substrate was aluminized to achieve an FeAl surface composition, and boron was also added to ductilize the coating. The developmental Cr-lean ORNL alloys with exceptional creep resistance were Cr-Al coated to achieve excellent oxidation resistance. Alloy wires of Ni-base were aluminized to provide an average composition of Ni{sub 3}Al for use as welding rods. Several different refractory metal alloys based on Cr-Cr{sub 2}Nb have been silicided, also with germanium additions, to provide excellent oxidation resistance. A couple of developmental Cr-Zr alloys were similarly coated and tested.
Electrical transport properties of (BN)-rich hexagonal (BN)C semiconductor alloys
Uddin, M. R.; Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X., E-mail: firstname.lastname@example.com [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX 79409 (United States); Ziemer, K. S. [Department of Chemical Engineering, Northeastern University, Boston, MA 02115 (United States)
The layer structured hexagonal boron nitride carbon semiconductor alloys, h-(BN)C, offer the unique abilities of bandgap engineering (from 0 for graphite to ?6.4 eV for h-BN) and electrical conductivity control (from semi-metal for graphite to insulator for undoped h-BN) through alloying and have the potential to complement III-nitride wide bandgap semiconductors and carbon based nanostructured materials. Epilayers of (BN)-rich h-(BN){sub 1-x}(C{sub 2}){sub x} alloys were synthesized by metal-organic chemical vapor deposition (MOCVD) on (0001) sapphire substrates. Hall-effect measurements revealed that homogeneous (BN)-rich h-(BN){sub 1-x}(C{sub 2}){sub x} alloys are naturally n-type. For alloys with x = 0.032, an electron mobility of about 20 cm{sup 2}/Vs at 650?¯K was measured. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition and analyze chemical bonding states. Both composition and chemical bonding analysis confirm the formation of alloys. XPS results indicate that the carbon concentration in the alloys increases almost linearly with the flow rate of the carbon precursor (propane (C{sub 3}H{sub 8})) employed during the epilayer growth. XPS chemical bonding analysis showed that these MOCVD grown alloys possess more C-N bonds than C-B bonds, which possibly renders the undoped h-(BN){sub 1-x}(C{sub 2}){sub x} alloys n-type and corroborates the Hall-effect measurement results.
Aluminum gallium nitride alloys and heterostructures: Growth, characterization and application
NASA Astrophysics Data System (ADS)
Li, Jing
AlGaN alloys and heterostructures were grown by MOCVD and characterized by using Hall measurement, time-resolved photoluminescence (PL) and x-ray diffraction (XRD). Si-doped n-type AlxGa1-xN alloys with x up to 0.5 and Mg-doped p-type AlxGa1-xN alloys with x up to 0.27 were grown. Highly conductive n-type AlxGa 1-xN alloys were obtained for x up to 0.5. Emission lines of band-to-impurity transitions of free electrons with neutral Mg acceptors as well as localized excitons have been observed in the p-type AlxGa1-xN alloys. PL spectra showed that Mg acceptor activation energies EA increase with Al content and the results agrees with Hall measurement. Picosecond time-resolved PL was used to study the optical properties of GaN/AlxGa1-xN MQWs with varying structural parameters. The optimal GaN/AlxGa1-xN ( x 0.2) MQW structures for UV light emitter applications are those with well (barrier) widths ranging from 12 to 42 A (40 to 80 A). The decreased quantum efficiency in GaN/AlxGa1-xN MQWs with well width Lw < 12 A is due to the enhanced carrier leakage to the underlying GaN epilayers, while the decreased quantum efficiency in MQWs with well width Lw > 42 A is associated with an increased nonradiative recombination rate as Lw approaching the critical thickness of MQWs. InxAlyGa1-xN quaternary alloys were grown on sapphire substrates. The dominant optical transition at low temperatures in InxAlyGa1-xN quaternary alloys was due to localized exciton recombination, while the localization effects in InxAlyGa1-xN quaternary alloys were combined with those of InGaN and AlGaN ternary alloys with comparable In and Al compositions. We can achieve not only higher emission energies but also higher quantum efficiency in InxAlyGa1-x N quaternary alloys than that of GaN. AlN epilayers with high optical qualities have been grown on sapphire substrates by MOCVD. Band-edge emission lines have been observed both at low and room temperatures and are at 6.017 and 6.033 eV at 10 K Both the optical quality and the quantum efficiency of AlN epilayers are comparable to GaN. AlGaN/GaN-based heterostructure field-effect transistors (HFETs) by employing the delta-doped barrier and the SiO2 insulated-gate are fabricated and characterized. The device grown on sapphire substrate has a high drain-current-driving and gate-control capabilities as well as a very high gate-drain breakdown voltage of 200 V for a gate length of 1 mum and a source-drain distance of 3 mum. The incorporation of the SiO2 insulated-gate and the delta-doped barrier into HFET structures reduces the gate leakage and improves the 2D channel carrier mobility.
F. Hua; G.M. Gordon; R.B. Rebak
The nuclear waste package design for Yucca Mountain (Nevada, USA), in its current configuration, consists of a double wall cylindrical container fabricated using a highly corrosion resistant Ni-based Alloy 22 for the outer barrier and type 316 stainless steel for the inner structural vessel. A mailbox-shaped drip shield fabricated primarily using Ti Grade 7 will cover the waste packages. The environmental degradation of the relevant materials have been extensively studied and modeled for over ten years. This paper reviews the state-of-the-art understanding of the degradation modes of Alloy 22 (N06022) due to its interaction with the predicted in-drift mountain conditions including temperature and types of electrolytes. Subjects discussed include thermal aging and phase stability, dry oxidation, general and localized corrosion, stress corrosion cracking and hydrogen induced cracking.
Grain boundary characterization in an X750 alloy
Kevin Fisher; Sebastien Teysseyre; Emmanuelle Marquis
Grain boundary chemistry in an X750 Ni alloy was analyzed by atom probe tomography in an effort to clarify the possible roles of elemental segregation and carbide presence on the stress corrosion cracking behavior of Ni alloys. Two types of cracks are observed: straight cracks along twin boundaries and wavy cracks at general boundaries. It was found that carbides (M23C6 and TiC) are present at both twin and general boundaries, with comparable B and P segregation for all types of grain boundaries. Twin boundaries intercept ? precipitates while the general boundaries wave around the ? and carbide precipitates. Near a crack tip, oxidation takes place on the periphery of carbide precipitate.
Multiple cell photoresponsive amorphous alloys and devices
Ovshinsky, S.R.; Adler, D.
This patent describes an improved photoresponsive tandem multiple solar cell device. The device comprising: at least a first and second superimposed cell of various materials. The first cell being formed of a silicon alloy material. The second cell including an amorphous silicon alloy semiconductor cell body having an active photoresponsive region in which radiation can impinge to produce charge carriers, the amorphous cell body including at least one density of states reducing element. The element being fluorine. The amorphous cell body further including a band gap adjusting element therein at least in the photoresponsive region to enhance the radiation absorption thereof, the adjusting element being germanium: the second cell being a multi-layer body having deposited semiconductor layers of opposite (p and n) conductivity type; and the first cell being formed with the second cell in substantially direct Junction contact therebetween. The first and second cells designed to generate substantially matched currents from each cell from a light source directed through the first cell and into the second cell.
NASA Astrophysics Data System (ADS)
Appel, O.; Gelbstein, Y.
We deal here with Sb and Bi doping effects of the n-type half-Heusler (HH) Ti0.3Zr0.35Hf0.35NiSn alloy on the measured thermoelectric properties. To date, the thermoelectric effects upon Bi doping on the Sn site of HH alloys have rarely been reported, while Sb has been widely used as a donor dopant. A comparison between the measured transport properties following arc melting and spark plasma sintering of both Bi- and Sb-doped samples indicates a much stronger doping effect upon Sb doping, an effect which was explained thermodynamically. Due to similar lattice thermal conductivity values obtained for the various doped samples, synthesized in a similar experimental route, no practical variations in the thermoelectric figure of merit values were observed between the various investigated samples, an effect which was attributed to compensation between the power factor and electrical thermal conductivity values regardless of the various investigated dopants and doping levels.
[Thermal expansion of Au-Pd-Ag system alloys. Casting stress and deformation of addition of Sn and In].
Ohkuma, K
To study the dimensional changes due to the release of casting stress in metal-ceramic alloys, a wheel-like pattern in which casting stress is liable to occur and rod- and barrel-like wax patterns in which the likelihood of such stress is low, were investigated with a phosphate-bonded investment compound. Furthermore, simultaneous casting was done using Au-Pd-Ag system alloys, 21 types of mother alloys and alloys with tin or indium or both, and accurate determinations of the thermal expansion rate with increased or decreased temperature were carried out. The results obtained were as follows. The mean thermal expansion rates of the mother alloys and the alloys with tin and indium upon increase and decrease of temperature were lowest for the large wheel-like pattern, followed by the small wheel-like pattern, rod-like pattern and barrel-like pattern, in that order. The mean thermal expansion rates of the mother alloys and the alloys with tin or indium or both were decreased when the palladium content was increased, but tended to increase when the silver content was higher. Gold had no influence on the thermal expansion rate. When the temperature decreased, the complex addition of tin and indium provided alloys showing only a slight deformation. PMID:2690394
Aluminum-silicon eutectic alloy improves electrical and mechanical contact to silicon carbide
NASA Technical Reports Server (NTRS)
Shier, J. S.
Alloy contact layer is made at relatively low temperature and has good wetting characteristics. Contacts adhere well to silicon carbide surface, penetrating about 300 to 500 angstroms into it. Contacts are ohmic on p-type silicon carbide and blocking on n-type.
Effect of aging on mechanical properties of aluminum-alloy rivets
NASA Technical Reports Server (NTRS)
Roop, Frederick C
Curves and tabular data present the results of strength tests made during and after 2 1/2 years of aging on rivets and rivet wire of 3/16-inch nominal diameter. The specimens were of aluminum alloy: 24s, 17s, and a17s of the duralumin type and 53s of the magnesium-silicide type.
In vitro cytotoxicity and hemocompatibility studies of Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys
Zheng, Yufeng
transformation of to in titanium alloys, a new type of Ti-based SMA has 1748-6041/10/044102+07$30.00 shape memory alloys This article has been downloaded from IOPscience. Please scroll down to see the full and hemocompatibility studies of Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys B L Wang1, L Li1 and Y F
High strength forgeable tantalum base alloy
NASA Technical Reports Server (NTRS)
Buckman, R. W., Jr.
Increasing tungsten content of tantalum base alloy to 12-15% level will improve high temperature creep properties of existing tantalum base alloys while retaining their excellent fabrication and welding characteristics.
Optimization of Iron Cobalt-based Nanocomposite Alloys for High Induction and Increased Resistivity
NASA Astrophysics Data System (ADS)
Shen, Shen
FeCo-based nanocrystalline soft magnetic materials are promising to provide high saturation induction, high Curie temperature and excellent soft magnetic properties for electric vehicle and high frequency power conversion applications. The increasing operation frequency of various inductive applications requires nanocomposite alloys with higher resistivity to suppress power losses. In this thesis, the method of measuring as-cast and annealed resistivity of melt-spun ribbon alloys by obtaining alloy densities was established. Archimedes method with deionized water as a medium was used to determine the density of crystalline alloys. A gas pycnometer using dry Helium gas as the medium exhibited improved accuracy in measuring the density of amorphous ribbon alloys compared to the conventional Archimedes method using a liquid medium. This method was applied to previously developed HITPERM (FeCoZrBCu) and HTX002 (FeCoBSiCu) type of alloys as well as carbon-containing (FeCoBCCu) alloys to guide composition adjustments pursuing for improved magnetic properties. In the HITPERM type of alloys, the composition dependence of as-cast resistivity was studied and simulated by Mott's two-current model with a rigid-band assumption which provided guidance for further adjusting alloy composition looking for higher resistivity. An alloy designed with the Fe:Co ratio for maximum as-cast resistivity and Hf as glass former exhibits low power loss values being approximately 1/4 of those measured on the alloy with the original HITPERM composition for a range of frequencies. The Al and Si additions were found effective to achieve a high resistivity of 151.9 muOñcm in the as-cast alloys but also lead to embrittlement of melt-spun ribbons. Composition adjustments on the HTX002 type of alloys which are castable in air and available for larger-scale production were also explored. Increasing the ferromagnetic late transition metal content by reducing glass formers was found effective to achieve a high saturation induction above 1.75 T for the electric vehicle applications where high induction is prioritized to reduce size and weight. Due to the insufficient glass former contents in these alloys, however, some unique issues such as castability limits, trade-off between high induction and low power losses, high temperature stability, etc. were studied. As-cast resistivity measurements were utilized to quantify the castability limits of maintaining amorphous nature in the as-cast state. The significant effects of Nb content on the trade-off between high induction and low power losses and on the high temperature crystallization processes were investigated. For the high frequency power conversion applications where high saturation induction can be sacrificed to some extent, HTX002 type of alloys were adjusted in composition pursuing increased resistivity to reduce power losses. Mixed early transition metal content was investigated and the combination of Ta and Nb was found optimal to suppress power losses. High early transition metal content up to 6 at% based on this combination was studied and resulted in larger-scale production. The effect of Co substitution for Fe was explored in carbon-containing alloys which are promising as high induction soft magnetic materials with acceptable low losses and low costs. Higher saturation induction, lower power losses and better high temperature stability of magnetization were exhibited when the Co content was properly chosen. However, these alloys exhibited low annealed resistivity which resulted in dramatic increase of eddy current loss with operation frequency and hence limited for low frequency applications.
