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In Vitro Corrosion and Cytocompatibility of ZK60 Magnesium Alloy Coated with Hydroxyapatite by a Simple Chemical Conversion Process for Orthopedic Applications
PubMed Central
Magnesium and its alloys—a new class of degradable metallic biomaterials—are being increasingly investigated as a promising alternative for medical implant and device applications due to their advantageous mechanical and biological properties. However, the high corrosion rate in physiological environments prevents the clinical application of Mg-based materials. Therefore, the objective of this study was to develop a hydroxyapatite (HA) coating on ZK60 magnesium alloy substrates to mediate the rapid degradation of Mg while improving its cytocompatibility for orthopedic applications. A simple chemical conversion process was applied to prepare HA coating on ZK60 magnesium alloy. Surface morphology, elemental compositions, and crystal structures were characterized using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction, respectively. The corrosion properties of samples were investigated by immersion test and electrochemical test. Murine fibroblast L-929 cells were harvested and cultured with coated and non-coated ZK60 samples to determine cytocompatibility. The degradation results suggested that the HA coatings decreased the degradation of ZK60 alloy. No significant deterioration in compression strength was observed for all the uncoated and coated samples after 2 and 4 weeks' immersion in simulated body fluid (SBF). Cytotoxicity test indicated that the coatings, especially HA coating, improved cytocompatibility of ZK60 alloy for L929 cells.
Wang, Bing; Huang, Ping; Ou, Caiwen; Li, Kaikai; Yan, Biao; Lu, Wei
Microstructure, in vitro corrosion and cytotoxicity of Ca-P coatings on ZK60 magnesium alloy prepared by simple chemical conversion and heat treatment.
Magnesium alloys are potential biodegradable materials for biomedical application. But their poor corrosion resistance may result in premature failure of implants. In this study, to solve this problem, Ca-P coatings were prepared on ZK60 magnesium alloy by a simple chemical conversion process and heat treatment. Surface characterization showed that a flake-like Dicalcium phosphate dihydrate (DCPD) (CaHPO?·2H?O) coating was formed on ZK60 alloy by the chemical conversion process. DCPD transformed into Dicalcium phosphate anhydrous (DCPa) (CaHPO?) and Ca?P?O? after heat treatment. Results of potentiodynamic polarization showed the corrosion potential of ZK60 was increased from -1666?mV to -1566?mV with DCPD coating, while -1515?mV was obtained after heat treatment. The corrosion current density of ZK60 was measured to be reduced from 35?µA/cm² to 3.5?µA/cm² with DCPD coating, while a further reduction to 1?µA/cm² was observed after heat treatment. This indicated that the coatings improved the substrate corrosion resistance significantly, and apparently, the heat-treated coating had a higher corrosion resistance. Immersion test demonstrated that both the coatings could provide protection for the substrate and the heat-treated coating could induce deposition of bone-like apatite. Cytotoxicity evaluation revealed that none of the samples induced toxicity to L-929 cells after 1- and 3-day culture. The cytocompatibility of ZK60 was improved by the coatings, with the following sequence: uncoated ZK60?ZK60?
Li, Kaikai; Wang, Bing; Yan, Biao; Lu, Wei
The anodization of ZK60 magnesium alloy in alkaline solution containing silicate and the corrosion properties of the anodized films
NASA Astrophysics Data System (ADS)
The anodization of ZK60 magnesium alloy in an alkaline electrolyte of 100 g/l NaOH + 20 g/l Na 2B 4O 7·10H 2O + 50 g/l C 6H 5Na 3O 7·2H 2O + 60g/l Na 2SiO 3·9H 2O was studied in this paper. The corrosion resistance of the anodic films was studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques and the microstructure and composition of films were examined by SEM and XRD. The influence of anodizing time was studied and the results show that the anodizing time of 60 min is suitable for acquiring films with good corrosion resistance. The influence of current density on the corrosion resistance of anodizing films was also studied and the results show that the film anodized at 20 mA/cm 2 has the optimum corrosion resistance. The film formed by anodizing in the alkaline solution with optimized parameters show superior corrosion resistance than that formed by the traditional HAE process. The XRD pattern shows that the components of the anodized film consist of MgO and Mg 2SiO 4.
Wu, Hai-lan; Cheng, Ying-liang; Li, Ling-ling; Chen, Zhen-hua; Wang, Hui-min; Zhang, Zhao
The in vitro degradation process and biocompatibility of a ZK60 magnesium alloy with a forsterite-containing micro-arc oxidation coating.
Magnesium has attracted much attention as a class of biodegradable metallic biomaterials. In this study, a silicate electrolyte-based micro-arc oxidation (MAO) treatment was adopted to prepare forsterite-containing MAO coatings on a ZK60 magnesium alloy in order to decrease the degradation rate and increase the biological property of the alloy. Four anodization voltages were chosen to prepare the MAO coatings. The cell experiment showed a cytotoxicity of grade 0 for the MAO-coated alloy to L929 cells and the hemolytic ratio was dramatically decreased for the MAO-coated alloy compared with the bare one. The corrosion resistance and the degradation behavior of the MAO-coated ZK60 alloy were studied using drop tests, electrochemical measurements and immersion tests. The results indicate that the MAO coating could effectively decrease the initial degradation rate of the alloy. The corrosion resistance of MAO coating was increased with the elevation of the preparation voltage. A degradation model for ZK60 alloy with a forsterite-containing MAO coating was proposed. Based on the model, the MAO-coated alloy experiences destruction and restoration simultaneously, and the coating fails in a peeling-off mode. PMID:23261923
Lin, Xiao; Tan, Lili; Zhang, Qiang; Yang, Ke; Hu, Zhuangqi; Qiu, Jianhong; Cai, Yong
Correlation of plastic deformation and dynamic recrystallization in magnesium alloy ZK60
Microsoft Academic Search
The mechanisms of plastic deformation and dynamic recrystallization (DRX) in a Mg–5.8% Zn–0.65% Zr alloy were studied by compression tests at temperatures between 423 and 723 K and at strain rates ranging from 10?5 to 10?1 s?1. It was shown that the mechanisms of DRX depended on the operating deformation mechanisms which changed with temperature. Low-temperature DRX (LTDRX below 473
A Galiyev; R Kaibyshev; G Gottstein
Microstructure, texture evolution, mechanical properties and corrosion behavior of ECAP processed ZK60 magnesium alloy for biodegradable applications.
Ultra-fine grained ZK60 Mg alloy was obtained by multi-pass equal-channel angular pressing at different temperatures of 250°C, 200°C and 150°C. Microstructural observations showed a significant grain refinement after ECAP, leading to an equiaxed and ultrafine grain (UFG) structure with average size of 600nm. The original extrusion fiber texture with planes oriented parallel to extrusion direction was gradually undermined during ECAP process and eventually it was substituted by a newly stronger texture component with considerably higher intensity, coinciding with ECAP shear plane. A combination of texture modification and grain refinement in UFG samples led to a marked reduction in mechanical asymmetric behavior compared to the as-received alloy, as well as adequate mechanical properties with about 100% improvement in elongation to failure while keeping relatively high tensile strength. Open circuit potential, potentiodynamic and weight loss measurements in a phosphate buffer solution electrolyte revealed an improved corrosion resistance of UFG alloy compared to the extruded one, stemming from a shift of corrosion regime from localized pitting in the as-received sample to a more uniform corrosion mode with reduced localized attack in ECAP processed alloy. Compression tests on immersed samples showed that the rate of loss of mechanical integrity in the UFG sample was lower than that in the as-received sample. PMID:24971801
Mostaed, Ehsan; Hashempour, Mazdak; Fabrizi, Alberto; Dellasega, David; Bestetti, Massimiliano; Bonollo, Franco; Vedani, Maurizio
In vitro degradation and biocompatibility of a strontium-containing micro-arc oxidation coating on the biodegradable ZK60 magnesium alloy
Magnesium alloys are promising biodegradable implant candidates for orthopedic application. In the present study, a phosphate-based micro-arc oxidation (MAO) coating was applied on the ZK60 alloy to decrease its initial degradation rate. Strontium (Sr) was incorporated into the coating in order to improve the bioactivity of the coating. The in vitro degradation studies showed that the MAO coating containing Sr owned a better initial corrosion resistance, which was mainly attributed to the superior inner barrier layer, and a better long-term protective ability, probably owning to its larger thickness, superior inner barrier layer and the superior apatite formation ability. The degradation of MAO coating was accompanied by the formation of degradation layer and Ca-P deposition layer. The in vitro cell tests demonstrated that the incorporation of Sr into the MAO coating enhanced both the proliferation of preosteoblast cells and the alkaline phosphatase activity of the murine bone marrow stromal cells. In conclusion, the MAO coating with Sr is a promising surface treatment for the biodegradable magnesium alloys.
Lin, Xiao; Yang, Xiaoming; Tan, Lili; Li, Mei; Wang, Xin; Zhang, Yu; Yang, Ke; Hu, Zhuangqi; Qiu, Jianhong
Effect of heat treatment on strain hardening of ZK60 Mg alloy
Strain hardening behaviors of extruded ZK60 Mg alloy under different heat treatments (T4, T5 and T6) were studied using uniaxial tensile tests at room temperature. Hardening capacity, strain hardening exponent as well as strain hardening rate curve were obtained according to true plastic stress–strain curves. T5 and T6 treatments decrease strain hardening of extruded ZK60 alloy, and subsequently give rise
Xianhua Chen; Fusheng Pan; Jianjun Mao; Jingfeng Wang; Dingfei Zhang; Aitao Tang; Jian Peng
Corrosion resistance enhancement of magnesium ZK60/SiC composite by Nd:YAG laser cladding
SciTech Connect
Magnesium-based metal matrix composites (MMCs) which possess high specific stiffness and strength are attractive in applications where it is advantageous to employ low density structural materials, such as in aerospace, automotive and sports industries. However, it is well known that magnesium is one of the most active structural metals, and is usually susceptible to galvanic corrosion when in contact with other materials, especially, in wet and salt-laden environments. The corrosion is enhanced when an additional phase is added to magnesium alloys because most of the magnesium/reinforcement systems are electrochemically unstable. Previous investigations have revealed that high power laser surface treatment is an efficient way to improve the corrosion resistance of magnesium alloys and their composite materials, without resulting in significant adverse effects on the properties of the bulk materials. In the present study, laser cladding of an Al-Si eutectic alloy on magnesium ZK60/SiC composite was performed using a multiwave Nd:YAG laser. In order to avoid excessive oxidation, argon shielding gas was blown directly into the laser-generated molten pool instead of using a vacuum condition.
Yue, T.M.; Wang, A.H.; Man, H.C. [Hong Kong Polytechnic Univ., Kowloon (Hong Kong). Dept. of Mfg. Engineering] [Hong Kong Polytechnic Univ., Kowloon (Hong Kong). Dept. of Mfg. Engineering
Compounded Surface Modification of ZK60 Mg Alloy by High Current Pulsed Electron Beam+Micro-plasma Oxidation
In this study, compounded surface modification technology-high current pulsed electron beam (HCPEB) + micro-plasma oxidation (MPO) was applied to treat ZK60 Mg alloys. The characteristics of the microstructure of ZK60 Mg alloy after single MPO and HCPEB+MPO compounded treatment were investigated by SEM. The results showed that the density of the ceramic layer of HCPEB+MPO-treated ZK60 Mg alloy was improved and defects were reduced compared to that under MPO treatment alone. Surface modified layer of ZK60 Mg alloys treated by HCPEB+MPO was divided into three zones, namely the top loose ceramic zone, middle compact zone and inside HCPEB-induced melted zone. Corrosion resistance of ZK60 Mg alloy before and after the compounded surface modification was measured in a solution of 3.5% NaCl by potentiodynamic polarization curves. It was found that the corrosion current density of ZK60 Mg alloys could be reduced by about three orders of magnitude, from 311 ?A/cm2 of the original sample to 0.2 ?A/cm2 of the HCPEB+MPO-treated sample. This indicates the great application potential of the HCPEB+MPO compounded surface modification technology in improving the corrosion resistance of ZK60 Mg alloys in the future.
Gao, Bo; Hao, Yi; Tu, Ganfeng; Shi, Weixi; Yu, Fuxiao; Li, Shiwei
Effects of cathode current density on structure and corrosion resistance of plasma electrolytic oxidation coatings formed on ZK60 Mg alloy
Current density is a key factor in plasma electrolytic oxidation (PEO) process. The aim of this paper is to study the effects of cathode current density on the composition, morphology, and corrosion resistance of ceramic coatings on ZK60 magnesium alloy prepared through bi-polar plasma electrolytic oxidation in Na3PO4 solution. The phase composition, morphology, and corrosion resistance were studied by X-ray
Peibo Su; Xiaohong Wu; Yun Guo; Zhaohua Jiang
Comparison of degradation behavior and the associated bone response of ZK60 and PLLA in vivo.
The aim of this study was to investigate whether ZK60, an extruded magnesium alloy, reacts in vivo with an appropriate host response, and to investigate how microarc oxidation treatment influences this in vivo corrosion behavior. Twelve cylinders were machined from as-extruded ZK60, with six cylinders treated with MAO and six left untreated; poly-l-lactic acid pins were used as a control to compare biocompatibility. These cylinders were implanted into the right distal femur of mice along the transepicondylar axis from the medial condyle. Microcomputerized tomography was used to quantitatively analyze corrosion in a nondestructive manner in vivo and the corrosion rate was calculated based on the volume measurements of the residual implants. The physiological response of the rats postimplantation was obtained by clinical observation and blood biochemical analysis. Histological analyses of the soft tissue around the implants were used to assess bone response in relation to the implants. The results obtained clearly indicate that the untreated ZK60 alloy showed high degradation rates in vivo, and that MAO treatment had a significant but unsatisfying effect on protecting the implant from further corrosion. Compared with PLLA, the ZK60 alloy showed good osteoconductivity and osteoinductivity, and, according to biochemical indicators, had good biocompatibility in vivo. PMID:23666894
Qi, Zheng-Rong; Zhang, Qiang; Tan, Li-Li; Lin, Xiao; Yin, Yi; Wang, Xiu-Li; Yang, Ke; Wang, Yan
Nitride Nanoparticle Addition to Beneficially Reinforce Hybrid Magnesium Alloys
This study is aimed at understanding the function of two nitride nanoparticles regarding altering the mechanical properties of hybrid magnesium alloys in relation to nanoparticle-matrix reactivity. Nitride nanoparticles were selected for reinforcement purposes due to the affinity between magnesium and nitrogen (in parallel with the well-known magnesium-oxygen affinity). AZ91/ZK60A and AZ31/AZ91 hybrid magnesium alloys were reinforced with AlN and Si3N4 nanoparticles (respectively) using solidification processing followed by hot extrusion. Each nitride nanocomposite exhibited higher tensile strength than the corresponding monolithic hybrid alloy. However, AZ91/ZK60A/AlN exhibited slightly lower tensile ductility than AZ91/ZK60A, while AZ31/AZ91/Si3N4 exhibited higher tensile ductility than AZ31/AZ91. The formation of high strain zones (HSZs) (from particle surfaces inclusive) during tensile deformation as a significant mechanism supporting ductility enhancement was addressed. AZ91/ZK60A/AlN exhibited lower and higher compressive strength and ductility (respectively) compared to AZ91/ZK60A, while AZ31/AZ91/Si3N4 exhibited higher and unchanged compressive strength and ductility (respectively) compared to AZ31/AZ91. Nanograin formation (recrystallization) during room temperature compressive deformation (as a toughening mechanism) in relation to nanoparticle-stimulated nucleation (NSN) ability was also discussed. The beneficial (as well as comparative) effects of the respective nitride nanoparticle on each hybrid alloy are studied in this article.
Paramsothy, Muralidharan; Chan, Jimmy; Kwok, Richard; Gupta, Manoj
Magnesium and magnesium alloys
This new handbook is the most comprehensive publication of engineering information on commercial magnesium alloys under one cover in the last sixty years. Prepared with the cooperation of the International Magnesium Association, it presents the industrial practices currently used throughout the world, as well as the properties of the products critical to their proper application. Contents include: general characteristics; physical metallurgy; melting, refining, alloying, recycling, and powder production; casting; heat treatment; forging, rolling, and extrusion; semisolid processing; forming; joining; cleaning and finishing; selection, application, and properties of grades and alloys; design considerations; mechanical behavior and wear resistance; fatigue and fracture-mechanics; high-temperature strength and creep; corrosion and stress-corrosion cracking; specification.
Avedesian, M.; Baker, H. [eds.
The Dynamic Flow and Failure Behavior of Magnesium and Magnesium Alloys
We review the dynamic behavior of magnesium alloys through a survey of the literature and a comparison with our own high-strain-rate experiments. We describe high-strain-rate experiments (at typical strain rates of 103 s-1) on polycrystalline pure magnesium as well as two magnesium alloys, AZ31B and ZK60. Both deformation and failure are considered. The observed behaviors are discussed in terms of the fundamental deformation and failure mechanisms in magnesium, considering the effects of grain size, strain rate, and crystallographic texture. A comparison of current results with the literature studies on these and other Mg alloys reveals that the crystallographic texture, grain size, and alloying elements continue to have a profound influence on the high-strain-rate deformation behavior. The available data set suggests that those materials loaded so as to initiate extension twinning have relatively rate-insensitive strengths up to strain rates of several thousand per second. In contrast, some rate dependence of the flow stress is observed for loading orientations in which the plastic flow is dominated by dislocation mechanisms.
Eswar Prasad, K.; Li, B.; Dixit, N.; Shaffer, M.; Mathaudhu, S. N.; Ramesh, K. T.
Magnesium silicide intermetallic alloys
Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not
Gh. Li; H. S. Gill; R. A. Varin
Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots\\u000a of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under\\u000a overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not
G. H. Li; H. S. Gill; R. A. Varin
Tensile and compressive properties of wrought magnesium alloys at high rates of strain
Impact tensile and compressive properties of three different wrought magnesium alloys (AZ31B-F, AZ61A-F and ZK60A-T5) are determined using two different versions of the split Hopkinson bar. Tension and compression specimens are machined from extruded bars parallel to the extrusion axis. Tensile and compressive stress-strain data at strain rates of 1000-2000/s are presented and compared with those at quasi-static and medium strain rates obtained on an Instron 4505 testing machine. The effects of strain rate and loading mode on the ultimate strength, ultimate strain and absorbed energy are examined in details. It is shown that the wrought magnesium alloys exhibit a pronounced asymmetric yield behavior in tension and compression at both low and high rates of strain. It is also shown that the ultimate strengths increase with increasing strain rate, and the strain rate dependence of the ultimate strain and absorbed energy differs, depending the wrought magnesium alloys tested.
Yokoyama, T.
Methods of induction melting an ultra-low-density magnesium silicide (Mg[sub 2]Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg[sub 2]Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 [times] 10[sup 5] Pa), at a temperature close to but not exceeding 1,105 C [+-] 5 C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg[sub 2]Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg[sub 2]Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg[sub 2]Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg[sub 2]Si matrix were found in the Mg[sub 2]Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.
Li, G.H.; Gill, H.S.; Varin, R.A. (Univ. of Waterloo, ON (Canada). Dept. of Mechanical Engineering)
Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not exceeding 1105 °C ± 5 °C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg2Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg2Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg2Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg2Si matrix were found in the Mg2Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.
Li, Gh.; Gill, H. S.; Varin, R. A.
An Introduction to Magnesium Alloys.
National Technical Information Service (NTIS)
This report describes the characteristics and properties of existing commercial magnesium alloys and compares these relative to each other. Although this report is not intended to serve as a source of design data for magnesium alloys, it was written to pr...
J. B. Hallowell H.R. Ogden
Magnesium Alloys and their Applications
In the recent years there has been a dramatic increase in research activity and also applications of magnesium alloys. The driving force is the growing demand by the automobile industry resulting from the pressure to reduce weight and hence to reduce the fuel consumption. The U.S. car industry incorporates the largest amount of magnesium at the present time. In Europe,
Karl U. Kainer
In the recent years there has been a dramatic increase in research activity and also applications of magnesium alloys. The driving force is the growing demand by the automobile industry resulting from the pressure to reduce weight and hence to reduce the fuel consumption. The U.S. car industry incorporates the largest amount of magnesium at the present time. In Europe, Volkswagen had a history of using magnesium in the VW Beetle. Volkswagen, in common with other major car producers has initiated a major research and development programme for advanced magnesium materials. The main emphasis of this book is in the field of general physical metallurgy and alloy development refelcting the need to provide a wider range of alloys both casting and wrought alloys to meet the increasing demands of industry. Other topics are nevertheless well represented such as casting, recycling, joining, corrosion, and surface treatment.
Kainer, Karl U.
Effects of Titanium Nitride Surface Coating on High Speed Impact Induced Damage of Magnesium Alloys at Cryogenic Temperature
This reports a summary of our recent high speed impact tests aiming to clarify the impact characteristic of magnesium alloy with titanium nitride coating. We placed 100 mm x 100 mm and 3 mm thick magnesium alloy plates, ZK60A-T5 at 298 K, 223 K and 153 K, which were coated with 1 micron thick titanium nitride layer based on a hollow cathode discharge method. We also tested with uncoated magnesium plates. The plates were impinged by 8 mm diameter aluminum alloy (Al2017-T4) spheres at impact speeds of 0.5 to 1.7 km/s in a two-stage light gas gun in the SWRC, IFS, Tohoku Univ. Two specimens were installed at 100 mm interval vertically to the spheres in a cryogenic test chamber [1]. Impact phenomena were visualized with shadowgraph arrangements and recorded with ImaCon 200. As a result, the effect of surface coating on surface fracture was examined. We found the increase of hole areas in proportional to the impact speed and a clear difference of penetration hole and fracture patterns between impact speed of 0.5 km/s and higher impact speeds. The titanium nitride coating was effective to favorably control the damage process. [1] Numata,D. et al., Shock Waves (2008), 18:169-183.
Takayama, K.; Numata, D.; Kubota, R.; Shimamoto, A.
Electrodeposition of magnesium and magnesium/aluminum alloys
Electrolytes and plating solutions for use in processes for electroplating and electroforming pure magnesium and alloys of aluminum and magnesium and also electrodeposition processes. An electrolyte of this invention is comprised of an alkali metal fluoride or a quaternary ammonium halide, dimethyl magnesium and/or diethyl magnesium, and triethyl aluminum and/or triisobutyl aluminum. An electrolyte may be dissolved in an aromatic hydrocarbon solvent to form a plating solution. The proportions of the component compounds in the electrolyte are varied to produce essentially pure magnesium or magnesium/aluminum alloys having varying selected compositions.
Mayer, Anton (Los Alamos, NM)
Mayer, A.
CO2 laser welding of magnesium alloys
Metallic alloys with a low mass density can be considered to be basic materials in aeronautic and automotive industry. Magnesium alloys have better properties than aluminum alloys in respect of their low density and high resistance to traction. The main problems of magnesium alloy welding are the inflammability, the crack formation and the appearance of porosity during the solidification. The
Mohammed Dhahri; Jean Eric Masse; J. F. Mathieu; Gerard Barreau; Michel L. Autric
Nondestructive spot test method for magnesium and magnesium alloys
NASA Technical Reports Server (NTRS)
A method for spot test identification of magnesium and various magnesium alloys commonly used in aerospace applications is described. The spot test identification involves color codes obtained when several drops of 3 M hydrochloric acid are placed on the surface to be tested. After approximately thirty seconds, two drops of this reacted acid is transferred to each of two depressions in a spot plate for additions of other chemicals with subsequent color changes indicating magnesium or its alloy.
Wilson, M. L. (inventor)
Stress Drop LED by Twinning during Initial Stage of Hot Compression of Twin-Roll Cast Mg-5.51%Zn-0.49%Zr Alloy
Flow stress behavior during initial stage of hot compression of twin-roll cast ZK60 magnesium alloy was characterized by employing deformation temperature of 300°C and 400°C, and a given strain rate of 10-2s-1. A stress drop during initial stage of hot compression at 300°C, generally led by dynamic recrystallization, was found to be attributed to twinning, correspondingly to dynamic recrystallization as deformation temperature was raised to 400°C.
Liu, Zhiyi; Xu, Jing; Hou, Yanhui; Kang, Sukbong
Imparting passivity to vapor deposited magnesium alloys
Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread implementation of magnesium alloys is currently hindered by their relatively poor corrosion resistance. The objective of this research dissertation is to develop a scientific basis for the creation of a corrosion resistant magnesium alloy. The corrosion resistance of magnesium alloys is affected by several interrelated factors. Among these are alloying, microstructure, impurities, galvanic corrosion effects, and service conditions, among others. Alloying and modification of the microstructure are primary approaches to controlling corrosion. Furthermore, nonequilibrium alloying of magnesium via physical vapor deposition allows for the formation of single-phase magnesium alloys with supersaturated concentrations of passivity-enhancing elements. The microstructure and surface morphology is also modifiable during physical vapor deposition through the variation of evaporation power, pressure, temperature, ion bombardment, and the source-to-substrate distance. Aluminum, titanium, yttrium, and zirconium were initially chosen as candidates likely to impart passivity on vapor deposited magnesium alloys. Prior to this research, alloys of this type have never before been produced, much less studied. All of these metals were observed to afford some degree of corrosion resistance to magnesium. Due to the especially promising results from nonequilibrium alloying of magnesium with yttrium and titanium, the ternary magnesium-yttrium-titanium system was investigated in depth. While all of the alloys are lustrous, surface morphology is observed under the scanning electron microscope. The corrosion rate of the nonequilibrium sputtered alloys, as determined by polarization resistance, is significantly reduced compared to the most corrosion resistant commercial magnesium alloys. The open circuit potentials of the sputter deposited alloys are significantly more noble compared to commercial, equilibrium phase magnesium alloys. Galvanic corrosion susceptibility has also been considerably reduced. Nonequilibrium magnesium-yttrium-titanium alloys have been shown to achieve passivity autonomously by alteration of the composition chemistry of the surface oxide/hydroxide layer. Self-healing properties are also evident, as corrosion propagation can be arrested after initial pitting of the material. A clear relationship exists between the corrosion resistance of sputter vapor deposited magnesium alloys and the amount of ion bombardment incurred by the alloy during deposition. Argon pressure, the distance between the source and the substrate, and alloy morphology play important roles in determining the ability of the alloy to develop a passive film. Thermal effects, both during and after alloy deposition, alter the stress state of the alloys, precipitation of second phases, and the mechanical stability of the passive film. An optimal thermal treatment has been developed in order to maximize the corrosion resistance of the magnesium-yttrium-titanium alloys. The significance of the results includes the acquisition of electrochemical data for these novel materials, as well as expanding the utilization of magnesium alloys by the improvement in their corrosion resistance. The magnesium alloys developed in this work are more corrosion resistant than any commercial magnesium alloy. Structural components comprised of these alloys would therefore exhibit unprecedented corrosion performance. Coatings of these alloys on magnesium components would provide a corrosion resistant yet galvanically-compatible coating. The broad impact of these contributions is that these new low-density, corrosion resistant magnesium alloys can be used to produce engine
Wolfe, Ryan C.
Formation of Magnesium Silicide by Mechanical Alloying
Elemental Mg and Si powders were mechanically alloyed in a planetary ball mill. The formation of magnesium silicide as well as the formation of magnesium oxide and hydride in the milled powders was studied in detail by X-ray diffraction and scanning differential calorimetry. It was found that direct formation of the magnesium silicide, Mg2Si, occurred after 10 hours of milling
Xiaoping Niu; Li Lu
In vitro and in vivo corrosion measurements of magnesium alloys
The in vivo corrosion of magnesium alloys might provide a new mechanism which would allow degradable metal implants to be applied in musculo-skeletal surgery. This would particularly be true if magnesium alloys with controlled in vivo corrosion rates could be developed. Since the magnesium corrosion process depends on its corrosive environment, the corrosion rates of magnesium alloys under standard in
Frank Witte; Jens Fischer; Jens Nellesen; Horst-Artur Crostack; Volker Kaese; Alexander Pisch; Felix Beckmann; Henning Windhagen
Precipitation and Hardening in Magnesium Alloys
Magnesium alloys have received an increasing interest in the past 12 years for potential applications in the automotive, aircraft, aerospace, and electronic industries. Many of these alloys are strong because of solid-state precipitates that are produced by an age-hardening process. Although some strength improvements of existing magnesium alloys have been made and some novel alloys with improved strength have been developed, the strength level that has been achieved so far is still substantially lower than that obtained in counterpart aluminum alloys. Further improvements in the alloy strength require a better understanding of the structure, morphology, orientation of precipitates, effects of precipitate morphology, and orientation on the strengthening and microstructural factors that are important in controlling the nucleation and growth of these precipitates. In this review, precipitation in most precipitation-hardenable magnesium alloys is reviewed, and its relationship with strengthening is examined. It is demonstrated that the precipitation phenomena in these alloys, especially in the very early stage of the precipitation process, are still far from being well understood, and many fundamental issues remain unsolved even after some extensive and concerted efforts made in the past 12 years. The challenges associated with precipitation hardening and age hardening are identified and discussed, and guidelines are outlined for the rational design and development of higher strength, and ultimately ultrahigh strength, magnesium alloys via precipitation hardening.
Nie, Jian-Feng
Hydrogen storage characteristics of ball-milled magnesium-nickel and magnesium-iron alloys
Of potential hydrogen storage materials, pure magnesium would be best from the standpoint of hydrogen capacity per unit mass. However, pure magnesium has poor hydriding kinetics. Alloying magnesium with nickel and other transition metals aids catalysis of the hydrogen dissociative chemisorption and yields other benefits by lowering the dehydrogenation temperature, although at the expense of decreased storage capacity. Magnesium-nickel alloys
R. L. Holtz; M. A. Imam
Impurity control and corrosion resistance of magnesium-aluminum alloy
The corrosion resistance of magnesium alloys is very sensitive to the contents of impurity elements such as iron. In this study, a series of diecast AXJ530 magnesium alloy samples were prepared with additions of Mn and Fe. Through a comprehensive phase diagram calculation and corrosion evaluation, the mechanisms for the tolerance limit of Fe in magnesium alloy are discussed. This adds a new dimension to control the alloying impurity in terms of alloying composition design and casting conditions.
Liu, M. [GM China Lab] [GM China Lab; Song, GuangLing [ORNL] [ORNL
Constitutive Modeling of Magnesium Alloy Sheets
Magnesium alloy sheets have unique mechanical properties: high in-plane anisotropy/asymmetry of yield stress and hardening response, which have not been thoroughly studied. The unusual mechanical behavior of magnesium alloys has been understood by the limited symmetry crystal structure of h.c.p metals and thus by deformation twinning. In this paper, the phenomenological continuum plasticity models considering the unusual plastic behavior of magnesium alloy sheet were developed for a finite element analysis. A new hardening law based on two-surface model was developed to consider the general stress-strain response of metal sheets such as Bauschinger effect, transient behavior and the unusual asymmetry. Three deformation modes observed during the continuous tension/compression tests were mathematically formulated with simplified relations between the state of deformation and their histories. In terms of the anisotropy and asymmetry of the initial yield stress, the Drucker-Prager's pressure dependent yield surface was modified to include the anisotropy of magnesium alloys. Also, characterization procedures of material parameters for the constitutive equations were presented and finally the correlation of simulation with measurements was performed to validate the proposed theory.
Lee, M. G.; Piao, K.; Wagoner, R. H.; Lee, J. K.; Chung, K.; Kim, H. Y.
Magnesium is the lightest of all metals used as the basis for constructional alloys. It is this property which entices automobile manufacturers to replace denser materials, not only steels, cast irons and copper base alloys but even aluminium alloys by magnesium based alloys. The requirement to reduce the weight of car components as a result in part of the introduction
B. L Mordike; T Ebert
The tensile properties of annealed samples of aluminum -magnesium alloys ; containing 0.001 to 2.8 wt. % magnesium have been determined in the irradiated ; and unirradiated condition. The increase in elastic limit caused by reactor ; irradiation is shown by two effects, an increase proportional to the integrated ; fast-neutron flux that is greater for alloys of lower magnesium
Development of ultra light magnesium-lithium alloys
Magnesium-lithium alloys are among the lowest density metallic materials. Addition of lithium, with a relative density of\\u000a 0·53, in magnesium reduces the density of the alloy significantly. Furthermore, addition of nearly 11 wt.% lithium converts\\u000a hexagonal close packed structure of pure magnesium to a body centered cubic lattice, markedly improving formability of the\\u000a alloy. The development of these alloys, however,
C R Chakravorty
Dendritic solidification of magnesium alloy AZ91
The magnesium alloy AZ91 has been studied under different solidification conditions, to establish the details of the as-cast\\u000a structure. The electron backscattered pattern (EBSP) technique has been used to determine the crystallographic directions\\u000a of the dendrite stem and the secondary arms. Under unidirectional solidification conditions, two different stem directions\\u000a were found: at a low temperature gradient and high growth velocity,
K. Pettersen; O. Lohne; N. Ryum
Feasibility study of twin roll casting process for magnesium alloys
This paper is concerned with the development of a strip casting technology for manufacturing magnesium alloy sheets. The aim of the work is to establish a manufacturing process and technology to facilitate the economical manufacture of high-quality magnesium alloy sheets. Magnesium alloy AZ31, AZ61, AM60 and AZ91 were used to investigate the appropriate manufacturing conditions for use in twin roll
H. Watari; T. Haga; N. Koga; K. Davey
On the precipitation of magnesium silicide in irradiated aluminium–magnesium alloys
Thermal neutron irradiation of aluminium or its alloys causes the production of silicon by transmutation. In aluminium–magnesium alloys, the transmutation-produced silicon reacts with magnesium and forms small precipitates. The precipitation in irradiated Al–Mg alloys is similar to the early stage of aging in thermally treated Al–Mg–Si alloys. This study evidences the simultaneous generation of two crystallographically different precipitate types. On
M. Verwerft
Protective coatings on magnesium and its alloys — a critical review
Magnesium and its alloys have excellent physical and mechanical properties for a number of applications. In particular its high strength:weight ratio makes it an ideal metal for automotive and aerospace applications, where weight reduction is of significant concern. Unfortunately, magnesium and its alloys are highly susceptible to corrosion, particularly in salt-spray conditions. This has limited its use in the automotive
J. E. Gray; B. Luan
Tuning the Hydrogen Storage in Magnesium Alloys
We investigate the hydrogen storage properties of promising magnesium alloys. MgH2 (7.6 wt % H) would be a very useful storage material if the (de)hydrogenation kinetics can be improved and the desorption temperature is markedly lowered. Using first principles calculations, we show that hydrides of Mg-transition metal (TM) alloys adopt a structure that promotes faster (de)hydrogenation kinetics, as is also observed in experiment [1]. Within the lightweight TMs, the most promising alloying element is titanium. Alloying Mg with Ti alone, however, is not sufficient to decrease the stability of the hydride phases, which is necessary to reduce the hydrogen desorption temperature [2]. We find that adding aluminium or silicon markedly destabilizes Mg-Ti hydrides and stabilizes Mg-Ti alloys. Finally, we show that controlling the structure of Mg-Ti-Al(Si) system by growing it as multilayers, has a beneficial influence on the thermodynamic properties and makes it a stronger candidate for hydrogen storage [3].[4pt] Ref: [1] S. Er et al., Phys. Rev. B, 79, 024105 (2009). [2] S. Er et al., J. Phys.: Condens. Matter, 22, 074208 (2010). [3] S. Er et al., J. Phys. Chem. Lett., 1, 1982 (2010).
Er, Suleyman; de Wijs, Gilles A.; Brocks, Geert
Guiding the experimental discovery of magnesium alloys
Magnesium alloys are among the lightest structural materials known and are of considerable technological interest. To develop superior magnesium alloys, experimentalists must have a thorough understanding of the concentration-dependent precipitates that form in a given system, and hence, the thermodynamic stability of crystal phases must be determined. This information is often lacking but can be supplied by first-principles methods. Within the high-throughput framework, AFLOW, T=0 K ground-state predictions are made by scanning a large set of known candidate structures for thermodynamic (formation energy) minima. The following 34 systems are investigated: AlMg, AuMg, CaMg, CdMg, CuMg, FeMg, GeMg, HgMg, IrMg, KMg, LaMg, MgMo, MgNa, MgNb, MgOs, MgPb, MgPd, MgPt, MgRb, MgRe, MgRh, MgRu, MgSc, MgSi, MgSn, MgSr, MgTa, MgTc, MgTi, MgV, MgW, MgY, MgZn, and MgZr (= systems in which the ab initio method predicts that no compounds are stable). Avenues for further investigation are clearly revealed by this work. These include stable phases predicted in compound-forming systems as well as phases predicted in systems reported to be non-compound-forming.
Taylor, Richard H.; Curtarolo, Stefano; Hart, Gus L. W.