Solidification of eutectic system alloys in space (M-19)
NASA Technical Reports Server (NTRS)
Ohno, Atsumi
It is well known that in the liquid state eutectic alloys are theoretically homogeneous under 1 g conditions. However, the homogeneous solidified structure of this alloy is not obtained because thermal convection and non-equilibrium solidification occur. The present investigators have clarified the solidification mechanisms of the eutectic system alloys under 1 g conditions by using the in situ observation method; in particular, the primary crystals of the eutectic system alloys never nucleated in the liquid, but instead did so on the mold wall, and the crystals separated from the mold wall by fluid motion caused by thermal convection. They also found that the equiaxed eutectic grains (eutectic cells) are formed on the primary crystals. In this case, the leading phase of the eutectic must agree with the phase of the primary crystals. In space, no thermal convection occurs so that primary crystals should not move from the mold wall and should not appear inside the solidified structure. Therefore no equiaxed eutectic grains will be formed under microgravity conditions. Past space experiments concerning eutectic alloys were classified into two types of experiments: one with respect to the solidification mechanisms of the eutectic alloys and the other to the unidirectional solidification of this alloy. The former type of experiment has the problem that the solidified structures between microgravity and 1 g conditions show little difference. This is why the flight samples were prepared by the ordinary cast techniques on Earth. Therefore it is impossible to ascertain whether or not the nucleation and growth of primary crystals in the melt occur and if primary crystals influence the formation of the equiaxed eutectic grains. In this experiment, hypo- and hyper-eutectic aluminum copper alloys which are near eutectic point are used. The chemical compositions of the samples are Al-32.4mass%Cu (Hypo-eutectic) and Al-33.5mass%Cu (hyper-eutectic). Long rods for the samples are cast by the Ohno Continuous Casting Process and they show the unidirectionally solidified structure. Each flight and ground sample was made of these same rods. The dimensions of all samples are 4.5 mm in diameter and 23.5 mm in length. Each sample is put in a graphite capsule and then vacuum sealed in a double silica ampoule. Then the ampoule is put in the tantalum cartridge and sealed by electron beam welding. For onbard experiments, a Continuous Heating Furnance (CHF) will be used for melting and solidifying samples under microgravity conditions. Six flight samples will be used. Four samples are hypo-eutectic and two are hyper-eutectic alloys. The surface of the two hypo-eutectic alloy samples are covered with aluminum oxide film to prevent Marangoni convection expected under microgravity conditions. Each sample will be heated to 700 C and held at that temperature for 5 min. After that the samples will be allowed to cool to 500 C in the furnace and they will be taken out of the furnace for He gas cooling. The heating and cooling diagrams for the flight experiments are shown. After collecting the flight samples, the solidified structures of the samples will be examined and the mechanisms of eutectic solidification under microgravity conditions will be determined. It is likely that successful flight experiment results will lead to production of high quality eutectic alloys and eutectic composite materials in space.
Development of Creep Constitutive Equation for Low-Alloy Steel
Kwang J. Jeong; Joon Lim; Il S. Hwang; Hee D. Kim; Martin M. Pilch; Tze Y. Chu
High-temperature creep tests were performed with an SA533B1 low-alloy steel under both constant load and constant stress conditions. Using the measured minimum creep strain rates as a function of stress and temperature, least-square fittings were made into a Bailey-Norton-type power law equation. Based on the constant stress test results, a constitutive equation was developed for steady-state creep. The constitutive equation
Specific heat and magnetic susceptibility in YNd alloys
NASA Astrophysics Data System (ADS)
Pureur, P.; Sereni, J. G.; Schaf, J.
We report on the specific heat and de magnetic susceptibility measurements of the YNd 4.5, 6.8 and 9.0 at % alloys. These systems present long-range SDW order just below the critical temperature. For temperatures well below TrmC, the spin glass type of behavior in manifest. An interpretation is given in terms of a disorder- and frustration-induced breaking of the SDW coherence into small domains.
Multicomponent alloy solidification: phase-field modeling and simulations.
Nestler, Britta; Garcke, Harald; Stinner, Bj—rn
A general formulation of phase-field models for nonisothermal solidification in multicomponent and multiphase alloy systems is derived from an entropy functional in a thermodynamically consistent way. General expressions for the free energy densities, for multicomponent diffusion coefficients, and for both weak and faceted types of surface energy and kinetic anisotropy are possible. A three-dimensional simulator is developed to show the capability of the model to describe phase transitions, complex microstructure formation, and grain growth in polycrystalline textures. PMID:15903684
Evaluation of Stress Corrosion Cracking Susceptibility Using Fracture Mechanics Techniques, Part 1. [environmental tests of aluminum alloys, stainless steels, and titanium alloys
NASA Technical Reports Server (NTRS)
Sprowls, D. O.; Shumaker, M. B.; Walsh, J. D.; Coursen, J. W.
Stress corrosion cracking (SSC) tests were performed on 13 aluminum alloys, 13 precipitation hardening stainless steels, and two titanium 6Al-4V alloy forgings to compare fracture mechanics techniques with the conventional smooth specimen procedures. Commercially fabricated plate and rolled or forged bars 2 to 2.5-in. thick were tested. Exposures were conducted outdoors in a seacoast atmosphere and in an inland industrial atmosphere to relate the accelerated tests with service type environments. With the fracture mechanics technique tests were made chiefly on bolt loaded fatigue precracked compact tension specimens of the type used for plane-strain fracture toughness tests. Additional tests of the aluminum alloy were performed on ring loaded compact tension specimens and on bolt loaded double cantilever beams. For the smooth specimen procedure 0.125-in. dia. tensile specimens were loaded axially in constant deformation type frames. For both aluminum and steel alloys comparative SCC growth rates obtained from tests of precracked specimens provide an additional useful characterization of the SCC behavior of an alloy.
Superconducting compounds and alloys research
NASA Technical Reports Server (NTRS)
Otto, G.
Resistivity measurements as a function of temperature were performed on alloys of the binary material system In sub(1-x) Bi sub x for x varying between 0 and 1. It was found that for all single-phase alloys (the pure elements, alpha-In, and the three intermetallic compounds) at temperatures sufficiently above the Debye-temperature, the resistivity p can be expressed as p = a sub o T(n), where a sub o and n are composition-dependent constants. The same exponential relationship can also be applied for the sub-system In-In2Bi, when the two phases are in compositional equilibrium. Superconductivity measurements on single and two-phase alloys can be explained with respect to the phase diagram. There occur three superconducting phases (alpha-In, In2Bi, and In5Bi3) with different transition temperatures in the alloying system. The magnitude of the transition temperatures for the various intermetallic phases of In-Bi is such that the disappearance or occurrence of a phase in two component alloys can be demonstrated easily by means of superconductivity measurements.
Oxidation of low cobalt alloys
NASA Technical Reports Server (NTRS)
Barrett, C. A.
Four high temperature alloys: U-700, Mar M-247, Waspaloy and PM/HIP U-700 were modified with various cobalt levels ranging from 0 percent to their nominal commercial levels. The alloys were then tested in cyclic oxidation in static air at temperatures ranging from 1000 to 1150 C at times from 500 to 100 1 hour cycles. Specific weight change with time and X-ray diffraction analyses of the oxidized samples were used to evaluate the alloys. The alloys tend to be either Al2O3/aluminate spinel or Cr2O3/chromite spinel formers depending on the Cr/Al ratio in the alloy. Waspaloy with a ratio of 15:1 is a strong Cr2O3 former while this U-700 with a ratio of 3.33:1 tends to form mostly Cr2O3 while Mar M-247 with a ratio of 1.53:1 is a strong Al2O3 former. The best cyclic oxidation resistance is associated with the Al2O3 formers. The cobalt levels appear to have little effect on the oxidation resistance of the Al2O3/aluminate spinel formers while any tendency to form Cr2O3 is accelerated with increased cobalt levels and leads to increased oxidation attack.
Nickel aluminide alloys with improved weldability
Santella, Michael L. (Knoxville, TN); Goodwin, Gene M. (Lenior City, TN)
Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys.
Nickel aluminide alloys with improved weldability
Santella, M.L.; Goodwin, G.M.
Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys. 5 figs.
Burner Rig Hot Corrosion of Five Ni-Base Alloys Including Mar-M247
NASA Technical Reports Server (NTRS)
Nesbitt, James A.; Helmink, R.; Harris, K.; Erickson, G.
The hot corrosion resistance of four new Ni-base superalloys was compared to that of Mar-M247 by testing in a Mach 0.3 burner rig at 900 C for 300 1-hr cycles. While the Al content was held the same as in the Mar-M247, the Cr and Co levels in the four new alloys were decreased while other strengthening elements (Re, Ta) were increased. Surprisingly, despite their lower Cr and Co contents, the hot corrosion behavior of all four new alloys was superior to that of the Mar-M247 alloy. The Mar-M247 alloy began to lose weight almost immediately whereas the other four alloys appeared to undergo an incubation period of 50-150 1-hr cycles. Examination of the cross-sectional microstructures showed regions of rampant corrosion attack (propagation stage) in all five alloys after 300 1-hr cycles . This rampant corrosion morphology was similar for each of the alloys with Ni and Cr sulfides located in an inner subscale region. The morphology of the attack suggests a classic "Type I", or high temperature, hot corrosion attack.
Powder data file as a tool for identification of dental gold alloys.
Bergman, M
In order to obtain data for a prospective powder data file for dental gold alloys X-ray diffraction photograms of 75 different gold alloys were taken using a Guinier-Hðgg camera and CuKalpha1 radiation. Before the X-ray photograms were taken the alloys had been heat treated at 700 degrees C, 800 degrees C or 900 degrees C depending on the solidus temperatures of the alloys. The lattice parameters of the samples were determined from the X-ray photograms. These data were supplemented by a specification of the interplanar spacings of the three strongest lines on the diffraction patterns and also by the relative intensities and Miller indices of these lines. An extensive library of reference films is to be collected and this and other details of the file are discussed. It is not intended that the file be used to identify a particular alloy but merely to identify the type of alloy. Thus it can serve as a guide to facilitate the proper selection of gold alloys within practical clinical dentistry. PMID:281858
Introduction to the viewpoint set on: Mechanical alloying
Schwarz, R.B. [Los Alamos National Lab., NM (United States). Center for Materials Science] [Los Alamos National Lab., NM (United States). Center for Materials Science
Mechanical Alloying (MA) is a high-energy ball milling technique used to prepare alloy powders with unique microstructures. MA starts with a mixture of powders (elemental or prealloyed) which are blended together in a ball mill. What differentiates MA from conventional blending in rotary mills is the kinetic energy of the colliding balls inside the mill. In conventional rotary mills the milling energy is small and the powder particles trapped between colliding balls may fracture, but the maximum pressure during the collisions is insufficient to produce a large amount of plastic deformation in the powder particles. In contrast, during MA the powder particles are not only fractured but are also heavily plastically deformed and cold welded. Due in part to its simplicity, MA has become a general tool used by material scientists to prepare a variety of alloy powders with metastable phases and/or microstructures. It is difficult, however, to predict the product of MA for a given starting powder. In general, the product depends on the milling parameters such as processing time and temperature, milling energy, and type of milling control agent used (added to prevent excessive agglomeration of the power during milling). Significant effort has been devoted to modeling the MA process to be able to predict the alloy product for any given set of milling parameters.
Acoustic emission from hydrogen saturated Type 304L stainless steel
Caskey; G. R. Jr
Effects of hydrogen on tensile deformation and fracture of austenitic stainless steels vary widely, depending upon the steel composition and treatment, hydrogen exposure, and loading conditions. In alloys such as Type 310 and Type 316 stainless steel, the ductility loss is small; and the fracture mode is unchanged. In contrast, Type 304L, 21-6-9, and Tenelon display large ductility losses with
Deoxidation of Titanium alloy using hydrogen
Yanqing Su; Liang Wang; Liangshun Luo; Xiaohong Jiang; Jingjie Guo; Hengzhi Fu
In this paper we present a simple and effective method to reduce the oxygen content of titanium alloys by using the mixture of hydrogen (H2)\\/Ar gases as the reactive atmosphere during the remelting process of titanium alloys. The experimental results show that the decrease of oxygen content of Ti64 alloy is related to the hydrogen fraction of the mixture gas
Alloy catalysts designed from first principles
Jeff Greeley; Manos Mavrikakis
The rational design of pure and alloy metal catalysts from fundamental principles has the potential to yield catalysts of greatly improved activity and selectivity. A promising area of research concerns the role that near-surface alloys (NSAs) can play in endowing surfaces with novel catalytic properties. NSAs are defined as alloys wherein a solute metal is present near the surface of
Temperature Gradients in Semiconductor Alloying Technology
E. P. EerNisse; H. W. Thompson
Experiments have been conducted with Ge and Si to define the metallurgical effects of temperature gradients in the alloying technology. These effects are defined in terms of the electrical characteristics of alloyed diodes and transistors and in terms of the physical appearance of the p-n junction. The presence of temperature gradients during the dissolution phase of an alloy cycle results
Alloy rotary kilns for hazardous waste disposal
J. V. Del Bene; J. K. Shah; E. F. Colburn
The major conclusions of the study of rotary kilns for processing abrasive, energetic or corrosive hazardous wastes are: Alloy kilns are preferable to smaller refractory lined kilns for abrasive and\\/or explosive feed materials. Alloy construction and bolted sections make alloy kilns transportable; a pyrolysis operating mode can reduce the equipment size for wastes with a high energy release rate. However,
Alchemy: transmuting base alloy specifications into implementations
Shriram Krishnamurthi; Kathi Fisler; Daniel J. Dougherty; Daniel Yoo
Alloy specifications are used to define lightweight models of systems. We present Alchemy, which compiles Alloy specifi- cations into implementations that execute against persistent databases. Alchemy translates a subset of Alloy predicates into imperative update operations, and it converts facts into database integrity constraints that it maintains automati- cally in the face of these imperative actions. In addition to presenting
High strength uranium-tungsten alloy process
Dunn, Paul S. (Santa Fe, NM); Sheinberg, Haskell (Los Alamos, NM); Hogan, Billy M. (Los Alamos, NM); Lewis, Homer D. (Bayfield, CO); Dickinson, James M. (Los Alamos, NM)
Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.
High strength uranium-tungsten alloys
Dunn, Paul S. (Santa Fe, NM); Sheinberg, Haskell (Los Alamos, NM); Hogan, Billy M. (Los Alamos, NM); Lewis, Homer D. (Bayfield, CO); Dickinson, James M. (Los Alamos, NM)
Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.
Characterizing Semiconductor Alloys for Infrared Sensors
NASA Technical Reports Server (NTRS)
Lehoczky, B. S. L.; Szofran, F. R.; Martin, B. G.
Report presents results of continuing program aimed at characterizing mercury/cadmium/tellurium alloys and eventually developing improved methods of preparing alloys for use as infrared sensors. Work covered by report includes series of differential thermal analysis (DTA) measurements of alloy compositions with x varied from 9 to 1 in 0.1 increments.
High-temperature nickel-brazing alloy
NASA Technical Reports Server (NTRS)
Powell, A. H.; Thompson, S. R.
Gold-nickel brazing alloy, with 5 percent indium added to depress the melting point, is used for brazing of nickel-clad silver electrical conductors which operate at temperatures to 1200 deg F. Alloy has low resistivity, requires no flux, and is less corrosive than other gold-nickel, gold-copper alloys.
Materials data handbook, aluminum alloy 6061
NASA Technical Reports Server (NTRS)
Sessler, J.; Weiss, V.
Comprehensive compilation of technical data on aluminum alloy 6061 is presented in handbook form. The text includes data on the properties of the alloy at cryogenic, ambient, and elevated temperatures and other pertinent information required for the design and fabrication of components and equipment utilizing this alloy.