Metallic alloys with a low mass density can be considered to be basic materials in aeronautic and automotive industry. Magnesium alloys have better properties than aluminum alloys in respect of their low density and high resistance to traction. The main problems of magnesium alloy welding are the inflammability, the crack formation and the appearance of porosity during the solidification. The laser tool is efficient to overcome the difficulties of manufacturing by conventional processing. Besides, the laser processing mainly using shielding gases allows an effective protection of the metal against the action of oxygen and a small heat affected zone. In this paper, we present experimental results about 5 kW CO2 laser welding of 4 mm-thick magnesium alloy plates provided by Eurocopter France. The focused laser beam has about 0.15 mm of diameter. We have investigated the following sample: WE43, alloy recommended in aeronautic and space applications, is constituted with Mg, Y, Zr, rare earth. More ductile, it can be used at high temperatures until 250 degrees Celsius for times longer than 5000 hours without effects on its mechanical properties. A sample of RZ5 (French Norm: GZ4TR, United States Norm ZE41) is composed of Mg, Zn, Zr, La, rare earth. This alloy has excellent properties of foundry and it allows to the realization of components with complex form. Also, it has a good resistance and important properties of tightness. The parameters of the process were optimized in the following fields: laser power: 2 to 5 kW, welding speed: 1 to 4.5 m/min, focal position: -3 mm to +3 mm below or on the top of the metal surface, shielding gas: helium with a flow of 10 to 60 l/min at 4 bars. Metallurgical analyses and mechanical control are made (macroscopic structure, microscopic structure, interpretations of the structures and localization of possible defects, analyse phases, chemical composition, hardness, tensile test etc.) to understand the parameters influence of welding on the obtained beads. For a given laser power, we considered that the welding speed as well as the focal position strongly influence the macroscopic and microscopic welding aspect, whereas the dependence with the flow of the protection gas is weak. For WE43, the bead appears correct in the macroscopic scale for a laser power of 2 kW, a speed of 2 m/min, a focal position on the metal surface or 1 mm under; and an output helium gas of 50 l/min. For RZ5, a correct weld is obtained with a 3 kW laser power, a welding speed of 2 m/min, a focal position of 1.5 mm under the surface and a 50 l/min output helium gas. The microscopic examination showed that the size of the grains has clearly reduced (reduction factor can be up to 35) without formation of porosities, neither cracks nor inclusions; indeed the measured Vickers microhardness of the weld bead is slightly higher than the basic metal. Experiments show that we obtained adequate parameters for high quality welding without using filler material. In future, we plan to weld at higher speed by optimizing the various parameters of the laser welding (power, focal position welding speed and gas flow, ...). Furthermore, we will try to weld samples with a thickness superior than 4 mm.
Dhahri, Mohammed; Masse, Jean Eric; Mathieu, J. F.; Barreau, Gerard; Autric, Michel L.
Corrosion resistant properties of polyaniline acrylic coating on magnesium alloy
The performance of the paint coating based on acrylic-polyaniline on magnesium alloy ZM 21 has been studied by electrochemical impedance spectroscopy in 0.5% NaCl solution. The polyaniline was prepared by chemical oxidative method of aniline with ammonium persulphate in phosphoric acid medium. The phosphate-doped polyaniline was characterized by FTIR and XRD methods. Acrylic paint containing the phosphate-doped polyaniline was prepared and coated on magnesium ZM 21 alloy. The coating was able to protect the magnesium alloy and no base metal dissolution was noted even after 75 days exposure to sodium chloride solution.
Sathiyanarayanan, S.; Azim, S. Syed; Venkatachari, G.
Potential automotive uses of wrought magnesium alloys
Vehicle weight reduction is one of the major means available to improve automotive fuel efficiency. High-strength steels, aluminum (Al), and polymers are already being used to reduce weight significantly, but substantial additional reductions could be achieved by greater use of low-density magnesium (Mg) and its alloys. Mg alloys are currently used in relatively small quantities for auto parts, generally limited to die castings (e.g., housings). Argonne National Laboratory`s Center for Transportation Research has performed a study for the Lightweight Materials Program within DOE`s Office of Transportation Materials to evaluate the suitability of wrought Mg and its alloys to replace steel/aluminum for automotive structural and sheet applications. Mg sheet could be used in body nonstructural and semi-structural applications, while extrusions could be used in such structural applications as spaceframes. This study identifies high cost as the major barrier to greatly increased Mg use in autos. Two technical R and D areas, novel reduction technology and better hot-forming technology, could enable major cost reductions.
Gaines, L.; Cuenca, R.; Wu, S. [Argonne National Lab., IL (United States); Stodolsky, F. [Argonne National Lab., IL (United States)]|[Argonne National Lab., Washington, DC (United States)
Infrared processing of magnesium wrought alloys
High density infrared (HDI) processing of magnesium alloy sheet allows rapid heat up and cool down and may facilitate a continuous cast/roll process, thereby reducing costs. In a previous study, a plasma arc lamp resulted in an anneal in seconds that compared well to a normal 1 h 500 C anneal. The current study on AZ31 used a bank of quartz infrared lamps both in a lab setting and in a demonstration test at a commercial facility (Manufacturing Sciences, Inc.). Typical reheats and anneals between rolling passes required 2 to 5 minutes for rolling 6 mm sheet down to 1 mm. Tensile tests showed comparable results to normal processing. The near surface microstructure was similar to the center of the sheets. No gross progressive or cumulative effect on mechanical properties was observed from pass to pass. Good surface quality with minimal edge cracking was produced.
Horton Jr, Joe A [ORNL; Blue, Craig A [ORNL; Muth, T [Manufacturing Sciences, Inc.; Bowles, Amanda L [ORNL; Agnew, Sean R [University of Virginia
Bearing tests of magnesium-alloy sheet
Bearing tests of AM-3S, AM-52S, and AM-C57S magnesium-alloy sheet in various thicknesses and tempers were made. Bearing yield and ultimate strengths were determined and compared for various edge distances and for various ratios of loading-pin diameter to sheet thickness. Tensile strengths were determined and ratios of average bearing yield and ultimate strength to tensile strength are given. The results of the tests indicated that ultimate bearing strengths increased with edge distances up to 1.5 to 2 times the diameter of the loading pin; that ultimate bearing strengths are a function of the ratio of pin diameter to sheet thickness; and that these properties are effected only slightly by increases in edge distance greater than 1.5 diameters.
Sharp, W H; Moore, R L
Bearing Tests of Magnesium-alloy Sheet
Hexavalent chromium compounds used for corrosion protection are one of the top hazardous waste materials generated by the U.S. Air Force and legislation is in effect to further restrict their use. Magnesium rich primers that utilize sacrificial magnesium metal pigment to cathodically protect aerospace aluminum alloy substrates are a potential alternative to chromated primers. This material has proven to be
Joel A. Johnson
Creep properties of a fiber-reinforced magnesium alloy
There are both similarities and differences between the creep behavior of f.c.c. metals and an h.c.p. metal such as magnesium. This paper examines these differences and examines the additional creep strengthening that may be introduced in a commercial magnesium alloy such as AZ91 through the introduction of an array of short alumina fibers.
V. Skleni?ka; T. G. Langdon
Chrome-free surface treatments for magnesium alloy
Conversion coatings for magnesium have traditionally been based on immersion treatment in a solution containing hexavalent chromium compounds. However, the need for a replacement surface treatment has been strongly emphasized by the present environmental drive to eliminate hexavalent chromium. The development of permanganate bath chemical conversion coatings for magnesium alloys was studied, using mass gain measurements, measurements of corrosion potential,
H. Umehara; M. Takaya; S. Terauchi
Column strength of magnesium alloy AM-57S
Tests were made to determine the column strength of extruded magnesium alloy AM-57S. Column specimens were tested with round ends and with flat ends. It was found that the compressive properties should be used in computations for column strengths rather than the tensile properties because the compressive yield strength was approximately one-half the tensile yield strength. A formula for the column strength of magnesium alloy AM-57S is given.
Holt, M
Performance of a magnesium–lithium alloy as an anode for magnesium batteries
In this work, we describe an evaluation of an Mg–Li alloy (Li: 13 wt %) for possible use in magnesium primary reserve batteries. Higher OCP for the Mg–Li alloy have been observed in 2 M MgCl2 and MgBr2 electrolyte. The corrosion rate of the Mg–Li alloy is found to be in the order: MgCl2 3)2 4 2 4)2. Mg–Li alloys
A. Sivashanmugam; T. Prem kumar; N. G. Renganathan; S. Gopukumar
In vitro corrosion and biocompatibility of binary magnesium alloys.
As bioabsorbable materials, magnesium alloys are expected to be totally degraded in the body and their biocorrosion products not deleterious to the surrounding tissues. It's critical that the alloying elements are carefully selected in consideration of their cytotoxicity and hemocompatibility. In the present study, nine alloying elements Al, Ag, In, Mn, Si, Sn, Y, Zn and Zr were added into magnesium individually to fabricate binary Mg-1X (wt.%) alloys. Pure magnesium was used as control. Their mechanical properties, corrosion properties and in vitro biocompatibilities (cytotoxicity and hemocompatibility) were evaluated by SEM, XRD, tensile test, immersion test, electrochemical corrosion test, cell culture and platelet adhesion test. The results showed that the addition of alloying elements could influence the strength and corrosion resistance of Mg. The cytotoxicity tests indicated that Mg-1Al, Mg-1Sn and Mg-1Zn alloy extracts showed no significant reduced cell viability to fibroblasts (L-929 and NIH3T3) and osteoblasts (MC3T3-E1); Mg-1Al and Mg-1Zn alloy extracts indicated no negative effect on viabilities of blood vessel related cells, ECV304 and VSMC. It was found that hemolysis and the amount of adhered platelets decreased after alloying for all Mg-1X alloys as compared to the pure magnesium control. The relationship between the corrosion products and the in vitro biocompatibility had been discussed and the suitable alloying elements for the biomedical applications associated with bone and blood vessel had been proposed. PMID:19000636
Gu, Xuenan; Zheng, Yufeng; Cheng, Yan; Zhong, Shengping; Xi, Tingfei
The equal channel angular pressing of magnesium and magnesium alloy powders
Applications for magnesium powders have generally been restricted to the area of pyrotechnology, but with improved safety measures and novel processing technologies there are now more opportunities opening up for magnesium powder metallurgy components. Conventional powder metallurgy involving liquid phase sintering may not be a viable option, however, due to the high reactivity of molten magnesium in air. Solid-state consolidation processes are therefore desirable, with direct powder extrusion and equal channel angular pressing (ECAP) offering real alternatives to the conventional press/sinter routes. With this move toward purely solid-state metallurgy come opportunities for alternative alloy design strategies, potentially leading to microstructures not readily achieved through traditional casting routes. This paper will discuss the suitability of the ECAP route for magnesium powder compaction and explore the novel alloying strategies that become available with the success of these solid-state powder metallurgical processes.
Moss, M.; Lapovok, R.; Bettles, C. J.
Creep behaviour of the ZM21 wrought magnesium alloy
Magnesium cast products have achieved a break-through into industrial lightweight applications, but the development is focusing on alloys belonging to the Mg–Al family, and only few alternative alloys, like the ZM21 alloy (2%Zn, 1%Mn) have been considered. Even though preliminary studies on ZM21 extrudability and high-temperature workability have been recently published, no information is available to date on its creep
M. El Mehtedi; S. Spigarelli; E. Evangelista; G. Rosen
Facile and fast fabrication of superhydrophobic surface on magnesium alloy
Superhydrophobic surface has many special functions and is widely investigated by researchers. Magnesium alloy is one of the lightest metal materials among the practice metals. It plays an important role in automobile, airplane and digital product for reducing devices weight. But due to the low standard potential, magnesium alloy has a high chemical activity and easily be corroded. That seriously impedes the application of magnesium alloy. In the process of fabrication a superhydrophobic surface on magnesium alloy, there are two ineluctable problems that must be solved: (1) high chemical activity and (2) the chemical activity is inhomogeneous on surface. In this study, we solved those problems by using the two characters to gain a rough surface on magnesium alloy and obtained a superhydrophobic surface after following modification process. The results show that the as-prepared superhydrophobic surface has obvious anti-corrosion effect in typically corrosive solution and naturally humid air. The delay-icing and self-cleaning effects are also investigated. The presented method is low-cost, fast and has great potential value in large-scale industry production.
Wang, Zhongwei; Li, Qing; She, Zuxin; Chen, Funan; Li, Longqin; Zhang, Xiaoxu; Zhang, Peng
In vitro decomposition study of coated magnesium alloys
In the last decade, magnesium has resurged as an important biomaterial. It's mechanical properties are very similar to natural bone, and it degrades in vivo to non toxic substances. Unfortunately, corrosion of pure magnesium in vivo is rapid, thus coated alloys that decrease it's corrosion could be used as implants in orthopedics. This presentation will describe the degradation results in a simulated body fluid (SBF).
Piersma, Tyler; White, Desiree; Cheng, Xinggou; Rabago-Smith, Montserrat; Lecronier, David
Magnesium and its alloys applications in automotive industry
The objective of this study is to review and evaluate the applications of magnesium in the automotive industry that can significantly\\u000a contribute to greater fuel economy and environmental conservation. In the study, the current advantages, limitations, technological\\u000a barriers and future prospects of Mg alloys in the automotive industry are given. The usage of magnesium in automotive applications\\u000a is also assessed
Mustafa Kemal Kulekci
Biodegradable Magnesium Alloys: A Review of Material Development and Applications
Magnesium based alloys possess a natural ability to biodegrade due to corrosion when placed within aqueous substances, which is promising for cardiovascular and orthopedic medical device applications. These materials can serve as a temporary scaffold when placed in vivo, which is desirable for treatments when temporary supportive structures are required to assist in the wound healing process. The nature of these materials to degrade is attributed to the high oxidative corrosion rates of magnesium. In this review, a summary is presented for magnesium material development, biocorrosion characteristics, as well as a biological translation for these results.
Persaud-Sharma, Dharam; McGoron, Anthony
Characterization and Degradation Study of Calcium Phosphate Coating on Magnesium Alloy Bone Implant In Vitro
Magnesium alloys have similar mechanical properties with natural bone, and they degrade within a certain time span. Therefore, magnesium alloys are suitable to be made as bone screws or plates. However, high susceptibility to corrosion has limited their applications in the orthopedic field. They would possess great medical functions if the degradation rates of magnesium alloys could be reduced. This
J. X. Yang; F. Z. Cui; Q. S. Yin; Y. Zhang; T. Zhang; X. M. Wang
A Study on Factors Affecting the Degradation of Magnesium and a Magnesium-Yttrium Alloy for Biomedical Applications
Controlling degradation of magnesium or its alloys in physiological saline solutions is essential for their potential applications in clinically viable implants. Rapid degradation of magnesium-based materials reduces the mechanical properties of implants prematurely and severely increases alkalinity of the local environment. Therefore, the objective of this study is to investigate the effects of three interactive factors on magnesium degradation, specifically, the addition of yttrium to form a magnesium-yttrium alloy versus pure magnesium, the metallic versus oxide surfaces, and the presence versus absence of physiological salt ions in the immersion solution. In the immersion solution of phosphate buffered saline (PBS), the magnesium-yttrium alloy with metallic surface degraded the slowest, followed by pure magnesium with metallic or oxide surfaces, and the magnesium-yttrium alloy with oxide surface degraded the fastest. However, in deionized (DI) water, the degradation rate showed a different trend. Specifically, pure magnesium with metallic or oxide surfaces degraded the slowest, followed by the magnesium-yttrium alloy with oxide surface, and the magnesium-yttrium alloy with metallic surface degraded the fastest. Interestingly, only magnesium-yttrium alloy with metallic surface degraded slower in PBS than in DI water, while all the other samples degraded faster in PBS than in DI water. Clearly, the results showed that the alloy composition, presence or absence of surface oxide layer, and presence or absence of physiological salt ions in the immersion solution all influenced the degradation rate and mode. Moreover, these three factors showed statistically significant interactions. This study revealed the complex interrelationships among these factors and their respective contributions to degradation for the first time. The results of this study not only improved our understanding of magnesium degradation in physiological environment, but also presented the key factors to consider in order to satisfy the degradation requirements for next-generation biodegradable implants and devices.
Johnson, Ian; Liu, Huinan
Microplasticity and fatigue of some magnesium-lithium alloys
The tensile microstrain behaviour of a series of magnesium-lithium alloys, with lithium contents up to 12.5 wt %, has been studied. The strain hardening exponents in the microstrain region were found to depend on the lithium content, the increase in which led to a change in crystal structure from hcp to bcc. The onset of cross-slip in the bcc alloys
R. E. Lee; W. J. D. Jones
Inverted disk centrifugal atomization of AZ91 magnesium alloy
Magnesium AZ91 alloy powder was produced by centrifugal atomization under various conditions using an inverted disk atomizer. The particle size distribution was obtained as a function of the disk shape and rotation speed. The microstructure of particles and their shape were examined and characterized. Their cooling rates were obtained from theoretical relations and related to the secondary dendrite arm spacing.
C. Labrecque; R. Angers; R. Tremblay; D. Dubé
Electroless plating of copper on AZ31 magnesium alloy substrates
Chemical surface preparation for copper film on magnesium alloy by both electroless plating and organic coatings was studied. Organic coating was made by immersing the samples into an organosilicon heat-resisting varnish. A subsequent metallization process verified the applicability of this method. In this method, the organic coating acted as an interlayer between the substrate and copper film. When the reaction
Hui Zhao; Zhanghong Huang; Jianzhong Cui
Friction-stir welding of magnesium alloy AZ31B
The challenges of significant weight reduction in the automobile industries in the U.S., Europe, and Japan in particular, and especially in the context of significant fuel savings, recyclability, and emission reduction, has promoted a focus on both aluminum [1] and magnesium alloy [2] substitutions and structural innovations. Correspondingly, new approaches and processes for joining extrusions and castings in body frames
J. A. Esparza; W. C. Davis; E. A. Trillo; L. E. Murr
Microstructural Stability of Magnesium Alloys during High Temperature Deformation
Superplastic forming (SPF) represents one feasible method to improve the formability of wrought magnesium alloy sheets at high temperatures. A fine grain structure not only improves the ductility but also increases the optimum strain rate thus, reducing the cost of SPF. Microstructural stability of AZ31 sheets have been characterized following different heat treatments. Second phase particles help to suppress grain
Zhan Gao
A new forge-welding process for weldng high-strength aluminum and ; magnesium alloys has been developed. This forge welding consists of heating the ; parts to be welded to a temperature which is high enough to allow good uniform ; flow of the materials without cracking and yet the temperature is sufficiently ; low that the samples are not overaged or
L. A. Cook; D. G. Shafer
Corrosion and Electrochemical Behavior of Binary Magnesium Alloys,
A systematic investigation of the effect of 23 elements on the corrosion behavior of magnesium alloys in a 3% solution of Sodium Chloride (NaCl) and in a humid atmosphere was carried out. The values of the stationary potentials and the variation of the po...
I. Y. Mukhina M. A. Timonova M. B. Al'tman T. I. Yershova
Acoustic emission during unloading of elastically stressed magnesium alloy
A magnesium alloy was quasi-statically cycled elastically between zero load and tension. Both loading and unloading stress delays were found, and the unloading stress delay was further studied. An analytical expression was written for the unloading stress delay which is an elastic constitutive parameter. The potential use of these results for the acoustic emission monitoring of elastic stress states is discussed.
Lee, S. S.; Williams, J. H., Jr.
Formation of defect bands in high pressure die cast magnesium alloys
Die cast magnesium components are being increasingly used worldwide because of the excellent castability and properties that magnesium alloys offer. High pressure die casting of thin-walled components is particularly suitable because of the excellent flow characteristics of molten magnesium alloys. Typical automotive applications for thin-walled castings include components such as instrument panels, steering wheels, door frames and seat frames. These
A. K Dahle; S Sannes; D. H St. John; H Westengen
Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread
Ryan C. Wolfe
In vitro degradation behavior and cytocompatibility of Mg-Zn-Zr alloys
Zinc and zirconium were selected as the alloying elements in biodegradable magnesium alloys, considering their strengthening effect and good biocompatibility. The degradation rate, hydrogen evolution, ion release, surface layer and in vitro cytotoxicity of two Mg–Zn–Zr alloys, i.e. ZK30 and ZK60, and a WE-type alloy (Mg–Y–RE–Zr) were investigated by means of long-term static immersion testing in Hank's solution, non-static immersion testing in Hank's solution and cell-material interaction analysis. It was found that, among these three magnesium alloys, ZK30 had the lowest degradation rate and the least hydrogen evolution. A magnesium calcium phosphate layer was formed on the surface of ZK30 sample during non-static immersion and its degradation caused minute changes in the ion concentrations and pH value of Hank's solution. In addition, the ZK30 alloy showed insignificant cytotoxicity against bone marrow stromal cells as compared with biocompatible hydroxyapatite (HA) and the WE-type alloy. After prolonged incubation for 7 days, a stimulatory effect on cell proliferation was observed. The results of the present study suggested that ZK30 could be a promising material for biodegradable orthopedic implants and worth further investigation to evaluate its in vitro and in vivo degradation behavior.
Huan, Z. G.; Leeflang, M. A.; Fratila-Apachitei, L. E.; Duszczyk, J.
Investigation of the Recrystallization Behavior of Dilute Alloys of Magnesium and Chromium.
An investigation into the recrystallization behavior of pure magnesium and some of its dilute binary alloys and pure chromium was made. Techniques for preparing thin foils of magnesium suitable for examination in the electron microscope were developed and...
C. H. Pitt E. L. Moore C. R. Brinkman T. G. Odekirk
Warm formability of aluminum-magnesium alloys
Manufacturers have become increasingly interested in near-net-shape forming of aluminum alloys as a means to reduce production costs and the weight of aircraft and automotive structures. To achieve the ductilities required for this process, we have examined extended ductility of Al-Mg alloys in the warm forming, or Class I creep, regime. We have studied a high-purity, binary alloy of Al-2.8Mg and ternary alloys of Al-xMg-0.5Mn with Mg concentrations from 1.0 to 6.6 wt. %. Tensile tests, including strain rates-change tests, have been performed with these materials at temperatures of 300 and 400C over a range 10{sup {minus}4} to 2 {times} 10{sup {minus}2} s{sup {minus}1}. A maximum tensile failure strain of 325% for the binary alloy and a maximum of 125% in the ternary alloys have been measured. The experimental results have been used to evaluate the effects of solute concentration, microstructure, temperature, and strain rate on flow stress ({sigma}), elongation to failure (e{sub f}), and strain-rate sensitivity (m) of these alloys.
Taleff, E.M. [Stanford Univ., CA (United States). Dept. of Mechanical Engineering; Henshall, G.A.; Lesuer, D.R.; Nieh, T.G. [Lawrence Livermore National Lab., CA (United States)
Mechanical alloys of magnesium - new materials for hydrogen energy
One of the possible paths for improving the kinetic characteristics of magnesium hydriding is addition of catalytic doses of metals or intermetallic compounds (IMC). The authors added four types of catalysts to magnesium: Ni, which forms with magnesium the intermetallide Mg/sub 2/Ni; Ce, Nb, and Ti, which form the hydrides CeH/sub 3/, NbH/sub 2/, and TiH/sub 2/; Fe and Co, and Si and C which form compounds having covalent bonds. It was shown that mechanical alloying is a promising method for obtaining hydrogen-storing materials, which while retaining a fairly high hydrogen absorption capacity, possess better kinetic characteristics as compared to Mg, especially in the case of hydriding.
Ivanov, E.Yu.
The Corrosion of Magnesium and of the Magnesium Aluminum Alloys Containing Manganese
The extensive use of magnesium and its alloys in aircraft has been seriously handicapped by the uncertainties surrounding their resistance to corrosion. This problem has been given intense study by the American Magnesium Corporation and at the request of the Subcommittee on Materials for Aircraft of the National Advisory Committee for Aeronautics this report was prepared on the corrosion of magnesium. The tentative conclusions drawn from the experimental facts of this investigation are as follows: the overvoltage of pure magnesium is quite high. On immersion in salt water the metal corrodes with the liberation of hydrogen until the film of corrosion product lowers the potential to a critical value. When the potential reaches this value it no longer exceeds the theoretical hydrogen potential plus the overvoltage of the metal. Rapid corrosion consequently ceases. When aluminum is added, especially when in large amounts, the overvoltage is decreased and hydrogen plates out at a much lower potential than with pure magnesium. The addition of small amount of manganese raises the overvoltage back to practically that of pure metal, and the film is again negative.
Boyer, J A
In vivo corrosion of four magnesium alloys and the associated bone response
Degrading metal alloys are a new class of implant materials suitable for bone surgery. The aim of this study was to investigate the degradation mechanism at the bone–implant interface of different degrading magnesium alloys in bone and to determine their effect on the surrounding bone. Sample rods of four different magnesium alloys and a degradable polymer as a control were
F. Witte; V. Kaese; H. Haferkamp; E. Switzer; A. Meyer-Lindenberg; C. J. Wirth; H. Windhagen
The Numerical Simulation for Extrusion Forming of Magnesium Alloy Pipes
Now magnesium alloy is the light metal materials of structural in engineering application, it has a wide potential of application and development in transport, communication equipment, aerospace and other fields. AZ31B magnesium alloy pipes is used to be the research object, and the extruded forming simulation for pipe was made by using finite element software ANSYS, under displacement loads. In order to make the pipe extrusion, the maximum stress of pipe must be bigger than the yield point of it, no matter the pipe was in strengthening phase or local deformation phase. According to the yield point and ultimate strength on the true stress-strain curve of pipe and yield criterion, it can be judged whether the pipe has plastic deformation or not, and it can be determined whether the load applied could make pipe achieve the purpose of extrusion or not.
Zhang, Daiquan; Chen, Guoping
Mechanical alloying of graphite and magnesium powders, and their hydrogenation
Graphite and elemental magnesium (Mg) powders, whose chemical compositions were C100?xMgx (0?x?40at.%), were mechanically alloyed (milled) in an argon gas atmosphere, and these powders were loaded with hydrogen in a high-pressure vessel at a temperature of 308K. The initial hydrogen gas pressure for hydrogenation experiment was 4MPa. The periodicity of the c-axis of the graphite crystal structure was destroyed completely
Akito Takasaki; Yoshio Furuya; Masanori Katayama
The Corrosion Protection of Magnesium Alloy AZ31B
Corrosion rates for bare and coated Magnesium alloy AZ31B have been measured. Two coatings, Dow-23(Trademark) and Tagnite(Trademark), have been tested by electrochemical methods and their effectiveness determined. Electrochemical methods employed were the scanning reference electrode technique (SRET), the polarization resistance technique (PR) and the electrochemical impedance spectroscopy technique (EIS). In addition, general corrosion and stress corrosion methods were employed to examine the effectiveness of the above coatings in 90 percent humidity. Results from these studies are presented.
Danford, M. D.; Mendrek, M. J.; Mitchell, M. L.; Torres, P. D.
Finite element simulation of magnesium alloys laser beam welding
In this paper, a three-dimensional finite element model is developed to simulate thermal history magnesium-based alloys during laser beam welding. Space–time temperature distributions in weldments are predicted from the beginning of welding to the final cooling. The finite element calculations were performed using Cast3M code with which the heat equation is solved considering a non-linear transient behaviour. The applied loading
Asma Belhadj; Jamel Bessrour; Jean-Eric Masse; Mahmoud Bouhafs; Laurent Barrallier
Intergranular Corrosion of an Aluminum-Magnesium-Silicon-Copper Alloy
The intergranular (intercrystalline) corrosion (IGC) of a heat-treated aluminum-magnesium-silicon-copper alloy was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM revealed that tall chimneys of corrosion product formed on the surface above the pits during oxygenated salt water immersion. It was postulated that pitting corrosion occurred first and that the corrosion chimneys maintained the acidic, chloride pit
T. D. Burleigh; E. D. Ludwiczak; R. A. Petri
Hydrogen storage in thin film magnesium–scandium alloys
Thorough electrochemical materials research has been performed on thin films of novel magnesium–scandium hydrogen storage alloys. It was found that palladium-capped thin films of MgxSc(1?x) with different compositions (ranging from x=0.50 –0.90) show an increase in hydrogen storage capacity of more than 5–20% as compared to their bulk equivalents using even higher discharge rates. The maximum reversible hydrogen storage capacity
R. A. H. Niessen; P. H. L. Notten
Potential applications of wrought magnesium alloys for passenger vehicles
Vehicle weight reduction is one of the major means available for improving automotive fuel efficiency. Although high-strength steels, aluminum (Al), and polymers are already being used to achieve significant weight reductions, substantial additional weight reductions could be achieved by increased use of magnesium (Mg) and its alloys, which have very low density. Magnesium alloys are currently used in relatively small quantities for auto parts; use is generally limited to die castings, such as housings. The Center for Transportation Research at Argonne National Laboratory has performed a study for the Lightweight Materials Program within DOE`s Office of Transportation Materials to evaluate the suitability of wrought Mg and its alloys to replace steel or aluminum for automotive structural and sheet applications. This study identifies technical and economic barriers to this replacement and suggests R&D areas to enable economical large-volume use. Detailed results of the study will be published at a later date. Magnesium sheet could be used in body nonstructural and semi-structural applications, while extrusions could be used in such structural applications as spaceframes. Currently, Mg sheet has found limited use in the aerospace industry, where costs are not a major concern. The major barrier to greatly increased automotive use is high cost; two technical R&D areas are identified that could enable major reductions in costs. These are novel reduction technology and better hot-forming technology, possibly operating at lower temperatures and involving superplastic behavior.
Gaines, L.; Cuenca, R.; Stodolsky, F.; Wu, S.
Mg-Zn-Y alloys with long-period stacking ordered structure: in vitro assessments of biodegradation behavior.
Using Dulbecco's modified eagle medium (DMEM) with 10% fetal bovine serum (FBS) as simulated body fluid, degradation behavior of Mg100-3x(Zn1Y2)x (1?x?3) alloy series with long period stacking order (LPSO) structures was investigated. As indicated, with increasing the volume fraction of LPSO phase, degradation rate of the alloys is accelerated. Further refining the grain size by microalloying with zirconium and warm extrusion has a significant effect to mitigate the degradation rate of the Mg97Zn1Y2 alloy. Time-dependent behavior during degradation of the magnesium alloys can be described using an exponential decay function of WR=exp(a+bt+ct(2)), where WR is normalized residual mass/volume of the alloy. A parameter named as degradation half-life period (t0.5) is suggested to quantitatively assess the degradation rate. For the localized-corrosion controlled alloys, the t0.5 parameter physically scales with electrochemical response ?E which is a range between corrosion potential (Ecorr) and pitting potential (Ept). In comparison with conventional engineering magnesium alloys such as the AZ31, WE43, ZK60 and ZX60 alloys, extruded Mg96.83Zn1Y2Zr0.17 alloy with LPSO structure exhibits a good combination of high mechanical strength, lower biodegradation rate and good biocompatibility. PMID:23910258
Zhao, Xu; Shi, Ling-ling; Xu, Jian
Sheet metal forming of magnesium wrought alloys — formability and process technology
New developments at the Institute for Metal Forming and Metal Forming Machine Tools show that magnesium sheets possess excellent forming behavior, if the process is conducted at elevated temperatures. For the evaluation of mechanical properties relevant for forming of magnesium sheets, uniaxial tensile tests have been carried out at various temperatures and strain rates.Deep drawing tests with magnesium alloys AZ31B,
E. Doege; K. Dröder
Endurance limit and threshold stress intensity of die cast magnesium and aluminium alloys at elevated temperatures
High cycle fatigue properties of the high-pressure die-cast magnesium alloys AZ91 hp, AS21 hp and AE42 hp and of the aluminium alloy AlSi9Cu3 are investigated at elevated temperatures. Fatigue tests are performed at ultrasonic cyclic frequency and load ratio R=?1. Compared with ambient air environment, the S–N curves determined in warm air of 125°C (magnesium alloys) and 150°C (aluminium alloy)
H. Mayer; M. Papakyriacou; B. Zettl; S. Vacic
Hot rolling characteristics of spray-formed AZ91 magnesium alloy
AZ91 magnesium alloy was prepared by spray forming. The spray-deposited alloy was subsequently hot-rolled with a 80% reduction at 350 °C. The microstructural features of the as-spray-deposited and hot-rolled alloy were examined by optical microscopy, scanning electron microscopy and X-ray diffractometry. The results show that the spray-formed AZ91 magnesium alloy has, compared with the as-cast ingot, a finer microstructure with
Xiao-feng WANG; Jiu-zhou ZHAO; Jie HE; Zhuang-qi HU
Biomedical coatings on magnesium alloys - a review.
This review comprehensively covers research carried out in the field of degradable coatings on Mg and Mg alloys for biomedical applications. Several coating methods are discussed, which can be divided, based on the specific processing techniques used, into conversion and deposition coatings. The literature review revealed that in most cases coatings increase the corrosion resistance of Mg and Mg alloys. The critical factors determining coating performance, such as corrosion rate, surface chemistry, adhesion and coating morphology, are identified and discussed. The analysis of the literature showed that many studies have focused on calcium phosphate coatings produced either using conversion or deposition methods which were developed for orthopaedic applications. However, the control of phases and the formation of cracks still appear unsatisfactory. More research and development is needed in the case of biodegradable organic based coatings to generate reproducible and relevant data. In addition to biocompatibility, the mechanical properties of the coatings are also relevant, and the development of appropriate methods to study the corrosion process in detail and in the long term remains an important area of research. PMID:22510401
Hornberger, H; Virtanen, S; Boccaccini, A R
Tribological Behaviour of the Ceramic Coating Formed on Magnesium Alloy
Micro-arc oxidation is a recently developed surface treatment technology under anodic oxidation. Through micro-arc oxidation, a ceramic coating is directly formed on the surface of magnesium alloy, by which its surface property is significantly improved. In this paper, a dense ceramic oxide coating was prepared on an AZ31 magnesium alloy by micro-arc oxidation in a NaOH-Na2SiO3-NaB4O7-(NaPO3)6 electrolytic solution. Micro-structure, surface morphology and phase composition were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The tribological behavior of the micro-arc oxidation ceramic coating under dry sliding against GCr15 steel was evaluated on a ball-on-disc test rig. The results showed that the AZ31 alloy was characterized by adhesion wear and scuffing under dry sliding against the steel, while the surface micro-arc oxidation ceramic coating experienced much abated adhesion wear and scuffing under the same testing conditions. The micro-arc oxidation ceramic coating showed good friction-reducing and fair antiwear ability in dry sliding against the steel.
Chen, Fei; Zhou, Hai; Chen, Qiang; Ge, Yuanjing; Lv, Fanxiu
Formation of Intermetallic Compound (IMC) in the H13Magnesium Alloy System
This paper documents research undertaken into the soldering of magnesium alloy high pressure die casting (HPDC). It is believed that the formation of intermetallic phases is because of the strong affinity for aluminium which exists in all magnesium alloy to iron which is the major element of all tool steel. Manganese plays an important role in this reaction. However, the
Caixang Tang
Properties of magnesium alloy joints welded by a CO2 laser beam
Because of their specific gravity, magnesium alloys find increasing applications in the automotive industry. Safety and travelling comfort requirements, satisfied by the use of steel or aluminium parts, are responsible for the increase in the car weight and, therefore, in increased fuel consumption and consequent environmental pollution. Replacement of these materials by magnesium alloys satisfies the two requirements while not
W. Kalita; J. Hoffman; A. Kolasa; P. Kolodziejczyk
Corrosion behavior of AZ31 magnesium alloy in simulated acid rain solution
The corrosion mechanism of AZ31 magnesium alloy used as automobile components and the influence of the concentration of Cl? ion in simulated acid rain (SAR) were studied by electrochemical tests and SEM. The results show that pitting corrosion happens around the AlMn phases locating at the grain boundary. The corrosion of AZ31 magnesium alloy in SAR is controlled by the
Feng LIU; Ying-wei SONG; Da-yong SHAN; En-hou HAN
Magnesium alloys: Corrosion properties. (Latest citations from the NTIS Bibliographic database). Published Search
The bibliography contains citations concerning the corrosion of alloys containing magnesium. References examine the effects of stress corrosion and metal fatigue. Hydrogen embrittlement of aircraft structural components and reactors is also discussed. Particular emphasis is placed upon the magnesium-aluminum alloys. (Contains 250 citations and includes a subject term index and title list.)
Not Available
Magnesium alloys: Corrosion properties. (Latest citations from the NTIS bibliographic database). Published Search
The bibliography contains citations concerning the corrosion of alloys containing magnesium. References examine the effects of stress corrosion and metal fatigue. Hydrogen embrittlement of aircraft structural components and reactors is also discussed. Particular emphasis is placed upon the magnesium-aluminum alloys. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)
Toward Solid-State Switchable Mirror Devices Using Magnesium-Rich Magnesium-Nickel Alloy Thin Films
All-solid-state devices with switchable mirror properties based on magnesium-rich magnesium-nickel alloy thin films have been prepared using magnetron sputtering. The structure of the devices was a Mg-Ni alloy (40 nm)\\/Pd (4 nm)\\/Ta2O5 (200 nm)\\/HxWO3 (500 nm)\\/ITO on a glass. The composition of the alloy was Mg5Ni. In the initial state, the devices showed a shiny metallic front side and a
Yasusei Yamada; Kazuki Tajima; Shanhu Bao; Masahisa Okada; Kazuki Yoshimura
Study of Forming Limit for Rotational Incremental Sheet Forming of Magnesium Alloy Sheet
As a lightweight material, magnesium is being increasingly used for automotive parts. However, due to a hexagonal-closed-packed\\u000a (hcp) crystal structure, in which only the basal plane can move, magnesium alloy sheets exhibit a low ductility and formability\\u000a at room temperature. Press forming of magnesium alloy sheets is conventionally performed at elevated temperatures of 200 °C\\u000a to 250 °C and thus is known
Jeounghan Kim; Youngsuk Kim
A Flow Stress Formulation of Magnesium Alloy at Elevated Temperature
Dynamic recrystallization (DRX) is the main softening mechanism of magnesium alloy AZ31B in hot deformation. Theoretically, in the flow rule the atomic diffusibility and the driving force of dislocation migration are dependent on the temperature, and the dislocation density and the cumulation of grain boundary energy are dependent on the strain rate. The peak stress will appear when the flow driving force and resistance force reach a balance, after which the stress descending will take place due to recrystallization fraction. Since the DRX is a thermally activated process, the recrystallized volume fraction can be regarded as the function of strain through Avrami equation. Based on this idea, the paper proposes a new constitutive model characterizing dynamic recrystallization for magnesium alloy AZ31B. The model is described by a peak stress and a strain softening rate, in which the peak stress depends only on Zener-Hollomon parameter and is determined through creep equation, and the strain softening rate is mainly dominated by the recrystallized volume fraction. As a result, the formulation of flow stress takes into account of temperature, strain and strain rate, and is characterized by DRX. The thermomechanical simulation tests of magnesium alloy AZ31B by using Gleeble-1500 were conducted, through which the parameters in flow stress model can be easily determined. Comparison shows that the maximum difference of flow stress between the model predictions and test values is approximately 2.32%. This indicates that the proposed constitutive model can be employed to represent the DRX behaviour of AZ31B.
Liu Juan; Cui Zhenshan [National Die and Mold CAD Eng. Research Center, Shanghai Jiao Tong University, Shanghai, 200030 (China); Ruan Liqun [Department of mechanical engineering, Kumamoto University, Kumamoto (Japan)
Modelling of Superplastic Forming of AZ31 Magnesium Alloy
In this study the constitutive equation of the superplastic AZ31 magnesium-based alloy is modelled by the power law relationship between the stress, the strain and the strain-rate and an accurate procedure for determining the constants of the material is presented. Moreover, the problem of optimizing the pressure-time load curve of a free forming process is investigated and resolved by means of a pressure jump forming process. The experimental tests, carried out to support the finite-element modelling, have shown good agreement between the numerical results and the experimental data.
Giuliano, G. [University of Cassino, Department of Industrial Engineering, via Di Biasio 43, 03043 Cassino (Italy)
As a lightweight material, magnesium is being increasingly used for automotive parts. However, due to a hexagonal-closed-packed (hcp) crystal structure, in which only the basal plane can move, magnesium alloy sheets exhibit a low ductility and formability at room temperature. Press forming of magnesium alloy sheets is conventionally performed at elevated temperatures of 200 °C to 250 °C and thus is known as energy consumed forming. Therefore, in view of an energy saving forming technology, we study magnesium alloy sheet forming by a rotational incremental sheet forming (RISF) at room temperature, where the rotational tool generates local heat of specimen enough to accelerate plastic deformation. The flow curves of the magnesium alloy sheet are obtained and calculated at elevated temperatures, while the yield loci of the magnesium alloy sheet are measured at room temperature. Using RISF, a square cup of 80-mm width, 80-mm length, and 25-mm height is then formed from a magnesium alloy sheet at room temperature. In addition, the strain distribution is obtained and compared with the forming limit curve (FLC) by considering the effect of the tool radius and is found to effectively predict the forming limit of a magnesium alloy sheet in RISF.
Park, Jingee; Kim, Jeounghan; Park, Nhokwang; Kim, Youngsuk
General and localized corrosion of magnesium alloys: A critical review
Magnesium (Mg) alloys as well as experimental alloys are emerging as light structural materials for current, new, and innovative applications. This paper describes the influence of the alloying elements and the different casting processes on the microstructure and performance of these alloys and corrosion. It gives a comprehensible approach for the resistance of these alloys to general, localized and metallurgically influenced corrosion, which are the main challenges for their use. Exposure to humid air with ˜65% relative humidity during 4 days gives 100-150 nm thickness. The film is amorphous and has an oxidation rate less than 0.01 µm/y. The pH values between 8.5 and 11.5 correspond to a relatively protective oxide or hydroxide film; however above 11.5 a passive stable layer is observed. The poor corrosion resistance of many Mg alloys can be due to the internal galvanic corrosion caused by second phases or impurities. Agitation or any other means of destroying or preventing the formation of a protective film leads to increasing corrosion kinetics. The pH changes during pitting corrosion can come from two different reduction reactions: reduction of dissolved oxygen (O) and that of hydrogen (H) ions. Filiform corrosion was observed in the uncoated AZ31, while general corrosion mainly occurred in some deposition coated alloys. Crevice corrosion can probably be initiated due to the hydrolysis reaction. Exfoliation can be considered as a type of intergranular attack, and this is observed in unalloyed Mg above a critical chloride concentration.
Ghali, Edward; Dietzel, Wolfgang; Kainer, Karl-Ulrich
Microstructural development of diffusion-brazed austenitic stainless steel to magnesium alloy using a nickel interlayer
The differences in physical and metallurgical properties of stainless steels and magnesium alloys make them difficult to join using conventional fusion welding processes. Therefore, the diffusion brazing of 316L steel to magnesium alloy (AZ31) was performed using a double stage bonding process. To join these dissimilar alloys, the solid-state diffusion bonding of 316L steel to a Ni interlayer was carried
Waled M. Elthalabawy; Tahir I. Khan
Diffusion Bonding Behavior and Characterization of Joints Made Between 316L Stainless Steel Alloy and AZ31 Magnesium Alloy
The 316L austenitic stainless steel and AZ31 magnesium alloy have physical and mechanical properties which makes these alloys suitable in a number of high technology based industries such as the aerospace and automotive sectors. However, for these alloys to be used in engineering applications, components must be fabricated and joined successfully. The differences in the physical and metallurgical properties between
Waled Mohamed Elthalabawy
Finite element analyses for optimization design of biodegradable magnesium alloy stent.
Stents made of biodegradable magnesium alloys are expected to provide a temporary opening into a narrowed arterial vessel until it remodels and will progressively disappear thereafter. Inferior mechanical properties and fast corrosion of the magnesium alloys are the two crucial factors that impede the clinical application of the magnesium alloy stents (MAS). In the present study, gradual strut width, addition of the peak-to-valley unit and introduction of the annealing technology were designed and investigated by finite element analysis in order to improve the performance of the MAS. Two experiments were carried out for a preliminary validation of the simulation. PMID:25063172
Li, Junlei; Zheng, Feng; Qiu, Xun; Wan, Peng; Tan, Lili; Yang, Ke
Magnesium alloys as a biomaterial for degradable craniofacial screws.
Recently, magnesium (Mg) alloys have received significant attention as potential biomaterials for degradable implants, and this study was directed at evaluating the suitability of Mg for craniofacial bone screws. The objective was to implant screws fabricated from commercially available pure Mg and alloy AZ31 in vivo in a rabbit mandible. First, Mg and AZ31 screws were compared to stainless steel screws in an in vitro pull-out test and determined to have a similar holding strength (?40N). A finite-element model of the screw was created using the pull-out test data, and this model can be used for future Mg alloy screw design. Then, Mg and AZ31 screws were implanted for 4, 8 and 12weeks, with two controls of an osteotomy site (hole) with no implant and a stainless steel screw implanted for 12weeks. Microcomputed tomography was used to assess bone remodeling and Mg/AZ31 degradation, both visually and qualitatively through volume fraction measurements for all time points. Histological analysis was also completed for the Mg and AZ31 at 12weeks. The results showed that craniofacial bone remodeling occurred around both Mg and AZ31 screws. Pure Mg had a different degradation profile than AZ31; however, bone growth occurred around both screw types. The degradation rate of both Mg and AZ31 screws in the bone marrow space and the muscle were faster than in the cortical bone space at 12weeks. Furthermore, it was shown that by alloying Mg, the degradation profile could be changed. These results indicate the promise of using Mg alloys for craniofacial applications. PMID:24384125
Henderson, Sarah E; Verdelis, Konstantinos; Maiti, Spandan; Pal, Siladitya; Chung, William L; Chou, Da-Tren; Kumta, Prashant N; Almarza, Alejandro J
Biofunctionalized anti-corrosive silane coatings for magnesium alloys.
Biodegradable magnesium alloys are advantageous in various implant applications, as they reduce the risks associated with permanent metallic implants. However, a rapid corrosion rate is usually a hindrance in biomedical applications. Here we report a facile two step procedure to introduce multifunctional, anti-corrosive coatings on Mg alloys, such as AZ31. The first step involves treating the NaOH-activated Mg with bistriethoxysilylethane to immobilize a layer of densely crosslinked silane coating with good corrosion resistance; the second step is to impart amine functionality to the surface by treating the modified Mg with 3-amino-propyltrimethoxysilane. We characterized the two-layer anticorrosive coating of Mg alloy AZ31 by Fourier transform infrared spectroscopy, static contact angle measurement and optical profilometry, potentiodynamic polarization and AC impedance measurements. Furthermore, heparin was covalently conjugated onto the silane-treated AZ31 to render the coating haemocompatible, as demonstrated by reduced platelet adhesion on the heparinized surface. The method reported here is also applicable to the preparation of other types of biofunctional, anti-corrosive coatings and thus of significant interest in biodegradable implant applications. PMID:23313945
Liu, Xiao; Yue, Zhilian; Romeo, Tony; Weber, Jan; Scheuermann, Torsten; Moulton, Simon; Wallace, Gordon
Calcium orthophosphate coatings on magnesium and its biodegradable alloys.
Biodegradable metals have been suggested as revolutionary biomaterials for bone-grafting therapies. Of these metals, magnesium (Mg) and its biodegradable alloys appear to be particularly attractive candidates due to their non-toxicity and as their mechanical properties match those of bones better than other metals do. Being light, biocompatible and biodegradable, Mg-based metallic implants have several advantages over other implantable metals currently in use, such as eliminating both the effects of stress shielding and the requirement of a second surgery for implant removal. Unfortunately, the fast degradation rates of Mg and its biodegradable alloys in the aggressive physiological environment impose limitations on their clinical applications. This necessitates development of implants with controlled degradation rates to match the kinetics of bone healing. Application of protective but biocompatible and biodegradable coatings able to delay the onset of Mg corrosion appears to be a reasonable solution. Since calcium orthophosphates are well tolerated by living organisms, they appear to be the excellent candidates for such coatings. Nevertheless, both the high chemical reactivity and the low melting point of Mg require specific parameters for successful deposition of calcium orthophosphate coatings. This review provides an overview of current coating techniques used for deposition of calcium orthophosphates on Mg and its biodegradable alloys. The literature analysis revealed that in all cases the calcium orthophosphate protective coatings both increased the corrosion resistance of Mg-based metallic biomaterials and improved their surface biocompatibility. PMID:24607420
Dorozhkin, Sergey V
Finite Element Simulation Of Magnesium AZ31 Alloy Sheet In Warm Hydroforming
Hydroforming of magnesium (Mg) alloy sheet metal offers the possibility to form geometrically complex sheet metal parts that are applicable within automotive and electronic industry etc. However, due to the limited formability of Mg alloy at ambient temperature hydroforming of Mg alloy sheet metal has to be conducted at elevated temperature. In the present study an experimental warm hydroforming process
Mikkel Steffensen; Joachim Danckert
Evaluation of magnesium ions release, biocorrosion, and hemocompatibility of MAO/PLLA-modified magnesium alloy WE42.
Magnesium alloys may potentially be applied as biodegradable metallic materials in cardiovascular stent. However, the high corrosion rate hinders its clinical application. In this study, a new approach was adopted to control the corrosion rate by fabricating a biocompatible micro-arc oxidation/poly-L-lactic acid (MAO/PLLA) composite coating on the magnesium alloy WE42 substrate and the biocompatibility of the modified samples was investigated. The scanning electronic microscope (SEM) images were used to demonstrate the morphology of the samples before and after being submerged in hanks solution for 4 weeks. The degradation was evaluated through the magnesium ions release rate and electrochemical impedance spectroscopy (EIS) test. The biocompatibility of the samples was demonstrated by coagulation time and hemolysis behavior. The result shows that the poly-L-lactic acid (PLLA) effectively improved the corrosion resistance by sealing the microcracks and microholes on the surface of the MAO coating. The modified samples had good compatibility. PMID:21053265
Lu, Ping; Cao, Lu; Liu, Yin; Xu, Xinhua; Wu, Xiangfeng
Mean flank temperature measurement in high speed dry cutting of magnesium alloy
Magnesium in the molten state is flammable when exposed to oxygen. The risk of fire is the main concern during cutting operation. High speed dry cutting is preferable in cutting magnesium alloys due to there being no extra part cleaning work required, the environmental benefits and the ecological concerns. However, fire ignition could happen when the cutting temperature is close
F. Z. Fang; L. C. Lee; X. D. Liu
Initial Evaluation of Advanced Powder Metallurgy Magnesium Alloys for Dynamic Applications.
The U.S. Army Research Laboratory (ARL) is interested in assessing the performance of different magnesium alloys. The ARL and the Joining and Welding Research Institute (JWRI) conducted a joint effort to develop and evaluate advanced powder metallurgy mag...
K. Kondoh T. Jones
Crystal Structure Formed in Mechanical Alloying Process of Mg-Al-Zn Powder Mixture Using Magnesium Alloy Machined Chips
For making the functional alloy powder from magnesium alloy scrap, Mg-Zn and Mg-Al-Zn powder mixtures, which aluminum and zinc powder were added with various contents to machined chips of AZ31 alloy, were mechanically alloyed for various milling times using planetary ball mill. Crystal phase formed in the obtained powder was investigated by X-ray diffraction and Vickers hardness of the powder
Hideki Oginuma; Eiji Yuasa
Preparation and corrosion resistance studies of zirconia coating on fluorinated AZ91D magnesium alloy
Novel anti-corrosion zirconia coating was prepared via the sol–gel method for AZ91D magnesium alloy using zirconium nitrate hydrate as a precursor modified with acetylacetone (AcAc). Magnesium alloy substrates were first fluorinated in 20% HF aqueous solution at room temperature for 20h, then, the zirconia coating was deposited on the fluorinated sample by dip coating. Basing on the sol–gel process, a
Qing Li; Xiankang Zhong; Junying Hu; Wei Kang
Fatigue behaviour of friction stir processed AZ91 magnesium alloy produced by high pressure die casting
The room temperature fatigue properties of AZ91 magnesium alloy produced by high pressure die casting (HPDC) as cast, heat treated, friction stir processed (FSP) and FSP and heat treated were studied. The fatigue properties of the material were evaluated for the HPDC magnesium alloy in the as-received state and after a solution treatment at 415 °C for 2 h and an ageing
P.. Cavaliere; P. P. De Marco
Calcium phosphate coating on magnesium alloy for modification of degradation behavior
Magnesium alloy has similar mechanical properties with natural bone, but its high susceptibility to corrosion has limited\\u000a its application in orthopedics. In this study, a calcium phosphate coating is formed on magnesium alloy (AZ31) to control\\u000a its degradation rate and enhance its bioactivity and bone inductivity. Samples of AZ31 plate were placed in the supersaturated\\u000a calcification solution prepared with Ca(NO3)2,
Fu-zhai Cui; Jing-xin Yang; Yan-peng Jiao; Qing-shui Yin; Yu Zhang; In-Seop Lee
Calcium phosphate coating on magnesium alloy by biomimetic method: Investigation of morphology, composition and formation process
Magnesium alloy has similar mechanical properties with natural bone and can degrade via corrosion in the electrolytic environment\\u000a of the human body. Calcium phosphate has been proven to possess bioactivity and bone inductivity. In order to integrate both\\u000a advantages, calcium phosphate coating was fabricated on magnesium alloy by a biomimetic method. Supersaturated calcification\\u000a solutions (SCSs) with different Ca\\/P ratio and
Jing-xin Yang; Yan-peng Jiao; Qing-shui Yin; Yu Zhang; Tao Zhang
A study on stress corrosion cracking and hydrogen embrittlement of AZ31 magnesium alloy
The stress corrosion cracking (SCC) behavior and pre-exposure embrittlement of AZ31 magnesium alloy have been studied by slow strain rate tensile (SSRT) tests in this paper. It is showed that AZ31 sheet material is susceptible to SCC in distilled water, ASTM D1387 solution, 0.01M NaCl and 0.1M NaCl solution. The AZ31 magnesium alloy also becomes embrittled if pre-exposed to 0.01M
R. G. Song; C. Blawert; W. Dietzel; A. Atrens
Forming limit of textured AZ31B magnesium alloy sheet at different temperatures
Repeated unidirectional bending (RUB) was carried out to improve the texture of commercial AZ31B magnesium alloy sheets. All specimens were prepared in the rolling direction. The forming limit diagrams (FLDs) of AZ31B magnesium alloy sheet were determined experimentally by conducting stretch-forming tests at room temperature, 100, 200 and 300 °C. Compared with the as-received sheet, the lowest limited strain of
Guang-sheng HUANG; Hua ZHANG; Xiao-yun GAO; Bo SONG; Lei ZHANG
Effect of overageing temperature on the superplastic behaviour in magnesium alloys
An especially fine-grained structure d<10?m is necessary for superplastic forming. Conventional magnesium alloys in cast condition show only a very coarse-grained structure with an average grain size of d>100?m. Yet through overageing and successive warm extrusion moulding a sufficient number of recrystallization nuclei are formed in the magnesium alloys so that during the final recrystallization treatment a very fine microstructure
V. Wesling; T. Ryspaev; A. Schram
An experimental investigation on friction stir welding of AZ31B magnesium alloy
The conventional fusion welding of magnesium alloys often produces porosity in the weld joint, which deteriorates its mechanical\\u000a properties. To solve this problem, friction stir welding (FSW), a solid-state welding technique, can be applied for joining\\u000a of magnesium alloys. In this investigation, an attempt was made to understand the effect of FSW process parameters such as\\u000a tool rotational speed, welding
G. Padmanaban; V. Balasubramanian
Indium-rich indium-magnesium and indium-lithium alloys
For comparison with the results obtained from alloys of indium with solute metals from Group IIB of the periodic table, the lattice spacings of indium-magnesium and indium-lithium alloys have been measured. Although the results show an unexpected scatter, they establish that neither magnesium nor lithium cause a marked axial ratio decrease. A possible reason for this behaviour is briefly discussed.The
J. Graham; G. V. Raynor
Novel hybrid sol–gel coatings for corrosion protection of AZ31B magnesium alloy
This work aims to develop and study new anticorrosion films for AZ31B magnesium alloy based on the sol–gel coating approach.Hybrid organic–inorganic sols were synthesized by copolymerization of epoxy-siloxane and titanium or zirconium alkoxides. Tris(trimethylsilyl) phosphate was also used as additive to confer additional corrosion protection to magnesium-based alloy. A sol–gel coating, about 5-?m thick, shows good adhesion to the metal
S. V. Lamaka; M. F. Montemor; A. F. Galio; M. L. Zheludkevich; C. Trindade; L. F. Dick; M. G. S. Ferreira
Preparation and properties of composite MAO/ECD coatings on magnesium alloy.
Magnesium alloys are potential biodegradable implants because of their outstanding biological performance and biodegradability in the bioenvironment. However, the rapid corrosion of magnesium and its alloys in human body fluids or blood plasma limits their clinical application. In the present work, we first fabricated porous micro-arc oxidation (MAO) coatings containing Ca/P on the magnesium alloy substrate by conducting MAO in the electrolyte containing calcium gluconate. Subsequently, hydroxyapatite (HA) coatings were prepared using electrochemical deposition (ECD) on the MAO coatings. Finally, a MAO/ECD composite coating was successfully fabricated on the magnesium alloy. The phase, morphology and composition of the biological coatings were monitored with X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy, and corrosion resistance was evaluated by means of electrochemical methods in a simulated body fluid. The experimental results indicated that the formation of HA-containing composite coatings on magnesium alloy effectively decreases its corrosion rate and more importantly endows it with a potential bioactivity. We believe that the combined use of MAO and ECD to modify magnesium alloys would make them more attractive for clinical applications. PMID:23018022
Zhao, Quanming; Guo, Xiong; Dang, Xiaoqian; Hao, Jianmin; Lai, Jianghua; Wang, Kunzheng
Enhanced antimicrobial properties, cytocompatibility, and corrosion resistance of plasma-modified biodegradable magnesium alloys.
Magnesium alloys are potential biodegradable materials and have received increasing attention due to their outstanding biological performance and mechanical properties. However, rapid degradation in the physiological environment and potential toxicity limit clinical applications. Recently, special magnesium-calcium (Mg-Ca) and magnesium-strontium (Mg-Sr) alloys with biocompatible chemical compositions have been reported, but the rapid degradation still does not meet clinical requirements. In order to improve the corrosion resistance, a rough, hydrophobic and ZrO(2)-containing surface film is fabricated on Mg-Ca and Mg-Sr alloys by dual zirconium and oxygen ion implantation. Weight loss measurements and electrochemical corrosion tests show that the corrosion rate of the Mg-Ca and Mg-Sr alloys is reduced appreciably after surface treatment. A systematic investigation of the in vitro cellular response and antibacterial capability of the modified binary magnesium alloys is performed. The amounts of adherent bacteria on the Zr-O-implanted and Zr-implanted samples diminish remarkably compared to the unimplanted control. In addition, significantly enhanced cell adhesion and proliferation are observed from the Zr-O-implanted sample. The results suggest that dual zirconium and oxygen ion implantation, which effectively enhances the corrosion resistance, in vitro biocompatibility and antimicrobial properties of Mg-Ca and Mg-Sr alloys, provides a simple and practical means to expedite clinical acceptance of biodegradable magnesium alloys. PMID:24140607
Zhao, Ying; Jamesh, Mohammed Ibrahim; Li, Wing Kan; Wu, Guosong; Wang, Chenxi; Zheng, Yufeng; Yeung, Kelvin W K; Chu, Paul K
In vitro biocompatibility and endothelialization of novel magnesium-rare Earth alloys for improved stent applications.
Magnesium (Mg) based alloys are the most advanced cardiovascular stent materials. This new generation of stent scaffold is currently under clinical evaluation with encouraging outcomes. All these Mg alloys contain a certain amount of rare earth (RE) elements though the exact composition is not yet disclosed. RE alloying can usually enhance the mechanical strength of different metal alloys but their toxicity might be an issue for medical applications. It is still unclear how RE elements will affect the magnesium (Mg) alloys intended for stent materials as a whole. In this study, we evaluated MgZnCaY-1RE, MgZnCaY-2RE, MgYZr-1RE, and MgZnYZr-1RE alloys for cardiovascular stents applications regarding their mechanical strength, corrosion resistance, hemolysis, platelet adhesion/activation, and endothelial biocompatibility. The mechanical properties of all alloys were significantly improved. Potentiodynamic polarization showed that the corrosion resistance of four alloys was at least 3-10 times higher than that of pure Mg control. Hemolysis test revealed that all the materials were non-hemolytic while little to moderate platelet adhesion was found on all materials surface. No significant cytotoxicity was observed in human aorta endothelial cells cultured with magnesium alloy extract solution for up to seven days. Direct endothelialization test showed that all the alloys possess significantly better capability to sustain endothelial cell attachment and growth. The results demonstrated the promising potential of these alloys for stent material applications in the future. PMID:24921251
Zhao, Nan; Watson, Nevija; Xu, Zhigang; Chen, Yongjun; Waterman, Jenora; Sankar, Jagannathan; Zhu, Donghui
In Vitro Biocompatibility and Endothelialization of Novel Magnesium-Rare Earth Alloys for Improved Stent Applications
Magnesium (Mg) based alloys are the most advanced cardiovascular stent materials. This new generation of stent scaffold is currently under clinical evaluation with encouraging outcomes. All these Mg alloys contain a certain amount of rare earth (RE) elements though the exact composition is not yet disclosed. RE alloying can usually enhance the mechanical strength of different metal alloys but their toxicity might be an issue for medical applications. It is still unclear how RE elements will affect the magnesium (Mg) alloys intended for stent materials as a whole. In this study, we evaluated MgZnCaY-1RE, MgZnCaY-2RE, MgYZr-1RE, and MgZnYZr-1RE alloys for cardiovascular stents applications regarding their mechanical strength, corrosion resistance, hemolysis, platelet adhesion/activation, and endothelial biocompatibility. The mechanical properties of all alloys were significantly improved. Potentiodynamic polarization showed that the corrosion resistance of four alloys was at least 3–10 times higher than that of pure Mg control. Hemolysis test revealed that all the materials were non-hemolytic while little to moderate platelet adhesion was found on all materials surface. No significant cytotoxicity was observed in human aorta endothelial cells cultured with magnesium alloy extract solution for up to seven days. Direct endothelialization test showed that all the alloys possess significantly better capability to sustain endothelial cell attachment and growth. The results demonstrated the promising potential of these alloys for stent material applications in the future.
... evaluate magnesium status, both laboratory tests and a clinical assessment might be required [ 6 ]. Recommended Intakes Intake ... a small extent. A meta-analysis of 12 clinical trials found that magnesium supplementation for 8–26 ...
Vertical vibration-assisted magnetic abrasive finishing and deburring for magnesium alloy
The ultimate goal of this project is to develop an efficient finishing process enabling unskilled operators to finish automatically the complicated micro-curved surface and edge surface of the magnesium alloy. The results achieved in the first phase as described in this paper focus on the basic characteristics of the plane and edge surface finishing and deburring of this alloy by
Shaohui Yin; Takeo Shinmura
Corrosion resistance of aged die cast magnesium alloy AZ91D
The corrosion behaviour of die cast magnesium alloy AZ91D aged at 160°C was investigated. The corrosion rate of the alloy decreases with ageing time in the initial stages and then increases again at ageing times greater than 45h. The dependence of the corrosion rate on ageing time can be related to the changes in microstructure and local composition during ageing.
Guangling Song; Amanda L Bowles; David H StJohn
Morphology of Corrosion Damage in Magnesium Alloys and Anion Effects on Passive Film Stability
The need for reduced weight in automotive applicati ons has lead directly to an increased interest in magne sium and its alloys. Magnesium has a very low specific gravity (1.74), but can have a reasonable stiffness compare d to aluminum, the other widely used lightweight metal. The materials properties of the alloys used are promisi ng. However, a major factor
Andrew Fones; Miguel Gonzalez Torreira
Application of YAG Laser TIG Arc Hybrid Welding to Thin AZ31B Magnesium Alloy Sheet
A magnesium alloy is said to be an ecological material with high ability of recycling and lightweight property. Especially, magnesium alloys are in great demand on account of outstanding material property as a structural material. Under these circumstances, research and development of welding process to join magnesium alloy plates are of great significance for wide industrial application of magnesium. In order to use it as a structure material, the welding technology is very important. TIG arc welding process is the most ordinary process to weld magnesium alloy plates. However, since the heat source by the arc welding process affects the magnesium alloy plates, HAZ of welded joint becomes wide and large distortion often occurs. On the other hand, a laser welding process that has small diameter of heat source seems to be one of the possible means to weld magnesium alloy in view of the qualitative improvement. However, the low boiling point of magnesium generates some weld defects, including porosity and solidification cracking. Furthermore, precise edge preparation is very important in butt-welding by the laser welding process, due to the small laser beam diameter. Laser/arc hybrid welding process that combines the laser beam and the arc is an effective welding process in which these two heat sources influence and assist each other. Using the hybrid welding, a synegistic effect is achievable and the disadvantages of the respective processes can be compensated. In this study, YAG laser/TIG arc hybrid welding of thin magnesium alloy (AZ31B) sheets was investigated. First of all, the effect of the irradiation point and the focal position of laser beam on the quality of a weld were discussed in hybrid welding. Then, it was confirmed that a sound weld bead with sufficient penetration is obtained using appropriate welding conditions. Furthermore, it was made clear that the heat absorption efficiency is improved with the hybrid welding process. Finally, the tensile tests of welded joints were performed, and it was confirmed that they have sufficient mechanical properties. As a result of this study, it is confirmed that, if the appropriate welding conditions are selected, sound welded joints of AZ31B magnesium alloy are obtainable by the YAG laser/TIG arc hybrid welding process.
Kim, Taewon; Kim, Jongcheol; Hasegawa, Yu; Suga, Yasuo
Applications for magnesium powders have generally been restricted to the area of pyrotechnology, but with improved safety\\u000a measures and novel processing technologies there are now more opportunities opening up for magnesium powder metallurgy components.\\u000a Conventional powder metallurgy involving liquid phase sintering may not be a viable option, however, due to the high reactivity\\u000a of molten magnesium in air. Solid-state consolidation
M. Moss; R. Lapovok; C. J. Bettles
All-solid-state devices with switchable mirror properties based on magnesium-rich magnesium-nickel alloy thin films have been prepared using magnetron sputtering. The structure of the devices was a Mg-Ni alloy (40 nm)/Pd (4 nm)/Ta2O5 (200 nm)/HxWO3 (500 nm)/ITO on a glass. The composition of the alloy was Mg5Ni. In the initial state, the devices showed a shiny metallic front side and a deep blue back side, namely, in a reflective state. The optical transmittance of the devices at a wavelength of 670 nm was modulated between ˜0.3% (the reflective state) and ˜40% (the transparent state) by applying a voltage of ± 5 V between the ITO and the Mg-Ni alloy layer. The color of the portion changed to the transparent state was relatively neutral. The transition from the reflective state to the transparent state started from the fringe of the electric contact on the Mg-Ni alloy side, and the transparent region spread gradually.
Yamada, Yasusei; Tajima, Kazuki; Bao, Shanhu; Okada, Masahisa; Yoshimura, Kazuki
Novel process for recycling magnesium alloy employing refining and solid oxide membrane electrolysis
Magnesium is the least dense engineering metal, with an excellent stiffness-to-weight ratio. Magnesium recycling is important for both economic and environmental reasons. This project demonstrates feasibility of a new environmentally friendly process for recycling partially oxidized magnesium scrap to produce very pure magnesium at low cost. It combines refining and solid oxide membrane (SOM) based oxide electrolysis in the same reactor. Magnesium and its oxide are dissolved in a molten flux. This is followed by argon-assisted evaporation of dissolved magnesium, which is subsequently condensed in a separate condenser. The molten flux acts as a selective medium for magnesium dissolution, but not aluminum or iron, and therefore the magnesium collected has high purity. Potentiodynamic scans are performed to monitor the magnesium content change in the scrap as well as in solution in the flux. The SOM electrolysis is employed in the refining system to enable electrolysis of the magnesium oxide dissolved in the flux from the partially oxidized scrap. During the SOM electrolysis, oxygen anions are transported out of the flux through a yttria stabilized zirconia membrane to a liquid silver anode where they are oxidized. Simultaneously, magnesium cations are transported through the flux to a steel cathode where they are reduced. The combination of refining and SOM electrolysis yields close to 100% removal of magnesium metal from partially oxidized magnesium scrap. The magnesium recovered has a purity of 99.6w%. To produce pure oxygen it is critical to develop an inert anode current collector for use with the non-consumable liquid silver anode. In this work, an innovative inert anode current collector is successfully developed and used in SOM electrolysis experiments. The current collector employs a sintered strontium-doped lanthanum manganite (La0.8Sr0.2MnO 3-delta or LSM) bar, an Inconel alloy 601 rod, and a liquid silver contact in between. SOM electrolysis experiments with the new LSM-Inconel current collector are carried out and performance comparable to the state-of-the-art SOM electrolysis for Mg production employing the non-inert anode has been demonstrated. In both refining and SOM electrolysis, magnesium solubility in the flux plays an important role. High magnesium solubility in the flux facilitates refining. On the other hand, lower magnesium solubility benefits the SOM electrolysis. The dissolution of magnesium imparts electronic conductivity to the flux. The effects of the electronic conductivity of the flux on the SOM electrolysis performance are examined in detail through experiments and modeling. Methods for mitigating the negative attributes of the electronic conductivity during SOM electrolysis are presented.
Guan, Xiaofei
Thermal Conductivity of Magnesium Alloys in the Temperature Range from -125 °C to 400 °C
Magnesium alloys have been widely used in recent years as lightweight structural materials in the manufacturing of automobiles, airplanes, and portable computers. Magnesium alloys have extremely low density (as low as 1738 kg · m-3) and high rigidity, which makes them suitable for such applications. In this study, the thermal conductivity of two different magnesium alloys made by twin-roll casting was investigated using the laser-flash technique and differential scanning calorimetry for thermal diffusivity and specific heat capacity measurements, respectively. The thermal diffusivity of the magnesium alloys, AZ31 and AZ61, was measured over the temperature range from -125 °C to 400 °C. The alloys AZ31 and AZ61 are composed of magnesium, aluminum, and zinc. The thermal conductivity gradually increased with temperature. The densities of AZ31 and AZ61 were 1754 kg · m-3 and 1777 kg · m-3, respectively. The thermal conductivity of AZ31 was about 25 % higher than that of AZ61, and this is attributed to the amount of precipitation.
Lee, Sanghyun; Ham, Hye Jeong; Kwon, Su Yong; Kim, Sok Won; Suh, Chang Min
Experimental Research on a Novel Iodine-125 Seed Strand Connected Using Magnesium Alloy AZ31.
Background and Purpose: Aim of this research is to study the in vivo degradation and biocompatibility in rabb its and the dose distribution of novel iodine-125 seed strands connected using magnesium alloy AZ31. Method: Thirtythree New Zealand rabbits were divided into three Groups (A, B, and C). All rabbits in Groups A and C were implanted with VX2 tumors. For Group A, radioactive iodine-125 seed strands were implanted into the VX2 tumors. For Group B, non-radioactive iodine-125 seed strands were implanted into thigh muscle. Rabbits in Group C were used as controls. Displacement of the seed strands was assessed using X-ray and CT. Blood and urine samples were collected from all groups to measure changes in magnesium ion concentrations. The changing effect of alloy AZ31 tube according to dose distribution of iodine-125 was evaluated using the Monte Carlo method. Results: In Groups A and B, 14 days after implantation, majority of the magnesium alloy tubes were fragmented, and 28 days after implantation, the magnesium alloy tubes were completely degraded. Small differences in dose distribution were observed between bare iodine-125 seeds and iodine-125 seed strands. Conclusions: Our results suggest that these novel iodine-125 seed strands connected using magnesium alloy AZ31 are promising anti-cancer drug for brachytherapy due to the rapid degradation of connective materials and even distribution of seed doses in tumors. Some recent patents are also outlined in this article. PMID:24483348
Li, Chuanxing; Zhang, Yanling; Chen, Dong; Duan, Guangfeng; Liu, Zhenyin; Zhang, Liang; Yang, Guang; Zhang, Tao; Lu, Ming-Jian; Singh, Sristi; Zhang, Weidong; Zhang, Fujun
An EBSP investigation of alternate microstructures for superplasticity in aluminum-magnesium alloys
This study proposes to provide insight into alternative grain boundary structures in two aluminum-magnesium alloys processed to achieve superplastic behavior. A commercially processes superplastic 5083 aluminum alloy, SKY5083, and a laboratory processed, non-commercial superplastic Al-10Mg-0.1Zr alloy have been selected for examination. Although alloy content, processing routes, and deformation conditions vary for each material, a comparison of results may provide evidence that alternate grain structures and boundary misorientation distributions may support superplasticity in the GBS regime, depending on the TMP processing and alloy system chosen.
McNelley, T.R.; McMahon, M.E. [Naval Postgraduate School, Monterey, CA (United States)] [Naval Postgraduate School, Monterey, CA (United States); Hales, S.J. [A.S. and M., Inc., Hampton, VA (United States)] [A.S. and M., Inc., Hampton, VA (United States)
Study of second phase in bioabsorbable magnesium alloys: Phase stability evaluation via Dmol3 calculation
Thermodynamical stabilities of four conventional second phases as well as magnesium matrix in bioabsorbable magnesium alloys were investigated theoretically via computer calculation method. Model of individual phase and systems including phase and four water molecular (phase-4H2O) were established to simulate the in vitro and in vivo environment. Local orbital density functional theory approach was applied to calculate the total energy for the individual phase and phase-4H2O system. The results demonstrated that all the second phases possessed higher phase stability compared with magnesium matrix, but the phase stability was quite different for different types of second phases or second phase-4H2O systems. Furthermore, a schematic process of inflammation reaction caused by magnesium alloy implants was proposed for the further evaluation on biocompatibility of different second phases.
Yang, Huazhe; Liu, Chen; Wan, Peng; Tan, Lili; Yang, Ke
Smart self-healing anti-corrosion vanadia coating for magnesium alloys
Eco-friendly vanadia based chemical conversion coating was applied for improving the corrosion resistance of a newly developed magnesium AZ31 HP–O alloy. The effect of vanadia solution concentrations (10, 30 and 50g\\/l) and pH (neutral pH 7 and pH 9) on the corrosion protection performance of a magnesium substrate were investigated. EIS and linear polarization techniques were used to evaluate the
Abdel Salam Hamdy; I. Doench; H. Möhwald
K? X-rays from magnesium, some of its compounds and alloys
Magnesium K?3,4 satellite spectra along with the K?1,2 diagram line and the K?' satellite line from magnesium, its oxide, halides, sulphate, acetate and binary alloys with silver, cadmium, indium, tin and antimony have been recorded in direct excitation using a Johann-type crystal spectrometer with a MoS2 crystal (2d = 12.30 Å). It is found that the chemical environment surrounding the
U D Misra; L M Watson
Chrome-free zirconia-based protective coatings for magnesium alloys
Environmentally friendly anti-corrosion surface treatment based on zirconium conversion coating was developed for magnesium AZ31D alloy. The effect of zirconate solution concentrations on the corrosion protection performance of magnesium substrate was studied. EIS and cyclic voltammetry techniques were used to evaluate the corrosion behavior in 3.5% NaCl. The surface resistance (Rp) of the uncoated AZ31D measured by EIS was approximately
Abdel Salam Hamdy; M. Farahat
Roundness and cylindricity verification of cylindrical workpieces of magnesium alloys obtained by intermittent dry machining
Magnesium is the lightest metal used in industry, above all for aerospace and automotive applications where weight reduction allows an improvement in the fuel efficiency and reducing CO2 emission. In this work, an experimental study was carried out in order to determine with which machining process, turning or milling, are obtained cylindrical bars of magnesium alloy UNS M11917 by intermittent dry cut with improved roundness and cylindricity finish.
de Agustina, B.; Clavijo, N.; Villeta, M.; Rubio, E.