Roll Casting of Aluminum Alloy Clad Strip
R. Nakamura; T. Haga; H. Tsuge; H. Watari; S. Kumai
Casting of aluminum alloy three layers of clad strip was tried using the two sets of twin roll casters, and effects of the casting parameters on the cladding conditions were investigated. One twin roll caster was mounted on the other twin roll caster. Base strip was 8079 aluminum alloy and overlay strips were 6022 aluminum alloy. Effects of roll-load of
Depth profiling of ion-implanted alloys
NASA Astrophysics Data System (ADS)
Campbell, A. B.; Sartwell, B. D.; Needham, P. B.
Proton-induced x-ray emission analysis (PIXEA) and inert gas ion sputtering (IS) have been utilized to generate elemental profiles for three types of ion-implanted iron alloys. The data were fitted (utilizing a computer program) with symmetrical Gaussian profiles yielding values for the range and range straggle. These parameters were then compared with those obtained from the theory of Lindhard, Scharff, and Schiott (LSS). Changes in the profiles due to annealing were investigated, and values for the diffusion coefficient were obtained assuming Fick's law. For 25-keV Ni+ and Cr+ in iron, the profiles as-implanted, agree reasonably well with LSS theory and exhibit ''normal'' diffusion characteristics at 500 ¯C. For 25-keV Al+ in iron, the profile as implanted is much broader than predicted and exhibits substantial enhanced diffusion at temperatures up to 500 ¯C.
Time-resolved photoluminescence studies of Al-rich AlGaN alloys
NASA Astrophysics Data System (ADS)
Li, Jing; Nam, Ki-Bum; Oder, Tom N.; Kim, KyoungHoon; Nakarmi, M. L.; Lin, Jing Y.; Jiang, Hongxing
Si-doped n-type AlxGa1MINxN alloys with x up to 0.5 and Mg-doped p-type AlxGa1-xN alloys with x up to 0.27 were grown by metal-organic chemical vapor deposition (MOCVD) on sapphire substrates. For the n-type AlxGa1-xN, we achieved highly conductive alloys for x up to 0.5. An electron concentration as high as 1x1018cm-3 was obtained in Si-doped Al0.5Ga0.5N alloys with an electron mobility of 16 cm_2)Vs at room temperature, as confirmed by Hall-effect measurements. Our results also revealed that the conductivity of AlxGa1-xN alloys continuously increases with an increase of Si doping level for a fixed value of Al content (X<0.5), the conductivities of AlxGa1-xN alloys decrease with increasing Al content for a given doping level; the critical Si-doping concentration needed to convert insulating AlxGa1-x)N with high Al contents (X>=0.4) to n- type conductivity is about 1 x 1018cm-3. Time- resolved photoluminescence studies carried out on these materials have shown that Si-doping reduces the effect of carrier localization in AlxGa1-xN alloys and a sharp drop in carrier localization energy occurs when the Si doping concentration increases above 1x1018cm-3, which directly correlates with the observed electrical properties. For the Mg-doped AlxGa1-xN alloys, p-type conduction was achieved for x up to 0.27, as confirmed by variable temperature Hall measurements. Emission lines of band-to-impurity transitions of free electrons with neutral Mg acceptors as well as localized excitons have been observed in the p-type AlxGa1-xN alloys. The Mg acceptor activation energies EA were deduces from photoluminescence spectra and were found to increase with Al content and agreed very well with those obtained by Hall measurements. From the measured activation energy as a function of Al content, EA versus x, the resistivity of Mg-doped AlxGa1-x with high Al contents can be deduced. Our results have also shown that PL measurements provide direct means of obtaining EA especially where this cannot be obtained accurately by electrical methods due to high resistance of p-type AlxGa1-xN with high Al content.
On the problem of theoretical estimation of alloying additives effect on susceptibility of zirconium alloys to nodular corrosion
NASA Astrophysics Data System (ADS)
Evdokimov, I. A.; Likhanskii, V. V.; Aliev, T. N.; Zborovskii, V. G.; Kolesnik, M. Y.
Several mechanisms of nodular corrosion are discussed in literature for Zr-based alloys. One of the mechanisms is attributed to instability of the uniform corrosion front with respect to transverse perturbations. According to this mechanism, a nonuniform field of mechanical stress is formed at the disturbed metal-oxide interface. It leads to redistribution of alloying elements in the vicinity of the corrosion front and concentration of additives in the metal becomes inhomogeneous. Depending on properties of the particular additive and its effect on local corrosion rate, the drift in the field of mechanical stress may lead to either enhancement or suppression of the arising perturbations. In the present paper, this approach for nodular corrosion understanding is further developed. An analytical solution for mechanical stresses in the metal-oxide system with undulated interface is reported. For undulations of small amplitude the solution is built in the frame of elastic theory. Results of analysis are applied to additives of Fe, Cr, Ni and Sn in Zircaloy-type alloys. Effects of both solutes and precipitates of these additives on susceptibility of alloys to nodular corrosion are considered.
Understanding the Cu-Zn brass alloys using a short-range-order cluster model: significance of specific compositions of industrial alloys
NASA Astrophysics Data System (ADS)
Hong, H. L.; Wang, Q.; Dong, C.; Liaw, Peter K.
Metallic alloys show complex chemistries that are not yet understood so far. It has been widely accepted that behind the composition selection lies a short-range-order mechanism for solid solutions. The present paper addresses this fundamental question by examining the face-centered-cubic Cu-Zn ?-brasses. A new structural approach, the cluster-plus-glue-atom model, is introduced, which suits specifically for the description of short-range-order structures in disordered systems. Two types of formulas are pointed out, [Zn-Cu12]Zn1~6 and [Zn-Cu12](Zn,Cu)6, which explain the ?-brasses listed in the American Society for Testing and Materials (ASTM) specifications. In these formulas, the bracketed parts represent the 1st-neighbor cluster, and each cluster is matched with one to six 2nd-neighbor Zn atoms or with six mixed (Zn,Cu) atoms. Such a cluster-based formulism describes the 1st- and 2nd-neighbor local atomic units where the solute and solvent interactions are ideally satisfied. The Cu-Ni industrial alloys are also explained, thus proving the universality of the cluster-formula approach in understanding the alloy selections. The revelation of the composition formulas for the Cu-(Zn,Ni) industrial alloys points to the common existence of simple composition rules behind seemingly complex chemistries of industrial alloys, thus offering a fundamental and practical method towards composition interpretations of all kinds of alloys.
Understanding the Cu-Zn brass alloys using a short-range-order cluster model: significance of specific compositions of industrial alloys.
Hong, H L; Wang, Q; Dong, C; Liaw, Peter K
Metallic alloys show complex chemistries that are not yet understood so far. It has been widely accepted that behind the composition selection lies a short-range-order mechanism for solid solutions. The present paper addresses this fundamental question by examining the face-centered-cubic Cu-Zn ?-brasses. A new structural approach, the cluster-plus-glue-atom model, is introduced, which suits specifically for the description of short-range-order structures in disordered systems. Two types of formulas are pointed out, [Zn-Cu12]Zn(1~6) and [Zn-Cu12](Zn,Cu)6, which explain the ?-brasses listed in the American Society for Testing and Materials (ASTM) specifications. In these formulas, the bracketed parts represent the 1(st)-neighbor cluster, and each cluster is matched with one to six 2nd-neighbor Zn atoms or with six mixed (Zn,Cu) atoms. Such a cluster-based formulism describes the 1st- and 2nd-neighbor local atomic units where the solute and solvent interactions are ideally satisfied. The Cu-Ni industrial alloys are also explained, thus proving the universality of the cluster-formula approach in understanding the alloy selections. The revelation of the composition formulas for the Cu-(Zn,Ni) industrial alloys points to the common existence of simple composition rules behind seemingly complex chemistries of industrial alloys, thus offering a fundamental and practical method towards composition interpretations of all kinds of alloys. PMID:25399835
Understanding the Cu-Zn brass alloys using a short-range-order cluster model: significance of specific compositions of industrial alloys
Hong, H. L.; Wang, Q.; Dong, C.; Liaw, Peter K.
Metallic alloys show complex chemistries that are not yet understood so far. It has been widely accepted that behind the composition selection lies a short-range-order mechanism for solid solutions. The present paper addresses this fundamental question by examining the face-centered-cubic Cu-Zn ?-brasses. A new structural approach, the cluster-plus-glue-atom model, is introduced, which suits specifically for the description of short-range-order structures in disordered systems. Two types of formulas are pointed out, [Zn-Cu12]Zn1~6 and [Zn-Cu12](Zn,Cu)6, which explain the ?-brasses listed in the American Society for Testing and Materials (ASTM) specifications. In these formulas, the bracketed parts represent the 1st-neighbor cluster, and each cluster is matched with one to six 2nd-neighbor Zn atoms or with six mixed (Zn,Cu) atoms. Such a cluster-based formulism describes the 1st- and 2nd-neighbor local atomic units where the solute and solvent interactions are ideally satisfied. The Cu-Ni industrial alloys are also explained, thus proving the universality of the cluster-formula approach in understanding the alloy selections. The revelation of the composition formulas for the Cu-(Zn,Ni) industrial alloys points to the common existence of simple composition rules behind seemingly complex chemistries of industrial alloys, thus offering a fundamental and practical method towards composition interpretations of all kinds of alloys. PMID:25399835
Development of New Titanium-Molybdenum Alloys with Changeable Young's Modulus for Spinal Fixture Devices
NASA Astrophysics Data System (ADS)
Zhao, Xingfeng; Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko
Metallic implant rods that are used to design spinal fixtures should have a Young's modulus that is not only sufficiently low to prevent stress shielding for the patient but also sufficiently high to suppress springback for the surgeon. Therefore, there is a need for novel titanium alloys with good biocompatibility and a changeable Young's modulus. Molybdenum is non-toxic, and Ti-Mo alloys possess good biocompatibility. In metastable ?-type Ti-Mo alloys, an ? phase can be introduced by deformation at room temperature. This study investigated the effects of deformation-induced phases on the mechanical properties of a metastable ?-type Ti-16Mo alloy. The experimental results indicate that the Young's modulus, tensile strength, and Vickers hardness are increased remarkably by cold rolling. The microstructural observation result by transmission electron microscopy (TEM) shows that the deformation-induced ? phase transformation occurs during cold rolling in the Ti-16Mo alloy. Therefore, the increase in Young's modulus of the alloy after cold rolling at room temperature can be attributed to a deformation-induced ? phase.
Study on Microstructures of Al-4 wt pct V Master Alloys
NASA Astrophysics Data System (ADS)
Meng, Yi; Cui, Jianzhong; Zhao, Zhihao; Zuo, Yubo
Aluminum (Al)-V master alloys have attracted attention, because they can potentially be efficient grain refiners for wrought aluminum alloys. In this paper, the microstructure and factors affecting the microstructure of Al-4 wt pct V master alloys were investigated by means of controlled melting and casting processes followed by structure examination. The results showed that the type and morphology of the V-containing phases in Al-V master alloys were strongly affected by the temperature of the melt, concentration of vanadium in solution in the melt and the cooling conditions. Two main V-containing phases, Al3V and Al10V, which have different shapes, were found in the alloys prepared by rapid solidification. The Al3V phase formed when there were both a high temperature (1273 K to 1673 K (1000 ¯C to 1400 ¯C)) and a relatively high vanadium content of 3 to 4 wt pct, while the Al10V phase formed at a low temperature (<1373 K (1100 ¯C)) or a low vanadium content in the range of 1 to 3 wt pct. The results also showed that the type of V-containing phase that formed in the Al-4 wt pct V master alloy was determined by the instantaneous vanadium content.
Ab initio atomistic thermodynamics study on the oxidation mechanism of binary and ternary alloy surfaces
NASA Astrophysics Data System (ADS)
Liu, Shi-Yu; Liu, Shiyang; Li, De-Jun; Wang, Sanwu; Guo, Jing; Shen, Yaogen
Utilizing a combination of ab initio density-functional theory and thermodynamics formalism, we have established the microscopic mechanisms for oxidation of the binary and ternary alloy surfaces and provided a clear explanation for the experimental results of the oxidation. We construct three-dimensional surface phase diagrams (SPDs) for oxygen adsorption on three different Nb-X(110) (X = Ti, Al or Si) binary alloy surfaces. On the basis of the obtained SPDs, we conclude a general microscopic mechanism for the thermodynamic oxidation, that is, under O-rich conditions, a uniform single-phase SPD (type I) and a nonuniform double-phase SPD (type II) correspond to the sustained complete selective oxidation and the non-sustained partial selective oxidation by adding the X element, respectively. Furthermore, by revealing the framework of thermodynamics for the oxidation mechanism of ternary alloys through the comparison of the surface energies of two separated binary alloys, we provide an understanding for the selective oxidation behavior of the Nb ternary alloy surfaces. Using these general microscopic mechanisms, one could predict the oxidation behavior of any binary and multi-component alloy surfaces based on thermodynamics considerations.
Microstructure Evaluation of Fe-BASED Amorphous Alloys Investigated by Doppler Broadening Positron Annihilation Technique
NASA Astrophysics Data System (ADS)
Lu, Wei; Huang, Ping; Wang, Yuxin; Yan, Biao
Microstructure of Fe-based amorphous and nanocrystalline soft magnetic alloy has been investigated by X-ray diffraction (XRD), transmission electronic microscopy (TEM) and Doppler broadening positron annihilation technique (PAT). Doppler broadening measurement reveals that amorphous alloys (Finemet, Type I) which can form a nanocrystalline phase have more defects (free volume) than alloys (Metglas, Type II) which cannot form this microstructure. XRD and TEM characterization indicates that the nanocrystallization of amorphous Finemet alloy occurs at 460¯C, where nanocrystallites of ?-Fe with an average grain size of a few nanometers are formed in an amorphous matrix. With increasing annealing temperature up to 500¯C, the average grain size increases up to around 12 nm. During the annealing of Finemet alloy, it has been demonstrated that positron annihilates in quenched-in defect, crystalline nanophase and amorphous-nanocrystalline interfaces. The change of line shape parameter S with annealing temperature in Finemet alloy is mainly due to the structural relaxation, the pre-nucleation of Cu nucleus and the nanocrystallization of ?-Fe(Si) phase during annealing. This study throws new insights into positron behavior in the nanocrystallization of metallic glasses, especially in the presence of single or multiple nanophases embedded in the amorphous matrix.
Diffusion phase transitions in alloys
NASA Astrophysics Data System (ADS)
Ustinovshchikov, Yu I.
We present a critical analysis of research on the thermodynamics, kinetics, and morphology of diffusion phase transitions in alloys. We show that diffusion phase transitions are mainly driven by the chemical potential difference due to a change in the sign of the chemical interaction among the component atoms. We explain how the sign of the chemical interaction energy can be obtained from experimental measurements. Examples are given to illustrate the kinetics and morphology of the ordering-separation phase transition in Ni- and Co-based alloys. We show how introducing the concept of the ordering-separation phase transition may affect our thinking in this area.
Study of the properties and the choice of alloys for bladed disks (blisks) and a method for their joining
NASA Astrophysics Data System (ADS)
Povarova, K. B.; Valitov, V. A.; Obsepyan, S. V.; Drozdov, A. A.; Bazyleva, O. A.; Valitova, E. V.
The choice of materials for the bladed disks (blisks) that are intended for next-generation aviation gas turbine engines is grounded. As blade materials, single crystals of light heterophase ?' + ? VKNA-type alloys based on the ?'(Ni3Al) intermetallic compound with an ordered structure are proposed. The choice of novel deformable EP975-type nickel superalloys, which are intended for operation at 800-850¯C, as the disk material is grounded. It is shown that the most effective method for forming one-piece joints of an Ni3Al-based alloy and a high-alloy EP975-type nickel superalloy is the new process of solid-phase pressure welding under conditions of high-temperature superplasticity. Solid-phase joints are formed for heterophase Ni3Al-based alloy single crystals and deformable EK61 and EP975 nickel alloys. The gradient structures in the zone of the solid-phase joints that form under the conditions of low- and high-temperature superplasticity at homologous temperatures of 0.6 T m and 0.9 T m are studied. The character and direction of the diffusion processes at the joint of an intermetallic alloy single crystal and a deformable polycrystalline alloy are determined.
Influence of shape and finishing on the corrosion of palladium-based dental alloys
Muris, Joris; Kleverlaan, Cornelis J.; Feilzer, Albert J.
PURPOSE The purpose of this study was to evaluate the effects of the surface treatment and shape of the dental alloy on the composition of the prosthetic work and its metallic ion release in a corrosive medium after casting. MATERIALS AND METHODS Orion Argos (Pd-Ag) and Orion Vesta (Pd-Cu) were used to cast two crowns and two disks. One of each was polished while the other was not. Two as-received alloys were also studied making a total of 5 specimens per alloy type. The specimens were submersed for 7 days in a lactic acid/sodium chloride solution (ISO standard 10271) and evaluated for surface structure characterization using SEM/EDAX. The solutions were quantitatively analysed for the presence of metal ions using ICP-MS and the results were statistically analysed with one-way ANOVA and a Tukey post-hoc test. RESULTS Palladium is released from all specimens studied (range 0.06-7.08 çgñcm-2ñweek-1), with the Pd-Cu alloy releasing the highest amounts. For both types of alloys, ion release of both disk and crown pairs were statistically different from the as-received alloy except for the Pd-Ag polished crown (P>.05). For both alloy type, disk-shaped pairs and unpolished specimens released the highest amounts of Pd ions (range 0.34-7.08 çgñcm-2ñweek-1). Interestingly, in solutions submerged with cast alloys trace amounts of unexpected elements were measured. CONCLUSION Shape and surface treatment influence ion release from dental alloys; polishing is a determinant factor. The release rate of cast and polished Pd alloys is between 0.06-0.69 çgñcm-2ñweek-1, which is close to or exceeding the EU Nickel Directive 94/27/EC compensated for the molecular mass of Pd (0.4 çgñcm-2ñweek-1). The composition of the alloy does not represent the element release, therefore we recommend manufacturers to report element release after ISO standard corrosion tests beside the original composition. PMID:25722839
Microstructure-property relationships in Al-Cu-Li-Ag-Mg Weldalite (tm) alloys, part 2
NASA Technical Reports Server (NTRS)
Langan, T. J.; Pickens, J. R.
The microstructure and mechanical properties of the ultrahigh strength Al-Cu-Li-Ag-Mg alloy, Weldalite (tm) 049, were studied. Specifically, the microstructural features along with tensile strength, weldability, Young's modulus and fracture toughness were studied for Weldalite (tm) 049 type alloys with Li contents ranging from 1.3 to 1.9 wt. pct. The tensile properties of Weldalite 049 and Weldalite 049 reinforced with TiB2 particles fabricated using the XD (tm) process were also evaluated at cryogenic, room, and elevated temperatures. In addition, an experimental alloy, similar in composition to Weldalite 049 but without the Ag+Mg, was fabricated. The microstructure of this alloy was compared with that of Weldalite 049 in the T6 condition to assess the effect of Ag+Mg on nucleation of strengthening phases in the absence of cold work.
Effect of High Temperature Aging on the Corrosion Resistance of Iron Based Amorphous Alloys
Day, S D; Haslam, J J; Farmer, J C; Rebak, R B
Iron-based amorphous alloys can be more resistant to corrosion than polycrystalline materials of similar compositions. However, when the amorphous alloys are exposed to high temperatures they may recrystallize (or devitrify) thus losing their resistance to corrosion. Four different types of amorphous alloys melt spun ribbon specimens were exposed to several temperatures for short periods of time. The resulting corrosion resistance was evaluated in seawater at 90 C and compared with the as-prepared ribbons. Results show that the amorphous alloys can be exposed to 600 C for 1-hr. without losing the corrosion resistance; however, when the ribbons were exposed at 800 C for 1-hr. their localized corrosion resistance decreased significantly.
Microstructural characterization of selected AEA/UCSB model FeCuMn alloys
Rice, P.M.; Stoller, R.E.
A set of 22 model ferritic alloys was purchased as part of a collaborative research program by the AEA Harwell Laboratory and the University of California at Santa Barbara. Nine of these alloys were selected by the Oak Ridge National Laboratory for use in a series of ion irradiation experiments investigating dispersed barrier hardening. These nine alloys contain varying amounts of copper, manganese, titanium, carbon, and nitrogen. The alloys have been characterized by transmission electron microscopy in the as-received condition to provide a baseline for comparison with the irradiated specimens. A description of the microstructural observations is provided for future reference. This summary focuses on the type and size distributions of the precipitates present; grain size and dislocation measurements are also included.
The Effects of Test Temperature, Temper, and Alloyed Copper on the Hydrogen-Controlled Crack Growth Rate of an Al-Zn-Mg-(Cu) Alloy
G.A. Young, Jr.; J.R. Scully
The hydrogen embrittlement controlled stage II crack growth rate of AA 7050 (6.09 wt.% Zn, 2.14 wt% Mg, 2.19 wt.% Cu) was investigated as a function of temper and alloyed copper level in a humid air environment at various temperatures. Three tempers representing the underaged, peak aged, and overaged conditions were tested in 90% relative humidity (RH) air at temperatures between 25 and 90 C. At all test temperatures, an increased degree of aging (from underaged to overaged) produced slower stage II crack growth rates. The stage II crack growth rate of each alloy and temper displayed Arrhenius-type temperature dependence with activation energies between 58 and 99 kJ/mol. For both the normal copper and low copper alloys, the fracture path was predominantly intergranular at all test temperatures (25-90 C) in each temper investigated. Comparison of the stage II crack growth rates for normal (2.19 wt.%) and low (0.06 wt.%) copper alloys in the peak aged and overaged tempers showed the beneficial effect of copper additions on stage II crack growth rate in humid air. In the 2.19 wt.% copper alloy, the significant decrease ({approx} 10 times at 25 C) in stage II crack growth rate upon overaging is attributed to an increase in the apparent activation energy for crack growth. IN the 0.06 wt.% copper alloy, overaging did not increase the activation energy for crack growth but did lower the pre-exponential factor, {nu}{sub 0}, resulting in a modest ({approx} 2.5 times at 25 C) decrease in crack growth rate. These results indicate that alloyed copper and thermal aging affect the kinetic factors that govern stage II crack growth rate. Overaged, copper bearing alloys are not intrinsically immune to hydrogen environment assisted cracking but are more resistant due to an increased apparent activation energy for stage II crack growth.
Alloy softening in binary iron solid solutions
NASA Technical Reports Server (NTRS)
Stephens, J. R.; Witzke, W. R.
An investigation was conducted to determine softening and hardening behavior in 19 binary iron-alloy systems. Microhardness tests were conducted at four temperatures in the range 77 to 411 K. Alloy softening was exhibited by 17 of the 19 alloy systems. Alloy softening observed in 15 of the alloy systems was attributed to an intrinsic mechanism, believed to be lowering of the Peierls (lattice friction) stress. Softening and hardening rates could be correlated with the atomic radius ratio of solute to iron. Softening observed in two other systems was attributed to an extrinsic mechanism, believed to be associated with scavenging of interstitial impurities.
Protective claddings for high strength chromium alloys
NASA Technical Reports Server (NTRS)
Collins, J. F.
The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).
Liquid metal ion source and alloy
Clark, Jr., William M. (Thousand Oaks, CA); Utlaut, Mark W. (Saugus, CA); Behrens, Robert G. (Los Alamos, NM); Szklarz, Eugene G. (Los Alamos, NM); Storms, Edmund K. (Los Alamos, NM); Santandrea, Robert P. (Santa Fe, NM); Swanson, Lynwood W. (McMinnville, OR)
A liquid metal ion source and alloy, wherein the species to be emitted from the ion source is contained in a congruently vaporizing alloy. In one embodiment, the liquid metal ion source acts as a source of arsenic, and in a source alloy the arsenic is combined with palladium, preferably in a liquid alloy having a range of compositions from about 24 to about 33 atomic percent arsenic. Such an alloy may be readily prepared by a combustion synthesis technique. Liquid metal ion sources thus prepared produce arsenic ions for implantation, have long lifetimes, and are highly stable in operation.
Semiempirical Analysis of Surface Alloy Formation
NASA Technical Reports Server (NTRS)
Bozzolo, Guillermo; Ferrante, John; Ibanez-Meier, Rodrigo
The BFS method for alloys is applied to the study of surface alloy formation. This method was previously used to examine the experimental STM observation of surface alloying of Au on Ni(110) for low Au coverages by means of a numerical simulation. In this work, we extend the study to include other cases of surface alloying for immiscible as well as miscible metals. All binary combinations of Ni, Au, Cu, and Al are considered and the simulation results are compared to experiment when data is available. The driving mechanisms of surface alloy formation are then discussed in terms of the BFS method and the available results.
Creep Behavior of Hydrogenated Zirconium Alloys
NASA Astrophysics Data System (ADS)
Sarkar, A.; Boopathy, K.; Eapen, J.; Murty, K. L.
Zirconium (Zr) alloys are the primary structural materials of most water reactors. Creep is considered to be one of the important degradation mechanisms of Zr alloys during reactor operating and repository conditions. Zr alloys pick up hydrogen (H2) during their service from the coolant water. Hydrogen can be present in solid solution or precipitated hydride form in Zr alloys depending upon the temperature and concentration. This study reviews the effect of hydrogen on creep behavior of Zr alloys used in the water reactors.
Bond Strength of Resin Cements to Noble and Base Metal Alloys with Different Surface Treatments
Raeisosadat, Farkhondeh; Ghavam, Maryam; Hasani Tabatabaei, Masoomeh; Arami, Sakineh; Sedaghati, Maedeh
Objectives: The bond strength of resin cements to metal alloys depends on the type of the metal, conditioning methods and the adhesive resins used. The purpose of this study was to evaluate the bond strength of resin cements to base and noble metal alloys after sand blasting or application of silano-pen. Materials and Method: Cylinders of light cured Z 250 composite were cemented to Degubond 4 (Au Pd) and Verabond (Ni Cr) alloys by either RelyX Unicem or Panavia F2, after sandblasting or treating the alloys with Silano-Pen. The shear bond strengths were evaluated. Data were analyzed by three-way ANOVA and t tests at a significance level of P<0.05. Results: When the alloys were treated by Silano-Pen, RelyX Unicem showed a higher bond strength for Degubond 4 (P=0.021) and Verabond (P< 0.001). No significant difference was observed in the bond strength of Panavia F2 to the alloys after either of surface treatments, Degubond 4 (P=0.291) and Verabond (P=0.899). Panavia F2 showed a higher bond strength to sandblasted Verabond compared to RelyX Unicem (P=0.003). The bond strength of RelyX Unicem was significantly higher to Silano-Pen treated Verabond (P=0.011). The bond strength of the cements to sandblasted Degubond 4 showed no significant difference (P=0.59). RelyX Unicem had a higher bond strength to Silano-Pen treated Degubond 4 (P=0.035). Conclusion: The bond strength of resin cements to Verabond alloy was significantly higher than Degubond 4. RelyX Unicem had a higher bond strength to Silano-Pen treated alloys. Surface treatments of the alloys did not affect the bond strength of Panavia F2. PMID:25628687
Stress corrosion cracking behavior of irradiated model austenitic stainless steel alloys.
Chung, H. M.; Karlsen, T. M.; Ruther, W. E.; Shack, W. J.; Strain, R. V.
Slow-strain-rate tensile tests (SSRTs) and posttest fractographic analyses by scanning electron microscopy were conducted on 16 austenitic stainless steel (SS) alloys that were irradiated at 289 C in He. After irradiation to {approx}0.3 x 10{sup 21} n{center_dot}cm{sup {minus}2} and {approx}0.9 x 10{sup 21} n{center_dot}cm{sup {minus}2} (E >1 MeV), significant heat-to-heat variations in the degree of intergranular and transgranular stress corrosion cracking (IGSCC and TGSCC) were observed. Following irradiation to a fluence of {approx}0.3 x 10{sup 21} n{center_dot}cm{sup {minus}2}, a high-purity laboratory heat of Type 316L SS (Si {approx} 0.024 wt%) exhibited the highest susceptibility to IGSCC. The other 15 alloys exhibited negligible susceptibility to IGSCC at this low fluence. The percentage of TGSCC on the fracture surfaces of SSRT specimens of the 16 alloys at {approx}0.3 x 10{sup 21} n{center_dot}cm{sup {minus}2} (E > 1 MeV) could be correlated well with N and Si concentrations; all alloys that contained <0.01 wt.% N and <1.0 wt. % Si were susceptible, whereas all alloys that contained >0.01 wt.% N or >1.0 wt.% Si were relatively resistant. High concentrations of Cr were beneficial. Alloys that contain <15.5 wt.% Cr exhibited greater percentages of TGSCC and IGSCC than those alloys with {approx}18 wt.% Cr, whereas an alloy that contains >21 wt.% Cr exhibited less susceptibility than the lower-Cr alloys under similar conditions.