A comparison of the deformation of magnesium alloys with aluminium and steel in tension, bending and buckling
A comparison was made between high pressure die cast and wrought magnesium alloys and formed mild steel and aluminium in tensile, bending and buckling deformation. It was found that the energy absorption properties of magnesium alloys were particularly good in bending and buckling, absorbing up to 50% more energy than the aluminium and over 10 times more energy than the
Mark Easton; Wei Qian Song; Trevor Abbott
An organic chromium-free conversion coating on AZ91D magnesium alloy
Traditional conversion coatings on magnesium alloys are usually immersed in a solution containing hexavalent chromium compounds. However, the replacement treatments have been proposed by the present environmental driving to eliminate hexavalent chromium. In this work, a tannic acid based conversion coating on AZ91D magnesium alloy was obtained by treatment in a solution containing tannic acid and ammonium metavanadate. SEM, XPS and IR were used to determine the morphology and structure of the conversion coatings. Continuous and uniform conversion coating was deposited on AZ91D alloy and the main components of the coatings were Al 2O 3, MgF 2 and penta-hydroxy benzamide-magnesium complex. The formation mechanism of the coating was discussed. Polarization measurement and salt spray test showed that the corrosion resistance of the conversion coating was much higher than that of traditional chromate conversion coating.
Chen, Xiaoming; Li, Guangyu; Lian, Jianshe; Jiang, Qing
Corrosion Behavior of AZ91D Magnesium Alloy in Three Different Physiological Environments
Magnesium alloys have been considered as promising biomedical materials and were studied in different physiological environments. In this work, corrosion behavior of AZ91D magnesium alloy in artificial saliva, simulated body fluid (SBF), and 3.5 wt.% NaCl solution was investigated using electrochemical techniques and a short-term immersion test. In contrast with other physiological environments, the amount of aggressive ions in artificial saliva is small. In addition, a protective film is formed on the surface of samples in artificial saliva. Experimental results suggest that corrosion resistance of AZ91D magnesium alloy in artificial saliva is better than that in c-SBF and 3.5 wt.% NaCl solution.
Zhou, Juncen; Li, Qing; Zhang, Haixiao; Chen, Funan
Corrosion resistance of a composite polymeric coating applied on biodegradable AZ31 magnesium alloy.
The high corrosion rate of magnesium alloys is the main drawback to their widespread use, especially in biomedical applications. There is a need for developing new coatings that provide simultaneously corrosion resistance and enhanced biocompatibility. In this work, a composite coating containing polyether imide, with several diethylene triamine and hydroxyapatite contents, was applied on AZ31 magnesium alloys pre-treated with hydrofluoric acid by dip coating. The coated samples were immersed in Hank's solution and the coating performance was studied by electrochemical impedance spectroscopy and scanning electron microscopy. In addition, the behavior of MG63 osteoblastic cells on coated samples was investigated. The results confirmed that the new coatings not only slow down the corrosion rate of AZ31 magnesium alloys in Hank's solution, but also enhance the adhesion and proliferation of MG63 osteoblastic cells, especially when hydroxyapatite nanoparticles were introduced in the coating formulation. PMID:23454214
Zomorodian, A; Garcia, M P; Moura e Silva, T; Fernandes, J C S; Fernandes, M H; Montemor, M F
Finite Element Analysis Of The Warm Deep Drawing Process Of Magnesium Alloys
The use of magnesium alloys meets the need of reducing weight of components (especially in automotive and aerospace industry) keeping unmodified their mechanical properties. The adoption of magnesium alloys in sheet forming processes (which allows optimal mechanical properties) is still limited, due to their low formability at room temperature caused by the hexagonal crystal structure. Conventional sheet forming processes (like Deep Drawing) have to be modified in order to allow the adoption of such lightweight materials. In this work, the authors aim to understand the process conditions and the parameters operating window which can lead to a successful improvement in the formability of a magnesium alloy (AZ31). A numerical Finite Element analysis based on experimental data (both warm DD tests and tensile tests) was performed to properly design the thermal gradient to superimpose during the DD process. The estimation of the critical condition occurrence was based on the calculated local temperature increase.
Palumbo, G.; Zhang, S. H.; Pinto, S.; Tricarico, L.; Xu, Y. C.; Zhang, K.
Numerical analysis of self-pierce riveting of AZ31 magnesium alloy sheets
Magnesium alloy sheet has a broad development prospect for lightweight metal in automotive industry. Selfpierce Riveting (SPR) process is a suitable joining technology to fasten materials of different nature. This paper is concerned with the development of numerical models of the SPR process of AZ31 magnesium alloy sheet. Based on DEFORM-2D finite element software, a two-dimensional axisymmetric model has been built for the SPR process. Then the distribution of stress and strain, and the stroke-load curve are analyzed in the forming process of the riveting. After a 2D simulation of SPR process, the quality of riveted joint is evaluated in terms of joint cross-sectional shape. The results show a better understanding of mechanical properties of SPR joints of magnesium alloy sheets. As a sufficient interlock and bottom thickness leading to a reasonably good joint, the numerical simulation method plays a significant role to predict the final strength of the joint.
Han, S. L.; Wu, Y. W.; Zeng, Q. L.; Gao, Y.
Interfacial chemistry of organic conversion film on AZ61 magnesium alloy surface
The anodic electrochemical behavior of AZ61 magnesium alloy in sodium hydroxide medium in the absence and presence of p-nitro-benzene-azo-resorcinol (PNBAR) was studied using electrochemical techniques. In the presence of PNBAR, organic conversion film formed on the surface of magnesium alloy. The nature of chemical mechanisms, bonds, and structures at the interface of PNBAR/magnesium alloy was investigated by using energy dispersive spectrometer (EDS) analysis and Fourier transform infrared spectroscopy. An in situ electrochemical deposition was evidenced to produce a corrosion protective barrier by the formation of organic conversion film of magnesium-PNBAR complex and to enhance film adhesion by the covalent bonds of Mg sbnd O sbnd N linkage. The linear sweep voltammetry experiments and the score tests were used to investigate the adhesion and evaluate the potential of corrosion resistance of organic conversion film. The results indicated the corrosion resistance of magnesium alloy was improved, the organic conversion film showed excellent adhesion not only to the substrate but also to the outer paint coatings.
Yang, Xu; Pan, Fusheng; Zhang, Dingfei
Design of experiment (DOE) study of biodegradable magnesium alloy synthesized by mechanical alloying using fractional factorial design
The biodegradable nature of magnesium (Mg) makes it a most highlighted and attractive to be used as implant materials. However, rapid corrosion rate of Mg alloys especially in electrolytic aqueous environment limits its performance. In this study, Mg alloy was mechanically milled by incorporating manganese (Mn) as alloying element. An attempt was made to study both effect of mechanical alloying and subsequent consolidation processes on the bulk properties of Mg-Mn alloys. 2k-2 factorial design was employed to determine the significant factors in producing Mg alloy which has properties closes to that of human bones. The design considered six factors (i.e. milling time, milling speed, weight percentage of Mn, compaction pressure, sintering temperature and sintering time). Density and hardness were chosen as the responses for assessing the most significant parameters that affected the bulk properties of Mg-Mn alloys. The experimental variables were evaluated using ANOVA and regression model. The main parameter investigated was compaction pressure.
Salleh, Emee Marina; Ramakrishnan, Sivakumar; Hussain, Zuhailawati
The aluminium-scandium-lithium-magnesium system as a potential source of superplastically formable alloys
Alloys from the aluminum-lithium-scandium-magnesium system have been cast and rolled for study. The goal is to evaluate this system for the development of superplastically formable, high strength alloys. Aluminum-scandium-magnesium alloys have shown potential as superplastic alloys. These alloys rely on small Al{sub 3}Sc (ordered L1{sub 2}) precipitates for grain structure stabilization and strengthening. Additional precipitation strengthening is required to raise their strength to levels sufficient for aircraft applications. The addition of lithium provides this additional strengthening through the formation of Al{sub 3}Li({delta}{prime}). To produce the alloys studied in this research, a unique induction melting furnace was constructed that incorporates special features to produce aluminum-lithium alloys with low hydrogen content. The furnace also features a water cooled, copper casting mold to achieve a moderately rapid solidification rate. This is because the amount of scandium used (0.5 wt %) is in excess of the solubility limit and Al{sub 3}Sc cannot be re-solutionized to any extent. It is therefore desired to super-saturate the matrix with as much scandium as possible for later precipitation. Two high lithium alloys were produced, ALS2 (nominal composition Al-2.2Li-O.5 Sc) and AlS4 (nominal composition Al-2.0Li-2.2Mg-0.5Sc) that were strengthened with {delta}{prime} (Al{sub 3}Li). These alloys exhibited strength and ductility superior to those of aluminum-lithium-(magnesium)-zirconium alloys. This is because the scandium containing alloys have developed a finer grain structure and the Al{sub 3}Sc precipitates contribute to the alloys strength. 41 refs., 29 figs.
Emigh, R.A.
Galvanic corrosion of magnesium alloy AZ91D in contact with an aluminium alloy, steel and zinc
An investigation was carried out into the galvanic corrosion of magnesium alloy AZ91D in contact with zinc, aluminium alloy A380 and 4150 steel. Specially designed test panels were used to measure galvanic currents under salt spray conditions. It was found that the distributions of the galvanic current densities on AZ91D and on the cathodes were different. An insulating spacer between
Guangling Song; Birgir Johannesson; Sarath Hapugoda; David StJohn
Characterization of fold defects in AZ91D and AE42 magnesium alloy permanent mold castings
Casting premium-quality magnesium alloy components for aerospace and automotive applications poses unique challenges. Magnesium alloys are known to freeze rapidly prior to filling a casting cavity, resulting in misruns and cold shuts. In addition, melt oxidation, solute segregation and turbulent metal flow during casting contribute to the formation of fold defects. In this research, formation of fold defects in AZ91D and AE42 magnesium alloys cast via the permanent mold casting process was investigated. Computer simulations of the casting process predicted the development of a turbulent metal flow in a critical casting region with abrupt geometrical transitions. SEM and light optical microscopy examinations revealed the presence of folds in this region for both alloys. However, each alloy exhibited a unique mechanism responsible for fold formation. In the AZ91D alloy, melt oxidation and velocity gradients in the critical casting region prevented fusion of merging metal front streams. In the AE42 alloy, limited solubility of rare-earth intermetallic compounds in the {alpha}-Mg phase resulted in segregation of Al{sub 2}RE particles at the leading edge of a metal front and created microstructural inhomogeneity across the fold.
Bichler, L. [Centre for Near-net-shape Processing of Materials, Ryerson University, 101 Gerrard St. E., Toronto, M5B 2K3 (Canada); Ravindran, C., E-mail: email@example.com [Centre for Near-net-shape Processing of Materials, Ryerson University, 101 Gerrard St. E., Toronto, M5B 2K3 (Canada)
Influence of Cobalt on the Properties of Load-Sensitive Magnesium Alloys
In this study, magnesium is alloyed with varying amounts of the ferromagnetic alloying element cobalt in order to obtain lightweight load-sensitive materials with sensory properties which allow an online-monitoring of mechanical forces applied to components made from Mg-Co alloys. An optimized casting process with the use of extruded Mg-Co powder rods is utilized which enables the production of magnetic magnesium alloys with a reproducible Co concentration. The efficiency of the casting process is confirmed by SEM analyses. Microstructures and Co-rich precipitations of various Mg-Co alloys are investigated by means of EDS and XRD analyses. The Mg-Co alloys' mechanical strengths are determined by tensile tests. Magnetic properties of the Mg-Co sensor alloys depending on the cobalt content and the acting mechanical load are measured utilizing the harmonic analysis of eddy-current signals. Within the scope of this work, the influence of the element cobalt on magnesium is investigated in detail and an optimal cobalt concentration is defined based on the performed examinations.
Klose, Christian; Demminger, Christian; Mroz, Gregor; Reimche, Wilfried; Bach, Friedrich-Wilhelm; Maier, Hans Jurgen; Kerber, Kai
Degradation and antibacterial properties of magnesium alloys in artificial urine for potential resorbable ureteral stent applications.
This article presents an investigation on the effectiveness of magnesium and its alloys as a novel class of antibacterial and biodegradable materials for ureteral stent applications. Magnesium is a lightweight and biodegradable metallic material with beneficial properties for use in medical devices. Ureteral stent is one such example of a medical device that is widely used to treat ureteral canal blockages clinically. The bacterial colony formation coupled with the encrustation on the stent surface from extended use often leads to clinical complications and contributes to the failure of indwelling medical devices. We demonstrated that magnesium alloys decreased Escherichia coli viability and reduced the colony forming units over a 3-day incubation period in an artificial urine (AU) solution when compared with currently used commercial polyurethane stent. Moreover, the magnesium degradation resulted in alkaline pH and increased magnesium ion concentration in the AU solution. The antibacterial and degradation properties support the potential use of magnesium-based materials for next-generation ureteral stents. Further studies are needed for clinical translation of biodegradable metallic ureteral stents. PMID:23564415
Lock, Jaclyn Y; Wyatt, Eric; Upadhyayula, Srigokul; Whall, Andrew; Nuñez, Vicente; Vullev, Valentine I; Liu, Huinan
Fast neutron activation analysis of oxide inclusions in magnesium alloy ingots
Magnesium will have an increasingly important role to play in the automotive industry's materials strategy. In addition to its obvious use as a lightweight alternative, magnesium offers advantages in areas such as component integration and NVH (noise, vibration and harshness). Although the metallic composition of magnesium alloys has been carefully defined, there is no uniform industry standard for non-metallic inclusions, such as oxides, which are believed to adversely impact the material's strength. A definitive test has been needed, preferably one that provides a highly sensitive, calibrated, nondestructive evaluation of the metal's bulk oxide content. In response to this need, fast neutron activation analysis (FNAA) has emerged as an important tool for providing highly accurate quantitative information on the oxygen content in magnesium alloys. Oxygen levels from less than 50 to several thousand ppm have been observed in these alloys, with the highest levels concentrated at the top center of the ingot. Several operational procedures have been developed to optimize the analysis, including: a new automated, blank-free procedure which pneumatically transports machined magnesium cylinders between the irradiation and counting facilities; the use of an oxygen standard prepared from polyethylene and titanium dioxide, machined to match the sample dimensions; and implementation of new background subtraction software.
Fuerst, C. D.; James, W. D.
Comparison of the thermal properties of AM20 and AS21 magnesium alloys
The present work is a study of the thermal properties of AS21 and AM20 magnesium alloys in the temperature range of 20–380°C. The thermal diffusivity and the thermal expansion coefficient (CTE) were measured and the thermal conductivity was calculated. The thermal diffusivity and the thermal conductivity of the alloys increase with increasing temperature. The temperature dependency of the CTE in
A. Rudajevová; P. Luká?
Solidification, growth mechanisms, and associated properties of Al-Si and magnesium lightweight casting alloys
Continually rising energy prices have inspired increased interest in weight reduction in the automotive and aerospace industries, opening the door for the widespread use and development of lightweight structural materials. Chief among these materials are cast Al-Si and magnesium-based alloys. Utilization of Al-Si alloys depends on obtaining a modified fibrous microstructure in lieu of the intrinsic flake structure, a process
Solidification, growth mechanisms, and associated properties of aluminum-silicon and magnesium lightweight casting alloys
Timothy Al Hosch
Tim A. Hosch
Microstructural stability and creep properties of die casting Mg–4Al–4RE magnesium alloy
The AE44 (Mg–4Al–4RE) alloy was prepared by a hot-chamber die casting method. The microstructure, microstructural stability and creep properties at 175 °C were investigated. The microstructure was analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and the Rietveld method. The results show that die cast AE44 magnesium alloy consists of ?-Mg, Al11RE3, Al2RE and Al2.12RE0.88 phases.
Tomasz Rzycho?; Andrzej Kie?bus; Jan Cwajna; Jaros?aw Mizera
Phase selection of ternary intermetallic compounds during solidification of high zinc magnesium alloy
The phase selection of ternary intermetallic compound ? phase (Mg32(Al, Zn)49) and ? phase (Al2Mg5Zn2) in high zinc magnesium alloys was studied by using scanning electron microscope, X-ray diffractometer and differential scanning calorimeter, etc. The results indicate that, when adding element Si in Mg-8Zn-4Al-0.3Mn (ZA84) alloy, ? phase is promoted, whereas ? phase is inhibited. The Chinese script-type Mg2Si and
Shao-kang GUAN; Chun-xiang ZHANG; Li-guo WANG; Li-hong WU; Pei-lei CHEN; Ya-li TANG
Formation of Ha-Containing Coating on AZ31 Magnesium Alloy by Micro-Arc Oxidation
Magnesium and its alloys are potential biodegradable implant materials due to their attractive biological properties. But the use of magnesium is still hampered by its poor corrosion resistance in physiological fluids. In this study, a HA-containing coating was fabricated by micro-arc oxidation (MAO). The active plasma species of micro-discharge was studied by optical emission spectroscopy (OES). The microstructure and composition were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion behavior and apatite-forming ability were studied by electrochemical tests and immersed samples in simulated body fluids (SBF). The results show that the microdischarge channel model is gas discharges and oxide layer discharges. The elements from the substrate and electrolyte take part in the formation of the coating. The MAO coating significantly improves the corrosion resistance of AZ31 magnesium alloy and enhances the apatite formation ability.
Tang, Hui; Li, Deyu; Chen, Xiuping; Wu, Chao; Wang, Fuping
Magnesium K?3,4 satellite spectra along with the K?1,2 diagram line and the K?' satellite line from magnesium, its oxide, halides, sulphate, acetate and binary alloys with silver, cadmium, indium, tin and antimony have been recorded in direct excitation using a Johann-type crystal spectrometer with a MoS2 crystal (2d = 12.30 Å). It is found that the chemical environment surrounding the emitting atoms affects the satellite intensity ratio (IK?4/IK?3) strongly. No obvious trend between the electronegativity differences of the compounds and the intensity ratios of the K?4/K?3 satellites is evident. No linear relationship between the satellite intensity ratios (IK?4/IK?3) and the magnesium content in the alloy is observed as reported by Baun and Fischer for the aluminium system. The origin of the K?3 and K?4 satellites is discussed.
Misra, U. D.; Watson, L. M.
Laser beam welding of AZ31B-H24 magnesium alloy.
The laser beam weldability of AZ31B magnesium alloy was examined with high power CW CO{sub 2} and pulsed Nd:YAG lasers. The low viscosity and surface tension of the melt pool make magnesium more difficult to weld than steel. Welding parameters necessary to obtain good welds were determined for both CW CO{sub 2} and pulsed Nd:YAG lasers. The weldability of the magnesium alloy was significantly better with the Nd:YAG laser. The cause of this improvement was attributed to the higher absorption of the Nd:YAG beam. A lower threshold beam irradiance was required for welding, and a more stable weldpool was obtained.
Leong, K. H.
Corrosion behaviors of Zn\\/Al–Mn alloy composite coatings deposited on magnesium alloy AZ31B (Mg–Al–Zn)
After being pre-plated a zinc layer, an amorphous Al–Mn alloy coating was applied onto the surface of AZ31B magnesium alloy with a bath of molten salts. Then the corrosion performance of the coated magnesium alloy was examined in 3.5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the single Zn layer was active in
Jifu Zhang; Wei Zhang; Chuanwei Yan; Keqin Du; Fuhui Wang
Superplastic behaviour of friction stir processed AZ91 magnesium alloy produced by high pressure die cast
The room temperature and hot tensile properties of AZ91 magnesium alloy produced by high pressure die cast after friction stir processing (FSP) were studied in the present paper. Such process is a modification of classical friction stir welding one in which the sheets are not joined but the stirring action of the tool, on the bulk material, is used to
P. Cavaliere; P. P. De Marco
Low-pressure die casting of magnesium alloy AM50: Response to process parameters
Low-pressure die casting (LPDC) process has been successfully used to produce sound magnesium alloy AM50 castings. The influence of process parameters: filling time, pressure holding time, die temperature, holding pressure and casting temperature, on the mechanical properties, microstructure and density of LPDC castings were studied. The optimal process parameters for LPDC casting have been experimentally determined as follows: filling time
Penghuai Fu; Alan A. Luo; Haiyan Jiang; Liming Peng; Yandong Yu; Chunquan Zhai; Anil K. Sachdev
Magnetic force improvement and parameter optimization for magnetic abrasive polishing of AZ31 magnesium alloy
The magnetic force acting on workpiece to be machined plays a significantly important role in magnetic abrasive polishing process. But in a case of polishing nonferrous materials, the strength of magnetic force is very low and it leads lower polishing efficiency. The magnesium alloy that has superior mechanical properties for industrial application such as a lightweight and high specific strength
Modeling of microstructure evolution of magnesium alloy during the high pressure die casting process
Two important microstructure characteristics of high pressure die cast magnesium alloy are the externally solidified crystals (ESCs) and the fully divorced eutectic which form at the filling stage of the shot sleeve and at the last stage of solidification in the die cavity, respectively. Both of them have a significant influence on the mechanical properties and performance of magnesium alloy die castings. In the present paper, a numerical model based on the cellular automaton (CA) method was developed to simulate the microstructure evolution of magnesium alloy during cold-chamber high pressure die casting (HPDC) process. Modeling of dendritic growth of magnesium alloy with six-fold symmetry was achieved by defining a special neighbourhood configuration and calculating of the growth kinetics from complete solution of the transport equations. Special attention was paid to establish a nucleation model considering both of the nucleation of externally solidified crystals in the shot sleeve and the massive nucleation in the die cavity. Meanwhile, simulation of the formation of fully divorced eutectic was also taken into account in the present CA model. Validation was performed and the capability of the present model was addressed by comparing the simulated results with those obtained by experiments.
Wu, Mengwu; Xiong, Shoumei
Plastic anisotropy and the role of non-basal slip in magnesium alloy AZ31B
Mechanistic explanations for the plastic behavior of a wrought magnesium alloy are developed using a combination of experimental and simulation techniques. Parameters affecting the practical sheet formability, such as strain hardening rate, strain rate sensitivity, the degree of anisotropy, and the stresses and strains at fracture, are examined systematically by conducting tensile tests of variously oriented samples at a range
Sean R. Agnew; Özgür Duygulu
Study on DC Double Pulse Metal Inert Gas (MIG) Welding of Magnesium Alloy
This article gives a preliminary research on direct current (DC) double pulse metal inert gas (MIG) welding of magnesium alloys. It will be an effort for broadening the application of this new MIG welding process. The unique parameters of DC double pulse MIG welding are selected to investigate their effects on weld bead geometry size and appearance of AZ31B Mg
Zhaodong Zhang; Xiangyu Kong
Evaluation of Microstructure and Mechanical Property of FSW Welded MB3 Magnesium Alloy
An experiment was carried out on the friction stir welding of MB3 magnesium alloy to determine welding parameters for obtaining an excellent weld appearance without void, cracking, or distortion. Frictional heat and plastic flow created fine and equiaxed grains in the weld nugget, and the elongated and recovered grains in the thermomechanically affected zone (TMAZ). The grains in the heat
Kuai-she WANG; Yang SHEN; Xi-rong YANG; Xun-hong WANG; Ke-wei XU
Modelling of laser cladding of magnesium alloys with pre-placed powders
As a surface engineering technique, high-power laser cladding, has shown great potential for improving the corrosion resistance of magnesium alloys. Its main advantage over other processes, is its ability to form relatively thick protective coatings on selected areas where improved properties are desired. It is also a 'clean' process. However, previous research studies have found that in laser cladding of
Li-Feng Guo
Microstructure-based multistage fatigue modeling of a cast AE44 magnesium alloy
The multistage fatigue model developed by McDowell et al. was modified to study the fatigue life of a magnesium alloy AE44 for automobile applications. The fractographic examination indicated three distinct stages of fatigue damage in the high cycle fatigue loading regime: crack incubation, microstructurally small crack growth, and long crack growth. Cracks incubated almost exclusively at the cast pores that
Y. Xue; M. F. Horstemeyer; D. L. McDowell; H. El Kadiri; J. Fan
The fracture properties of a fibre–metal laminate based on magnesium alloy
A range of fibre–metal laminates (FML) based on a lightweight magnesium alloy have been manufactured and tested. Two types of composite reinforcement have been investigated, a woven carbon fibre reinforced epoxy and a unidirectional glass fibre reinforced polypropylene. Initial tests using the single cantilever beam geometry (SCB) have shown that little or no surface treatment is required to achieve a
P. Cortés; W. J. Cantwell
Study on the dissimilar magnesium alloy and copper lap joint by TIG welding
Dissimilar magnesium alloy and copper were welded by TIG in the form of lap welding. Intermetallic compounds in the interfacial region of the dissimilar joint were observed. It was shown that the intermetallic compounds were the cause of the joint embrittlement. The tensile strength of the joint was about 25MPa. While with the iron plate as interlayer, the embrittleness of
Liu Liming; Wang Shengxi; Zhao Limin
Elastic Properties and Internal Friction of Two Magnesium Alloys at Elevated Temperatures
The elastic properties and internal friction of two magnesium alloys were studied from 25 C to 450 C using Resonant Ultrasound Spectroscopy (RUS). The Young's moduli decrease with increasing temperature. At 200 C, a change in the temperature dependence of the elastic constants is observed. The internal friction increases significantly with increasing temperature above 200 C. The observed changes in
M. Freels; P. K. Liaw; E. Garlea; J. S. Morrell; M. Radiovic
Effect of Hydraulic Pressure on Warm Hydro Mechanical Deep Drawing of Magnesium Alloy Sheet
The uniaxial tensile test and hydraulic bulging test of AZ31 magnesium alloy sheets were applied to study the influence of temperature on the material properties and obtain the forming limit curves at different temperatures. Numerical simulations of warm hydro mechanical deep drawing were carried out to investigate the effect of hydraulic pressure on the formability of a cylindrical cup, and
Wei Liu; Linzhi Wu; Shijian Yuan
Scanning probe microscope observations of fatigue process in magnesium alloy AZ31 near the fatigue limit
In this study, fatigue crack initiation and propagation behavior of magnesium alloy AZ31 within a crystal grain near the fatigue limit were investigated in detail using a scanning probe microscope (SPM). At a stress amplitude slightly higher than the fatigue limit, cracks are arrested by the grain boundary for an extended period.
Z. Y. Nan; S. Ishihara; T. Goshima; R. Nakanishi
Effect of deep cryogenic treatment on microstructure, creep and wear behaviors of AZ91 magnesium alloy
This paper focuses on the effect of deep cryogenic treatment (?196°C) on microstructure and mechanical properties of AZ91 magnesium alloy. The execution of deep cryogenic treatment on samples changed the distribution of ? precipitates. The tiny laminar ? particles almost dissolved in the microstructure and the coarse divorced eutectic ? phase penetrated into the matrix. This microstructural modification resulted in
Kaveh Meshinchi Asl; Alireza Tari; Farzad Khomamizadeh
A Feasiblity Study on Spot Friction Welding of Magnesium Alloy AZ31
Spot friction welding (SFW) is a novel variant of the linear friction stir welding process with the potential to create strong joints between similar, as well as dissimilar sheet metals. It is particularly suitable for soft, low melting point metals such as aluminum, magnesium, and their alloys where resistance spot welding can cause defects such as voids, trapped gas and
Michael L Santella; Tsung-Yu Pan; D Alan Frederick; William Schwartz
Structure-property relations and modeling of small crack fatigue behavior of various magnesium alloys
Lightweight structural components are important to the automotive and aerospace industries so that better fuel economy can be realized. Magnesium alloys in particular are being examined to fulfill this need due to their attractive stiffness- and strength-to-weight ratios when compared to other materials. However, when introducing a material into new roles, one needs to properly characterize its mechanical properties. Fatigue behavior is especially important considering aerospace and automotive component applications. Therefore, quantifying the structure-property relationships and accurately predicting the fatigue behavior for these materials are vital. This study has two purposes. The first is to quantify the structure-property relationships for the fatigue behavior in an AM30 magnesium alloy. The second is to use the microstructural-based MultiStage Fatigue (MSF) model in order to accurately predict the fatigue behavior of three magnesium alloys: AM30, Elektron 21, and AZ61. While some studies have previously quantified the MSF material constants for several magnesium alloys, detailed research into the fatigue regimes, notably the microstructurally small crack (MSC) region, is lacking. Hence, the contribution of this work is the first of its kind to experimentally quantify the fatigue crack incubation and MSC regimes that are used for the MultiStage Fatigue model. Using a multi-faceted experimental approach, these regimes were explored with a replica method that used a dual-stage silicone based compound along with previously published in situ fatigue tests. These observations were used in calibrating the MultiStage Fatigue model.
Bernard, Jairus Daniel
A process for recovering Th from Th-Mg alloy, utilizing liquid Li ; extraction, was investigated. Dissolution of Th--Mg alloy in liquid Li metal ; resulted in the formation of a Li-Mg alloy solution and the precipitation of Th ; as a finely divided solid. Th separation was accomplished by filtration through ; stainless steel filters. Over 99.7% of the introduced
Study of the decomposition of the magnesium-based solid solutions in Mg-Sm-Tb alloys
Kinetics and structural transformations upon the decomposition of a magnesium-based supersaturated solid solution in Mg-Sm-Tb alloys have been studied at various relations between the concentrations of terbium and samarium. It has been established that with increasing terbium content in the alloys the strengthening upon the decomposition of the supersaturated magnesium-based solid solution increases. The decomposition of the supersaturated magnesium-based solid solution in the Mg-Sm-Tb alloys with a percentage ratio (wt %) Tb: Sm of about 2.5 exhibits signs characteristic of the decomposition of the supersaturated solid solution in binary Mg-Tb alloys. With allowance for the equilibrium Mg-Sm-Tb phase diagram, this gives grounds to suppose that samarium is mainly dissolved in the products of the decomposition of the magnesium solid solution that are characteristic of Mg-Tb alloys.
Luk'yanova, E. A.; Rokhlin, L. L.; Dobatkina, T. V.; Tabachkova, N. Yu.
Some Key Issues and Accesses to the Application of Magnesium Alloys
The status of Mg alloy application, and then some key issues limiting their applications and the corresponding accesses were briefly discussed. It was supposed that development of new alloys with high performance and low cost, investigating advanced forming technology, and development of credible and effective surface modification technologies and related equipment were the urgent tasks in present. Correspondingly, three aspects of researches were carried out. (1) A new alloy with high strength and elongation, but low RE and Zn contents, named ZW21, was invented. (2) Semisolid ingots of AZ91D, AM60 and ZW21 alloys available for thixoforming were prepared. Thixoforming increased the ultimate tensile strength of AZ91D alloy by 20% compared with permanent mould casting. (3) A new kind of micro arc oxidation equipment with a capacity of treating 6m2 surface was developed and has been used to treating motorcycle hub of magnesium alloy.
Hao, Yuan; Chen, Tijun; Ma, Ying; Li, Yuandong; Yan, Fengyun; Huang, Xiaofeng
Protective Coatings for Magnesium Alloys. Part 3. Coordination Chemistry of the Magnesium Ion.
The coordination chemistry of magnesium ions was studied with respect to neutral, but polar, unidentate ligands in the presence of various donor anions. Complexes of the type (MgLn)A2 were prepared. Chemical analysis, infrared spectral data, and electrica...
D. L. Venezky
Divorced eutectic in a HPDC magnesium–aluminum alloy
The morphology of the eutectic in a thin-wall high pressure die cast (HPDC) U-shape AM60 magnesium box was investigated by light microscope, SEM, TEM and EPMA. The extremely fast cooling rate taking place in the solidification process produces a highly segregated zone near the boundaries of small grains and a fine distribution of ? particles, which is typical of a
S. Barbagallo; H. I. Laukli; O. Lohne; E. Cerri
Effect of Magnesium as an Alloying Element in Inconel 718.
Six 50-lb heats of Inconel 718 were prepared with magnesium contents ranging from 1 to 350 ppm. Half were vacuum arc remelted and half were arc-remelted under 1/2 atm of argon. The homogenized ingots were extruded and some bar segments were flattened. Ups...
G. Saul S. Inouye W. H. Couts
Biocompatibility of rapidly solidified magnesium alloy RS66 as a temporary biodegradable metal.
Biodegradable magnesium-based alloys are very promising materials for temporary implants. However, the clinical use of magnesium-based alloys is often limited by rapid corrosion and by insufficient mechanical stability. Here we investigated RS66, a magnesium-based alloy with extraordinary physicochemical properties of high tensile strength combined with a high ductility and a homogeneous grain size of ~1 ?m which was obtained by rapid solidification processing and reciprocal extrusion. Using a series of in vitro and in vivo experiments, we analyzed the biodegradation behavior and the biocompatibility of this alloy. In vitro, RS66 had no cytotoxic effects in physiological concentrations on the viability and the proliferation of primary human osteoblasts. In vivo, RS66 cylinders were implanted into femur condyles, under the skin and in the muscle of adult rabbits and were monitored for 1, 2, 3, 4 and 8 weeks. After explantation, the RS66 cylinders were first analyzed by microtomography to determine the remaining RS66 alloy and calculate the corrosion rates. Then, the implantation sites were examined histologically for healing processes and foreign body reactions. We found that RS66 was corroded fastest subcutaneously followed by intramuscular and bony implantation of the samples. No clinical harm with transient gas cavities during the first 6 weeks in subcutaneous and intramuscular implantation sites was observed. No gas cavities were formed around the implantation site in bone. The corrosion rates in the different anatomical locations correlated well with the local blood flow prior to implantation. A normal foreign body reaction occurred in all tissues. Interestingly, no enhanced bone formation could be observed around the corroding samples in the condyles. These data show that RS66 is biocompatible, and due to its interesting physicochemical properties, this magnesium alloy is a promising material for biodegradable implants. PMID:23416472
Willbold, Elmar; Kalla, Katharina; Bartsch, Ivonne; Bobe, Katharina; Brauneis, Maria; Remennik, Sergei; Shechtman, Dan; Nellesen, Jens; Tillmann, Wolfgang; Vogt, Carla; Witte, Frank
Research activities of biomedical magnesium alloys in China
The potential application of Mg alloys as bioabsorable/biodegradable implants have attracted much recent attention in China. Advances in the design and biocompatibility evaluation of bio-Mg alloys in China are reviewed in this paper. Bio-Mg alloys have been developed by alloying with the trace elements existing in human body, such as Mg-Ca, Mg-Zn and Mg-Si based systems. Additionally, novel structured Mg alloys such as porous, composited, nanocrystalline and bulk metallic glass alloys were tried. To control the biocorrosion rate of bio-Mg implant to match the self-healing/regeneration rate of the surrounding tissue in vivo, surface modification layers were coated with physical and chemical methods.
Zheng, Yufeng; Gu, Xuenan
Microstructure and Corrosion Characterization of Squeeze Cast AM50 Magnesium Alloys
Squeeze casting of magnesium alloys potentially can be used in lightweight chassis components such as control arms and knuckles. This study documents the microstructural analysis and corrosion behavior of AM50 alloys squeeze cast at different pressures between 40 and 120 MPa and compares them with high-pressure die cast (HPDC) AM50 alloy castings and an AM50 squeeze cast prototype control arm. Although the corrosion rates of the squeeze cast samples are slightly higher than those observed for the HPDC AM50 alloy, the former does produce virtually porosity-free castings that are required for structural applications like control arms and wheels. This outcome is extremely encouraging as it provides an opportunity for additional alloy and process development by squeeze casting that has remained relatively unexplored for magnesium alloys compared with aluminum. Among the microstructural parameters analyzed, it seems that the ?-phase interfacial area, indicating a greater degree of ? network, leads to a lower corrosion rate. Weight loss was the better method for determining corrosion behavior in these alloys that contain a large fraction of second phase, which can cause perturbations to an overall uniform surface corrosion behavior.
Sachdeva, Deepika; Tiwari, Shashank; Sundarraj, Suresh; Luo, Alan A.
Effect of Second-Phase Precipitates on Local Elongation in Extruded Magnesium Alloys
The effect of precipitates on room-temperature tensile ductility, specifically post-uniform elongation (local elongation), was investigated in three magnesium alloys. The alloys were prepared by extrusion and had different types of precipitate morphology. Tensile tests revealed an almost total absence of local elongation in an alloy with intergranular precipitate particles (a few hundred nanometers in diameter), in spite of a relatively high total elongation to fracture of 17%. On the other hand, an alloy with densely dispersed fine intragranular precipitates (up to a few tens of nanometers in diameter) showed the highest local elongation at 17% and an alloy with a sparse dispersion showed moderate local elongation. The fracture surfaces of the latter two alloys had a primarily ductile appearance with dimples. For the specimen that showed the highest local elongation, twinning was observed in the necked portion, whereas very few twins were observed in the uniformly elongated portion. It was suggested that fine precipitates in the grain interior inhibit the formation of twins, a feature that can be exploited to enhance local elongation in magnesium alloys.
Watanabe, Hiroyuki
Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature
Using lightweight materials is the emerging need in order to reduce the vehicle's energy consumption and pollutant emissions. Being a lightweight material, magnesium alloys are increasingly employed in the fabrication of automotive and electronic parts. Presently, magnesium alloys used in automotive and electronic parts are mainly processed by die casting. The die casting technology allows the manufacturing of parts with complex geometry. However, the mechanical properties of these parts often do not meet the requirements concerning the mechanical properties (e.g. endurance strength and ductility). A promising alternative can be forming process. The parts manufactured by forming could have fine-grained structure without porosity and improved mechanical properties such as endurance strength and ductility. Because magnesium alloy has low formability resulted form its small slip system at room temperature it is usually formed at elevated temperature. Due to a rapid increase of usage of magnesium sheets in automotive and electronic industry it is necessary to assure database for sheet metal formability and plastic yielding properties in order to optimize its usage. Especially, plastic yielding criterion is a critical property to predict plastic deformation of sheet metal parts in optimizing process using CAE simulation. Von-Mises yield criterion generally well predicts plastic deformation of steel sheets and Hill'1979 yield criterion predicts plastic deformation of aluminum sheets. In this study, using biaxial tensile test machine yield loci of AZ31 magnesium alloy sheet were obtained at elevated temperature. The yield loci ensured experimentally were compared with the theoretical predictions based on the Von-Mises, Hill, Logan-Hosford, and Barlat model.
Park, Jingee; Lee, Jongshin; You, Bongsun; Choi, Seogou; Kim, Youngsuk
Evaluation of magnesium alloys with alternative surface finishing for the proliferation and chondro-differentiation of human mesenchymal stem cells
Articular cartilage has little capacity for self-repair. As a result, continuous mechanical stress can lead to the degradation of articular cartilage, culminating in progressive damage and joint degeneration. Tissue engineering has arisen as a promising therapeutic approach to cartilage repair. Magnesium alloys are one of the most important metallic biomaterials emerging in this area due to their biocompatibility, bio-absorbability and especially to their mechanical properties. These properties make magnesium alloys a promising biomaterial in the regeneration of cartilage tissue. Objective. This study was undertaken to analyze the influence of surface characteristics of magnesium alloys in the adhesion, proliferation and differentiation of human mesenchymal stem cells (MSCs). Methods. Two commercial magnesium alloys (AZ31B and ZM21) were subjected to different treatments in order to obtain four different surfaces in each alloy. Human MSCs were seeded into the magnesium alloys and analyzed for their proliferation and chondrogenesis differentiation ability. Results. Human MSCs showed a greater proliferation and chondro-differentiation when cultured in the ZM21 magnesium alloy with a surface finishing of fine sanding, polishing, and etching.
Trinidad, J.; Arruebarrena, G.; Sáenz De Argandoña, E.; Ruiz De Eguino, G.; Infante, A.; Rodríguez, C. I.
Antibacterial Properties of Magnesium Alloy AZ31B: In - vitro Studies using the Biofilm-forming Bacterium Pseudomonas sp
Magnesium (Mg 2+ ) alloys attract the focus of industries such as the telecom and computer industries and medical and household appliances due to their strength and weightlessness. However, magnesium is one of the major cell components of bacteria, which implicates it in microbial attachment and growth. To understand its involvement in bacterial attachment that leads to microbiologically influenced corrosion
Kanavillil Nandakumar; Kurissery R Sreekumari; Yasushi Kikuchi
Corrosion relationships as a function of time and surface roughness on a structural AE44 magnesium alloy
Pit initiation, growth, and coalescence corrosion mechanisms of an AE44 magnesium alloy subjected to a salt-water environment were quantified. Stereological quantities were evaluated using optical microscopy, scanning electron microscopy, and laser beam profilometry. Three corrosion mechanisms clearly arose: pitting, intergranular, and general. Pitting began as the result of localized galvanic dissolution between the intermetallics and magnesium matrix. Intergranular corrosion arose
Roxanna B. Alvarez; Holly J. Martin; M. F. Horstemeyer; Mei. Q. Chandler; Neil Williams; Paul T. Wang; Augusto Ruiz
Comparison of corrosion pitting under immersion and salt-spray environments on an as-cast AE44 magnesium alloy
The corrosion mechanisms of pitting, intergranular corrosion, and general corrosion were examined on an AE44 magnesium alloy subjected to immersion and salt-spray environments. The two environments show similar trends with respect to weight loss and thickness loss, although the immersion environment induces greater amounts of weight loss of magnesium. With respect to the corrosion mechanisms, the two environments show definitive
Holly J. Martin; M. F. Horstemeyer; Paul T. Wang
Hydroforming of magnesium (Mg) alloy sheet metal offers the possibility to form geometrically complex sheet metal parts that are applicable within automotive and electronic industry etc. However, due to the limited formability of Mg alloy at ambient temperature hydroforming of Mg alloy sheet metal has to be conducted at elevated temperature. In the present study an experimental warm hydroforming process using a low melting point alloy as forming medium is presented and on the basis of this a 2D thermo-mechanical finite element model is setup in order to analyze the temperature distribution in the Mg alloy workpiece during forming. The results show that the temperature in the workpiece is nearly uniform and nearly identical to the temperature of the forming medium.
Steffensen, Mikkel; Danckert, Joachim [Department of Production, Aalborg University, Fibigerstraede 16, 9220 Aalborg (Denmark)
Steffensen, Mikkel; Danckert, Joachim
Corrosion Behavior of Magnesium Alloy AP65 in 3.5% Sodium Chloride Solution
Magnesium alloy AP65 was prepared by melting and casting. The corrosion behavior of the as-cast and solid solution (T4)-treated AP65 alloys in 3.5% sodium chloride solution was investigated by corrosion morphology observation, immersion test, and electrochemical measurements. The results show that the second phase Mg17Al12 surrounded by a lead-enriched area distributes discontinuously along the grain boundaries in the as-cast AP65 alloy. The lead-enriched areas with high activity are susceptible to be attacked during immersion test and can act as places for preferential anodic dissolution. The corrosion resistance of the as-cast AP65 alloy can be improved after T4 treatment and the T4-treated alloy suffers general corrosion.
Wang, Nai-guang; Wang, Ri-chu; Peng, Chao-qun; Feng, Yan
Magnesium alloys as body implants: fracture mechanism under dynamic and static loadings in a physiological environment.
It is essential that a metallic implant material possesses adequate resistance to cracking/fracture under the synergistic action of a corrosive physiological environment and mechanical loading (i.e. stress corrosion cracking (SCC)), before the implant can be put to actual use. This paper presents a critique of the fundamental issues with an assessment of SCC of a rapidly corroding material such as magnesium alloys, and describes an investigation into the mechanism of SCC of a magnesium alloy in a physiological environment. The SCC susceptibility of the alloy in a simulated human body fluid was established by slow strain rate tensile (SSRT) testing using smooth specimens under different electrochemical conditions for understanding the mechanism of SCC. However, to assess the life of the implant devices that often possess fine micro-cracks, SCC susceptibility of notched specimens was investigated by circumferential notch tensile (CNT) testing. CNT tests also produced important design data, i.e. threshold stress intensity for SCC (KISCC) and SCC crack growth rate. Fractographic features of SCC were examined using scanning electron microscopy. The SSRT and CNT results, together with fractographic evidence, confirmed the SCC susceptibility of both smooth and notched specimens of a magnesium alloy in the physiological environment. PMID:22075121
Choudhary, Lokesh; Raman, R K Singh
In vitro degradation and mechanical integrity of calcium-containing magnesium alloys in modified-simulated body fluid
The successful applications of magnesium-based alloys as degradable orthopaedic implants are mainly inhibited due to their high degradation rates in physiological environment and consequent loss in the mechanical integrity. This study examines the degradation behaviour and the mechanical integrity of calcium-containing magnesium alloys using electrochemical techniques and slow strain rate test (SSRT) method, respectively, in modified-simulated body fluid (m-SBF). Potentiodynamic
M. Bobby Kannan; R. K. Singh Raman
Hybrid laser–TIG welding, laser beam welding and gas tungsten arc welding of AZ31B magnesium alloy
Welding of AZ31B magnesium alloy was carried out using hybrid laser–TIG (LATIG) welding, laser beam welding (LBW) and gas tungsten arc (TIG) welding. The weldability and microstructure of magnesium AZ31B alloy welded using LATIG, LBW and TIG were investigated by OM and EMPA. The experimental results showed that the welding speed of LATIG was higher than that of TIG, which
Liu Liming; Wang Jifeng; Song Gang
Quality issues in laser welding of automotive aluminum and magnesium alloys
Achievement of defect-free and structurally sound welds based on scientific principles has been an important goal of contemporary welding research. In the welding of aluminum and magnesium alloys, porosity formation and alloying element loss have been two major quality problems. The research to be presented focuses on the alleviation of these problems through quantitative understanding of alloying element loss and porosity formation during laser welding. The instability of the keyhole was the main cause of macro-porosity formation during laser welding of thin plates of aluminum alloys 5182 and 5754. A computer model was developed to understand the formation and prevention of macroporosity. The stability of keyhole was not a major factor in pore formation during laser welding of die-cast magnesium alloy AM60B. Well controlled remelting of the welded metal led to the removal of gas bubbles and reduced porosity in the welded metal. Loss of alloying elements due to vaporization resulted in significant changes in the composition of the weld metal. Numerical computations of heat transfer and fluid flow and mass transfer were helpful in understanding and controlling compositional changes due to evaporation. Taken as a whole, the research to be presented is a contribution to the growing quantitative knowledge base in fusion welding. Expansion of this knowledge base is necessary, if not essential, to solve important quality problems in fusion welding based on scientific principles.
Zhao, Hailiang
Improving the mechanical properties of magnesium and a magnesium alloy through severe plastic deformation
Pure Mg and Mg alloys generally exhibit only limited ductilities at ambient temperatures. Experiments were conducted to evaluate the potential for improving the mechanical properties of pure Mg and an Mg–0.9% Al alloy at room temperature by subjecting these materials to severe plastic deformation through the procedure of equal-channel angular pressing (ECAP). It is shown that ECAP may be applied
Akihiro Yamashita; Zenji Horita; Terence G Langdon
Effect of galvanic corrosion between precipitate and matrix on corrosion behavior of Ascast magnesium-aluminum alloys
In the present study, the corrosion behavior of an as-cast magnesium alloy was studies focusing on the galvanic corrosion\\u000a between a precipitate and Mg-rich matrix. Through immersion and electrochemical tests, the variation of the corrosion behavior\\u000a with the alloy composition and alloy system was discussed in detail. The corrosion rate of an as-cast alloy increased abruptly\\u000a to 9 wt.% Al
Choong Do Lee; Choon Sik Kang; Kwang Seon Shin
High-Strength Aluminum Alloys with Zinc, Magnesium, and Copper
4.5% Mg and 1.5 – 2.5% Cu, whereas the alloys with 10% Zn have r = 800 MPa at 3.5 – 5% Mg and 0.5 – 1.0% Cu. Alloys of the same strength with 7 and 10% Zn lie in the solid solution range parallel to the Al – Cu side. An increase in the copper content provides a lower
I. N. Fridlyander
Plastic deformation and surface damage mechanisms during hot-forming of aluminum and magnesium alloy sheets
Material transfer and adhesion to die surface are major tribological issues encountered during hot-forming of aluminum and magnesium alloys, reducing process efficiency. This study aimed at understanding the tribological contact interface generated between material and die surface under dynamic conditions created by simultaneous effect of temperature and strain rate. Micromechanisms of plastic deformation occurring under simulated hot-forming conditions were identified and related to the coefficient of friction (COF). Sliding contact experiments were done using specially designed tribometer (operating temperature: 25 to 545°C, strain rate: 10-3 to 10-1s-1). COF of AA5083(Al-4.5%Mg-0.7%Mn) and AZ31(Mg-3%Al-0.7%Zn) alloys were measured during their plastic deformation by the simultaneous effect of temperature and strain rate. The as received and plastically deformed surfaces were characterized using optical interferometry, SEM, FIB and TEM. Additionally, the force required to break the asperity junction formed at the first contact, or junction strength, was measured for both materials at different temperatures. Deformation mechanisms identified for AA5083 in the temperature range of 420 to 545°C and strain rate range of 5x10-3 to 4x10-2 s-1 included diffusional flow, grain boundary sliding (GBS) and solute drag (SD) creep. Friction maps outlining general relationships between tribological behaviour and micromechanisms controlling deformation under a set of temperature, strain and strain rate were developed. GBS induced high surface roughness, resulting in high COF. Low average roughness and retention of strength reduced COF in SD region. Dynamic recrystallization was an additional factor controlling material transfer in magnesium AZ31 alloy. Changes in oxide layer morphology were established based on the microstructural characterization of sample's surface and subsurface. In AA5083 alloy, crack formation at temperatures <450°C or oxide ligament formation at temperature >500°C were found in the magnesium rich surface oxide. Magnesium rich surface oxide reduced COF, and low COF was found in the material having high magnesium. AZ31 alloy always showed lower COF compared to AA5083. This was confirmed by junction strength experiment where adhesion strength was found to be low in high magnesium content material. Therefore, this investigation on the plastic deformation and surface damage mechanism, and their relation with the tribological behaviour provided better understanding of the hot-forming process.
Das, Sarmistha
Cold Spray Al-5% Mg Coatings for the Corrosion Protection of Magnesium Alloys
Poor corrosion resistance is a significant limitation of magnesium alloys as structural materials. To address this problem, the objective of this study was to apply to a magnesium alloy a corrosion-resistant barrier coating that has galvanic compatibility with magnesium and a hardness value no less than that of magnesium. Aluminum coatings were applied to ZE41A-T5 Mg by the cold spray process. A custom-made high-purity Al-5 wt.% Mg powder was produced by spray metal forming for the coating evaluation. In addition, coatings of commercially pure Al (99.5 wt.%), high-purity Al (99.95 wt.%), AA5356, and AA4047 were used for comparison. Coating evaluation included mechanical testing (hardness and adhesion strength) and corrosion testing (salt spray, galvanic coupling, and crevice corrosion). The Al-5% Mg powder resulted in the best overall performance, including a high hardness, 125 Hv100, and an adhesion strength, over 60 MPa, when treated for over 1000 h in a salt spray chamber and with a low galvanic current.
Deforce, Brian S.; Eden, Timothy J.; Potter, John K.
The tensile electroplasticity of magnesium AZ31 alloy with a single pulse of electric current
The tensile electroplasticity of magnesium AZ31 alloy with a single pulse of electric current is experimentally investigated. A single pulse of electric current with a relatively short duration is applied to the specimen while the specimen is being deformed in plastic region under quasi-static tensile loads. Experimental parameters are selected so that the maximum temperature at the application of the electric current is significantly lower than the general warm forming temperature of the magnesium alloy. A nearly instant decrease of the flow stress (stress-drop) occurs at the application of the electric current. Once the electric current is removed, the flow stress shows a strain hardening until the failure of the specimen. The result of the parameter study shows that the stress-drop and the following hardening behavior strongly depend on the magnitude of the electric energy density (electric energy per unit area).
Vinh, Nguyen Thai; Kim, Min-Sung; Yu, Hyeong-Ho; Hong, Sung-Tae; Kim, Moon-Jo; Han, Heung-Nam; Han, Kyung-Sik
Characterization of damage evolution in an AM60 magnesium alloy by computed tomography
Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories, California (SNL) are collaborating on the development of new techniques to study damage evolution and growth in material specimens subjected to mechanical loading. These techniques include metallography, radiography, computed tomography (CT) and modeling. The material specimens being studied include cast magnesium and aluminum alloys, and forged stainless steel. We will concentrate on characterizing monotonically loaded magnesium alloy specimens using computed tomography. Several notched tensile specimens were uniaxially loaded to different percentages of the failure load. Specimens were initially characterized by radiography and computed tomography to determine the preloaded state. Subsequent CT scans were performed after the samples were loaded to different percentages of the load failure. The CT volumetric data are being used to measure void size, distribution and orientation in all three dimensions nondestructively to determine the effect of void growth on the mechanical behavior of the materials.
Waters, Amy; Green, Robert [Center for Nondestructive Evaluation, 3400 N. Charles St., Baltimore, Maryland 21218 (United States); Martz, Harry; Dolan, Ken; Rikard, Derrill [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); Horstemeyer, Mark [Sandia National Laboratories, 7011 East Ave., Livermore, California 94550 (United States)
Preparation and characterization of graphite-dispersed styrene-acrylic emulsion composite coating on magnesium alloy
In this work, an electrically conductive, corrosion resistant graphite-dispersed styrene-acrylic emulsion composite coating on AZ91D magnesium alloy was successfully produced by the method of anodic deposition. The microstructure, composition and conductivity of the composite coating were characterized using optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR) and four electrode volume resistivity instrument, respectively. The corrosion resistance of the coating was evaluated using potentiodynamic polarization measurements and salt spray tests. It is found that the graphite-dispersed styrene-acrylic emulsion composite coating was layered structure and displayed good electrical conductivity. The potentiodynamic polarization tests and salt spray tests reveal that the composite coating was successful in providing superior corrosion resistance to AZ91D magnesium alloy.
Zhang, Renhui; Liang, Jun; Wang, Qing
Biodegradation behavior of micro-arc oxidized AZ31 magnesium alloys formed in two different electrolytes
Degradation behavior of coated magnesium alloys is among most prominent factors for their biomedical applications. In this study, bio-corrosion behavior of micro-arc oxidized magnesium AZ31 alloys formed in silicate and phosphate baths was investigated in r-SBF medium. For this purpose polarization behavior and open circuit profile of the coated samples were achieved by electrochemical and immersion tests, respectively. Moreover, the morphology and composition of the coatings were evaluated before and after immersion test using scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The results showed that the phosphate film had better corrosion resistance and greater thickness than silicate film and, in turn, the lesser degradability in SBF solution, so that Ca2+ and PO43- containing compounds were more abundant on silicate film than phosphate film. Moreover phosphate film had greater surface roughness and lesser hydrophilic nature.
Seyfoori, A.; Mirdamadi, Sh.; Khavandi, A.; Raufi, Z. Seyed
Surface Modification of Magnesium Alloy by Mg2Si Coating Technology
Surface modification technology on magnesium alloys has been developed by using Mg-Si thin films via a glow discharge sputtering process, in employing Mg2Si bulky materials fabricated by powder metallurgy (PM) process as targets. This is because Mg2Si sintered materials have high hardness and Young's modulus, in particular, a superior corrosion resistance to the conventional stainless steel. The Mg-Si thin film, having 1-2µm thickness, deposited on the AZ31 substrate improved the mechanical properties, wear and corrosion resistance compared to the conventional magnesium alloys. In particular, the effect of crystalline/amorphous structures of Mg-Si thin films on these properties was investigated in detail.
Kondoh, Katsuyoshi; Yamaguchi, Takashi; Serikawa, Tadashi; Oginuma, Hideki
Solution softening in magnesium alloys: the effect of solid solutions on the dislocation core structure and nonbasal slip
There is a pressing need to improve the ductility of magnesium alloys so that they can be applied as lightweight structural materials. In this study, a mechanism for enhancing the ductility of magnesium alloys has been pursued using the atomistic method. The generalized stacking fault (GSF) energies for basal and prismatic planes in magnesium were calculated by using density functional theory, and the effect of the GSF energy on the dislocation core structures was examined using a semidiscrete variational Peierls-Nabarro model. Yttrium was found to have an anomalous influence on the solution softening owing to a reduction in the GSF energy gradient.
Tsuru, T.; Udagawa, Y.; Yamaguchi, M.; Itakura, M.; Kaburaki, H.; Kaji, Y.
Solution softening in magnesium alloys: the effect of solid solutions on the dislocation core structure and nonbasal slip.
There is a pressing need to improve the ductility of magnesium alloys so that they can be applied as lightweight structural materials. In this study, a mechanism for enhancing the ductility of magnesium alloys has been pursued using the atomistic method. The generalized stacking fault (GSF) energies for basal and prismatic planes in magnesium were calculated by using density functional theory, and the effect of the GSF energy on the dislocation core structures was examined using a semidiscrete variational Peierls-Nabarro model. Yttrium was found to have an anomalous influence on the solution softening owing to a reduction in the GSF energy gradient. PMID:23220883
Tsuru, T; Udagawa, Y; Yamaguchi, M; Itakura, M; Kaburaki, H; Kaji, Y
Laser Beam Welding of AZ31 Magnesium Alloy with Filler Strip
The 2-mm AZ31 magnesium alloy sheets were laser beam welded using filler metal in the shape of strip. Two kinds of the filler strips, i.e., AZ31 and AZ31 +1.5 wt% Mn were adopted. The effects of the filler strip on the microstructures and tensile properties of the welded joints were investigated. As compared with the autogenous welding process, the welding process
Qiong Chen; Hongge Yan; Jihua Chen; Peilan Zeng; Zhaohui Yu; Bin Su
Electroless nickel-plating on die cast magnesium alloy AZ91D
Electroless nickel-plating on die cast magnesium alloy AZ91D was investigated. Growth of the electroless nickel-plating coating was characterized using scanning electron microscopy. Corrosion resistance of the coating was evaluated by open circuit potential and potentiodynamic polarization curves in 3.5% (mass fraction) NaCl solution. The results show that plating deposition is initiated on the crevices and then spread onto primary ?
JIA Su-qiu; JIA Shu-sheng; YAO Jun
Microstructure and tensile properties of friction stir welded AZ31B magnesium alloy
The microstructural change in AZ31B-H24 magnesium (Mg) alloy after friction stir welding (FSW) was examined. The effects of tool rotational speed and welding speed on the microstructure and tensile properties were evaluated. The grain size was observed to increase after FSW, resulting in a drop of microhardness across the welded region from about 70 HV in the base metal to
N. Afrin; D. L. Chen; X. Cao; M. Jahazi
Basal plane texture and flow pattern in friction stir weld of a magnesium alloy
The microtextures in a friction-stir-welded magnesium (Mg) alloy, AZ61, with a nugget-shaped stir zone were analyzed by orientation\\u000a imaging microscopy (OIM). The base material had a (0002) ?uvi0? texture ((0002) parallel to the sheet plane, ?uvi0? parallel to the welding direction). Friction stir welding produced texture components different from those of the base material\\u000a in the stir zone. Except for
Seung Hwan C. Park; Yutaka S. Sato; Hiroyuki Kokawa
Nucleation and growth of fatigue cracks in magnesium alloys with various structures
Materials and Methods. We used six magnesium alloys (MA2-1, MA2-1pch, MA15, IMV6, MA21, and MAI2), whose chemical compositions, modes of heat treatment, and mechanical properties are given in Table i. Thermal hardening of MAI2 in modes T6 and T8 resulted in a larger grain size for the a solid solution and smaller dimensions for the grains of MggNd intermetallide by
N. M. Grinberg; V. A. Serdyuk; T. I. Malinkina; A. S. Kamyshkov
Thermodynamic activity of magnesium in several highly-solvating liquid alloys
An emf technique is reported using porous alumina tubes to contain reference metals and alloys in a molten salt electrolyte.\\u000a Data are reported for the activity of magnesium and its temperature derivative in several liquid metal solvents. These include\\u000a lead (650 °C), tin (800 °C), bismuth (850 °C), antimony (850 °C), and mixtures of tin and antimony (800 °). In
Charles A. Eckert; Robert B. Irwin; Jeffery S. Smith
By combining the fuzzy-logic method and Taguchi method, this study investigates the optimum parameters for the multiple performance characteristics index (MPCI) of the hot-extrusion process for magnesium alloy sheets of AZ31 and AZ61. Process parameters include billet heating temperature, initial extrusion speed, container temperature, and lubricant. Depending on individual quality characteristics, the optimal parameter combination for the Taguchi method would
Su-Hai Hsiang; Yi-Wei Lin
Microstructural Evolution of UFG Magnesium Alloy Produced by Accumulative Back Extrusion (ABE)
Accumulative back extrusion (ABE) is a recently developed severe plastic deformation process. In this article, the effects of deformation ratio (inner punch diameter\\/outer punch diameter) employed for ABE on the microstructure, grain size distribution, and Mg17Al12 phase precipitation in AZ91 magnesium alloys were investigated. The results showed that the deformation ratio has significant effect on the microstructure of processed material.
Ghader Faraji; Mahmoud Mosavi Mashhadi; Hyoung Seop Kim
Preparation and Characterization of 8YSZ Thermal Barrier Coatings on Rare Earth-Magnesium Alloy
Thermal barrier coatings (TBCs) of zirconia stabilized by 8 wt.% yttria (8YSZ) on top of rare earth-magnesium alloy were fabricated\\u000a by atmospheric plasma spraying. Three coatings were prepared by controlling the substrate temperature with different cooling\\u000a media including cold water, compressed air, and natural cooling during deposition. The phase compositions, mechanical properties,\\u000a and thermal shock resistance of these coatings were investigated.
Xizhi Fan; Yangjia Liu; Zhenhua Xu; Ying Wang; Binglin Zou; Lijian Gu; Chunjie Wang; Xiaolong Chen; Zuhair S. Khan; Daowu Yang; Xueqiang Cao
Fatigue Crack Growth Mechanisms in High-Pressure Die-Cast Magnesium Alloys
Microstructure-affected micromechanisms of fatigue crack growth operating near the limit plasticity regime were experimentally identified for the four main commercial high-pressure die-cast (HPDC) magnesium alloys: AM50, AM60, AZ91, and AE44. These fatigue micromechanisms manifested by the concomitant effects of casting pores, interdendritic Al-rich solid solution layer, beta-phase particles, Mn-rich inclusions, rare earth-rich intermetallics, dendrite cell size, and surface segregation phenomena.
Haitham El Kadiri; M. F. Horstemeyer; J. B. Jordon; Yibin Xue
A two-step processing route for achieving a superplastic forming capability in dilute magnesium alloys
Superplastic ductilities were achieved in a dilute magnesium alloy containing 0.6% Zr through the use of a two-step processing procedure in which the basal planes are initially aligned through extrusion and the grain size is then refined using equal-channel angular pressing. The results show a maximum tensile elongation of >400% at 573 K when using an initial strain rate of
Zenji Horita; Kiyoshi Matsubara; Koichi Makii; Terence G. Langdon
Chrome-free neodymium-based protective coatings for magnesium alloys
The microstructure of chrome-free neodymium-based conversion coating on magnesium alloy was investigated and the corrosion resistance was evaluated as well. The micro-morphology, transverse section, crystal structure and composition of the coating were observed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), respectively. The corrosion resistance was evaluated by potentiodynamic polarization curve and electrochemical impedance spectroscopy
Guo Jin; Yuyun Yang; Xiufang Cui; Erbao Liu; Zhongyu Wang; Qingfen Li
Conversion-coating treatment for magnesium alloys by a permanganate–phosphate solution
A chrome-free conversion coating treatment, a mainly permanganate–phosphate solution, was developed in this study for magnesium and its alloys. The morphology of the conversion-coated layer was observed using SEM; the crystal structure and the composition was analysed and determined by using XRD and XPS. The XRD results indicated that amorphous structures existed that covered the coated specimen. The solution treated
Kwo Zong Chong; Teng Shih Shih
Three-dimensional injection molding simulation of AZ91D semi-solid magnesium alloy
Magnesium alloys are increasingly used in automotive, aeronautic and electronic applications to produce high performance,\\u000a light weight parts. In the thixomolding process a semi-solid slurry is injected into a mold at controlled temperature such\\u000a that the melt has specific flow behavior. This allows the fabrication of near net shape components with controlled microstructure\\u000a and good mechanical properties. The numerical modeling
Florin Ilinca; Jean-François Hétu; Jean-François Moisan; Frank Ajersch
Tribology and Tool Wear of Hot Dip Galvanized Zinc Magnesium Alloys on Cold Rolled Steel Sheets
Recently zinc based coatings on cold rolled steel with improved functionality in terms of forming and\\/or corrosion behaviour have been intensively investigated in the steel industry1,2,3. One of the most promising products are zinc magnesium alloys produced in hot dip galvanizing process. These coatings were already introduced in construction industry a few years ago1. With some modifications the improved properties
A. E. Raab; E. Berger; J. Freudenthaler; F. Leomann; C. Walch
Optical properties of switchable mirrors based on magnesium-calcium alloy thin films
Switchable mirrors based on magnesium-calcium alloy thin films were prepared using a direct-current magnetron sputtering method and their gasochromic properties have been investigated. Pd-capped Mg1-zCaz (0.04
Y. Yamada; S. Bao; K. Tajima; M. Okada; K. Yoshimura
Y. Yamada; S. Bao; K. Tajima; M. Okada; K. Yoshimura
Corrosion protection of composite coating combining ceramic layer, copper layer and benzotriazole layer on magnesium alloy
A novel composite coating was fabricated on AZ91 magnesium alloy by applying a composite surface treatment which combined the methods of plasma electrolytic oxidation (PEO) pre-treatment, electroless copper and benzotriazole (BTA) passivation. The cross-section microstructures and chemical compositions of coating were examined using scanning electron microscopy (SEM) equipped with energy dispersive analysis of X-rays (EDX). Potentiodynamic polarization curves and salt
Yong-feng JIANG; Ye-feng BAO; Guo-wei ZHANG
Investigation of plasma electrolytic oxidation process on AZ91D magnesium alloy
Ceramic coatings oxidized for different time periods were prepared to characterize the plasma electrolytic oxidation (PEO) process of AZ91D magnesium alloy. The coatings were analyzed using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscope and potentiodynamic polarization measurement. The results show that the PEO coatings perform different growth behaviors at different PEO stages, and different morphologies are exhibited on ?-
Guo-Hua Lv; Huan Chen; L. Li; Er-Wu Niu; Huan Pang; Bin Zou; Si-Ze Yang
Preparation and performance of a novel multifunctional plasma electrolytic oxidation composite coating formed on magnesium alloy
Plasma electrolytic oxidation (PEO) in an alkaline phosphate electrolyte was used to produce a novel multifunctional polytetrafluoroethylene\\u000a (PTFE)-containing oxide composite coatings on AM60B magnesium alloys. The composition and microstructure of the PTFE-containing\\u000a PEO coatings were analyzed by X-ray photoelectron spectroscope (XPS), X-ray diffraction (XRD), and scanning electron microscope\\u000a (SEM). The electrochemical corrosion behavior, tribological properties, and wetting properties of the
Jie Guo; Liping Wang; S. C. Wang; J. Liang; Qunji Xue; Fengyuan Yan
Formation process of composite plasma electrolytic oxidation coating containing zirconium oxides on AM50 magnesium alloy
The formation processes of a composite ceramic coating on AM50 magnesium alloy prepared by plasma electrolytic oxidation (PEO) in a K2ZrF6 electrolyte solution were studied by scanning electron microscope (SEM) and energy dispersive X-ray spectroscope (EDX). Electrochemical impedance spectroscopy (EIS) tests were used to study the variation of the corrosion resistance of the coating during the PEO treatment. The results
Feng LIU; Da-yong SHAN; Ying-wei SONG; En-hou HAN
Galvanic corrosion properties of differently PVD-treated magnesium die cast alloy AZ91
Different types of PVD coatings and plasma treatments were applied for the surface treatment of magnesium die cast alloy AZ91 specimens. The different types of surface treatment were all developed by the authors and the fundamental properties are described elsewhere. The coating systems were:•9 ?m CrN hard coating•3 ?m TiN coating•0.5 ?m plasma anodisation layer and 3 ?m Al2O3 coatingThe
H. Hoche; C. Blawert; E. Broszeit; C. Berger
Sol–gel silica coatings on ZE41 magnesium alloy for corrosion protection
Silica coatings have been applied on the surface of ZE41 magnesium alloy following the organic sol–gel route and the dip-coating technique. Three different concentrations of sol solution and two densification temperatures of the coating (400°C and 500°C) were used to optimize the compaction of the coatings and as a result reach the corrosion protection of the metallic substrate tests in
A. J. López; E. Otero; J. Rams
Microstructure-affected micromechanisms of fatigue crack growth operating near the limit plasticity regime were experimentally identified for the four main commercial high-pressure die-cast (HPDC) magnesium alloys: AM50, AM60, AZ91, and AE44. These fatigue micromechanisms manifested by the concomitant effects of casting pores, interdendritic Al-rich solid solution layer, ?-phase particles, Mn-rich inclusions, rare earth-rich intermetallics, dendrite cell size, and surface segregation phenomena. These concomitant mechanisms clearly delineated the fatigue durability observed for the AM50, AM60, AZ91, and AE44 Mg alloys in both the low- and high-cycle fatigue regimes.
El Kadiri, Haitham; Horstemeyer, M. F.; Jordon, J. B.; Xue, Yibin
Biodegradable poly(lactide-co-glycolide) coatings on magnesium alloys for orthopedic applications.
Polymeric film coatings were applied by dip coating on two magnesium alloy systems, AZ31 and Mg4Y, in an attempt to slow the degradation of these alloys under in vitro conditions. Poly(lactic-co-glycolic acid) polymer in solution was explored at various concentrations, yielding coatings of varying thicknesses on the alloy substrates. Electrochemical corrosion studies indicate that the coatings initially provide some corrosion protection. Degradation studies showed reduced degradation over 3 days, but beyond this time point however, do not maintain a reduction in corrosion rate. Scanning electron microscopy indicates inhomogeneous coating durability, with gas pocket formation in the polymer coating, resulting in eventual detachment from the alloy surface. In vitro studies of cell viability utilizing mouse osteoblast cells showed improved biocompatibility of polymer coated substrates over the bare AZ31 and Mg4Y substrates. Results demonstrate that while challenges remain for long term degradation control, the developed polymeric coatings nevertheless provide short term corrosion protection and improved biocompatibility of magnesium alloys for possible use in orthopedic applications. PMID:23053803
Ostrowski, Nicole J; Lee, Boeun; Roy, Abhijit; Ramanathan, Madhumati; Kumta, Prashant N
Mechanical Behavior of a Magnesium Alloy Nanocomposite Under Conditions of Static Tension and Dynamic Fatigue
In this paper, the intrinsic influence of nano-alumina particulate (Al2O3p) reinforcements on microstructure, microhardness, tensile properties, tensile fracture, cyclic stress-controlled fatigue, and final fracture behavior of a magnesium alloy is presented and discussed. The unreinforced magnesium alloy (AZ31) and the reinforced composite counterpart (AZ31/1.5 vol.% Al2O3) were manufactured by solidification processing followed by hot extrusion. The elastic modulus, yield strength, and tensile strength of the nanoparticle-reinforced magnesium alloy were noticeably higher than the unreinforced counterpart. The ductility, quantified by elongation-to-failure, of the composite was observably lower than the unreinforced monolithic counterpart (AZ31). The nanoparticle-reinforced composite revealed improved cyclic fatigue resistance over the entire range of maximum stress at both the tested load ratios. Under conditions of fully reversed loading ( R = -1) both materials showed observable degradation in behavior quantified in terms of cyclic fatigue life. The conjoint influence of reinforcement, processing, intrinsic microstructural features and loading condition on final fracture behavior is presented and discussed.
Srivatsan, T. S.; Godbole, C.; Quick, T.; Paramsothy, M.; Gupta, M.
Biocorrosion of magnesium alloys: a new principle in cardiovascular implant technology?
Objectives: To develop and test a new concept of the degradation kinetics of newly developed coronary stents consisting of magnesium alloys. Methods: Design of a coronary stent prototype consisting of the non-commercial magnesium based alloy AE21 (containing 2% aluminium and 1% rare earths) with an expected 50% loss of mass within six months. Eleven domestic pigs underwent coronary implantation of 20 stents (overstretch injury). Results: No stent caused major problems during implantation or showed signs of initial breakage in the histological evaluation. There were no thromboembolic events. Quantitative angiography at follow up showed a significant (p < 0.01) 40% loss of perfused lumen diameter between days 10 and 35, corresponding to neointima formation seen on histological analysis, and a 25% re-enlargement (p < 0.05) between days 35 and 56 caused by vascular remodelling (based on intravascular ultrasound) resulting from the loss of mechanical integrity of the stent. Inflammation (p < 0.001) and neointimal plaque area (p < 0.05) depended significantly on injury score. Planimetric degradation correlated with time (r = 0.67, p < 0.01). Conclusion: Vascular implants consisting of magnesium alloy degradable by biocorrosion seem to be a realistic alternative to permanent implants.