Thin semiconductor alloy films: Fabrication and physical properties
NASA Astrophysics Data System (ADS)
Liu, Xinyu
The main emphasis of this thesis is on fabrication and physical properties of thin semiconductor alloy films. We investigated the detailed processes which play a role in fabricating these materials, and systematically investigated the links between the fabrication processes and physical properties of the alloys of interest. Wide-gap semiconductor ternary alloys based on combining group-II and group-VI elements were grown by molecular beam epitaxy (MBE) over a wide range of compositions. The indices of refraction of these II-VI ternary alloys were measured at wavelengths below their respective energy gaps. A set of empirical parameters were establish for each alloy family, which can then be used to calculate the index of refraction for an arbitrary alloy composition at arbitrary wavelength. We applied the single effective oscillator (SEO) model to the experimental data in order to examine the effect of the covalency (or ionicity) of these semiconductor alloys, and to establish a method for extrapolating physical properties for different zinc-blende II-VI compounds. Furthermore, to fit the data near the energy gap, an additional term was added to the SEO model, which accounts for the effect of the direct energy gap. In addition to our investigation of II-VI-based alloys, we also fabricated ferromagnetic semiconductor III-Mn-V alloys using a low temperature MBE technique. A thorough investigation of the physical properties (such as growth, magnetic, and transport properties) of III-Mn-V alloys was carried out. Specifically, we have studied two issues involving these materials: low temperature annealing of GaMnAs under different strain conditions; and fabrication of hybrid magnetic structures comprised of GaMnAs and ZnMnSe, the latter system involving antiferromagnetic interactions between the Mn ions. Furthermore, we fabricated semiconductor superlattices of ZnSe1-x Tex and GaAs1-xSbx in which the chemical composition x varies sinusoidally along the direction of growth, and we studied the physical properties of these novel structures. The sinusoidal nature of the compositional profiles of these materials was inferred from the presence of only a single superlattice Fourier component in the x-ray diffraction spectra. Superlattice formation is additionally supported by systematic photoluminescence data. In the end, we have fabricated and studied various digital alloys of III-V/Mn, where Mn-containing monolayers are "inserted" periodically in the III-V host material. Most of these digital structures exhibited ferromagnetism at low temperature, as demonstrated by hysteresis loops in the magnetization, and a metallic p-type conductivity with a strong anomalous Hall effect. The GaSb/Mn digital system exhibited high temperature ferromagnetic behavior, as demonstrated by a strong anomalous Hall effect characterized by hysteresis loops up to 400 K.
Passive Corrosion Behavior of Alloy 22
R.B. Rebak; J.H. Payer
Alloy 22 (NO6022) was designed to stand the most aggressive industrial applications, including both reducing and oxidizing acids. Even in the most aggressive environments, if the temperature is lower than 150 F (66 C) Alloy 22 would remain in the passive state having particularly low corrosion rates. In multi-ionic solutions that may simulate the behavior of concentrated ground water, even at near boiling temperatures, the corrosion rate of Alloy 22 is only a few nano-meters per year because the alloy is in the complete passive state. The corrosion rate of passive Alloy 22 decreases as the time increases. Immersion corrosion testing also show that the newer generation of Ni-Cr-Mo alloys may offer a better corrosion resistance than Alloy 22 only in some highly aggressive conditions such as in hot acids.
Environmental fatigue in aluminum-lithium alloys
NASA Technical Reports Server (NTRS)
Piascik, Robert S.
Aluminum-lithium alloys exhibit similar environmental fatigue crack growth characteristics compared to conventional 2000 series alloys and are more resistant to environmental fatigue compared to 7000 series alloys. The superior fatigue crack growth behavior of Al-Li alloys 2090, 2091, 8090, and 8091 is due to crack closure caused by tortuous crack path morphology and crack surface corrosion products. At high R and reduced closure, chemical environment effects are pronounced resulting in accelerated near threshold da/dN. The beneficial effects of crack closure are minimized for small cracks resulting in rapid growth rates. Limited data suggest that the 'chemically small crack' effect, observed in other alloy system, is not pronounced in Al-Li alloys. Modeling of environmental fatigue in Al-Li-Cu alloys related accelerated fatigue crack growth in moist air and salt water to hydrogen embrittlement.
Aqueous recovery of actinides from aluminum alloys
Gray, J.H.; Chostner, D.F.; Gray, L.W.
Early in the 1980's, a joint Rocky Flats/Savannah River program was established to recover actinides from scraps and residues generated during Rocky Flats purification operations. The initial program involved pyrochemical treatment of Molten Salt Extraction (MSE) chloride salts and Electrorefining (ER) anode heel metal to form aluminum alloys suitable for aqueous processing at Savannah River. Recently Rocky Flats has expressed interest in expanding the aluminum alloy program to include treatment of chloride salt residues from a modified Molten Salt Extraction process and from the Electrorefining purification operations. Samples of the current aluminum alloy buttons were prepared at Rocky Flats and sent to Savannah River Laboratory for flowsheet development and characterization of the alloys. A summary of the scrub alloy-anode heel alloy program will be presented along with recent results from aqueous dissolution studies of the new aluminum alloys. 2 figs., 4 tabs.
Hydrogen storage properties of new ternary system alloys: La 2MgNi 9, La 5Mg 2Ni 23, La 3MgNi 14
T Kohno; H Yoshida; F Kawashima; T Inaba; I Sakai; M Yamamoto; M Kanda
The hydrogen storage properties of the new ternary system alloys, La2MgNi9, La5Mg2Ni23, La3MgNi14, were investigated. As a result, the negative electrode of the La5Mg2Ni23 alloy (La0.7Mg0.3Ni2.8Co0.5) showed a large discharge capacity (410 mAh\\/g), 1.3 times larger than that of AB5 type alloys. These ternary system alloys were found to be mainly composed of stacked AB5 and AB2 structure subunits in
Materials data handbook: Stainless steel type 301
NASA Technical Reports Server (NTRS)
Muraca, R. F.; Whittick, J. S.
A summary of the materials property information for stainless steel type 301 is presented. The scope of the information includes physical and mechanical properties at cryogenic, ambient, and elevated temperatures. Information on material procurement, metallurgy of the alloy, corrosion, environmental effects, fabrication, and bonding is developed.
Ohmic contact for P type indium phosphide
NASA Technical Reports Server (NTRS)
Hawrylo, Frank Z. (Inventor)
A body including P type indium phosphide has an ohmic contact thereon of an alloy of by weight 81% to 86% gold (Au), 11% to 14% germanium (Ge) and 2% to 5% zinc (Zn). This contact has a low resistance and good adhesion to the indium phosphide body.
Tool wear in turning of titanium alloy after thermohydrogen treatment
NASA Astrophysics Data System (ADS)
Wei, Weihua; Xu, Jiuhua; Fu, Yucan; Yang, Shubao
The influence of hydrogen contents on the tool wear has been mainly focused on the flank wear of the common tool, and the influence of hydrogen contents on the rake crater wear (main wear type) of the tool, particularly for the fine granular material tool, has been less investigated comprehensively. In this paper, for the purpose of researching the influence of hydrogen contents on tool wear, the titanium alloy Ti-6Al-4V is hydrogenated at 800 ¯C by thermohydrogen treatment technology and the turning experiments are carried out by applying uncoated WC-Co cemented carbide tool. The three-dimensional video microscope is used to take photos and measure tool wear. The results show that both of crater wear depth ( K T) and average flank wear width ( V B) firstly decreases and then increases with the increasing of hydrogen content. The maximum reducing amplitude of K T and V B is about 50% and 55%, respectively. Under the given conditions, the optimum hydrogen content is 0.26%. It is considered that the reduction of cutting temperature is an important factor for improving tool wear after the Ti-6Al-4V alloy is properly hydrogenated. Furthermore, the reasons of hydrogen effect on the tool wear are chiefly attributed to comprehensive effect of hydrogen contents on microstructure, physical properties and dynamic mechanical properties of the Ti-6Al-4V alloy. The proposed research provides the basic data for evaluating the machinability of hydrogenation Ti-6Al-4V alloy, and promotes practical application of thermohydrogen treatment technology in titanium alloys.
XRD study on the electrochemical hydriding\\/dehydriding behavior of the LaMgNiCotype hydrogen storage alloys
Yongfeng Liu; Hongge Pan; Mingxia Gao; Yongquan Lei; Qidong Wang
Electrochemical hydriding\\/dehydriding behavior of the LaMgNi-based alloy La0.7Mg0.3(Ni0.85Co0.15)3.5 consisting of a (La,Mg)Ni3 phase with the PuNi3-type rhombohedral structure and a LaNi5 phase with the CaCu5-type hexagonal structure was systematically investigated by means of X-ray diffraction (XRD) analyses. The results indicate that the PuNi3-type rhombohedral structure and the CaCu5-type hexagonal structure of the alloy are still preserved during hydriding\\/dehydriding process. For
Alcoa: the alloy constraint analyzer
Daniel Jackson; Ian Schechter; Hya Shlyahter
Alcoa is a tool for analyzing object models. It has a range of uses. At one end, it can act as a support tool for object model diagrams, checking for consistency of multiplicities and generating sample snapshots. At the other end, it embodies a lightweight formal method in which subtle properties of behaviour can be investigated.Alcoa's input language, Alloy, is
Alcoa: the Alloy constraint analyzer
Daniel Jackson; Ian Schechter; Ilya Shlyakhter
Alcoa is a tool for analyzing object models. It has a range of uses. At one end, it can act as a support tool for object model diagrams, checking for consistency of multiplicities and generating sample snapshots. At the other end, it embodies a lightweight formal method in which subtle properties of behaviour can be investigated. Alcoa's input language, Alloy,
Introduction to hydrogen in alloys
Westlake, D.G.
Substitutional alloys, both those that form hydrides and those that do not, are discussed, but with more emphasis on the former than the latter. This overview includes the following closely related subjects: (1) the significant effects of substitutional solutes on the pressure-composition-temperature (PCT) equilibria of metal-hydrogen systems, (2) the changes in thermodynamic properties resulting from differences in atom size and from modifications of electronic structure, (3) attractive and repulsive interactions between H and solute atoms and the effects of such interactions on the pressure dependent solubility for H, (4) H trapping in alloys of Group V metals and its effect on the terminal solubility for H (TSH), (5) some other mechanisms invoked to explain the enhancement (due to alloying) of the (TSH) in Group V metals, and (6) H-impurity complexes in alloys of the metals Ni, Co, and Fe. Some results showing that an enhanced TSH may ameliorate the resistance of a metal to hydrogen embrittlement are presented.
Recent developments in light alloys
NASA Technical Reports Server (NTRS)
Woodward, R W
This report is intended to cover the progress that has been made in both the manufacture and utility of light alloys in the United States since the first part of 1919. Duralumin is extensively discussed both as to manufacture and durability.
NASA Astrophysics Data System (ADS)
Leibs, Chris; Ross, Ian; Syed, Maarij; Siahmakoun, Azad
We have performed surface plasmon resonance (SPR) experiments in the Kretchmann configuration on prisms coated with 500Ý10 nm single metal and alloy thin-films. The thin films are grown by magnetron sputtering and are binary alloy films (Nickel/Chrome with 80/20 concentration). In addition, for comparison we will also present results for pure metal films (Nickel and Chromium). We have observed a pronounce SPR signal at 41.24^o Ý0.01at 633 nm for the Nichrome film while neither of the metal thin-films (Ni or Cr) yields an SPR effect. Aided by the surface morphology and the SPR signal observations, we modeled the effective dielectric constant of the metal alloy by comparing the SPR response of the alloy to that of the individual metal films. We will also show how SPR results can be better understood by analyzing the SPR data correlated with ellipsometric data obtained from these films as well as x-ray analysis (for composition and structure information), and AFM analysis (for surface topography).
Iron alloys with new functional properties obtained during reverse martensitic transformation
NASA Astrophysics Data System (ADS)
Sagaradze, V. V.; Danilchenko, V. E.; L'Heritier, P.; Sagaradze, I. V.
It was shown that different types of the austenite (homogeneous and inhomogeneous polyhedral, or submicrocrystalline and nanocrystalline plate austenite) can be formed, providing new functional properties of various steels and alloys. The austenite formed during a partial ?to? transformation increases considerably the strength of the martensite, enhances the coercive force and improves the square shape of the hysteresis loop of maraging steels. The thermal expansion coefficient of the austenitic alloy type 32Ni can be adjusted over broad limits thanks to different ?to? transformation conditions. A stainless steel with a structure of alternating laths of the martensite and the austenite has a high resistance to radiation void formation.
Irradiation growth in zirconium and its alloys
NASA Astrophysics Data System (ADS)
Rogerson, A.
The UKAEA Northern Research Laboratories (Risley) have recently completed an underlying research study on irradiation growth in zirconium and its alloys. During this study, irradiation growth measurements have been made on a range of well-characterized single-crystal and polycrystalline iodide zirconium, commercial alloys Zircaloy-2 and Zr-2.5 wt% Nb, and high-purity zirconium-tin alloys in different metallurgical conditions following irradiation in the DIDO reactor at AERE Harwell. Irradiations were performed in three rigs operating at irradiation temperatures between 353 and 673 K. An important feature of the experimental programme was the capability to perform repeat length measurements on individual growth specimens at intervals during their irradiation programme. This facility has allowed accurate monitoring of the growth phenomenon and changes in growth behaviour induced by the combined effects of irradiation temperature and accumulated fast neutron dose over large dose ranges. This paper reviews the main experimental results from this programme and discusses them in terms of current understanding of the growth process. Thus, it has been observed that, in annealed Zircaloy-2 at temperatures between 553 and 673 K, a transition from saturating growth to accelerating growth rates occurs with increasing dose. The dose above which this "growth breakaway" takes place is seen to be inversely dependent on irradiation temperature in mis temperature range. The well-documented difference in growth behaviour between annealed and cold-worked Zircaloy-2 observed at relatively low irradiation temperatures, in which cold-worked material grows at a high linear rate over large dose ranges, is not observed at 673 K. Comparison is made with reported results on similar material irradiated in other irradiation facilities. The growth data are interpreted in terms of recent theories regarding the development during fast neutron irradiation of a cold-worked microstructure consisting of < a>- and < c>-type dislocations. Irradiation growth behaviour of annealed polycrystalline iodide zirconium between 353 and 673 K contrasts strongly with that in annealed Zircaloy-2 with low irradiation growth rates being observed over a large dose and temperature range. The influence of key irradiation parameters on the growth process have been examined in a series of studies initiated as part of a collaborative programme with AECL Chalk River Nuclear Labs. Final results from the studies on annealed and deformed single-crystal zirconium are reported here. They show that growth saturates rapidly at low dose in annealed single-crystal material irradiated at 353 and 553 K but that a gradual increase in growth strain is observed on irradiation to high dose at 553 K. Single-crystal specimens heavily swaged prior to irradiation at 353 K and given different pre-irradiation heat-treatments exhibit high near-linear or accelerating growth rates. These growth data are interpreted in terms of the importance of grain boundaries and twin boundaries as sinks for point defects which allow point defect separation and hence growth to continue to high dose. Finally, the results of growth experiments performed on Zr-0.1% Sn and Zr-1.5% Sn alloys at 353 and 553 K are reviewed. These experiments confirm the important role played by alloying additions and impurities on the growth process in zirconium and Zircaloy-2.