Heublein, B; Rohde, R; Kaese, V; Niemeyer, M; Hartung, W; Haverich, A
Yield Asymmetry Design of Magnesium Alloys by Integrated Computational Materials Engineering
Deformation asymmetry of magnesium alloys is an important factor on machine design in automobile industry. Represented by the ratio of compressive yield stress (CYS) against tensile yield stress (TYS), deformation asymmetry is strongly related to microstructure, characterized by texture and grain size. Modified intermediate phi-model, a polycrystalline viscoplasticity model, is used to predict the deformation behavior of magnesium alloys with different grain sizes. Validated with experimental results, integrated computational materials engineering is applied to find out the route in achieving desired asymmetry by thermomechanical processing. In some texture, for example, rolled texture, CYS/TYS is smaller than 1 under different loading directions. In some texture, for example, extruded texture, asymmetry is large along normal direction. Starting from rolled texture, the asymmetry will increased to close to 1 along rolling direction after compressed to a strain of 0.2. Our model shows that grain refinement increases CYS/TYS. Besides texture control, grain refinement can also optimize the yield asymmetry. After the grain size decreased to a critical value, CYS/TYS reaches to 1 since CYS increases much faster than TYS. By tailoring the microstructure using texture control and grain refinement, it is achievable to optimize yield asymmetry in wrought magnesium alloys.
Li, Dongsheng; Joshi, Vineet V.; Lavender, Curt A.; Khaleel, Mohammad A.; Ahzi, Said
Biocompatibility of fluoride-coated magnesium-calcium alloys with optimized degradation kinetics in a subcutaneous mouse model.
The principle of biodegradation has been considered for many years in the development of cardiovascular stents, especially for patients with congenital heart defects. A variety of materials have been examined with regard to their suitability for cardiovascular devices. Iron- and magnesium-based stents were investigated intensively during the last years. It has been shown, that iron, or iron based alloys have slow degradation kinetics whereas magnesium-based systems exhibit rapid degradation rates. Recently we have developed fluoride coated binary magnesium-calcium alloys with reduced degradation kinetics. These alloys exhibit good biocompatibility and no major adverse effects toward smooth muscle and endothelial cells in in vitro experiments. In this study, these alloys were investigated in a subcutaneous mouse model. Fluoride coated (fc) magnesium, as well as MgCa0.4%, MgCa0.6%, MgCa0.8%, MgCa1.0%, and a commercially available WE43 alloy were implanted in form of (fc) cylindrical plates into the subcutaneous tissue of NMRI mice. After a 3 and 6 months follow-up, the (fc) alloy plates were examined by histomorphometric techniques to assess their degradation rate in vivo. Our data indicate that all (fc) alloys showed a significant corrosion. For both time points the (fc) MgCa alloys showed a higher corrosion rate in comparison to the (fc) WE43 reference alloy. Significant adverse effects were not observed. Fluoride coating of magnesium-based alloys can be a suitable way to reduce degradation rates. However, the (fc) MgCa alloys did not exhibit decreased degradation kinetics in comparison to the (fc) WE43 alloy in a subcutaneous mouse model. PMID:22767427
Drynda, Andreas; Seibt, Juliane; Hassel, Thomas; Bach, Friedrich Wilhelm; Peuster, Matthias
In vitro and in vivo evaluation of the surface bioactivity of a calcium phosphate coated magnesium alloy.
Magnesium has shown potential application as a bio-absorbable biomaterial, such as for bone screws and plates. In order to improve the surface bioactivity, a calcium phosphate was coated on a magnesium alloy by a phosphating process (Ca-P coating). The surface characterization showed that a porous and netlike CaHPO(4).2H(2)O layer with small amounts of Mg(2+) and Zn(2+) was formed on the surface of the Mg alloy. Cells L929 showed significantly good adherence and significantly high growth rate and proliferation characteristics on the Ca-P coated magnesium alloy (p<0.05) in in-vitro cell experiments, demonstrating that the surface cytocompatibility of magnesium was significantly improved by the Ca-P coating. In vivo implantations of the Ca-P coated and the naked alloy rods were carried out to investigate the bone response at the early stage. Both routine pathological examination and immunohistochemical analysis demonstrated that the Ca-P coating provided magnesium with a significantly good surface bioactivity (p<0.05) and promoted early bone growth at the implant/bone interface. It was suggested that the Ca-P coating might be an effective method to improve the surface bioactivity of magnesium alloy. PMID:19111896
Xu, Liping; Pan, Feng; Yu, Guoning; Yang, Lei; Zhang, Erlin; Yang, Ke
Development of a Binary Zn-Based Solder Alloy for Joining Wrought Magnesium Alloy AZ31B
In the present article, the wrought magnesium alloy AZ31B sheets were soldered by means of high-frequency induction heating device using a novel binary Zn-based solder alloy in argon gas shield condition. The interfacial microstructure, phase constitution, and fracture morphology of the soldered joint were studied. The microhardness and shear strength of the soldered joint were tested. The experimental results exhibit that ?-Mg solid solution and ?-MgZn phase were formed in soldering region. Moreover, the ?-Mg7Zn3 phase in the original Zn-based solder alloy disappeared completely after the soldering process due to the fierce alloying between the molten binary Zn-based solder alloy and the base metal AZ31B during soldering. Test results show that the shear strength of the soldered joint is 28 MPa. The fracture morphology of the soldered joint displays an intergranular fracture mode, and the crack originates from ?-Mg + ?-MgZn eutectoid structure. The interaction between the molten Zn-based solder alloy and the base metal AZ31B leads the Zn-based solder alloy to be transformed into Mg-based soldering metal during soldering.
Ma, Li; Long, Weimin; Qiao, Peixin; He, Dingyong; Li, Xiaoyan
Poly(L-lactic acid)/hydroxyapatite/collagen composite coatings on AZ31 magnesium alloy for biomedical application.
Surface modification of biomedical magnesium alloy using composite coating shows an attemptable approach for the development of Mg-based biomaterials with excellent cytocompatibility. Hydroxyapatite/collagen composite was preliminarily fabricated by biomineralization, the bioactive poly(l-lactic acid)/hydroxyapatite/collagen composite coatings were spin coated on AZ31 magnesium alloy using poly(l-lactic acid) solution mixed with hydroxyapatite/collagen particles, and the resultant materials and coatings were characterized in structure and related properties; furthermore, the in vitro degradation behavior of modified magnesium alloy in 1.5-fold Hank's solution was investigated. The results show that hydroxyapatite/collagen composite achieved chemical bonding between hydroxyapatite and collagen similar to natural bone; composite coatings on AZ31 magnesium alloy retained the bioactive functional groups of the componential materials and improved the corrosion resistance of Mg alloy; the mass fraction of hydroxyapatite/collagen particles incorporated into the composite affected the porous structure, interfacial adhesion and thus the corrosion resistance of the composite coating due to phase separation as well as volume concentration effects of polymer solution. Composite coatings suppressed the sharp rising of pH value and the released Mg(2+) from substrate to extensive degree, and the degradation behavior of the modified magnesium alloy was supposed to be correlated to microstructure of the coating as well as the synergistic reactions among alkaline- and acidic-degraded products. PMID:23851659
Wang, Zhen-Lin; Yan, Yu-Hua; Wan, Tao; Yang, Hui
Electron beam-assisted healing of nanopores in magnesium alloys
Nanopore-based sensing has emerged as a promising candidate for affordable and powerful DNA sequencing technologies. Herein, we demonstrate that nanopores can be successfully fabricated in Mg alloys via focused electron beam (e-beam) technology. Employing in situ high-resolution transmission electron microscopy techniques, we obtained unambiguous evidence that layer-by-layer growth of atomic planes at the nanopore periphery occurs when the e-beam is spread out, leading to the shrinkage and eventual disappearance of nanopores. The proposed healing process was attributed to the e-beam-induced anisotropic diffusion of Mg atoms in the vicinity of nanopore edges. A plausible diffusion mechanism that describes the observed phenomena is discussed. Our results constitute the first experimental investigation of nanopores in Mg alloys. Direct evidence of the healing process has advanced our fundamental understanding of surface science, which is of great practical importance for many technological applications, including thin film deposition and surface nanopatterning.
Zheng, He; Liu, Yu; Cao, Fan; Wu, Shujing; Jia, Shuangfeng; Cao, Ajing; Zhao, Dongshan; Wang, Jianbo
Friction Stir Lap Welding of Magnesium Alloy to Steel: A Preliminary Investigation
An initial study was made to evaluate the feasibility of joining Magnesium alloy AZ31 sheet to galvanized steel sheet in lap configuration using friction stir welding (FSW). Two different automotive sheet steels were used for comparative evaluation of the dissimilar joining potential; a 0.8mm thick, electro galvanized (EG) mild steel, and a 1.5mm thick hot dipped galvanized (HDG) high-strength, low-alloy steel (HSLA). These steels were joined to 2.33mm thick AZ31B magnesium sheet. A single FSW tool design was used for both dissimilar welds, and process parameters were kept the same. Average peak load for the AZ31-1.5 mm steel weld joint in lap shear mode was found to be 6.3 ± 1.0 kN. For the AZ31-0.8 mm steel weld, joint strength was 5.1 ± 1.5 kN. Microstructural investigation indicates melting of the Zn coating at the interface and subsequent alloying with the Mg sheet resulting in formation of solidified Zn-Mg alloy layer at AZ31/steel interface.
Jana, Saumyadeep; Hovanski, Yuri; Grant, Glenn J.
Comparative in vitro study and biomechanical testing of two different magnesium alloys.
In this in vitro study, magnesium plates of ZEK100 and MgCa0.8 alloy similar to common titanium alloy osteosynthesis plates were investigated as degradable biomedical materials with a focus on primary stability. Immersion tests were performed in Hank's Balanced Salt Solution at 37. The bending strength of the samples was determined using the four-point bending test according to ISO 9585:1990. The initial strength of the noncorroded ZEK100 plate was 11% greater than that of the MgCa0.8 plate; both were approximately 65% weaker than a titanium plate. The bending strength was determined after 48 and 96?h of immersion in Hank's Balanced Salt Solution; both magnesium alloys decreased by approximately 7% after immersion for 96?h. The degradation rate and the Mg(2+) release of ZEK100 were lower than those of MgCa0.8. Strong pitting and filiform corrosion were observed in the MgCa0.8 samples after 96?h of immersion. The surface of the ZEK100 plates exhibited only small areas of filiform corrosion. The results of this in vitro study indicate that the ZEK100 alloy may be more suitable for biomedical applications. PMID:24105427
Weizbauer, Andreas; Modrejewski, Christian; Behrens, Sabine; Klein, Helmut; Helmecke, Patrick; Seitz, Jan-Marten; Windhagen, Henning; Möhwald, Kai; Reifenrath, Janin; Waizy, Hazibullah
Thermodynamic and kinetic destabilization of magnesium hydride using Mg-In solid solution alloys.
Efforts to thermodynamically destabilize magnesium hydride (MgH2), so that it can be used for practical hydrogen storage applications, have been a difficult challenge that has eluded scientists for decades. This letter reports that MgH2 can indeed be destabilized by forming solid solution alloys of magnesium with group III and IVB elements, such as indium. Results of this research showed that the equilibrium hydrogen pressure of a Mg-0.1In alloy is 70% higher than that of pure MgH2. The temperature at 1 bar hydrogen pressure (T1bar) of Mg-0.1In alloy was reduced to 262.9 °C from 278.9 °C, which is the T1bar of pure MgH2. Furthermore, the kinetic rates of dehydrogenation of Mg-0.1In alloy hydride doped with a titanium intermetallic (TiMn2) catalyst were also significantly improved compared with those of MgH2. PMID:23855837
Zhou, Chengshang; Fang, Zhigang Zak; Lu, Jun; Zhang, Xiaoyi
As a surface engineering technique, high-power laser cladding, has shown great potential for improving the corrosion resistance of magnesium alloys. Its main advantage over other processes, is its ability to form relatively thick protective coatings on selected areas where improved properties are desired. It is also a 'clean' process. However, previous research studies have found that in laser cladding of magnesium alloys, the problem of a high degree of dilution cannot be easily overcome. Moreover, in-depth studies using analytical or numerical modelling can rarely be found in the literature for addressing laser cladding with pre-placed powders with the aim of predicting the level of dilution. In the first phase of this study, a simplified thermal model based on the finite element method (FEM) was developed to study the phenomenon of dilution in laser cladding of a magnesium alloy. In the model, the powder bed was treated as a continuum, and a high power continuous wave (CW) laser was employed. The results of the simulations of the FEM model together with those of the statistical analyses showed that although, under normal cladding conditions, a process window can be established for achieving good interfacial bonding between the substrate and the clad coating, a low dilution level was extremely difficult to achieve. This was primarily attributed to the low melting point and the high thermal diffusivity of magnesium as well as the relatively long laser-material interaction time. To overcome the dilution problem, the double-layer cladding technique was explored, and was found to be able to produce low dilution clads with improved corrosion resistance. In considering the improvement of corrosion resistance that can be caused by laser surface modification to magnesium alloys, a comparison was made between the techniques of laser surface melting and laser cladding. The results of the potentiodynamic polarisation tests showed that the improvement obtained from laser surface melting was far less than that could be provided by laser cladding. Although, laser surface melting could effect a rapid solidification, and as a consequence, a homogenised microstructure was obtained, this has not changed the extreme position of magnesium in the electrochemical series nor has it changed the fact that magnesium cannot form self-healing passivating surface films in corrosive environments. On the contrary, the application of laser cladding could completely change the surface chemistry of magnesium alloys and create a more noble surface coating. However, it must be recognised that to benefit most from laser cladding, a low level of dilution is desirable. Accordingly, a careful selection of the laser processing parameters is needed. To achieve this, the 3-D numerical FEM model presented in the present research has shown to be of great value. (Abstract shortened by UMI.)
Guo, Li-Feng
Energy investigations on the mechanical properties of magnesium alloyed by X = C, B, N, O and vacancy
The generalized stacking fault (GSF) energies and surface energies of magnesium and its alloys with alloying atoms X = C, B, N, O and vacancy have been investigated using the first-principles methods. It is found that the predominant reducing effects of the alloying atoms and vacancy on the stacking fault energy are resulted from the position of them in the 1st layer near the slip plane. The stacking fault energies are nearly the same as the pure magnesium while the alloying atoms and vacancy are placed in the 2nd, 3rd, 4th, 5th and 6th layers. It has been shown that O strongly reduces the GSF energy of Mg. The alloying atoms C, B and N increase the surface energy, but O and vacancy reduce the surface energy of Mg. The ductilities of Mg and Mg alloys have been discussed based on the Rice criterion by using the ratio between surface energy and unstable stacking fault energy.
Wu, Xiao-Zhi; Liu, Li-Li; Wang, Rui; Gan, Li-Yong; Liu, Qing
Potential bioactivity of coatings formed on AZ91D magnesium alloy by plasma electrolytic anodizing.
Magnesium is a potential candidate as biodegradable orthopedic implant thanks to its remarkable mechanical properties closed to those of natural bone. But its low corrosion resistance in the body fluid is a limiting factor. By using electrolytic plasma (or microarc) anodizing process, 10-20 ?m protective coatings were formed on AZ91D magnesium alloys at a constant current density of 20 mA cm(-2). The effect of a small addition of CaO (1-3 g L(-1)) to a classical electrolytic bath (made of KOH 3 mol L(-1), KF 0.5 mol L(-1), and K(2)HPO(4) 1 mol L(-1)) was studied. The anodic films, investigated by X-ray diffraction and scanning electron microscope-energy dispersive spectroscopy, show a porous structure containing crystallized Mg(OH)(2), MgO, MgAl(2)O(4), as well as Ca and P elements. The 1 g L(-1) CaO-containing electrolyte leads to morphology and composition permitting optimum corrosion behavior evaluated by stationary electrochemical measurements and impedance spectroscopy. This improvement is associated with both the appearing of a "sealing" layer and the precipitation of an outermost Ca/P-containing layer (hydroxyapatite like) in simulated body fluid. The control of the corrosion behavior of coated magnesium alloys is therefore required to enhance their potential bioactivity. PMID:22807000
Vu, Thanh-Nam; Veys-Renaux, Delphine; Rocca, Emmanuel
Modifying AM60B Magnesium Alloy Die Cast Surfaces by Friction Stir Processing
These experiments were done to evaluate the feasibility of locally modifying the surface properties of magnesium alloys with friction-stir processing. The magnesium alloy used for the study was high-pressure die-cast AM60B, nominally Mg-6Al-0.13 Mn (wt. %). Friction-stir passes were made with a translation speed of 1.7 mm/s using tool-rotation speeds of 1,250 rpm or 2,500 rpm. Stir passes with good appearance were obtained under both conditions. In some cases up to five passes were overlapped on a single bar to produce stir zones with cross-sectional dimensions of about 1.5 mm x 10 mm. Metallographic examinations indicated that the stir zones were largely comprised of a magnesium solid solution with equiaxed grains on the order of 5-10 {micro}m in size. Hardness mapping showed that the stir zones experienced increases of 16-25% compared to the as-cast metal. Room-temperature testing showed that, compared to the cast metal, the stir zones had flow stresses nearly 20% higher with about twice the tensile elongation.
Santella, Michael L [ORNL; Feng, Zhili [ORNL; Degen, Cassandra [South Dakota School of Mines and Technology; Pan, Dr. Tsung-Yu [Ford Motor Company
Development of Very High Strength and Ductile Dilute Magnesium Alloys by Dispersion of Quasicrystal Phase
Very high strengths, with tensile yield strength from 377 to 405 MPa, combined with elongation to failure of over 12 pct, have been achieved in Mg-Zn-Y dilute alloys by direct extrusion. Alloys Mg-6 xZn- xY, where x = 0.2, 0.35, and 0.5 (at. pct) were chill cast in a steel mold and direct extruded at a temperature in the range 508 K to 528 K (235 °C to 255 °C), which produced an average grain size of about 1 ?m. Quasicrystalline i-phase particles were dispersed in the matrix with size ranging from 50 nm to 1 ?m. In addition, high density of nano-precipitates of average size 15 nm was dispersed in matrix. Thus we have developed magnesium alloys of very high strength combined with ductility by a simple process using extrusion with very little addition of yttrium.
Singh, Alok; Osawa, Yoshiaki; Somekawa, Hidetoshi; Mukai, Toshiji; Parrish, Catherine J.; Shih, Donald S.
Forming limit diagram analysis based on crystal plasticity for magnesium alloy sheets
In the sheet metal forming industry, forming limit diagram (FLD) is a useful tool for quantifying metals formability. However, the experimental measurement of FLD is difficulty, time consuming and expensive process. It would be useful if FLD calculated with a theoretical model could replace experimental measurements. In this research, a rate independent crystal plasticity model is developed to analyze the plastic deformation of hexagonal close packed (HCP) materials by incorporating the crystallography of deformation twinning in plasticity model. The numerical simulations of FLD for AZ31 magnesium alloy are performed based on the crystal plasticity model incorporated within the Marciniak- Kuczynski (M-K) approach. The approach allows for the incorporation of initial texture, evolution of texture, and texture-induced anisotropy. The effects of mechanical twinning on plastic deformation and FLD behavior for AZ31 alloy are also incorporated. Finally, the calculation of the FLD for AZ31 alloy successfully predicts the experimental tendency that phenomenological plasticity model cannot reproduce.
Tang, Weiqin; Li, Dayong; Peng, Yinghong; Zhang, Shaorui
Novel magnesium alloy Mg-2La caused no cytotoxic effects on cells in physiological conditions.
Using several different in vitro assays, a new biodegradable magnesium alloy Mg-2La, composed of 98% magnesium and 2% lanthanum, was investigated as a possible implant material for biomedical applications. An in vitro cytotoxicity test, according to EN ISO 10993-5/12, with L929 and human osteoblastic cells identified no toxic effects on cell viability at physiological concentrations (at 50% dilutions and higher). The metabolic activity of human osteoblasts in the 100% extract was decreased to <70% and was therefore rated as cytotoxic. The degradation rates of Mg-2La were evaluated in phosphate buffered saline and four different cell culture media. The degradation rates were shown to be influenced by the composition of the solution, and the addition of fetal bovine serum slightly accelerated the corrosive process. The results of these in vitro experiments suggest that Mg-2La is a promising candidate for use as an orthopedic implant material. PMID:24907760
Weizbauer, Andreas; Seitz, Jan-Marten; Werle, Peter; Hegermann, Jan; Willbold, Elmar; Eifler, Rainer; Windhagen, Henning; Reifenrath, Janin; Waizy, Hazibullah
Spectroscopic study of plasma during electrolytic oxidation of magnesium- and aluminium-alloy
We present the results of an optical emission spectroscopy study of Plasma during Electrolytic Oxidation (PEO) of magnesium- and aluminum-alloy. Plasma electron number density Ne diagnostics is performed either from the H? line shape or from the width or shift of non-hydrogenic ion lines of aluminum and magnesium. The line profile analysis of the H? suggests presence of two PEO processes characterized by relatively low electron number densities Ne?1.2×1015 cm-3 and Ne?2.3×1016 cm-3. Apart from these two low Ne processes, there is the third one related to the ejection of evaporated anode material through micro-discharge channels. This process is characterized by larger electron density Ne=(1.2-1.6)1017 cm-3, which is detected from the shape and shift of aluminum and magnesium singly charged ion lines. Two low Ne values detected from the H? and large Ne measured from the widths and shift of ion lines suggest presence of three types of discharges during PEO with aluminum- and magnesium-alloy anode. On the basis of present and earlier results one can conclude that low Ne processes do not depend upon anode material or electrolyte composition.The electron temperature of 4000 K and 33,000 K are determined from relative intensities of Mg I and O II lines, respectively. The attention is drawn to the possibility of Ne application for Te evaluation using Saha equation what is of importance for PEO metal plasma characterization. During the course of this study, difficulties in the analysis of spectral line shapes are encountered and the ways to overcome some of the obstacles are demonstrated.
Jovovi?, J.; Stojadinovi?, S.; Šišovi?, N. M.; Konjevi?, N.
Assessment of a one-step intelligent self-healing vanadia protective coatings for magnesium alloys in corrosive media
Eco-friendly vanadia based chemical conversion coating was applied for improving the corrosion resistance of a newly developed magnesium AZ31 HP-O alloy. The effect of vanadia solution concentrations (10, 30 and 50g\\/l) and pH on the corrosion protection performance of magnesium substrate were investigated. EIS and cyclic voltammetry techniques were used to evaluate the electrochemical behavior in 3.5% NaCl. Results showed
Evaluation of magnesium-yttrium alloy as an extraluminal tracheal stent.
Tracheomalacia is a relatively rare problem, but can be challenging to treat, particularly in pediatric patients. Due to the presence of mechanically deficient cartilage, the trachea is unable to resist collapse under physiologic pressures of respiration, which can lead to acute death if left untreated. However, if treated, the outcome for patients with congenital tracheomalacia is quite good because the cartilage tends to spontaneously mature over a period of 12 to 18 months. The present study investigated the potential for the use of degradable magnesium-3% yttrium alloy (W3) to serve as an extraluminal tracheal stent in a canine model. The host response to the scaffold included the formation of a thin, vascularized capsule consisting of collagenous tissue and primarily mononuclear cells. The adjacent cartilage structure was not adversely affected as observed by bronchoscopic, gross, histologic, and mechanical analysis. The W3 stents showed reproducible spatial and temporal fracture patterns, but otherwise tended to corrode quite slowly, with a mix of Ca and P rich corrosion product formed on the surface and observed focal regions of pitting. The study showed that the approach to use degradable magnesium alloys as an extraluminal tracheal stent is promising, although further development of the alloys is required to improve the resistance to stress corrosion cracking and improve the ductility. PMID:23554285
Luffy, Sarah A; Chou, Da-Tren; Waterman, Jenora; Wearden, Peter D; Kumta, Prashant N; Gilbert, Thomas W
Magnesium ion stimulation of bone marrow stromal cells enhances osteogenic activity, simulating the effect of magnesium alloy degradation.
Magnesium alloys are being investigated for load-bearing bone fixation devices due to their initial mechanical strength, modulus similar to native bone, biocompatibility and ability to degrade in vivo. Previous studies have found Mg alloys to support bone regeneration in vivo, but the mechanisms have not been investigated in detail. In this study, we analyzed the effects of Mg(2+) stimulation on intracellular signaling mechanisms of human bone marrow stromal cells (hBMSCs). hBMSCs were cultured in medium containing 0.8, 5, 10, 20 and 100mM MgSO4, either with or without osteogenic induction factors. After 3weeks, mineralization of extracellular matrix (ECM) was analyzed by Alizarin red staining, and gene expression was analyzed by quantitative polymerase chain reaction array. Mineralization of ECM was enhanced at 5 and 10mM MgSO4, and collagen type X mRNA (COL10A1, an ECM protein deposited during bone healing) expression was increased at 10mM MgSO4 both with and without osteogenic factors. We also confirmed the increased production of collagen type X protein by Western blotting. Next, we investigated the mechanisms of intracellular signaling by analyzing the protein production of hypoxia-inducible factor (HIF)-1? and 2? (transcription factors of COL10A1), vascular endothelial growth factor (VEGF) (activated by HIF-2?) and peroxisome proliferator-activated receptor gamma coactivator (PGC)-1? (transcription coactivator of VEGF). We observed that 10mM MgSO4 stimulation enhanced COL10A1 and VEGF expression, possibly via HIF-2? in undifferentiated hBMSCs and via PGC-1? in osteogenic cells. These data suggest possible ECM proteins and transcription factors affected by Mg(2+) that are responsible for the enhanced bone regeneration observed around degradable Mg orthopedic/craniofacial devices. PMID:24512978
Yoshizawa, Sayuri; Brown, Andrew; Barchowsky, Aaron; Sfeir, Charles
The effect of current mode and discharge type on the corrosion resistance of plasma electrolytic oxidation (PEO) coated magnesium alloy AJ62
Magnesium alloys are increasingly being used as lightweight materials in the automotive, defense, electronics, biomaterial and aerospace industries. However, their inherently poor corrosion and wear resistance have, so far, limited their application. Plasma electrolytic oxidation (PEO) in an environmentally friendly aluminates electrolyte has been used to produce oxide coatings with thicknesses of ~80?m on an AJ62 magnesium alloy. Optical emission
R. O. Hussein; P. Zhang; X. Nie; Y. Xia; D. O. Northwood
Fabrication of biomimetic hydrophobic films with corrosion resistance on magnesium alloy by immersion process
Biomimetic hydrophobic films of crystalline CeO2 were prepared on magnesium alloy by an immersion process with cerium nitrate solution and then modified with DTS (CH3(CH2)11Si(OCH3)3). The CeO2 films fabricated with 20-min immersion yield a water contact angle of 137.5 ± 2°, while 20-min DTS treatment on top of CeO2 can further enhance the water contact angle to 146.7 ± 2°. Then corrosion-resistant property of these prepared films against NaCl solution was investigated and elucidated using electrochemical measurements.
Liu, Yan; Lu, Guolong; Liu, Jindan; Han, Zhiwu; Liu, Zhenning
Temperature dependence of magnesium alloy spall strength in the temperature range of 90...750K
The paper presents the results of studies of the temperature dependence behavior of magnesium alloy MA14T1 spall strength. The studies were performed using a light-gas gun by the impact method with the measurement of stress-waves profiles by a two-channel laser interferometer VISAR within one velocity loading range (~345 m/s). The temperature dependence of spall strength within the temperature range of 90°K...750°K was obtained. Changes in the shape and the amplitude of the elastic precursor in the specified temperature range were measured.
Pavlenko, Alexander; Malugina, Svetlana; Kazakov, D. N.; Bychkov, V. V.
Synthesis of hybrid sol-gel coatings for corrosion protection of we54-ae magnesium alloy
The present work shows some preliminary results related to the synthesis, characterization and corrosion evaluation of different hybrid sol-gel coatings applied on the WE54-AE magnesium alloy attending to the two experimental variables, i.e. the precursors ratio and the aging time, which may affect the quality and the electrochemical properties of the coatings resultant. The experimental results confirmed that, under some specific experimental conditions, it was possible to obtain homogeneous and uniform, porous coatings with good corrosion resistance that also permit to accommodate corrosion inhibitors.
Hernández-Barrios, C. A.; Duarte, N. Z.; Hernández, L. M.; Peña, D. Y.; Coy, A. E.; Viejo, F.
Microstructure-affected micromechanisms of fatigue crack growth operating near the limit plasticity regime were experimentally\\u000a identified for the four main commercial high-pressure die-cast (HPDC) magnesium alloys: AM50, AM60, AZ91, and AE44. These\\u000a fatigue micromechanisms manifested by the concomitant effects of casting pores, interdendritic Al-rich solid solution layer,\\u000a ?-phase particles, Mn-rich inclusions, rare earth-rich intermetallics, dendrite cell size, and surface segregation phenomena.
Interactions between laser and arc plasma during laser-arc hybrid welding of magnesium alloy
This paper presents the results of the investigation on the interactions between laser and arc plasma during laser-arc hybrid welding on magnesium alloy AZ31B using the spectral diagnose technique. By comparably analyzing the variation in plasma information (the shape, the electron temperature and density) of single tungsten inert gas (TIG) welding with the laser-arc hybrid welding, it is found that the laser affects the arc plasma through the keyhole forming on the workpiece. Depending on the welding parameters there are three kinds of interactions taking place between laser and arc plasma.
Liu, Liming; Chen, Minghua
The 316L austenitic stainless steel and AZ31 magnesium alloy have physical and mechanical properties which makes these alloys suitable in a number of high technology based industries such as the aerospace and automotive sectors. However, for these alloys to be used in engineering applications, components must be fabricated and joined successfully. The differences in the physical and metallurgical properties between these two alloys prevents the use of conventional fusion welding processes commonly employed in aerospace and transport industry. Therefore, alternative techniques need to be developed and diffusion bonding technology is a process that has considerable potential to join these two dissimilar alloys. In this research work both solid-state and transient liquid phase (TLP) bonding processes were applied. The solid-state bonding of 316L steel to AZ31 magnesium alloy was possible at a bonding temperature of 550°C for 120 minutes using a pressure of 1.3 MPa. The interface characterization of the joint showed a thin intermetallic zone rich in Fe-Al was responsible for providing a metallurgical bond. However, low joint shear strengths were recorded and this was attributed to the poor surface to surface contact. The macro-deformation of the AZ31 alloy prevented the use of higher bonding pressures and longer bonding times. In order to overcome these problems, the TLP bonding process was implemented using pure Cu and Ni foils as interlayers which produced a eutectic phase at the bonding temperature. This research identified the bonding mechanism through microstructural and differential scanning calorimetry investigations. The microstructural characterization of the TLP joints identified intermetallics which became concentrated along the 316L steel/AZ31 bond interface due to the "pushing effect" of the solid/liquid interface during isothermal solidification stage of bonding. The size and concentration of the intermetallics had a noticeable effect on the final joint strength properties. TLP bonding using electrodeposited coatings of Cu and Ni were used as a way of controlling the volume of eutectic liquid formed at the joint. Theoretical and experimental work showed that the use of thin coatings was successful in reducing the size and amount of intermetallics formed at the joint and this had the effect on increasing joint shear strength values.
Elthalabawy, Waled Mohamed
Aqueous Corrosion Behavior of Micro Arc Oxidation (MAO)-Coated Magnesium Alloys: A Critical Review
Magnesium (Mg) and its alloys, in the current era of persistently growing engineering demands, have become the most promising materials finding widespread industrial applications. Numerous processes are available for surface protection of Mg and its alloys to potentially minimize corrosion damage. The micro arc oxidation (MAO), a fairly recent and eco-friendly coating process, emerged as a novel means to provide an adherent, hard, scratch-resistant, wear-resistant, and corrosion-resistant coatings on Mg alloys. However, the successful utilization of such coatings demands a thorough understanding of the influence of a relatively large number of process parameters such as electrolytic composition, presence of insoluble additives in the electrolyte, electrical parameters employed, and the composition of the Mg alloy substrate on the corrosion resistance. The detailed influence of all the above parameters on the corrosion behavior of Mg alloys is critically reviewed and presented in this article. In addition, this article also reviews the recent trends in terms of duplexing the MAO process using different techniques/processes such that the composite coatings are produced with enhanced corrosion resistance.
Rama Krishna, L.; Sundararajan, G.
Biomimetic coating of magnesium alloy for enhanced corrosion resistance and calcium phosphate deposition.
Degradable metals have been suggested as biomaterials with revolutionary potential for bone-related therapies. Of these candidate metals, magnesium alloys appear to be particularly attractive candidates because of their non-toxicity and outstanding mechanical properties. Despite their having been widely studied as orthopedic implants for bone replacement/regeneration, their undesirably rapid corrosion rate under physiological conditions has limited their actual clinical application. This study reports the use of a novel biomimetic peptide coating for Mg alloys to improve the alloy corrosion resistance. A 3DSS biomimetic peptide is designed based on the highly acidic, bioactive bone and dentin extracellular matrix protein, phosphophoryn. Surface characterization techniques (scanning electron microscopy, energy dispersive X-ray spectroscopy and diffuse-reflectance infrared spectroscopy) confirmed the feasibility of coating the biomimetic 3DSS peptide onto Mg alloy AZ31B. The 3DSS peptide was also used as a template for calcium phosphate deposition on the surface of the alloy. The 3DSS biomimetic peptide coating presented a protective role of AZ31B in both hydrogen evolution and electrochemical corrosion tests. PMID:23816653
Cui, W; Beniash, E; Gawalt, E; Xu, Z; Sfeir, C
Magnesium alloys: predicting in vivo corrosion with in vitro immersion testing.
Magnesium (Mg) and its alloys have been proposed as degradable replacements to commonly used orthopedic biomaterials such as titanium alloys and stainless steel. However, the corrosion of Mg in a physiological environment remains a difficult characteristic to accurately assess with in vitro methods. The aim of this study was to identify a simple in vitro immersion test that could provide corrosion rates similar to those observed in vivo. Pure Mg and five alloys (AZ31, Mg-0.8Ca, Mg-1Zn, Mg-1Mn, Mg-1.34Ca-3Zn) were immersed in either Earle's balanced salt solution (EBSS), minimum essential medium (MEM), or MEM-containing 40 g/L bovine serum albumin (MEMp) for 7, 14, or 21 days before removal and assessment of corrosion by weight loss. This in vitro data was compared to in vivo corrosion rates of the same materials implanted in a subcutaneous environment in Lewis rats for equivalent time points. The results suggested that, for the alloys investigated, the EBSS buffered with sodium bicarbonate provides a rate of degradation comparable to those observed in vivo. In contrast, the addition of components such as (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) (HEPES), vitamins, amino acids, and albumin significantly increased corrosion rates. Based on these findings, it is proposed that with this in vitro protocol, immersion of Mg alloys in EBSS can be used as a predictor of in vivo corrosion. PMID:22331609
Walker, Jemimah; Shadanbaz, Shaylin; Kirkland, Nicholas T; Stace, Edward; Woodfield, Tim; Staiger, Mark P; Dias, George J
Analytical Method for Forming Limit Diagram Prediction with Application to a Magnesium ZEK100-O Alloy
A significant barrier to broader implementation of magnesium alloys is their poor room temperature formability, a consequence of the anisotropic response of the Mg hexagonal closed-packed (hcp) crystal structure. Additions of rare earth (RE) elements, such as in the ZEK100 alloys, weaken the texture and improve formability. Room temperature forming limit analyses of RE-containing Mg alloys, particularly Mg ZEK100, have not been explored to any significant extent in the literature. In this paper, strain-based forming limit diagrams (FLDs) are derived for an Mg ZEK100-O alloy (Zn1.34Zr0.23Nd0.182, wt.%) using an analytical method that combines the vertex theory of Storen and Rice (J Mech Phys Solids, 23:421-441, 1979), the anisotropic yield criterion of Barlat and Lian (Int J Plast, 5:51-66, 1989), and a hardening law. The method does not rely on assumptions about pre-existing defects, is broadly applicable to sheet alloys exhibiting in-plane anisotropy requiring a higher-order yield criterion, and requires only minimal experimental inputs. Results from the analytical method are compared with experimentally derived FLDs based upon the well-known Nakajima test and tensile deformation, and with predictions from an existing analytical method for FLDs. Close agreement between the experimentally derived FLDs and the present theoretical method was obtained. Sheet materials where the theoretical method does not apply are also discussed.
Min, Junying; Hector, Louis G.; Lin, Jianping; Carter, Jon T.
Surface characteristics and corrosion behaviour of WE43 magnesium alloy coated by SiC film
Amorphous SiC film has been successfully fabricated on the surface of WE43 magnesium alloy by plasma enhanced chemical vapour deposition (PECVD) technique. The microstructure and elemental composition were analyzed by transmission electron microscopy (TEM), glancing angle X-ray diffraction (GAXRD) and X-ray photoelectron spectroscopy (XPS), respectively. The immersion test indicated that SiC film could efficiently slow down the degradation rate of WE43 alloy in simulated body fluid (SBF) at 37 ± 1 °C. The indirect toxicity experiment was conducted using L929 cell line and the results showed that the extraction medium of SiC coated WE43 alloys exhibited no inhibitory effect on L929 cell growth. The in vitro hemocompatibility of the samples was investigated by hemolysis test and blood platelets adhesion test, and it was found that the hemolysis rate of the coated WE43 alloy decreased greatly, and the platelets attached on the SiC film were slightly activated with a round shape. It could be concluded that SiC film prepared by PECVD made WE43 alloy more appropriate to biomedical application.
Li, M.; Cheng, Y.; Zheng, Y. F.; Zhang, X.; Xi, T. F.; Wei, S. C.
Effects of sealing treatment on corrosion resistance and degradation behavior of micro-arc oxidized magnesium alloy wires
The effects of three different sealing treatments on micro-arc oxidized (MAO) medical magnesium alloy wires using boiling water, zirconia sol-gel, and organic gelatin-hydroxyapatite (HA) coatings on the surface morphology, corrosion resistance, and degradation behavior in simulated body fluid (SBF) and simulated intestinal fluid (SIF) are investigated. The treatments involving boiling water or gelatin-HA coating can effectively seal the discharge channels making the surface pores less and smaller. The treatments also improve the corrosion resistance of the MAO magnesium alloy wires, especially the samples with the gelatin-HA coatings which also exhibit reduced degradation in both simulated physiological environments.
Chu, C. L.; Han, X.; Xue, F.; Bai, J.; Chu, P. K.
Tribological properties of the AZ91D magnesium alloy hardened with silicon carbide and by severe plastic deformation
Results of investigation of the tribological contact characteristics of R18 tool steel in interface with AZ91D magnesium alloy\\u000a hardened with SiC disperse powder filler and by severe plastic deformation (SPD)—specifically, equal-channel angular pressing\\u000a (ECAP)—are presented. It is established that introduction of the SiC powder filler into the magnesium alloy increases the\\u000a friction coefficient and reduces the wear rate. The size
V. I. Semenov; Y.-R. Jeng; S.-J. Huang; Y.-Zh. Dao; S.-J. Hwang; L. Sh. Shuster; S. V. Chertovskikh; P.-Ch. Lin
Endothelialization of Novel Magnesium-Rare Earth Alloys with Fluoride and Collagen Coating
Magnesium (Mg) alloys are promising scaffolds for the next generation of cardiovascular stents because of their better biocompatibility and biodegradation compared to traditional metals. However, insufficient mechanical strength and high degradation rate are still the two main limitations for Mg materials. Hydrofluoric acid (HF) treatment and collagen coating were used in this research to improve the endothelialization of two rare earth-based Mg alloys. Results demonstrated that a nanoporous film structure of fluoride with thickness of ~20 ?m was formed on the Mg material surface, which improved the corrosion resistance. Primary human coronary artery endothelial cells (HCAECs) had much better attachment, spreading, growth and proliferation (the process of endothelialization) on HF-treated Mg materials compared to bare- or collagen-coated ones.
Zhao, Nan; Workman, Benjamin; Zhu, Donghui
Lawrence Livermore National Lab and Sandia National Laboratories, CA are collaborating on the development of new techniques to study damage evolution and growth in material specimens subjected to mechanical loading. These techniques include metallography, radiography, computed tomography (CT) and modeling. The material specimens being studied include cast magnesium and aluminum alloys, and forged stainless steel. The authors concentrate on characterizing monotonically loaded Mg alloy specimens using CT. Several notched tensile specimens were uniaxially loaded to different percentages of the failure load. Specimens were initially characterized by radiography and computed tomography to determine the preloaded state. Subsequent CT scans were performed after the samples were loaded to different percentages of the load failure. The CT volumetric data are being used to measure void size, distribution and orientation in all three dimensions nondestructively to determine the effect of void growth on the mechanical behavior of the materials.
Waters, A.; Green, R.E.; Martz, H.; Dolan, K.; Horstemeyer, M.; Derrill, R.
Plastic deformation macrolocalization during serrated creep of an aluminum-magnesium Al-6 wt % Mg alloy
The nonlinear dynamics of the space-time structure of macrolocalized deformation is studied by a set of high-speed in situ methods under the conditions of serrated creep in an aluminum-magnesium Al-6 wt % Mg alloy at room temperature. Macroscopic deformation jumps with an amplitude of several percent are detected in the creep curve of this alloy. It is found that a complex space-time structure of macrolocalized deformation bands moving in a correlated manner forms spontaneously in the material during the development of a deformation jump. The difference between the observed picture of deformation bands and the well-known Portevin-Le Chatelier classification of deformation bands is discussed.
Shibkov, A. A.; Zolotov, A. E.; Zheltov, M. A.; Denisov, A. A.; Gasanov, M. F.
Formation of microarc oxidation coatings on magnesium alloy with photocatalytic performance
Microarc oxidation (MAO) coatings were prepared on AZ91D magnesium alloy in a phosphate electrolyte with and without TiO2 nanoparticles. The effect of TiO2 nanoparticles in the electrolyte on the thickness, surface morphology, composition, structure, corrosion resistance and photocatalytic performance of the coatings were investigated. The appearance and structure of the coatings changed significantly after the TiO2 nanoparticles were added into the electrolyte. The coatings produced in the phosphate electrolyte displayed a grayish white appearance and were mainly composed of MgO and Mg3(PO4)2. However, the coatings formed in the electrolyte with various TiO2 nanoparticles had a blueish color and, additionally, contained the rutile TiO2 and Mg2TiO4. The results of corrosion and photocatalytic measurements show that the coatings formed in the electrolyte with TiO2 nanoparticles not only provided better corrosion protection for magnesium alloy but also exhibited photocatalytic properties.
Li, Weiping; Tang, Mingqi; Zhu, Liqun; Liu, Huicong
High-strain-rate superplasticity at low temperature in a ZK61 magnesium alloy produced by powder metallurgy
In the present study, superplastic behavior of a pseudo single phase magnesium alloy, ZK61, was investigated at about half the absolute melting point. The material was produced by the P/M route, and had a fine grain size of [approximately]500 nm. It is demonstrated that the P/M ZK61 alloy can behave in a superplastic manner at a high strain rate of 1 [times] 10[sup [minus]2] s[sup [minus]1] albeit at the low temperature.
Watanabe, Hiroyuki; Mukai, Toshiji (Osaka Municipal Technical Research Inst. (Japan)); Mabuchi, Mamoru (National Industrial Research Inst. of Nagoya (Japan)); Higashi, Kenji (Osaka Prefecture Univ., Sakai (Japan). Coll. of Engineering)
Computational microstructure analyzing technique for quantitative characterization of shrinkage and gas pores in pressure die cast AZ91 magnesium alloys
Pressure die cast AZ91 magnesium alloy contains both shrinkage and gas microporosity. Quantification and characterization of shrinkage and gas microporosity is expected to be useful to understand the processing-properties-microstructure correlations. However, conventional image analysis techniques do not permit a separate quantification and characterization of shrinkage and gas microporosity. A computational microstructural (image) analyzing technique has been developed by the use
D. G. Leo Prakash; B. Prasanna; D. Regener
The surface modified composite layer formation with boron carbide particles on magnesium alloy surfaces through pulse gas tungsten arc treatment
A novel fabrication process of surface modified composite layer by pulse current gas tungsten arc (GTA) surface modification process was used to deposit B4C particles on the surface of magnesium alloy AZ31. This method is an effective technique in producing a high performance surface modified composite layer. During the pulse current GTA surface modification process, considerable convection can exist in
W. B. Ding; H. Y. Jiang; X. Q. Zeng; D. H. Li; S. S. Yao
Selection of FSW tool pin profile, shoulder diameter and material for joining AZ31B magnesium alloy – An experimental approach
In this investigation, an attempt was made to select proper tool pin profile, tool shoulder diameter and tool material to friction stir weld AZ31B magnesium alloy. Five tool pin profiles, five tool materials and three tool shoulder diameters were used to fabricate the joints. Tensile properties of the joints were evaluated and correlated with the weld zone microstructure and hardness.
Influence of shot peening on corrosion properties of biocompatible magnesium alloy AZ31 coated by dicalcium phosphate dihydrate (DCPD).
Magnesium alloys are promising materials for biomedical applications because of many outstanding properties like biodegradation, bioactivity and their specific density and Young's modulus are closer to bone than the commonly used metallic implant materials. Unfortunately their fatigue properties and low corrosion resistance negatively influenced their application possibilities in the field of biomedicine. These problems could be diminished through appropriate surface treatments. This study evaluates the influence of a surface pre-treatment by shot peening and shot peening+coating on the corrosion properties of magnesium alloy AZ31. The dicalcium phosphate dihydrate coating (DCPD) was electrochemically deposited in a solution containing 0.1M Ca(NO3)2, 0.06M NH4H2PO4 and 10mL/L of H2O2. The effect of shot peening on the surface properties of magnesium alloy was evaluated by microhardness and surface roughness measurements. The influence of the shot peening and dicalcium phosphate dihydrate layer on the electrochemical characteristics of AZ31 magnesium alloy was evaluated by potentiodynamic measurements and electrochemical impedance spectroscopy in 0.9% NaCl solution at a temperature of 22±1°C. The obtained results were analyzed by the Tafel-extrapolation method and equivalent circuit method. The results showed that the application of shot peening process followed by DCPD coating improves the properties of the AZ31 surface from corrosion and mechanical point of view. PMID:24863232
Mhaede, Mansour; Pastorek, Filip; Hadzima, Branislav
In situ spectroscopic ellipsometry study of the hydrogenation process of switchable mirrors based on magnesium-nickel alloy thin films
The hydrogenation process of switchable mirrors using magnesium-nickel alloy thin films including a thin palladium cap layer was analyzed by measuring the variation in ellipsometric angles Psi and Delta using in situ spectroscopic ellipsometry. The process was divided into three phases and each phase was identified as follows. The first phase was the process in which the solid solution was
Y. Yamada; S. Bao; K. Tajima; M. Okada; M. Tazawa; A. Roos; K. Yoshimura
Electrochemical corrosion behaviour of plasma electrolytic oxidation coatings on AM50 magnesium alloy formed in silicate and phosphate based electrolytes
PEO coatings were produced on AM50 magnesium alloy by plasma electrolytic oxidation process in silicate and phosphate based electrolytes using a pulsed DC power source. The microstructure and composition of the PEO coatings were analyzed by scanning electron microscopy (SEM) and X-ray Diffraction (XRD). The corrosion resistance of the PEO coatings was evaluated using open circuit potential (OCP) measurements, potentiodynamic
J. Liang; P. Bala Srinivasan; C. Blawert; M. Störmer; W. Dietzel
Growth process of plasma electrolytic oxidation films formed on magnesium alloy AZ91D in silicate solution
In order to get a clear picture for describing the growth process of the oxide film formed on magnesium alloy AZ91D under plasma electrolytic oxidation (PEO) in alkaline silicate solution, the characteristics of PEO films formed at different reaction stages were systemically investigated. The results of morphologies, compositions and electronic properties indicated that the PEO films had a different growth
Hongping Duan; Chuanwei Yan; Fuhui Wang
Effects of humidity and contact material on fretting fatigue behavior of an extruded AZ61 magnesium alloy
Fretting fatigue tests of the extruded AZ61 magnesium alloy with the same contact material under low and high humidity were carried out to investigate basic fretting fatigue characteristics and effect of humidity on fretting fatigue behavior. Influence of contact material was also studied by using JIS S45C carbon steel contact material. Degradation of fatigue strength due to fretting was much
Anchalee Saengsai; Yukio Miyashita; Yoshiharu Mutoh
Comparative biomechanical and radiological characterization of osseointegration of a biodegradable magnesium alloy pin and a copolymeric control for osteosynthesis.
Magnesium alloys offer great advantages as degradable implant material for pediatric fracture fixation and hold the potential to overcome certain critical shortcomings inherent to currently used degradable (co)polymers. Besides good biocompatibility and appropriate degradation kinetics, sufficient implant anchorage in host bone is critical to prevent implant failure. Bone-implant anchorage of biodegradable magnesium alloys, however, has not yet been related and compared to that of copolymers, their degradable counterparts currently in clinical use. The aim of this study, therefore, was to comparatively assess bone-implant interface strength and the amount of peri-implant bone of a biodegradable magnesium alloy pin (Mg-Y-Nd-HRE) and a self-reinforced copolymeric control (85/15 poly(l-lactic-co-glycolic acid)). To this purpose, push-out testing, microfocus computed tomography (?CT), histological and scanning electron microscopic examination was performed after 4, 12 and 24 weeks of transcortical implantation in 72 rats. Biomechanical testing revealed significantly higher ultimate shear strength for the magnesium alloy pins than for the copolymeric controls at all 3 timepoints (P?0.001 for all comparisons). As evaluated by ?CT, the amount of bone present near the interface and in a wider radius (up to 0.5mm) around it was higher in the magnesium alloy implants at 4 weeks, without significant differences at 12 and 24 weeks. Histological examination confirmed direct bone-to-implant contact for both implant types. In vivo degradation of implants did not induce any noticeable local or systemic inflammation. This data suggests that the investigated degradable magnesium alloy rod exhibits markedly superior bone-implant interface strength and a greater amount of peri-implant bone than a self-reinforced copolymeric control currently in use; thus it fulfills a crucial prerequisite for its successful clinical deployment as an alternative degradable orthopedic implant material. Further studies, however, are warranted to evaluate the long-term degradation behavior and biocompatibility of the investigated degradable magnesium-based alloy. PMID:24001403
Lindtner, Richard A; Castellani, Christoph; Tangl, Stefan; Zanoni, Gerald; Hausbrandt, Peter; Tschegg, Elmar K; Stanzl-Tschegg, Stefanie E; Weinberg, Annelie-Martina
Continually rising energy prices have inspired increased interest in weight reduction in the automotive and aerospace industries, opening the door for the widespread use and development of lightweight structural materials. Chief among these materials are cast Al-Si and magnesium-based alloys. Utilization of Al-Si alloys depends on obtaining a modified fibrous microstructure in lieu of the intrinsic flake structure, a process which is incompletely understood. The local solidification conditions, mechanisms, and tensile properties associated with the flake to fiber growth mode transition in Al-Si eutectic alloys are investigated here using bridgman type gradient-zone directional solidification. Resulting microstructures are examined through quantitative image analysis of two-dimensional sections and observation of deep-etched sections showing three-dimensional microstructural features. The transition was found to occur in two stages: an initial stage dominated by in-plane plate breakup and rod formation within the plane of the plate, and a second stage where the onset of out-of-plane silicon rod growth leads to the formation of an irregular fibrous structure. Several microstructural parameters were investigated in an attempt to quantify this transition, and it was found that the particle aspect ratio is effective in objectively identifying the onset and completion velocity of the flake to fiber transition. The appearance of intricate out-of-plane silicon instability formations was investigated by adapting a perturbed-interface stability analysis to the Al-Si system. Measurements of silicon equilibrium shape particles provided an estimate of the anisotropy of the solid Si/liquid Al-Si system and incorporation of this silicon anisotropy into the model was found to improve prediction of the instability length scale. Magnesium alloys share many of the benefits of Al-Si alloys, with the added benefit of a 1/3 lower density and increased machinability. Magnesium castings often contain additions of heavier elements, such as zinc, zirconium, and rare earth elements, which significantly improve high temperature performance. However, additions of these elements can lead to macrosegregational effects in castings, which are detectable by radiographic scans. The effect of these flow-line indications on alloy mechanical properties is not well quantified. An examination of these flow-line indications and their effects on mechanical properties in three magnesiumbased casting alloys was performed here in order to determine the best practice for dealing with affected castings. Preliminary results suggest the flow-lines do not measurably impact bulk material properties. Three additional methods of characterizing three-dimensional material structures are also presented: a minimum spanning tree analysis is utilized to quantify local structure in Cu-Zr liquid phase simulations obtained from molecular dynamics; the radial distribution function is applied to directionally solidified Al-Si structures in an attempt to extract local spacing data; and the critical diameter measurement is also defined and applied to irregular eutectic Al-Si structures.
Hosch, Timothy Al
Dispersion strengthened aluminum-4 pct magnesium alloy made by mechanical alloying
Mechanical alloying is a unique high energy milling process for producing metal powders with a controlled microstructure.\\u000a When applied to aluminum based alloys, a uniform, equiaxed fine dispersion of oxygen- and carbon-based particles is obtained.\\u000a In addition, a very fine grain structure, pinned by the dispersoid, is generated. Relatively low volume loadings of dispersoid\\u000a may be employed to achieve attractive
J. S. Benjamin; R. D. Schelleng
Design factors influencing weldability of the Mg-4Y-3RE cast magnesium alloy
Due to low density and good strength properties, magnesium alloys are increasingly used as a structural material They are used, amongst others, for large-size castings in sand moulds, pressure and precision castings. Welding and pad welding is used to repair casting defects, such as misruns, micro-shrinkage, cracks, etc. The most frequent reason for disqualifying of welded joints made to repair the castings is hot cracking which occurs as a result of tensile stresses formed in the material during welding. The Mg-4Y-3RE (WE43) alloy with addition of yttrium and rare earth and zirconium elements used for testing is creep resistant to 300°C. The alloy is used in the automotive industry, for example for engine blocks and in aerospace industry for gearbox housings. This paper describes the welding and remelting tests of the Mg-4Y-3RE (WE43) castings in conditions of constant and variable stiffness. It has been concluded that hot cracks are formed as a result of eutectic melting in the areas of contact of ? - Mg solid solution crystals.
Kierzek, A.; Adamiec, J.
Microstructure and Mechanical Properties of AZ31 Magnesium Alloy Sheet by Hot Rolling
AZ31 magnesium alloy sheets with a thickness of about 2mm were prepared by using a unique hot rolling process which was featured by heating the rolls during rolling. Two different rolling routes were used to achieve the final thickness through 6 passes of rolling. The major rolling parameters were chosen as the same for both rolling routes except that the roll temperature was set to be 400°C for route A and the 1st to 4th passes of route B, but lowered to 350°C for the 5th and 6th passes of route B. The microstructure and mechanical properties of the alloy sheets were comparatively investigated. The results showed that dynamic recrystallization occurred during hot rolling, and by choosing the processing parameters appropriately the grain size could be refined steadily with increasing rolling passes. The final alloy sheet prepared by 6 passes of rolling via the rolling route B was featured by a very fine microstructure, with the grain size being 5?m in average. Correspondingly, it presented very high strength and tensile elongation, with its yield strength and tensile elongation achieving 206MPa and 26.4% in the transverse, and 196MPa and 27.6% in the rolling direction, respectively.
Miao, Qing; Hu, Lianxi; Wang, Erde; Liang, Shujin; Chao, Hongying
Influence of Laser Processing Parameters on Microstructure and Corrosion Kinetics of Laser-Treated ZE41 Magnesium Alloy
In the present study, surface melting of a magnesium alloy, ZE41, was performed with an Nd:YAG laser using different laser parameters. The microstructure of the laser-treated and untreated specimens was analyzed by optical and scanning electron microscopy and X-ray diffraction. Corrosion resistance of the different laser-treated specimens along with the untreated alloy was characterized using electrochemical impedance spectroscopy and weight loss measurements in 0.001 M sodium chloride solution. Although the laser processing parameters influenced the microstructure and the melt depth of the laser-treated zone, these had little effect on the corrosion resistance of the alloy.
Chakraborty Banerjee, P.; Singh Raman, R. K.; Durandet, Y.; McAdam, G.
Mathematical modeling and experimental study of squeeze casting of magnesium alloy AM50A and aluminum alloy A356
In recent years, the squeeze casting process has been widely used with various aluminum alloys to manufacture near-net shape automotive components. Preliminary research has also demonstrated technical feasibility potential of squeeze casting for magnesium. A better understanding of squeeze casting process is essential for applying the process for the production of large automotive components, such as engine block, using aluminum and magnesium. Meanwhile, simulation can help to achieve the analysis and optimization of the casting process. Unfortunately, for squeeze casting, no appropriate model is presently available. In this study, a mathematical model has been developed to simulate the transport phenomena and solidification occurring in squeeze casting process. The model was based on the control-volume finite difference approach and on an enthalpy method. An experimental system was developed capable of characterizing local in-cavity pressures, determining casting/die interfacial heat transfer, and observing pressurized solidification phenomena taking place in squeeze casting of aluminum and magnesium alloys. It was found that, during squeeze casting process, the local cavity pressure distribution was inhomogeneous. Experimental correlations of heat transfer coefficient were integrated into the model with local cavity pressures estimated by a force balance approach. Hence, instead of using static boundary condition, a dynamic boundary condition was established in the model. In order to minimize the deviation of calculation, experimental correlations between solidification temperatures and applied pressures were also integrated into the model. The predicted results, including cooling curves, solidification times, and local pressure cavity pressures, were compared with the experimental measurements and they were found to be in good agreement. The model was further advanced to predict shrinkage porosity during squeeze casting by a newly proposed criterion based on "burst-feeding" theory. The proposed model is able to predict the occurrence and location of porosity formation under a specified applied pressure and holding time. Comparison of the experimental results with the result of computations, the model not only successfully predicted the occurrence of porosity under certain circumstances, but also indicated the correct locations where porosity formed. Hence, it can be used for the optimization of the squeeze casting process.
Yu, Fang
Recently zinc based coatings on cold rolled steel with improved functionality in terms of forming and/or corrosion behaviour have been intensively investigated in the steel industry. One of the most promising products are zinc magnesium alloys produced in hot dip galvanizing process. These coatings were already introduced in construction industry a few years ago. With some modifications the improved properties of the coating are also interesting for automotive industry. In the present work the tribological potential of hot dip galvanized zinc magnesium coatings (HDG/ZM) produced at an industrial line under regular production, was studied in terms of sliding properties, adhesive and abrasive tool wear.First a short introduction into surface morphology of HDG/ZM will be given. For the tribological characterization of the material, which is the main topic of the contribution, different tests were performed on hot dip galvanised zinc magnesium material and results were compared with classic hot dip galvanized zinc coating (HDG/Z). The investigations are mainly based on the strip draw test which allows the determination of the friction coefficient directly by using a constant contact pressure. Deep drawing property was tested by forming model cups. The abrasive tool wear was tested using a standard test for material used in automotive industry. The adhesive tool wear was investigated by characterizing the coating material transferred to the tool in the strip draw test.All performed tests show an improved drawability of HDG/ZM compared to classical HDG/Z reference material. However the most promising difference between HDG/ZM and HDG/Z is that galling was found to be less for HDG/ZM than for HDG/Z. Therefore HDG/ZM is an interesting system not only with respect to corrosion protection but also in terms of tribology and provides clear advantages in formability.
Raab, A. E.; Berger, E.; Freudenthaler, J.; Leomann, F.; Walch, C. [Research and Development, Forming Technology voestalpine Stahl GmbH, Voest-Alpine Strasse 3, 4031 Linz (Austria)
Recently zinc based coatings on cold rolled steel with improved functionality in terms of forming and/or corrosion behaviour have been intensively investigated in the steel industry1,2,3. One of the most promising products are zinc magnesium alloys produced in hot dip galvanizing process. These coatings were already introduced in construction industry a few years ago1. With some modifications the improved properties of the coating are also interesting for automotive industry. In the present work the tribological potential of hot dip galvanized zinc magnesium coatings (HDG/ZM) produced at an industrial line under regular production, was studied in terms of sliding properties, adhesive and abrasive tool wear. First a short introduction into surface morphology of HDG/ZM will be given. For the tribological characterization of the material, which is the main topic of the contribution, different tests were performed on hot dip galvanised zinc magnesium material and results were compared with classic hot dip galvanized zinc coating (HDG/Z). The investigations are mainly based on the strip draw test which allows the determination of the friction coefficient directly by using a constant contact pressure. Deep drawing property was tested by forming model cups. The abrasive tool wear was tested using a standard test for material used in automotive industry. The adhesive tool wear was investigated by characterizing the coating material transferred to the tool in the strip draw test. All performed tests show an improved drawability of HDG/ZM compared to classical HDG/Z reference material. However the most promising difference between HDG/ZM and HDG/Z is that galling was found to be less for HDG/ZM than for HDG/Z. Therefore HDG/ZM is an interesting system not only with respect to corrosion protection but also in terms of tribology and provides clear advantages in formability.
Raab, A. E.; Berger, E.; Freudenthaler, J.; Leomann, F.; Walch, C.
Development of Magnesium Flat Cell Battery.
A second series of five cell stacks was assembled using AZ21X1 magnesium alloy anode plates. The six lots included increased quantities of magnesium bromide and magnesium perchlorate electrolytes, two concentrations of magnesium perchlorate electrolyte an...
P. F. Albert
Metallurgical Evaluation of AZ31B-H24 Magnesium Alloy Friction Stir Welds
Friction Stir welding of 3.175 mm (0.125 in.) thick plates of AZ31-H24 magnesium alloy was performed using several travel velocities and tool-rotation speeds. After production the welds were cross-sectioned and a metallurgical characterization was performed using optical microscopy, and scanning electron microscopy. Assessment of the weld nugget or "stirred zone" shows evidence of dynamic recrystallization and the start of grain growth in some spots of this region compared to the parent metal. Recrystallization was identified in the thermomechanically affected zone (TAZ) as well. The mechanical properties of the weld are correlated with the corresponding microstructures present in the weld nugget and TMAZ. Corrosion resistance of the weld was assessed using Electrochemical Impedance Spectroscopy (EIS) techniques and immersion tests in a corrosive environment; it showed better corrosion resistance than the base metal.
Pareek, M.; Polar, A.; Rumiche, F.; Indacochea, J. E.
Monitoring evolution of stress in individual grains and twins in a magnesium alloy aggregate
Crystallographic twinning is a strain accommodation mechanism extensively observed in low-symmetry crystals. In hexagonal metals (HCP), twinning transformation results in abrupt crystallographic reorientation of grain domains, and strongly affects the mechanical response, texture evolution, plastic formability and internal stress evolution. Recent fundamental advances in constitutive descriptions ofHCP's indicate the need for a basic characterization oftwinning mechanisms. Here we use the emerging technique of 3DXRD [9-12], for the first time, to in-situ monitor the twin nucleation and growth in individual grains inside the bulk of a magnesium alloy aggregate. At the same time, we accomplish the first direct measurement of the evolving triaxial stress states in both the parent grain and its twin. We show that the stress state of the twin is radically different from that of the parent and interpret the three-dimensional response in the light of the constraints placed on the parent and the twin by the surrounding polycrystalline medium.
Clausen, Bjorn [Los Alamos National Laboratory; Aydiner, Cahit C [Los Alamos National Laboratory; Tome, Carlos N [Los Alamos National Laboratory; Brown, Donald W [Los Alamos National Laboratory; Bernier, Joel V [LLNL; Lienert, Ulrich [ANL
Punchless Drawing of Magnesium Alloy Sheet under Cold Condition and its Computation
The punchless drawing with Maslennikov's technique was applied to the circular cup drawing of magnesium alloy AZ31B sheet under cold condition. The elastic rubber ring was used instead of the `hard' punch, where the compressed ring dragged the sheet inward the die cavity. Attainable circumferential strain of the blank was increased by this technique with repetitive drawing operation. Thickness of the rubber pad affected little the attainable strain. The shape appearance became better when a harder rubber was used. The cup forming by single drawing operation was also tested using a small die shoulder radius. The LDR of 1.250 was obtained with the straight cup wall. Further, the computation of the punchless drawing was also conducted for the single drawing operation. The computed deformation pattern was well consistent with the corresponding experimental result.
Yamashita, Minoru; Hattori, Toshio; Sato, Joji
Constitutive acoustic-emission elastic-stress behavior of magnesium alloy
Repeated laoding and unloading of a magnesium alloy below the macroscopic yield stress result in continuous acoustic emissions which are generally repeatable for a given specimen and which are reproducible between different specimens having the same load history. An acoustic emission Bauschinger strain model is proposed to describe the unloading emission behavior. For the limited range of stress examined, loading and unloading stress delays of the order of 50 MN/sq m are observed, and they appear to be dependent upon the direction of loading, the stress rate, and the stress history. The stress delay is hypothesized to be the manifestation of an effective friction stress. The existence of acoustic emission elastic stress constitutive relations is concluded, which provides support for a previously proposed concept for the monitoring of elastic stresses by acoustic emission.
Williams, J. H., Jr.; Emerson, G. P.
Evolution of stress in individual grains and twins in a magnesium alloy aggregate.
This is an in situ measurement of the full stress tensor and its evolution in a growing deformation twin and, simultaneously, in the grain where the twin forms. The combined information provides a detailed picture of the grain-twin interaction. The three-dimensional x-ray diffraction method using 80.7 keV synchrotron x rays allows us to in situ investigate a grain within the bulk of a magnesium alloy (AZ31) sample that is compressed to activate the {l_brace}10{bar 1}2{r_brace} <{bar 1}011> tensile twin system. We observe that the stress state of the twin is drastically different from the one of the grain in which it is embedded. We analyze such result in terms of the shear transformation associated with twinning and the dimensional constraints imposed by the surrounding aggregate.
Aydiner, C. C.; Bernier, J. V.; Clausen, B.; Lienert, U.; Tome, C. N.; Brown, D. W.; X-Ray Science Division; LANL; LLNL
Statistical analysis on static recrystallization texture evolution in cold-rolled AZ31 magnesium alloy sheet.
Cast AZ31B-H24 magnesium alloy, comprising Mg with 3.27 wt% Al and 0.96 wt% Zn, was cold rolled and subsequently annealed. Global texture evolutions in the specimens were observed by X-ray diffractometry after the thermomechanical processing. Image-based microstructure and texture for the deformed, recrystallized, and grown grains were observed by electron backscattered diffractometry. Recrystallized grains could be distinguished from deformed ones by analyzing grain orientation spread. Split basal texture of ca. ±10-15° in the rolling direction was observed in the cold-rolled sample. Recrystallized grains had widely spread basal poles at nucleation stage; strong {0001} basal texture developed with grain growth during annealing. PMID:23920167
Park, Jun-Ho; Ahn, Tae-Hong; Choi, Hyun-Sik; Chung, Jung-Man; Kim, Dong-Ik; Oh, Kyu Hwan; Han, Heung Nam
Influence of edge effects on local corrosion rate of magnesium alloy/mild steel galvanic couple.
The effect of the insulator-mixed-material edge on the galvanic corrosion rate of magnesium alloy (AE44)-mild steel (MS) couple is experimentally studied using scanning vibrating electrode technique (SVET), profilometry, and classical electrochemistry. The local and average corrosion rates estimated from the experimental depth of anodic attack profile of AE44-MS couple are validated by 2D and 3D corrosion numerical models. Our study demonstrates experimentally and theoretically that the presence of the insulator edge increases the local current density, which enhances the corrosion rate. The extent of the local corrosion rate enhancement and its effect on the overall corrosion rate of the mixed material is discussed and depends on the mixed material's geometry and the edge type. PMID:23046096
Trinh, Dao; Dauphin Ducharme, Philippe; Mengesha Tefashe, Ushula; Kish, Joseph R; Mauzeroll, Janine
Wear resistance of AZ91D magnesium alloy processed by improved laser surface remelting
We investigate the effects of laser surface remelting on the wear resistance of the AZ91D magnesium alloy. A CO2 continuous laser was used to treat the samples. The sample surface was strengthened by laser-treated area in the shape of stripes. The wear resistance was improved by marked microstructural characteristics, due to the notable effect of laser treatment, such as the grain refinement and very small sized ?-Mg17Al12 dendrite. The microhardness was increased up to 130 HV. And the wear volume loss was reduced by ~70%. The variations in some laser parameters, the output power and the laser scanning speed, also influenced the microstructure and related wear resistance.
Zhang, Zhihui; Lin, Pengyu; Ren, Luquan
Mechanism and Microstructure of Oxide Fluxes for Gas Tungsten Arc Welding of Magnesium Alloy
Five single oxide fluxes—MgO, CaO, TiO2, MnO2, and Cr2O3—were used to investigate the effect of active flux on the depth/width ratio in AZ31B magnesium alloy. The microstructure and mechanical property of the tungsten inert gas (TIG) welding seam were studied. The oxygen content in the weld seam and the arc images during the TIG welding process were analyzed. A series of emission spectroscopy of weld arc for TIG welding for magnesium with and without flux were developed. The results showed that for the five single oxide fluxes, all can increase the weld penetration effectively and grain size in the weld seam of alternating current tungsten inert gas (ACTIG) welding of the Mg alloy. The oxygen content of the welds made without flux is not very different from those produced with oxide fluxes not considering trapped oxide. However, welds that have the best penetration have a relatively higher oxygen content among those produced with flux. It was found that the arc images with the oxide fluxes were only the enlarged form of the arc images without flux; the arc constriction was not observed. The detection of arc spectroscopy showed that the metal elements in the oxides exist as the neutral atom or the first cation in the weld arc. This finding would influence the arc properties. When TIG simulation was carried out on a plate with flux applied only on one side, the arc image video showed an asymmetric arc, which deviated toward the flux free side. The thermal stability, the dissociation energy, and the electrical conductivity of oxide should be considered when studying the mechanism for increased TIG flux weld penetration.
Liu, L. M.; Zhang, Z. D.; Song, G.; Wang, L.
Laser Keyhole Welding of Dissimilar Ti-6Al-4V Titanium Alloy to AZ31B Magnesium Alloy
Laser keyhole welding of Ti-6Al-4V titanium alloy to AZ31B magnesium alloy was developed, and the correlations of process parameters, joint properties, and bonding mechanism were studied. The results show that the offset from the laser beam center on AZ31B side to the edge of the weld seam plays a big role in the joint properties by changing the power density irradiated at the Ti-Mg initial interface. The optimal range of the offset is 0.3 to 0.4mm in the present study. Some lamellar and granular Ti-rich mixtures are observed in the fusion zone, which is formed by intermixing melted Ti-6Al-4V with liquid AZ31B. The maximum ultimate tensile strength of the joints reaches 266 MPa. Furthermore, the fracture surface consists of scraggly remaining weld metal and smooth Ti surface. The higher the failure strength, the smaller the proportion of smooth Ti surface to whole interface is. Finally, the bonding mechanism of the interfacial layer is summarized by the morphologies and test results of fracture surfaces.
Gao, M.; Wang, Z. M.; Li, X. Y.; Zeng, X. Y.
Corrosion protection and improved cytocompatibility of biodegradable polymeric layer-by-layer coatings on AZ31 magnesium alloys.
Composite coatings of electrostatically assembled layer-by-layer anionic and cationic polymers combined with an Mg(OH)2 surface treatment serve to provide a protective coating on AZ31 magnesium alloy substrates. These ceramic conversion coating and layer-by-layer polymeric coating combinations reduced the initial and long-term corrosion progression of the AZ31 alloy. X-ray diffraction and Fourier transform infrared spectroscopy confirmed the successful application of coatings. Potentiostatic polarization tests indicate improved initial corrosion resistance. Hydrogen evolution measurements over a 2 week period and magnesium ion levels over a 1 week period indicate longer range corrosion protection and retention of the Mg(OH)2 passivation layer in comparison to the uncoated substrates. Live/dead staining and DNA quantification were used as measures of biocompatibility and proliferation while actin staining and scanning electron microscopy were used to observe the cellular morphology and integration with the coated substrates. The coatings simultaneously provided improved biocompatibility, cellular adhesion and proliferation in comparison to the uncoated alloy surface utilizing both murine pre-osteoblast MC3T3 cells and human mesenchymal stem cells. The implementation of such coatings on magnesium alloy implants could serve to improve the corrosion resistance and cellular integration of these implants with the native tissue while delivering vital drugs or biological elements to the site of implantation. PMID:23684762
Ostrowski, Nicole; Lee, Boeun; Enick, Nathan; Carlson, Benjamin; Kunjukunju, Sangeetha; Roy, Abhijit; Kumta, Prashant N
High corrosion resistance of electroless NiP with chromium-free conversion pre-treatments on AZ91D magnesium alloy
Phosphate-manganese, tannic acid and vanadium conversion coatings were proposed as an effective pre-treatment layer between electroless Ni-P coating and AZ91D magnesium alloy substrate to replace the traditional chromate plus HF pre-treatment. The electrochemical results show that the chrome-free coatings plus electroless Ni-P coating on the magnesium alloy has the lowest corrosion current density and most positive corrosion potential compared with
J. SUDAGAR; Jian-she LIAN; Xiao-min CHEN; Peng LANG; Ya-qin LIANG
Effect of magnesium on the lead induced corrosion and SCC of alloy 800 in neutral crevice solution at high temperature
Dissolved magnesium species in the feed water reduce the incidence of lead-induced stress corrosion cracking (PbSCC) of Alloy 800. The passivity of material was improved by replacing a part of chlorides in the lead-contaminated chemistry with magnesium chloride, as indicated by: (1) a higher pitting potential; (2) lower passive current densities; (3) a film structure with less defects and more spinel oxides. According to the constant extension rate tensile (CERT) tests conducted in the neutral crevice solutions at 300 °C, lead contamination would reduce the ultimate tensile strength (UTS) and elongation of material. The CERT test results were in agreement with the fracture morphology observations. Magnesium addition significantly reduced the detrimental effect of lead contamination.
Palani, A.; Lu, B. T.; Tian, L. P.; Luo, J. L.; Lu, Y. C.
Transient Heat and Material Flow Modeling of Friction Stir Processing of Magnesium Alloy using Threaded Tool
A three-dimensional transient computational fluid dynamics (CFD) model was developed to investigate the material flow and heat transfer during friction stir processing (FSP) in an AZ31B magnesium alloy. The material was assumed to be a non-Newtonian viscoplastic fluid, and the Zener-Hollomon parameter was used to describe the dependence of material viscosity on temperature and strain rate. The material constants used in the constitutive equation were determined experimentally from compression tests of the AZ31B Mg alloy under a wide range of strain rates and temperatures. A dynamic mesh method, combining both Lagrangian and Eulerian formulations, was used to capture the material flow induced by the movement of the threaded tool pin. Massless inert particles were embedded in the simulation domain to track the detailed history of material flow. The actual FSP was also carried out on a wrought Mg plate where temperature profiles were recorded by embedding thermocouples. The predicted transient temperature history was found to be consistent with that measured during FSP. Finally, the influence of the thread on the simulated results of thermal history and material flow was studied by comparing two models: one with threaded pin and the other with smooth pin surface.