Structural Properties of Mismatched Alloys
NASA Astrophysics Data System (ADS)
Mousseau, Normand
The problem of understanding the local structure of disordered alloys has been around for a long time. In this thesis, I look more specifically at the effect of size-mismatch disorder in binary alloys under many forms: metallic and semiconductor alloys, bulk and surfaces, two and three dimensional systems. I have studied the limitations of a central-force model (CFM) and an embedded-atom potential (EAM) in describing the local structure of binary metallic alloys composed of Ag, Au, Cu, Ni, Pd, or Pt. Although an analytical model developed using the CFM explains qualitatively well the experimental and numerical results, in many cases, it is important to add electronic density effects through a more sophisticated potential like EAM in order to agree quantitatively with experiment. I have also looked at amorphous and crystalline silicon-germanium alloys. It turns out that the effect of size-mismatch is the same on a crystalline and an amorphous lattice. In the latter case, it can be seen as a perturbation of the much larger disorder due to the amorphisation process. However, the analytical predictions differ, for both the crystalline and amorphous alloys, from the experimental results. If one is to believe the data, there is only one possible explanation for this inconsistency: large amounts of hydrogen are present in the samples used for the measurements. Since the data analysis of EXAFS results is not always straightforward, I have proposed some experiments that could shed light on this problem. One of these experiments would be to look at the (111) surface of a Si-Ge alloy with a scanning tunneling microscope. I also present in this thesis the theoretical predictions for the height distribution at the surface as well as some more general structural information about the relaxation in the network as one goes away from the surface. Finally, I have studied the effect of size -mismatch in a purely two dimensional lattice, looking for mismatch-driven phase transitions. Although it is possible to map size-mismatch on an effective temperature at low disorder, I have not been able to find any indication that a hexatic phase exists in these 2d systems. Since systems were studied with different potentials in very large unit cells, the conclusion is that the hexatic phase is not universal for two dimensional networks.
Microstructure and Strength Characteristics of Alloy 617 Welds
T.C. Totemeier; H. Tian; D.E. Clark; J.A. Simpson
Three types of high-temperature joints were created from alloy 617 base metal: fusion welds, braze joints, and diffusion bonds. The microstructures of all joint types and tensile properties of fusion welds and braze joints were characterized. Sound fusion welds were created by the GTAW process with alloy 617 filler wire. Cross-weld tensile strengths were equal to the parent metal at temperatures of 25, 800, and 1000¯C; ductilities of the joints were only slightly lower than that of the parent metal. Failure occurred in the weld fusion zone at room temperature and in the parent metal at elevated temperatures. Incomplete wetting occurred in joints produced by vacuum brazing using AWS BNi-1 braze alloy, believed to be due to tenacious Al and Ti oxide formation. Incompletely bonded butt joints showed relatively poor tensile properties. A second set of braze joints has been created with faying surfaces electroplated with pure Ni prior to brazing; characterization of these joints is in progress. Conditions resulting in good diffusion bonds characterized by grain growth across the bondline and no porosity were determined: vacuum bonding at 1150¯C for 3 hours with an initial uniaxial stress of 20 MPa (constant ram displacement). A 15 çm thick pure Ni interlayer was needed to achieve grain growth across the bondline. Tensile testing of diffusion bonds is in progress
Metallurgical Bonding Development of V-4Cr-4Ti Alloy for the DIII-D Radiative Divertor Program
Smith, J.P.; Johnson, W.R.; Trester, P.W.
General Atomics (GA), in conjunction with the Department of Energy`s (DOE) DIII-D Program, is carrying out a plan to utilize a vanadium alloy in the DIII-D tokamak as part of the DIII-D Radiative Divertor (RD) upgrade. The V-4Cr-4Ti alloy has been selected in the U.S. as the leading candidate vanadium alloy for fusion applications. This alloy will be used for the divertor fabrication. Manufacturing development with the V-4Cr-4Ti alloy is a focus of the DIII-D RD Program. The RD structure, part of which will be fabricated from V-4Cr-4Ti alloy, will require many product forms and types of metal/metal bonded joints. Metallurgical bonding methods development on this vanadium alloy is therefore a key area of study by GA. Several solid state (non-fusion weld) and fusion weld joining methods are being investigated. To date, GA has been successful in producing ductile, high strength, vacuum leak tight joints by all of the methods under investigation. The solid state joining was accomplished in air, i.e., without the need for a vacuum or inert gas environment to prevent interstitial impurity contamination of the V-4Cr-4Ti alloy.
Optical absorption properties of dispersed gold and silver alloy nanoparticles.
Wilcoxon, Jess
The oldest topic in nanoscience is the size-dependent optical properties of gold and silver colloids or nanoparticles, first investigated scientifically by Michael Faraday in 1857. In the modern era, advances in both synthesis and characterization have resulted in new insights into the size-dependent absorbance of Au and Ag nanoparticles with sizes below the classical limit for Mie theory. In this paper we discuss the synthesis and properties of core/shell and nanoalloy particles of Au and Ag, compare them to particles of pure gold and silver, and discuss how alloying affects nanoparticle chemical stability. We show that composition, size, and nanostructure (e.g., core/shell vs quasi-random nanoalloy) can all be employed to adjust the optical absorbance properties. The type of nanostructure--core/shell vs alloy--is reflected in their optical absorbance features. PMID:19708105
The Weathering of Aluminum Alloy Sheet Materials Used in Aircraft
NASA Technical Reports Server (NTRS)
Mutchler, Willard
This report presents the results of an investigation of the corrosion of aluminum alloy sheet materials used in aircraft. It has for its purpose to study the causes of corrosion embrittlement in duralumin-type alloys and the development of methods for its elimination. The report contains results, obtained in an extensive series of weather-exposure tests, which reveal the extent to which the resistance of the materials to corrosion was affected by variable factors in their heat treatment and by the application of various surface protective coatings. The results indicate that the sheet materials are to be regarded as thoroughly reliable, from the standpoint of their permanence in service, provided proper precautions are taken to render them corrosion-resistant.
INCOLOY alloy 803, a cost effective alloy for high temperature service
Ganesan, P.; Plyburn, J.A.; Tassen, C.S. [INCO Alloys International, Inc., Huntington, WV (United States)
INCOLOY alloy 800 was the first of the 800 series of alloys invented by Inco Alloys International in the 1940`s. Because of its excellent oxidation and carburization resistance as well as high temperature creep strength, alloy 800 found uses for many applications such as heat treating hardware, petrochemical processing, home appliances, food processing, industrial heating, super-heater and re-heater tubing and soon became the workhorse material for the chemical processing industries. Alloy 803 has superior resistance to oxidation and carburization without sacrificing mechanical properties. In this paper the history of alloy 800 with introductions of alloys 800H and 800HT and the differences in properties and chemical compositions among them will be described. The development of alloy 803 for petrochemical applications is also covered. The performance of alloy 803 in cyclic oxidation, carburization and sulfidation tests will be presented and compared with several alloys including alloy HPM. The mechanical properties of alloy 803 including room temperature and high temperature tensile data and stress rupture and creep strengths up to 1,093 C (2,000 F) will be presented. The choice of available filler metals and welding electrodes to join alloy 803, using gas metal arc welding and shielded metal arc welding processes, will also be presented.
A study of the microstructures and the effects of coating on Nd2Fe14B alloys
A. Ahmad; P. J. McGuiness; I. R. Harris
The microstructures of a range of as-cast and homogenized Nd-Fe-B-type alloys have been investigated. In the as-cast condition, all of the materials with compositions close to that of stoichiometry contain elemental free iron. Results indicate that this free iron can be removed completely from the Nd12.28Fe81.87B5.85 (Nd2.1Fe 14B) alloy by homogenization. Fine particles of the homogenized alloys and of the
Effect of the high-speed impact of a shaped-charge jet on the strength of titanium alloys
NASA Astrophysics Data System (ADS)
Minakov, V. N.; Minakov, N. V.; Puchkova, V. Yu.; Rudyk, N. D.; Khomenko, G. E.
The effect of the high-speed impact of a shaped-charge jet on the structure and strength of commercially pure VT1 titanium and VT22, VT3-1, and PT-3V titanium alloys is studied in comparison with AK6 aluminum alloy and Br OTsS bronze. The strength is characterized in terms of the microhardness. The microhardness versus structure is analyzed in the near-surface layer along the channel formed by the shaped-charge jet. The results obtained are used to qualitatively estimate the structural modification, type of fracture, and strength of targets made of the alloys.
Small angle scattering study concerning the effect of residual elements on the radiation behaviour of iron alloys
NASA Astrophysics Data System (ADS)
Ulbricht, A.; B—hmert, J.; Grosse, M.; Strunz, P.
For better understanding of the influence of the deleterious elements on the neutron embrittlement of reactor pressure vessel steels, the microstructural evolution due to neutron irradiation was investigated by SANS experiments at ternary iron alloys with different contents of copper and phosphorus. In every case irradiation produces nanoscaled inhomogeneities. The volume fraction of the inhomogeneities increases with the copper content but not with the phosphorus content. Surprisingly, the high-pure alloy shows a relatively high irradiation effect. The irradiation defects vary in type and kinetic of evolution for the different alloys.
Alloy substantially free of dendrites and method of forming the same
de Figueredo, Anacleto M. (West Newton, MA); Apelian, Diran (West Boylston, MA); Findon, Matt M. (Monson, MA); Saddock, Nicholas (S. Windson, CT)
Described herein are alloys substantially free of dendrites. A method includes forming an alloy substantially free of dendrites. A superheated alloy is cooled to form a nucleated alloy. The temperature of the nucleated alloy is controlled to prevent the nuclei from melting. The nucleated alloy is mixed to distribute the nuclei throughout the alloy. The nucleated alloy is cooled with nuclei distributed throughout.
Effect of Ti Substitution on Thermoelectric Properties of W-Doped Heusler Fe2VAl Alloy
NASA Astrophysics Data System (ADS)
Mikami, M.; Ozaki, K.; Takazawa, H.; Yamamoto, A.; Terazawa, Y.; Takeuchi, T.
Effects of element substitutions on thermoelectric properties of Heusler Fe2VAl alloys were evaluated. By W substitution at the V site, the thermal conductivity is reduced effectively because of the enhancement of phonon scattering resulting from the introduction of W atoms, which have much greater atomic mass and volume than the constituent elements of Fe2VAl alloy. W substitution is also effective to obtain a large negative Seebeck coefficient and high electrical conductivity through an electron injection effect. To change the conduction type from n-type to p-type, additional Ti substitution at the V site, which reduces the valence electron density, was examined. A positive Seebeck coefficient as high as that of conventional p-type Fe2VAl alloy was obtained using a sufficient amount of Ti substitution. Electrical resistivity was reduced by the hole doping effect of the Ti substitution while maintaining low thermal conductivity. Compared with the conventional solo-Ti-substituted p-type Fe2VAl alloy, the ZT value was improved, reaching 0.13 at 450 K.
Status of Testing and Characterization of CMS Alloy 617 and Alloy 230
Ren, Weiju [ORNL; Santella, Michael L [ORNL; Battiste, Rick [ORNL; Terry, Totemeier [Idaho National Laboratory (INL); Denis, Clark [Idaho National Laboratory (INL)
Status and progress in testing and characterizing CMS Alloy 617 and Alloy 230 tasks in FY06 at ORNL and INL are described. ORNL research has focused on CMS Alloy 617 development and creep and tensile properties of both alloys. In addition to refurbishing facilities to conduct tests, a significant amount of creep and tensile data on Alloy 230, worth several years of research funds and time, has been located and collected from private enterprise. INL research has focused on the creep-fatigue behavior of standard chemistry Alloy 617 base metal and fusion weldments. Creep-fatigue tests have been performed in air, vacuum, and purified Ar environments at 800 and 1000 C. Initial characterization and high-temperature joining work has also been performed on Alloy 230 and CCA Alloy 617 in preparation for creep-fatigue testing.
BAs-GaAs Semiconductor Alloys as a Photovoltaic Alternative to Nitride Alloys
Hart, G. L. W.; Zunger, A.
Nitrogen alloyed III-V semiconductor compounds have been intensely studied in recent years due to unusual effects caused by nitrogen alloying. These effects are exploited in band gap engineering for specific applications such as solar cells and blue lasers.
Hacker, Randi; Tsutsui, William
Broadcast Transcript: According to the Japanese, you can tell a lot about a person by their blood type: Type A is the farmer, calm and responsible; Type B is the hunter, independent and creative; Type AB is humanistic, cool and sociable; and Type O...
The relative stress-corrosion-cracking susceptibility of candidate aluminum-lithium alloys for aerospace applications
NASA Technical Reports Server (NTRS)
Pizzo, P. P.
Stress corrosion tests of Al-Li-Cu powder metallurgy alloys are described. Alloys investigated were Al-2.6% Li-1.4% and Al-2.6% Li-1.4% Cu-1.6% Mg. The base properties of the alloys were characterized. Process, heat treatment, and size/orientational effects on the tensile and fracture behavior were investigated. Metallurgical and electrochemical conditions are identified which provide reproducible and controlled parameters for stress corrosion evaluation. Preliminary stress corrosion test results are reported. Both Al-Li-Cu alloys appear more susceptible to stress corrosion crack initiation than 7075-T6 aluminum, with the magnesium bearing alloy being the most susceptible. Tests to determine the threshold stress intensity for the base and magnesium bearing alloys are underway. Twelve each, bolt loaded DCB type specimens are under test (120 days) and limited crack growth in these precracked specimens has been observed. General corrosion in the aqueous sodium chloride environment is thought to be obscuring results through crack tip blunting.
The effect of zirconium on the isothermal oxidation of nominal Ni-14Cr-24Al alloys
NASA Technical Reports Server (NTRS)
Kahn, A. S.; Lowell, C. E.; Barrett, C. A.
The isothermal oxidation of Ni-14Cr-24Al-xZr-type alloys was performed in still air at 1100, 1150, and 1200 C for times up to 200 hr. The zirconium content of the alloys varied from 0-0.63 atom percent (a/o). The oxidized surfaces were studied by optical microscopy, X-ray diffraction, and scanning electron microscopy. The base alloy was an alumina former with the zirconium-containing alloys also developing some ZrO2. The addition of zirconium above 0.066 a/o increased the rate of weight gain relative to the base alloy. Due to oxide penetratio, the weight gain increased with Zr content; however, the scale thickness did not increase. The Zr did increase the adherence of the oxide, particularly at 1200 C. The delta W/A vs. time data fit the parabolic model of oxidation. The specific diffusion mechanism operative could not be identified by analysis of the calculated activation energies. Measurements of the Al2O3 scale lattice constants yielded the same values for all alloys.
Potential High-Temperature Shape-Memory Alloys Identified in the Ti(Ni,Pt) System
NASA Technical Reports Server (NTRS)
Noebe, Ronald D.; Biles, Tiffany A.; Garg, Anita; Nathal, Michael V.
"Shape memory" is a unique property of certain alloys that, when deformed (within certain strain limits) at low temperatures, will remember and recover to their original predeformed shape upon heating. It occurs when an alloy is deformed in the low-temperature martensitic phase and is then heated above its transformation temperature back to an austenitic state. As the material passes through this solid-state phase transformation on heating, it also recovers its original shape. This behavior is widely exploited, near room temperature, in commercially available NiTi alloys for connectors, couplings, valves, actuators, stents, and other medical and dental devices. In addition, there are limitless applications in the aerospace, automotive, chemical processing, and many other industries for materials that exhibit this type of shape-memory behavior at higher temperatures. But for high temperatures, there are currently no commercial shape-memory alloys. Although there are significant challenges to the development of high-temperature shape-memory alloys, at the NASA Glenn Research Center we have identified a series of alloy compositions in the Ti-Ni-Pt system that show great promise as potential high-temperature shape-memory materials.
EXAFS studies of the microstructure of semiconductor alloys, defects and semiconductor-metal interfaces
NASA Astrophysics Data System (ADS)
Bunker, Bruce A.
The Extended X-ray Absorption Fine Structure (EXAFS) technique is an extremely useful probe of atomic-scale structure, revealing bond lengths, types and number of neighbors, and vibronic motion of atoms. Further, this information is available for the various constituent atomic species separately. The technique is applicable to microcrystalline materials, amorphous, or glassy materials, to disordered alloys. The applications of EXAFS to the study of disordered semiconductor alloys and to semiconductor surfaces and interfaces are shown. Results are presented for four different systems. First, it is shown that bond lengths are essentially constant as a function of composition x in the dilute magnetic semiconductor Zn(1-x)Mn(x)Se, where the lattice constant changes by over 0.1 wavelength and the alloy undergoes a zincblende-to-wurtzite transition as a function of composition. This result implies a large local distortion in the alloy structure. In the second example, it is shown that the local alloy disorder in the IV-VI alloy Pb(1-x)Ge(x)Te is enough to induce a ferroelectric phase transition. The third example concerns Fe-implanted in Si. Using EXAFS, it is shown that the lattice expands in a breathing-mode distortion about the Fe, while the second-shell actually contracts. Finally, it is shown that by using total external reflection of X-rays and EXAFS, buried interfaces such as Al-GaAs interface may be studied.
Surface alloying of thin-walled metallic tube fragments using pulsed gas plasma flows
NASA Astrophysics Data System (ADS)
Yakushin, V. L.; Hein, A. T.; Dzhumaev, P. S.; Kalin, B. A.; Leont'eva-Smirnova, M. V.; Pol'skii, V. I.
A technique is developed and conditions are determined for the surface liquid-phase alloying with aluminum and chromium of thin-walled tubes made of 12% Cr type steels with the use of high-temperature pulsed gas plasma flows. The surface morphology of the samples subjected to alloying is shown to depend on the type and thickness of a deposited film and the plasma treatment conditions. The optimum plasma treatment conditions are determined; as a result, alloying elements are rather uniformly distributed in a 10-?mthick near-surface layer at a preliminarily deposited film thickness of 0.5 ?m. In this case, the average aluminum content in the surface layer changes in the range 6-18 wt % and the chromium content increases from 12 to 25-40 wt %.
Metallurgical characterization of the fracture of several high strength aluminum alloys
NASA Technical Reports Server (NTRS)
Bhandarkar, M. D.; Lisagor, W. B.
The fracture behavior for structural aluminum alloys (2024, 6061, 7075, and 7178) was examined in selected heat treatments. The investigation included tensile, shear, and precracked notch-bend specimens fractured at ambient temperature under monotonic loading. Specimens were obtained from thin sheets and thick plates and were tested in longitudinal and transverse orientations at different strain rates. Microstructures of alloys were examined using the optical microscope and the scanning electron microscope with associated energy dispersive X ray chemical analysis. Several different types of second phase particles, some not reported by other investigators, were identified in the alloys. Fracture morphology was related to microstructural variables, test variables, and type of commercial product. Specimen orientation examined in the present investigation had little effect on fracture morphology. Test strain rate changes resulted in some change in shear fracture morphology, but not in fracture morphology of tensile specimens.
Corrosion resistance and in vitro response of a novel Ti35Nb2Ta3Zr alloy with a low Young's modulus.
Guo, Yongyuan; Chen, Desheng; Lu, Weijie; Jia, Yuhua; Wang, Liqiang; Zhang, Xianlong
? type titanium alloys have attracted much attention in the biomedical field because they consist of non-cytotoxic elements, show high corrosion resistance, and are biologically compatible. In this study, a novel ? type titanium alloy (Ti35Nb3Zr2Ta) with a Young's modulus of 48 GPa was fabricated and the alloy's corrosion resistance and in vitro response were determined. The results indicate that the novel alloy exhibits comparable corrosion resistance when compared with Ti6Al4V, but in vitro experiments show that osteoblasts attach, spread, proliferate, and differentiate better on Ti35Nb2Ta3Zr than on Ti6Al4V. The high corrosion resistance and satisfactory biocompatibility make the novel Ti35Nb3Zr2Ta alloy a promising biomaterial for surgical implants. PMID:24002775
Characterization of Two ODS Alloys: Chromium-18 ODS and Chromium-9 ODS
NASA Astrophysics Data System (ADS)
Goddard, Julianne
ODS alloys, or oxide dispersion strengthened alloys, are made from elemental or pre-alloyed metal powders mechanically alloyed with oxide powders in a high-energy attributor mill, and then consolidated by either hot isostatic pressing or hot extrusion causing the production of nanometer scale oxide and carbide particles within the alloy matrix; crystalline properties such as creep strength, ductility, corrosion resistance, tensile strength, swelling resistance, and resistance to embrittlement are all observed to be improved by the presence of nanoparticles in the matrix. The presented research uses various methods to observe and characterize the microstructural and microchemical properties of two experimental ODS alloys, 18Cr ODS and 9Cr ODS. The results found aid in assessing the influence of chemical and structural variations on the effectiveness of the alloy, and further aid in the optimization of these advanced alloys for future use in nuclear cladding and structural applications in Generation IV nuclear reactors. Characterization of these alloys has been conducted in order to identify the second-phase small precipitates through FESEM, TEM, EDS, Synchrotron X-ray diffraction analysis, and CuKalpha XRD analysis of bulk samples and of nanoparticles after extraction from the alloy matrix. Comparison of results from these methods allows further substantiation of the accuracy of observed nanoparticle composition and identification. Also, TEM samples of the two alloys have been irradiated in-situ with 1 MeV Kr and 300 keV Fe ions to various doses and temperatures at the IVEM-Tandem TEM at Argonne National Laboratory and post-irradiated characterization has been conducted and compared to the pre-irradiated characterization results in order to observe the microstructural and microchemical evolution of nanoparticles under irradiation. Overall in the as-received state, the initial Y2O3 is not found anymore and in addition to oxide particles the alloys contain carbides. In both alloys a good correlation between the EDAX and XRD results is found both before and after extraction of the nanoparticles from the matrix. Both alloys show the presence of Y-Ti-O particles as well as Al-containing compounds, and Cr-carbides of the M23C6 type. The oxide particles in 18Cr ODS appear to be stable under irradiation up to 20dpa at 500¯C. There may be a decrease in density and increase in average size in both particle families. In the 9Cr ODS alloy, comparison of results from both methods of analysis also shows the presence (in the as-received state) of a combination of carbides and Y-containing oxides, and Al-containing compounds are also found. After irradiation small Y-Ti-O particles appear to be enriched with Cr and C, and larger particles show indications of amorphization at 25¯C. Further irradiations on both alloys will provide deeper insight into the structural and chemical stability of the oxide and carbide nanoparticles and the merit of both alloys as structural and cladding materials in future nuclear applications.
Tribological Performance of 6061 Aluminum Alloy\\/Graphite Materials under Oil-Lubricated and Dry Sliding Conditions
Jen Fin Lin; Ying Chong Yung; Chi Yuan Tsao
A thrust-on-washer adapter was used to stimulate flat-on-flat-type contacts under lubricated and dry sliding conditions. The upper specimens were made of a cast aluminum alloy, A356.0 Al, and the lower specimens were prepared by powder metallurgy. Fine graphite particles were mixed with 6061 aluminum alloy powders, by means of cold pressing and sintering to create a self-lubricating composite material by
Resistance of medium-carbon complex-alloy steels under the influence of impact-abrasive effects
K. R. Chaikovskii; Yu. Yu. Demina; K. A. Lanskaya; A. G. Rakhshtadt; L. S. Livshits
The wear resistance of medium-carbon complex-alloy chromium-nickel steels was studied. The specimens were medium-carbon complex-alloy steel of the Kh3N3MFB type. Isothermal soaking in the subcritical temperature ranges during heat treatment promoted an increased steel resistance to brittle failure as a result of austenite impoverishment and combining martensite with carbon. Results of the impact-abrasive wear test were found to confirm that
Machinability of hypereutectic silicon-aluminum alloys
NASA Astrophysics Data System (ADS)
Tanaka, T.; Akasawa, T.
The machinability of high-silicon aluminum alloys made by a P/M process and by casting was compared. The cutting test was conducted by turning on lathes with the use of cemented carbide tools. The tool wear by machining the P/M alloy was far smaller than the tool wear by machining the cast alloy. The roughness of the machined surface of the P/M alloy is far better than that of the cast alloy, and the turning speed did not affect it greatly at higher speeds. The P/M alloy produced long chips, so the disposal can cause trouble. The size effect of silicon grains on the machinability is discussed.
Nickel aluminide alloy suitable for structural applications
Liu, Chain T. (Oak Ridge, TN)
Alloys for use in structural applications based upon NiAl to which are added selected elements to enhance room temperature ductility and high temperature strength. Specifically, small additions of molybdenum produce a beneficial alloy, while further additions of boron, carbon, iron, niobium, tantalum, zirconium and hafnium further improve performance of alloys at both room temperature and high temperatures. A preferred alloy system composition is Ni--(49.1.+-.0.8%)Al--(1.0.+-.0.8%)Mo--(0.7.+-.0.5%)Nb/Ta/Zr/Hf--(nearly zero to 0.03%)B/C, where the % is at. % in each of the concentrations. All alloys demonstrated good oxidation resistance at the elevated temperatures. The alloys can be fabricated into components using conventional techniques.
Nickel aluminide alloy suitable for structural applications
Liu, C.T.
Alloys are disclosed for use in structural applications based upon NiAl to which are added selected elements to enhance room temperature ductility and high temperature strength. Specifically, small additions of molybdenum produce a beneficial alloy, while further additions of boron, carbon, iron, niobium, tantalum, zirconium and hafnium further improve performance of alloys at both room temperature and high temperatures. A preferred alloy system composition is Ni--(49.1{+-}0.8%)Al--(1.0{+-}0.8%)Mo--(0.7 + 0.5%)Nb/Ta/Zr/Hf--(nearly zero to 0.03%)B/C, where the % is at. % in each of the concentrations. All alloys demonstrated good oxidation resistance at the elevated temperatures. The alloys can be fabricated into components using conventional techniques. 4 figs.
High-temperature property data: Ferrous alloys
Rothman, M.F.
In this book over 250 alloys are organized by AISI number into 10 major sections: Irons, Carbon Steels, Alloy Steels, Low Alloy Constructional Steels, Ultra High Strength Steels, Tool Steels, Maraging Steels, Wrought Stainless Steels, Heat Resistnat Casting Alloys, and Iron Based Rought Superalloys. Each alloy record lists the designation, specifications, UNS number, composition, product forms and a comment on the high-temperature properties and applications. Referenced data is then given for physical properties such as density, specific heat, thermal conductivity, thermal expansion, electrical conductivity, Poisson's ratio, moduli of elasticity and rigidity, etc. Mechanical properties follow, and include tensile properties, shearing and bearing properties, impact properties, creep, stress rupture and stress relaxation and fatigue properties. The last part of the alloy record gives other effects of temperature, such as hot hardness, corrosion, and growth.
Annealing behavior of high permeability amorphous alloys
Rabenberg, L.
Effects of low temperature annealing on the magnetic properties of the amorphous alloy Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ were investigated. Annealing this alloy below 400/sup 0/C results in magnetic hardening; annealing above 400/sup 0/C but below the crystallization temperature results in magnetic softening. Above the crystallization temperature the alloy hardens drastically and irreversibly. Conventional and high resolution transmission electron microscopy were used to show that the magnetic property changes at low temperatures occur while the alloy is truly amorphous. By imaging the magnetic microstructures, Lorentz electron microscopy has been able to detect the presence of microscopic inhomogeneities in this alloy. The low temperature annealing behavior of this alloy has been explained in terms of atomic pair ordering in the presence of the internal molecular field. Lorentz electron microscopy has been used to confirm this explanation.
21 CFR 872.3060 - Noble metal alloy.
Code of Federal Regulations, 2013 CFR
...2013-04-01 2013-04-01 false Noble metal alloy. 872.3060 Section 872.3060... Prosthetic Devices Ï 872.3060 Noble metal alloy. (a) Identification . A noble metal alloy is a device composed primarily of...
21 CFR 872.3710 - Base metal alloy.
Code of Federal Regulations, 2012 CFR
...2012-04-01 2012-04-01 false Base metal alloy. 872.3710 Section 872.3710 ...DEVICES Prosthetic Devices Ï 872.3710 Base metal alloy. (a) Identification . A base metal alloy is a device composed primarily of...
21 CFR 872.3710 - Base metal alloy.
Code of Federal Regulations, 2011 CFR
...2011-04-01 2011-04-01 false Base metal alloy. 872.3710 Section 872.3710 ...DEVICES Prosthetic Devices Ï 872.3710 Base metal alloy. (a) Identification . A base metal alloy is a device composed primarily of...
21 CFR 872.3710 - Base metal alloy.
Code of Federal Regulations, 2014 CFR
...2014-04-01 2014-04-01 false Base metal alloy. 872.3710 Section 872.3710 ...DEVICES Prosthetic Devices Ï 872.3710 Base metal alloy. (a) Identification. A base metal alloy is a device composed primarily of...
21 CFR 872.3060 - Noble metal alloy.
Code of Federal Regulations, 2012 CFR
...2012-04-01 2012-04-01 false Noble metal alloy. 872.3060 Section 872.3060... Prosthetic Devices Ï 872.3060 Noble metal alloy. (a) Identification . A noble metal alloy is a device composed primarily of...
21 CFR 872.3060 - Noble metal alloy.
Code of Federal Regulations, 2011 CFR
...2011-04-01 2011-04-01 false Noble metal alloy. 872.3060 Section 872.3060... Prosthetic Devices Ï 872.3060 Noble metal alloy. (a) Identification . A noble metal alloy is a device composed primarily of...
Copper and nickel adherently electroplated on titanium alloy
NASA Technical Reports Server (NTRS)
Brown, E. E.
Anodic treatment of titanium alloy enables electroplating of tightly adherent coatings of copper and nickel on the alloy. The alloy is treated in a solution of hydrofluoric and acetic acids, followed by the electroplating process.
21 CFR 872.3080 - Mercury and alloy dispenser.
Code of Federal Regulations, 2014 CFR
...2014-04-01 2014-04-01 false Mercury and alloy dispenser. 872.3080 Section...DEVICES Prosthetic Devices Ï 872.3080 Mercury and alloy dispenser. (a) Identification. A mercury and alloy dispenser is a device...
21 CFR 872.3080 - Mercury and alloy dispenser.
Code of Federal Regulations, 2013 CFR
...2013-04-01 2013-04-01 false Mercury and alloy dispenser. 872.3080 Section...DEVICES Prosthetic Devices Ï 872.3080 Mercury and alloy dispenser. (a) Identification. A mercury and alloy dispenser is a device...
21 CFR 872.3080 - Mercury and alloy dispenser.
Code of Federal Regulations, 2012 CFR
...2012-04-01 2012-04-01 false Mercury and alloy dispenser. 872.3080 Section...DEVICES Prosthetic Devices Ï 872.3080 Mercury and alloy dispenser. (a) Identification. A mercury and alloy dispenser is a device...
21 CFR 872.3710 - Base metal alloy.
Code of Federal Regulations, 2010 CFR
...2010-04-01 2010-04-01 false Base metal alloy. 872.3710 Section 872.3710 ...DEVICES Prosthetic Devices Ï 872.3710 Base metal alloy. (a) Identification . A base metal alloy is a device composed primarily of...
21 CFR 872.3060 - Noble metal alloy.
Code of Federal Regulations, 2010 CFR
...2010-04-01 2010-04-01 false Noble metal alloy. 872.3060 Section 872.3060... Prosthetic Devices Ï 872.3060 Noble metal alloy. (a) Identification . A noble metal alloy is a device composed primarily of...
The effects of cleaning on the kinetics of in vitro metal release from dental casting alloys.
Wataha, J C; Craig, R G; Hanks, C T
The kinetics of the release of elements from six dental casting alloys into cell-culture medium was assessed by means of atomic absorption spectroscopy. Alloys were evaluated in the polished and polished-cleaned conditions so that the effects of cleaning could be determined. Auger scanning microscopy was used for analysis of the surfaces of selected alloys before and after exposure to the cell-culture medium. Release patterns for each element were characterized by the shape of the dissolution vs. time curve, concentration of the element at 12 h as a percentage of the 72-hour concentration, and the relative slope of the curve from 48 to 72 h. Three patterns of release were observed for elements in these alloys. Type I patterns had logarithmic shapes with relatively large 12-hour concentrations and low 48-72-hour slopes. Type II patterns had logarithmic shapes but with moderate 12-hour concentrations and 48-72-hour slopes. Type III patterns were polynomial in shape, had relatively low 12-hour concentrations, and had large 48-72-hour slopes. Cleaning did not change the pattern of release but did generally significantly decrease the quantities of elements released (p = 0.05). The type of dissolution vs. time curve appeared to be dependent upon the element and the composition of the alloy. When cleaning reduced dissolution, surface analyses showed that the cleaning process increased the abundance of elements such as Au and Pd and reduced the abundance of Ag and Cu. Elements which were released from the alloys were more abundant on the surface than in the bulk in both polished and polished-cleaned conditions.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1629458
Luminescence properties of oxide coatings on aluminum alloys
NASA Astrophysics Data System (ADS)
Pershukevich, P. P.; Shabrov, D. V.; Osipov, V. P.; Schreiber, J.; Lapina, V. A.
This is a study of the luminescence properties of coatings formed on aluminum alloys by anodizing in electrolytic solutions based on oxalic, sulfuric, and tartaric-sulfonic acids. At least two emission centers, with band maxima in the ranges of 390-410 and 470-510 nm, can be reliably identified in the photoluminescence spectra. The first type of center is characterized by single-band photoluminescence excitation spectra and the second, by two-band spectra. An analysis of the two-band photoluminescence excitation (PLE) spectra in the range of 470-510 nm shows that the position of the narrow short-wavelength PLE spectrum near 272 nm is independent of the type of acid used in the anodization process. The position and shape of the other PLE spectral bands depend both on the type of acid used and on the processing of the alloy or alumina surfaces. It is assumed that defect-free alumina centers are responsible for the 272 nm PLE band, while the other photoluminescence bands are caused primarily by different divacancies of oxygen ( {F_2^+} , F 2, and {F_2^{+2}} centers) whose origin is governed by the type of electrolyte.
Machinability of hypereutectic silicon-aluminum alloys
T. Tanaka; T. Akasawa
The machinability of high-silicon aluminum alloys made by a P\\/M process and by casting was compared. The cutting test was\\u000a conducted by turning on lathes with the use of cemented carbide tools. The tool wear by machining the P\\/M alloy was far smaller\\u000a than the tool wear by machining the cast alloy. The roughness of the machined surface of the
Nickel Aluminide Alloys Made By Rapid Solidification
NASA Technical Reports Server (NTRS)
Ray, Ranjan
Collection of reports describes experimental metallurgical studies of nickel aluminide alloys made by rapid-solidification powder-metallurgy process. Process incorporates ultrafine dispersions of hard, stable refractory compounds and rare-earth oxides into alloys. Effects of dispersoids on high-temperature mechanical properties (flow stress, and compressive and tensile creep) of alloys investigated. Results indicate specific additives result in improved strength and ductility.
Fabrication and magnetic properties of granular alloys
A. Gavrin; C. L. Chien
Granular alloys of iron with other transition metals have been fabricated in both Al2O3 and SiO2 matrices. Both stable (Fe-Ni, Fe-Co) and metastable (Fe-Cu) alloys have been achieved. Under appropriate deposition conditions, the grains are single-phase alloys ranging in size from 15 to 50 A?. Superparamagnetism and enhanced coercivity have been observed, and the effect of grain size on these
Dispersion strengthened superalloys by mechanical alloying
John S. Benjamin
A new process called mechanical alloying has been developed which produces homogeneous composite particles with an intimately\\u000a dispersed, uniform internal structure. Materials formed by hot consolidation of this powder achieve the long-sought combination\\u000a of dispersion strengthening and age-hardening in a high temperature alloy. While the process is amenable to making a variety\\u000a of alloys, its first use has been to
C. F. Cheng; S. F. Bubar; J. J. McCarthy
Three high-strength titanium alloys, (Ti--6Al--4V), (Ti--6Al--6V--2Sn), ; and (Ti--13V--11Cr--3Al), were corrosion tested in 800 deg F ammoniated water at ; pH 10. There was no significant change in mechanical properties before and after ; exposure in test solution for two alloys, (Ti -- 6Al --4V) and (Ti-- 6Al --2Sn). ; The high vanadiumchromium alloy (Ti -- 13V -- 11Cr-- 3Al)
Mechanism of copper-nickel alloy electrodeposition
E. Chassaing; K. Vu Quang; R. Wiart
The codeposition kinetics of copper and nickel alloys in complexing citrate ammonia electrolytes has been investigated by means of polarization and electrochemical impedance techniques. It is confirmed that the two-step discharge of the complexed cupric species Cu(II)Cit is diffusion-controlled during the alloy deposition, resulting in an increase in the nickel content of the alloy with electrode polarization. Impedance spectra are
High toughness-high strength iron alloy
NASA Technical Reports Server (NTRS)
Stephens, J. R.; Witzke, W. R. (inventors)
An iron alloy is provided which exhibits strength and toughness characteristics at cryogenic temperatures. The alloy consists essentially of about 10 to 16 percent by weight nickel, about 0.1 to 1.0 percent by weight aluminum, and 0 to about 3 percent by weight copper, with the balance being essentially iron. The iron alloy is produced by a process which includes cold rolling at room temperature and subsequent heat treatment.
Alloy nanoparticle synthesis using ionizing radiation
Nenoff, Tina M. (Sandia Park, NM); Powers, Dana A. (Albuquerque, NM); Zhang, Zhenyuan (Durham, NC)
A method of forming stable nanoparticles comprising substantially uniform alloys of metals. A high dose of ionizing radiation is used to generate high concentrations of solvated electrons and optionally radical reducing species that rapidly reduce a mixture of metal ion source species to form alloy nanoparticles. The method can make uniform alloy nanoparticles from normally immiscible metals by overcoming the thermodynamic limitations that would preferentially produce core-shell nanoparticles.
Tribochemical equilibrium in mechanical alloying of metals
K. B. Gerasimov; A. A. Gusev; E. Y. Ivanov; V. V. Boldyrev
The structure of the product in mechanical alloying depends both on the elemental composition and the milling conditions. An increase of ball energy led to more pronounced crystallinity of the product. Mechanical alloying at small ball energy leads to the formation of amorphous alloys for Zr-Co and Cu-Ti systems. Demixing of Ti3Cu4 into crystalline TiCu and TiCu4 and demixing of
Controlling quality of ferroalloys and alloying additives in the manufacture of nickel alloys for nuclear applications
Nickel alloys supplied to the nuclear industry must meet strict requirements for quality and traceability of constituents. Ensuring that end products meet those requirements involves careful control of the raw materials used in melting the alloys. Especially important is an effective system of quality control for purchasing and consuming ferroalloys and alloying additives. Development and operation of such a system
CrNiMoCo surface alloying layer formed by plasma surface alloying in pure iron
Xiaoping Liu; Yuan Gao; Zhonghou Li; Zhong Xu; Wenhuai Tian; Bin Tang
Using double glow plasma alloying technique, a multi-elements alloyed layer containing elements of Cr, Ni, Mo and Co was formed on the surface of pure iron. After undergoing suitable aging treatment followed solid solution treatment, the formed alloying layer keeps a good combination of corrosion resistance and wear resistance. The relationship between the process parameters of heat treatments and the
Properties and microstructures for dual alloy combinations of three superalloys with alloy 901
NASA Technical Reports Server (NTRS)
Harf, F. H.
Dual alloy combinations have potential for use in aircraft engine components such as turbine disks where a wide range of stress and temperature regimes exists during operation. Such alloy combinations may directly result in the conservation of elements which are costly or not available domestically. Preferably, a uniform heat treatment yielding good properties for both alloys should be used. Dual alloy combinations of iron rich Alloy 901 with nickel base superalloys Rene 95, Astroloy, or MERL 76 were not isostatically pressed from prealloyed powders. Individual alloys, alloy mixtures, and layered alloy combinations were given the heat treatments specified for their use in turbine disks or appropriate for Alloy 901. Selected specimens were overaged for 1500 hr at 650 C. Metallographic examinations revealed the absence of phases not originally present in either alloy of a combination. Mechanical tests showed adequate properties in combinations of Rene 95 or Astroloy with Alloy 901 when given the Alloy 901 heat treatment. Combinations with MERL 76 had better properties when given the MERL 76 heat treatment. The results indicate that these combinations are promising candidates for use in turbine disks.
Vacuum annealing of titanium alloys
E. A. Borisova; I. I. Shashenkova; A. I. Krivko; T. V. Barasheva
1.The optimal temperature range for hydrogen removal in vacuum annealing is 550650¯C. The holding time depends on the hydrogen concentration, the thickness of the section, and the hydrogen concentration desired.2.The presence of oxide films formed during annealing in air at temperatures up to 500¯C has no effect on the properties of titanium alloys after subsequent vacuum annealing.3.During vacuum annealing of
Goodwin, F.E. [International Lead Zinc Research Organization Inc., Research Triangle Park, NC (United States)
Recent advances in the technology and applications of lead and its alloys include improved batteries for electric vehicles, and lead-containing dampers that impart earthquake resistance to buildings and highway structures. For zinc, notable accomplishments include further development of zinc-coated steels for automotive and construction applications, and development of an extrusion process for zinc over steel pipe in the oil production industry.
Hard magnetic bulk amorphous alloys
A. Inoue; T. Zhang; A. Takeuchi
An amorphous phase in Ln-Fe-Al (Ln=Nd and Pr) systems is formed in wide composition ranges of 0 to 90 at% Fe and 0 to 93 at% Al by melt spinning. Ferromagnetic Ln90-xFexAl10 bulk amorphous alloys with high coercive force (iHc) at room temperature are obtained by copper mold casting. The maximum diameter of the cylindrical amorphous samples is 12 mm
Molybdenum disilicide alloy matrix composite
Petrovic, J.J.; Honnell, R.E.; Gibbs, W.S.
Compositions of matter consisting of matrix materials having silicon carbide dispersed throughout them and methods of making the compositions are disclosed. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms. 3 figures.
Molybdenum disilicide alloy matrix composite
Petrovic, John J. (Los Alamos, NM); Honnell, Richard E. (Los Alamos, NM); Gibbs, W. Scott (Los Alamos, NM)
Compositions of matter consisting of matrix materials having silicon carbide dispersed throughout them and methods of making the compositions. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms.
Molybdenum disilicide alloy matrix composite
Petrovic, John J. (Los Alamos, NM); Honnell, Richard E. (Los Alamos, NM); Gibbs, W. Scott (Los Alamos, NM)
Compositions of matter consisting of matrix matrials having silicon carbide dispersed throughout them and methods of making the compositions. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms.
A high speed twin roll caster for aluminum alloy strip
T Haga; S Suzuki
A melt drag twin roll caster (MDTRC) was devised in order to cast aluminum alloy strips at a speed higher than 30m\\/min. A3003 alloy, A5182 alloy, Al6mass%Si alloy and Al12mass%Si alloy were cast into thin strips using the MDTRC. These alloys could be cast into strips at a speed of up to 60m\\/min. The thickness of the strips was about
Abstract types have existential type
John C. Mitchell; Gordon D. Plotkin
Abstract data type declarations appear in typed programming languages like Ada, Alphard, CLU and ML. This form of declaration binds a list of identifiers to a type with associated operations, a composite value we call a data algebra. We use a second-order typed lambda calculus SOL to show how data algebras may be given types, passed as parameters, and returned