Yu, Zhenzhen; Zhang, Wei; Choo, Hahn; Feng, Zhili
PHB, crystalline and amorphous magnesium alloys: promising candidates for bioresorbable osteosynthesis implants?
In this study various biodegradable materials were tested for their suitability for use in osteosynthesis implants, in particular as elastically stable intramedullary nails for fracture treatment in paediatric orthopaedics. The materials investigated comprise polyhydroxybutyrate (PHB), which belongs to the polyester family and is produced by microorganisms, with additions of ZrO2 and a bone graft substitute; two crystalline magnesium alloys with significantly different degradation rates ZX50 (MgZnCa, fast) and WZ21 (MgYZnCa, slow); and MgZnCa bulk metallic glasses (BMG). Push-out tests were conducted after various implantation times in rat femur meta-diaphysis to evaluate the shear forces between the implant material and the bone. The most promising materials are WZ21 and BMG, which exhibit high shear forces and push-out energies. The degradation rate of ZX50 is too fast and thus the alloy does not maintain its mechanical stability long enough during the fracture-healing period. PHB exhibits insufficient mechanical properties: it degrades very slowly and the respective low shear forces and push-out energy levels are unsatisfactory. PMID:24364952
Celarek, Anna; Kraus, Tanja; Tschegg, Elmar K; Fischerauer, Stefan F; Stanzl-Tschegg, Stefanie; Uggowitzer, Peter J; Weinberg, Annelie M
Surface composite nanostructures of AZ91 magnesium alloy induced by high current pulsed electron beam treatment
High current pulsed electron beam (HCPEB) treatment was conducted on an AZ91 cast magnesium alloy with accelerating voltage 27 kV, energy density 3 J/cm2 and pulse duration 2.5 ?s. The surface microstructure was characterized by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS), and transmission electron microscope (TEM). The surface corrosion property was tested with electrochemical method in 3.5 wt.% NaCl solution. It is found that after 1 pulse of HCPEB treatment, the initial eutectic ? phase and Mg17Al12 particles started to dissolve in the surface modified layer of depth ?15 ?m. When using 15 HCPEB pulses, the Al content in surface layer increased noticeably, and the phase structure was modified as composite nanostructures consisted of nano-grained Mg3.1Al0.9 domains surrounded by network of Mg17Al12 phase. The HCPEB treated samples showed an improved corrosion resistance with cathodic current density decreased by two orders of magnitude as compared to the initial AZ91 alloy.
Li, M. C.; Hao, S. Z.; Wen, H.; Huang, R. F.
Microstructure and Fatigue Properties of a Friction Stir Lap Welded Magnesium Alloy
Friction stir welding (FSW), being an enabling solid-state joining technology, can be suitably applied for the assembly of lightweight magnesium (Mg) alloys. In this investigation, friction stir lap welded (FSLWed) joints of AZ31B-H24 Mg alloy were characterized in terms of the welding defects, microstructure, hardness, and fatigue properties at various combinations of tool rotational rates and welding speeds. It was observed that the hardness decreased from the base metal (BM) to the stir zone (SZ) across the heat-affected zone (HAZ) and thermomechanically affected zone (TMAZ). The lowest value of hardness appeared in the SZ. With increasing tool rotational rate or decreasing welding speed, the average hardness in the SZ decreased owing to increasing grain size, and a Hall-Petch-type relationship was established. Fatigue fracture of the lap welds always occurred at the interface between the SZ and TMAZ on the advancing side where a larger hooking defect was present (in comparison with the retreating side). The welding parameters had a significant influence on the hook height and the subsequent fatigue life. A relatively "cold" weld, conducted at a rotational rate of 1000 rpm and welding speed of 20 mm/s, gave rise to almost complete elimination of the hooking defect, thus considerably (over two orders of magnitude) improving the fatigue life. Fatigue crack propagation was basically characterized by the formation of fatigue striations concomitantly with secondary cracks.
Naik, B. S.; Chen, D. L.; Cao, X.; Wanjara, P.
ZM-21 magnesium alloy corrosion properties and cryogenic to elevated temperature mechanical properties
The mechanical properties of bare ZM-21 magnesium alloy flat tensile specimens were determined for test temperatures of +400 F, +300 F, +200 F, +80 F, 0 F, -100 F, -200 F, and -320 F. The ultimate tensile and yield strengths of the material increased with decreasing temperature with a corresponding reduction in elongation values. Stress corrosion tests performed under: (1) MSFC atmospheric conditions; (2) 95% relative humidity; and (3) submerged in 100 ppm chloride solution for 8 weeks indicated that the alloy is not susceptible to stress corrosion. The corrosion tests indicated that the material is susceptible to attack by crevice corrosion in high humidity and chemical type attack by chloride solution. Atmospheric conditions at MSFC did not produce any adverse effects on the material, probably due to the rapid formation of a protective oxide coating. In both the mechanical properties and the stress corrosion evaluations the test specimens which were cut transverse to the rolling direction had superior properties when compared to the longitudinal properties.
Montana, J. W.; Nelson, E. E.
Atomistic analysis of short range interaction and local chemical order in LPSO structures of Magnesium alloys
Magnesium alloys have been object of interest as lightweight material with high strength weight ratio. In particular Long Period Stacking Ordered (LPSO) structure phases show to have a strong influence in enhancing mechanical properties of such kind alloys. However the chemical order of the interacting atomic species in the Mg lattice has not been fully understood. We perform first principles Density Functional Theory (DFT) calculation to compute formation energies as well as interaction energies of the doping atoms in both Faced Centered Cubic (FCC) and Hexagonal Close Packed (HCP) Mg lattices. In particular we consider the Mg-Al-Gd and Mg-Zn-Y ternary systems. We also calculate activation energies for vacancy assisted doping atoms diffusion in order to perform a further analysis of the kinetics of the process. In order to describe short range interaction and cluster formation in the Mg matrix, we build an on lattice potential based on first principles DFT interaction energies. By means of these inter-atomic potentials, we perform Monte Carlo simulations to analyze the chemical order occurring in LPSO Mg-Al-Gd structures.
Fronzi, Marco; Kimizuka, Hajime; Matsubara, Kazuki; Ogata, Shigenobu
Corrosion behaviour of magnesium alloys coated with TiN by cathodic arc deposition in NaCl and Na{sub 2}SO{sub 4} solutions
Magnesium-based light-metal alloys belong to a class of structural materials with increasing industrial attention. Magnesium alloys show the lowest density among the engineering metallic materials, low cost and large availability. However, the limitations according to mechanical strength and the low corrosion resistance restrict their practical application. In this study, TiN was coated on magnesium-based AZ91 magnesium-aluminium-zinc alloy using cathodic arc PVD process. The corrosion behaviours of uncoated and coated magnesium alloys in 1% NaCl, 3% NaCl and 3% Na{sub 2}SO{sub 4} solutions and the influence of the coatings on the corrosion behaviour of the substrate were investigated utilizing potentiodynamic polarization tests. A potentiostat for electrochemical corrosion tests, a cathodic arc physical vapour deposition coating system for coating processes, a scanning electron microscopy for surface examination and elemental analysis of the coatings were used in this study. It was determined that corrosion resistance of magnesium alloys can be increased with TiN coating on the alloys using cathodic arc PVD process.
Altun, Hikmet [Department of Mechanical Engineering, Ataturk University, 25240, Erzurum (Turkey)], E-mail: email@example.com; Sinici, Hakan [Department of Mechanical Engineering, Ataturk University, 25240, Erzurum (Turkey)
An A Priori Hot-Tearing Indicator Applied to Die-Cast Magnesium-Rare Earth Alloys
Hot-tearing susceptibility is an important consideration for alloy design. Based on a review of previous research, an a priori indicator for the prediction of an alloy's hot-tearing susceptibility is proposed in this article and is applied to a range of magnesium-rare earth (RE)-based alloys. The indicator involves taking the integral over the solid fraction/temperature curve between the temperature when feeding becomes restricted (coherency) and that when a three-dimension network of solid is formed (coalescence). The hot-tearing propensity of Mg-RE alloys is found to vary greatly depending on which RE is primarily used, due to the difference in the solidification range. Mg-Nd alloys are the most susceptible to hot tearing, followed by Mg-Ce-based alloys, while Mg-La alloys show almost no hot tearing. The proposed indicator can be well applied to hot-tearing propensity of the Mg-RE alloys. It is expected that the indicator could be used as an estimation of the relative hot-tearing propensity in other alloy systems as well.
Easton, Mark A.; Gibson, Mark A.; Zhu, Suming; Abbott, Trevor B.
On the influence of process variables on the thermal conditions and properties of high pressure die-cast magnesium alloys
The influence of pressure and velocity in high-pressure magnesium die casting on the thermal conditions and on the casting properties is studied. Specimens with the shape of a tensile test plate with a thickness of 12 mm and a length of 295 mm were cast using the alloys AM20HP, AM50HP, AS41, AE42, AZ91HP. Two gate velocities of the liquid metal
Nahed A. El-Mahallawy; Mohamed A Taha; Engenius Pokora; Friedrich Klein
Application of Flat-Clad Optical Fiber Bragg Grating Sensor in Characterization of Asymmetric Fatigue Deformation of Extruded Magnesium Alloy
We report the application of a novel flat-cladding optical fiber Bragg grating sensor array in the characterization of low cycle fatigue deformation behavior of an extruded AZ31 magnesium alloy. The results obtained from optical fiber sensors showed strong asymmetry of stress-strain hysteresis loops, espe- cially at high strain amplitudes, due to the occurrence of twinning in compression and detwinning in
Xijia Gu; Cheng Li; Aihan Feng; Daolun Chen
Electrochemical formation of Mg–Li alloys at solid magnesium electrode from LiCl–KCl melts
This work presents a study on electrochemical formation of Mg–Li alloys on solid magnesium electrode in a molten LiCl–KCl (50:50, wt.%) system at 753K. Cyclic voltammetry and open circuit chronopotentiometry were employed to investigate the electrode reaction. For an Mg electrode, the electroreduction of Li(I) takes place at more positive potential values than at the inert W electrode indicating the
Yong De Yan; Mi Lin Zhang; Wei Han; Dian Xue Cao; Yi Yuan; Yun Xue; Zeng Chen
Initial corrosion behavior of AZ91 magnesium alloy in simulating acid rain under wet-dry cyclic condition
Corrosion behavior of AZ91 magnesium alloy in simulating acid rain under wet-dry cyclic condition was investigated. The results show that corrosion potential shifts positively and the corrosion current density decreases at low wet-dry cyclic time. Further increase of the cyclic time results in the negative movement of corrosion potential and the increase of current density. SEM observation indicates that corrosion
Wan-qiu ZHOU; Da-yong SHAN; En-hou HAN; Wei KE
Bonding of Mg and Al with Mg–Al eutectic alloy and its application in aluminum coating on magnesium
Magnesium and aluminum were bonded successfully by using Mg–Al eutectic alloy as the solder under different pressures at 450°C in atmosphere. The microstructures of the Mg\\/Al joints were characterized by SEM, the composition analyzed by EDS, and their bond strengths measured by the bend test. The results show that the bond strength of these Mg\\/Al joints is improved with increasing
Xianrong Li; Wei Liang; Xingguo Zhao; Yan Zhang; Xiaopeng Fu; Fencheng Liu
A chrome-free conversion coating for magnesium–lithium alloy by a phosphate–permanganate solution
A chrome-free conversion coating on magnesium–lithium alloy was obtained from a phosphate–permanganate solution. The morphology, the composition and the corrosion resistance of this coating were examined. The thin and non-penetrating cracked morphology with some deposits existed on the phosphate–permanganate conversion coating. The main elements of the conversion coating were Mg, O, K, P and Mn. The results of the electrochemical
Hua Zhang; Guangchun Yao; Shulan Wang; Yihan Liu; Hongjie Luo
Optimization of Processing Parameters During Laser Cladding of ZE41AT5 Magnesium Alloy Castings Using Taguchi Method
A continuous wave 4 kW Nd:YAG laser welding system was employed to clad single beads on machined 6.2-mm thick ZE41A-T5 aerospace magnesium alloy sand castings using nominal 1.6-mm filler rods of the parent metal. Based on the quality criterion of minimum dilution ratio, the Taguchi experimental method was used to optimize different process parameters and to identify the dominating factors. It
X. Cao; M. Xiao; M. Jahazi; J. Fournier; M. Alain
Effects of dust and salt particles on the formation and spreading of micro-droplets on AZ91 magnesium alloy
The effects of dust and salt particles on the formation and spreading of micro-droplets on as-cast AZ91 magnesium alloy in an atmosphere of water vapor were investigated using an environmental scanning electron microscope (ESEM). The in situ observations results indicated that both dust particle and AlMn phase stimulated the formation and spreading of micro-droplets, but had few influences on the
Jian Chen; Jianqiu Wang; Enhou Han; Wei Ke
Influence of chloride ion concentration on the electrochemical corrosion behaviour of plasma electrolytic oxidation coated AM50 magnesium alloy
The electrochemical degradation of a silicate- and a phosphate-based plasma electrolytic oxidation (PEO) coated AM50 magnesium alloy obtained using a pulsed DC power supply was investigated using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) in NaCl solutions of different chloride ion concentrations viz., 0.01M, 0.1M, 0.5M and 1M. The surface of the PEO coated specimens after 50h of immersion\\/EIS testing
J. Liang; P. Bala Srinivasan; C. Blawert; W. Dietzel
Effect of electrolyte additives on performance of plasma electrolytic oxidation films formed on magnesium alloy AZ91D
Various plasma electrolytic oxidation (PEO) films were prepared on magnesium alloy AZ91D in a silicate bath with different additives such as phosphate, fluoride and borate. Effects of the additives on chemical composition and corrosion resistance of the PEO films were examined by means of scanning electron microscopy (SEM), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The
Influence of shot peening on notched fatigue strength of the high-strength wrought magnesium alloy AZ80
Influence of shot peening (SP) on notched fatigue strength of the high-strength wrought magnesium alloy AZ80 has been investigated by using different SP media (including glass, Zirblast B30 and Ce–ZrO2 (ZrO2 stabilized by Ce) shots) and various Almen intensities. The results showed that shot peening improved the notched fatigue strength of AZ80 more effectively than the un-notched fatigue strength. The
P. Zhang; J. Lindemann; C. Leyens
Microstructure characterization and micro- and nanoscale mechanical behaviour of magnesium-aluminum and magnesium-aluminum-calcium alloys
The application in the automotive industry of the as-cast AM50 alloy (Mg-5.0 wt.%%Al-0.3 wt.%Mn) has been limited by its low creep resistance at elevated temperatures. Permanent mold cast (PM) Mg-Al-Ca alloys with calcium additions (0 ˜ 2.0 wt.%) were investigated in this study due to their potential for improving the high temperature creep strength. The microstructures of the die cast (DC) or PM AM50 alloys consisted of an intergranular beta-Mg17Al12 phase surrounded by a region of Al-rich eutectic alpha-Mg phase, sometimes with attached Al8Mn5 particles. In this study, significant grain refinement was observed in the PM Mg-Al-Ca alloys with Ca addition to the AM50 alloy. The grain refining effect was confirmed by quantitative image analysis through measurement of the secondary dendrite arm spacing (SDAS). The intergranular phases in Mg-Al-Ca alloys with 0.5 or 1.0 wt.% Ca were beta-Mg17Al 12 and (Al, Mg)2Ca phases. As the Ca addition was increased to 1.5 wt.% Ca, the (beta-Mg17Al12 phase was completely replaced by a (Al, Mg)2Ca phase. Differential scanning calorimetry (DSC) results showed that the (Al, Mg)2Ca phase was thermally more stable than the beta-Mg 17Al12 phase, which contributed to the better creep strength of the Mg-Al-Ca alloys. The change in heating/cooling rates played an important role in the redistribution of alloying elements and the dissolution or precipitation of the eutectic phases in the as-cast Mg alloys during DSC runs. The micro- and nano-scale hardness and composite modulus of the PM Mg-Al-Ca alloys increased with increasing Ca content, and the indentation size effect (ISE) was also observed in the as-cast Mg-Al and Mg-Al-Ca alloys. PM AC52 alloy (Mg-5.0wt.%Al-2.0wt.%Ca) was a much more creep resistant alloy than other Mg-Al-Ca alloys with lower Ca contents because of the higher solute content in the primary alpha-Mg in the as-cast state and also because of the presence of nano precipitates within the primary alpha-Mg. The size and volume fraction of the precipitates and the solute content within the primary alpha-Mg of the AC52 alloys were related to the different solidification rates, which directly influence the nano indentation creep strength of the alloys.
Han, Lihong
Characterization of ceramic PVD thin films on AZ31 magnesium alloys
Ceramic thin films have been widely used to protect the metal substrate as coatings in the past years. In order to improve the poor corrosion resistance of AZ31 magnesium alloy, the study in this paper used the electron beam evaporation method to prepare ceramic PVD films on its surface with TiO 2 and Al 2O 3 as donors, respectively. Atomic force microscopy (AFM), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) were used to investigate the surface morphology, composition and microstructure of the thin films. Both films deposited on AZ31 took on compact top surface morphologies and grew as amorphous structures on substrate. AES test not only showed that films compositions deviated the standard stoichiometric ratios, but also found that element Mg diffused into films and existed as magnesium oxide in the TiO x film as well as the AlO x film. In the electrochemical corrosion test, the AlO x coating on AZ31 exhibited the largest electrochemical impedance in a 3.5% NaCl solution. But it did not show better corrosion resistance than others for the poorer adhesion. Even if its thickness was small, the TiO x coating on AZ31 exhibited the best corrosion resistance in this study. According to the observation and analysis, the damage of these films on AZ31 in aggressive solutions was mainly due to the existence of pores, microcracks, vacancies and poor adhesion between coating and substrate.
Wu, Guosong; Zeng, Xiaoqin; Ding, Wenbin; Guo, Xingwu; Yao, Shoushan
Magnesium Rich Primer for Chrome Free Protection of Aluminum Alloys (Preprint).
Hexavalent chromium compounds used for corrosion protection are one of the top hazardous waste materials generated by the U.S. Air Force and legislation is in effect to further restrict their use. Magnesium rich primers that utilize sacrificial magnesium ...
J. A. Johnson
Surface composition, microstructure and corrosion resistance of AZ31 magnesium alloy irradiated by high-intensity pulsed ion beam
High-intensity pulsed ion beam (HIPIB) irradiation of AZ31 magnesium alloy is performed and electrochemical corrosion experiment of irradiated samples is carried out by using potentiodynamic polarization technology in order to explore the effect of HIPIB irradiation on corrosion resistance of magnesium alloy. The surface composition, cross-sectional morphology and microstructure are characterized by using electron probe microanalyzer, optical microscope and transmission electron microscope, respectively. The results indicated that HIPIB irradiation leads to a significant improvement in corrosion resistance of magnesium alloy, in terms of the considerable increase in both corrosion potential and pitting breakdown potential. The microstructural refinement and surface purification induced by HIPIB irradiation are responsible for the improved corrosion resistance. - Research Highlights: {yields} A modified layer about 30 {mu}m thick is obtained by HIPIB irradiation. {yields} Selective ablation of element/impurity phase having lower melting point is observed. {yields} More importantly, microstructural refinement occurred on the irradiated surface. {yields} The modified layer exhibited a significantly improved corrosion resistance. {yields} Improved corrosion resistance is ascribed to the combined effect induced by HIPIB.
Li, P., E-mail: email@example.com [Department of Physics and Information Engineering, Shangqiu Normal University, Shangqiu 476000 (China); Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Lei, M.K., E-mail: firstname.lastname@example.com [Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Zhu, X.P. [Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China)
Electrochemical characteristics of calcium-phosphatized AZ31 magnesium alloy in 0.9 % NaCl solution.
Magnesium alloys suffer from their high reactivity in common environments. Protective layers are widely created on the surface of magnesium alloys to improve their corrosion resistance. This article evaluates the influence of a calcium-phosphate layer on the electrochemical characteristics of AZ31 magnesium alloy in 0.9 % NaCl solution. The calcium phosphate (CaP) layer was electrochemically deposited in a solution containing 0.1 M Ca(NO3)2, 0.06 M NH4H2PO4 and 10 ml l(-1) of H2O2. The formed surface layer was composed mainly of brushite [(dicalcium phosphate dihidrate (DCPD)] as proved by energy-dispersive X-ray analysis. The surface morphology was observed by scanning electron microscopy. Immersion test was performed in order to observe degradation of the calcium phosphatized surfaces. The influence of the phosphate layer on the electrochemical characteristics of AZ31, in 0.9 % NaCl solution, was evaluated by potentiodynamic measurements and electrochemical impedance spectroscopy. The obtained results were analysed by the Tafel-extrapolation method and equivalent circuits method. The results showed that the polarization resistance of the DCPD-coated surface is about 25 times higher than that of non-coated surface. The CaP electro-deposition process increased the activation energy of corrosion process. PMID:24477876
Hadzima, Branislav; Mhaede, Mansour; Pastorek, Filip
Fabrication of nanocrystalline aluminum-magnesium alloy powders by electrodeposition and their characterization
Aluminum-magnesium alloy powders can potentially be used as hydrogen storage materials. In order to enhance the kinetics of hydrogenation it is desirable to have agglomerates of fine powders with very small grain size. In this study, nanocrystalline Al-Mg alloys in the form of powders were successfully fabricated by the electrodeposition technique using an organometallic based electrolyte. Mg was introduced into the electrolyte by a process called "pre-electrodeposition". The mechanism for Mg accumulation can be explained considering the electrode reactions as well as the chemical changes in the electrolyte. Using a copper cathode, the effects of the electrolyte composition and current density on composition of the deposit, its constituent phases and morphology were investigated. The magnesium content of the deposits improved with increasing Mg concentration in the electrolyte, temperature and current density. Depending on the composition, the deposits consisted of FCC-Al(Mg) and HCP-Mg(Al) phases and no intermetallic phase was found except for long deposition times. Generally, the deposits formed initially on the copper substrate with three dendritic morphologies namely, rod-like, feather-like and small globular, which eventually evolved into the large globular morphology. This observation is attributed to the establishment of spherical diffusion conditions at the sharp dendrite tips. Potentiostatic studies suggested that the appearance of different morphologies is associated with differing rates of deposition. While the initial dendrites consisted of the FCC Al-rich phase, the large globular morphology manifested as both FCC Al-rich and HCP Mg-rich phases, with the latter always forming over the former. The observation of formation of only the FCC phase implies that the nucleation barrier for the HCP phase on the copper substrate is quite high. The investigation of the effect of substrate, namely, Cu, graphite and Mg, revealed that the HCP phase can directly nucleate on an oxide-free Mg surface. This finding can be explained in terms of surface/interfacial energies. Detailed TEM analysis revealed that the observed morphologies consist of randomly distributed nanocrystalline grains except for the feather-like dendrites, which exhibited a strong crystallographic texture.
Tatiparti, Sankara Sarma V.
Formation and stability of organic acid monolayers on magnesium alloy AZ31: The role of alkyl chain length and head group chemistry
Magnesium wrought alloy AZ31 has a 30% lower density than aluminum alloys and provides the opportunity to reduce vehicle weight and hence to reduce fuel consumption. Today, the use in industrial applications is limited due to low corrosion resistance. Carboxylic and phosphonic acids were investigated as promising alternatives for corrosion protection on AZ31 magnesium wrought alloy. Adsorption and orientation of organic monolayers were studied as a function of aliphatic chain lengths and head groups. As final result, the octadecylphosphonic acid led to a measureable lowering of the corrosion current density and inhibited the growth of the oxide film under humid conditions.
Szillies, S.; Thissen, P.; Tabatabai, D.; Feil, F.; Fürbeth, W.; Fink, N.; Grundmeier, G.
Infiltration and wetting of alumina particulate preforms by aluminum and aluminum-magnesium alloys
The infiltration and wetting of alumina particulates by Al and by Al-Mg alloys was studied through pressure infiltration experiments. In these experiments, a noninvasive capacitance technique was used to determine the infiltration front position as a function of time. An unsaturated slug flow model was used to interpret the infiltration results and determine capillary pressures characteristic of the infiltration process. The characteristic capillary pressures for Al, Al-2Mg, and Al-3Mg at 750 C and Al-2Mg at 850 C were not significantly different. Therefore, contrary to usual belief, Mg did not significantly aid the pressure infiltration process. At 750 C, the maximum values of the contact angle calculated from these capillary pressure were 106 deg for Al and 105 deg for Al-2Mg and Al-3Mg. These contact angle values indicate substantial removal of the oxide layer on the surface of the liquid metal during the infiltration process. The small difference in the contact angles indicates that magnesium had little effect on the wetting of alumina by aluminum. The small effect of Mg on the wetting may be due to absence of reactive wetting at the infiltration speeds present in the experiments and to partial disruption of the oxide layer on the surface of the liquid metal during the infiltration process.
Jonas, T.R. [American National Can Beverage Technical Center, Elk Grove Village, IL (United States); Cornie, J.A.; Russel, K.C. [Massachusetts Inst. of Tech., Cambridge, MA (United States)
The goal of this work is to understand the inter-relationship between the initial properties of continuous-cast magnesium alloy (AZ31B) sheets and their subsequent formability and post-formed mechanical performance for use in cost-effective, lightweight, automotive body panels. As-received sheets, provided by the Automotive Metals Division (AMD-602) team, were characterized by surface roughness measurements using mechanical profilometry. The arithmetic mean deviation of profile (Ra) and the maximum two-point height of profile (Ry) of the as-received sheets ranged from ~0.2-2 ?m and ~2-15 ?m, respectively. Several commercial lubricants were evaluated by thermal analysis and the liquid phase of the lubricants was found to evaporate/decompose upon heating leaving behind a solid residue upon heating to temperatures exceeding ~125-150°C. Elevated temperature bending-under-tension (BUT) friction tests were conducted at 350°C and the coefficient-of-friction values ranged from a minimum of ~0.1 (for tungsten disulfide lubricant) to ~0.7 when no lubricant was used. These results, in conjunction with those from the forming trials conducted by the AMD-602 team, will be eventually used to determine the role of sheet-die friction in determining the formability of AZ31B sheets.
Rohatgi, Aashish; Herling, Darrell R.; Nyberg, Eric A.
Microstructure and properties of duplex (Ti:N)-DLC/MAO coating on magnesium alloy
Ti and N co-doped diamond-like carbon ((Ti:N)-DLC) film was deposited on the MAO coated substrate using a hybrid beam deposition system, which consists of a DC magnetron sputtering of Ti target and a linear ion source (LIS) with C2H2 and N2 precursor gas. The microstructure and properties of the duplex (Ti:N)-DLC/MAO coating were investigated. Results indicate that the (Ti:N)-DLC top film with TiN crystalline phase was formed. Ti and N co-doping resulted in the increasing ID/IG ratio. The significant improvement in the wear and corrosion resistance of duplex (Ti:N)-DLC/MAO coating was mainly attributed to the increased binding strength, lubrication characteristics and chemical inertness of (Ti:N)-DLC top film. The superior low-friction and anti-corrosion properties of duplex (Ti:N)-DLC/MAO coating make it a good candidate as protective coating on magnesium alloy.
Yang, Wei; Ke, Peiling; Fang, Yong; Zheng, He; Wang, Aiying
Continuous Twin Screw Rheo-Extrusion of an AZ91D Magnesium Alloy
The twin screw rheo-extrusion (TSRE) is designed to take advantage of the nondendritc microstructure and thixotropic characterization of semisolid-metal slurries and produce simple metal profiles directly from melts. The extrusion equipment consists of a rotor-stator high shear slurry maker, a twin screw extruder, and a die assembly. The process is continuous and has a potential for significantly saving energy, manufacturing cost, and enhancing efficiency. The present investigation was carried out to study the process performance for processing rods of an AZ91D magnesium alloy and the microstructure evolution during processing. The semisolid slurry prepared by the process was characterized by uniformly distributed nondendritic granular primary phase particles. AZ91D rods with uniform and fine microstructures and moderate mechanical properties were produced. For the given slurry making parameters, decreasing extrusion temperature was found to improve microstructures and properties. The mechanisms of particle granulation and refinement and the effect of processing parameters on process performance and thermal management are discussed.
Xia, M.; Huang, Y.; Cassinath, Z.; Fan, Z.
Microstructure and mechanical properties of AZ91 magnesium alloy subject to deep cryogenic treatments
AZ91 magnesium alloy was subjected to a deep cryogenic treatment. X-ray diffraction (XRD), scanning electronic microscopy (SEM), and transmission electronic microscopy (TEM) methods were utilized to characterize the composition and microstructure of the treated samples. The results show that after two cryogenic treatments, the quantity of the precipitate hardening ? phase increases, and the sizes of the precipitates are refined from 8-10 ?m to 2-4 ?m. This is expected to be due to the decreased solubility of aluminum in the matrix at low temperature and the significant plastic deformation owing to internal differences in thermal contraction between phases and grains. The polycrystalline matrix is also noticeably refined, with the sizes of the subsequent nanocrystalline grains in the range of 50-100 nm. High density dislocations are observed to pile up at the grain boundaries, inducing the dynamic recrystallization of the microstructure, leading to the generation of a nanocrystalline grain structure. After two deep cryogenic treatments, the tensile strength and elongation are found to be substantially increased, rising from 243 MPa and 4.4% of as-cast state to 299 MPa and 5.1%.
Li, Gui-rong; Wang, Hong-ming; Cai, Yun; Zhao, Yu-tao; Wang, Jun-jie; Gill, Simon P. A.
Modelling the Thermo-Mechanical Behavior of Magnesium Alloys during Indirect Extrusion
One of the basic metal forming process for semi-finished products is extrusion. Since extrusion involves complex thermo-mechanical and multiaxial loading conditions resulting in large strains, high strain rates and an increase in temperature due to deformation, a proper yield criterion and hardening law should be used in the numerical modelling of the process. A phenomenological model based on a plastic potential has been proposed that takes strain, strain rate and temperature dependency on flow behaviour into consideration. A hybrid methodology of experiment and finite element simulation has been adopted in order to obtain necessary model parameters. The anisotropy/asymmetry in yielding was quantified by tensile and compression tests of specimens prepared from different directions. The identification of the corresponding model parameters was performed by a genetic algorithm. A fully coupled thermo-mechanical analysis has been used in extrusion simulations for calculation of the temperature field by considering heat fluxes and heat generated due to plastic deformation. The results of the approach adopted in this study appeared to be successful showing promising predictions of the experiments and thus may be extended to be applicable to other magnesium alloys or even other hcp metals.
Steglich, D. [GKSS Research Centre, Geesthacht (Germany); G.I.F.T., POSTECH, Pohang, Gyeongbuk (Korea, Republic of); Ertuerk, S.; Bohlen, J.; Letzig, D. [GKSS Research Centre, Geesthacht (Germany); Brocks, W. [Faculty of Engineering, Christian-Albrechts-University of Kiel (Germany)
Steglich, D.; Ertürk, S.; Bohlen, J.; Letzig, D.; Brocks, W.
Influence of circumferential notch and fatigue crack on the mechanical integrity of biodegradable magnesium-based alloy in simulated body fluid.
Applications of magnesium alloys as biodegradable orthopaedic implants are critically dependent on the mechanical integrity of the implant during service. In this study, the mechanical integrity of an AZ91 magnesium alloy was studied using a constant extension rate tensile (CERT) method. The samples in two different geometries that is, circumferentially notched (CN), and circumferentially notched and fatigue cracked (CNFC), were tested in air and in simulated body fluid (SBF). The test results show that the mechanical integrity of the AZ91 magnesium alloy decreased substantially (?50%) in both the CN and CNFC samples exposed to SBF. Fracture surface analysis revealed secondary cracks suggesting stress corrosion cracking susceptibility of the alloy in SBF. PMID:21210510
Bobby Kannan, M; Singh Raman, R K; Witte, F; Blawert, C; Dietzel, W
Biocorrosion and osteoconductivity of PCL/nHAp composite porous film-based coating of magnesium alloy
The present study was aimed at designing a novel porous hydroxyapatite/poly(?-caprolactone) (nHAp/PCL) hybrid nanocomposite matrix on a magnesium substrate with high and low porosity. The coated samples were prepared using a dip-coating technique in order to enhance the bioactivity and biocompatibility of the implant and to control the degradation rate of magnesium alloys. The mechanical and biocompatible properties of the coated and uncoated samples were investigated and an in vitro test for corrosion was conducted by electrochemical polarization and measurement of weight loss. The corrosion test results demonstrated that both the pristine PCL and nHAp/PCL composites showed good corrosion resistance in SBF. However, during the extended incubation time, the composite coatings exhibited more uniform and superior resistance to corrosion attack than pristine PCL, and were able to survive severe localized corrosion in physiological solution. Furthermore, the bioactivity of the composite film was determined by the rapid formation of uniform CaP nanoparticles on the sample surfaces during immersion in SBF. The mechanical integrity of the composite coatings displayed better performance (˜34% higher) than the uncoated samples. Finally, our results suggest that the nHAp incorporated with novel PCL composite membranes on magnesium substrates may serve as an excellent 3-D platform for cell attachment, proliferation, migration, and growth in bone tissue. This novel as-synthesized nHAp/PCL membrane on magnesium implants could be used as a potential material for orthopedic applications in the future.
Abdal-hay, Abdalla; Amna, Touseef; Lim, Jae Kyoo
Resistance-Spot-Welded AZ31 Magnesium Alloys: Part I. Dependence of Fusion Zone Microstructures on Second-Phase Particles
A comparison of microstructural features in resistance spot welds of two AZ31 magnesium (Mg) alloys, AZ31-SA (from supplier A) and AZ31-SB (from supplier B), with the same sheet thickness and welding conditions, was performed via optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). These alloys have similar chemical composition but different sizes of second-phase particles due to manufacturing process differences. Both columnar and equiaxed dendritic structures were observed in the weld fusion zones of these AZ31 SA and SB alloys. However, columnar dendritic grains were well developed and the width of the columnar dendritic zone (CDZ) was much larger in the SB alloy. In contrast, columnar grains were restricted within narrow strip regions, and equiaxed grains were promoted in the SA alloy. Microstructural examination showed that the as-received Mg alloys contained two sizes of Al8Mn5 second-phase particles. Submicron Al8Mn5 particles of 0.09 to 0.4 ?m in length occured in both SA and SB alloys; however, larger Al8Mn5 particles of 4 to 10 ?m in length were observed only in the SA alloy. The welding process did not have a great effect on the populations of Al8Mn5 particles in these AZ31 welds. The earlier columnar-equiaxed transition (CET) is believed to be related to the pre-existence of the coarse Al8Mn5 intermetallic phases in the SA alloy as an inoculant of ?-Mg heterogeneous nucleation. This was revealed by the presence of Al8Mn5 particles at the origin of some equiaxed dendrites. Finally, the columnar grains of the SB alloy, which did not contain coarse second-phase particles, were efficiently restrained and equiaxed grains were found to be promoted by adding 10 ?m-long Mn particles into the fusion zone during resistance spot welding (RSW).
Xiao, L.; Liu, L.; Zhou, Y.; Esmaeili, S.
Fatigue-Property Enhancements of Magnesium Alloy, AZ31B, through Equal-Channel-Angular Pressing (ECAP)
The fatigue behavior of magnesium-alloy, AZ31B, pre-strained by Equal-Channel-Angular Pressing (ECAP) was studied as a function of the accumulated plastic-strain level and the orientation of the samples (along and parallel to the ECAP pressing direction). The material was processed via route BC, at 200 oC, for 1, 2, and 8 passes, with and without a back-pressure applied on the billet during ECAP. The low-cycle fatigue behavior of the AZ31B alloy is shown to be anisotropic and texture-dependent. Due to the initial texture orientation, the specimens loaded parallel to the ECAP pressing direction have a longer fatigue life than the samples loaded perpendicular to it. The low-cycle fatigue life of the AZ31B alloy is enhanced by ECAP. The fatigue-property improvement is discussed in the light of the grain-size refinement, enhanced ductility, and texture evolution.
Wu, Liang [ORNL; Stoica, G. M. [University of Tennessee, Knoxville (UTK); Liao, Hao Hsiang [University of Tennessee, Knoxville (UTK); Agnew, Sean R [University of Virginia; Payzant, E Andrew [ORNL; Wang, Gongyao [ORNL; Fielden, Douglas [ORNL; Chen, Lijia [Shenyang University of Technology; Liaw, Peter K [University of Tennessee, Knoxville (UTK)
In-vitro characterization of stress corrosion cracking of aluminium-free magnesium alloys for temporary bio-implant applications.
The complex interaction between physiological stresses and corrosive human body fluid may cause premature failure of metallic biomaterials due to the phenomenon of stress corrosion cracking. In this study, the susceptibility to stress corrosion cracking of biodegradable and aluminium-free magnesium alloys ZX50, WZ21 and WE43 was investigated by slow strain rate tensile testing in a simulated human body fluid. Slow strain rate tensile testing results indicated that each alloy was susceptible to stress corrosion cracking, and this was confirmed by fractographic features of transgranular and/or intergranular cracking. However, the variation in alloy susceptibility to stress corrosion cracking is explained on the basis of their electrochemical and microstructural characteristics. PMID:25063163
Choudhary, Lokesh; Singh Raman, R K; Hofstetter, Joelle; Uggowitzer, Peter J
Evaluating the improvement of corrosion residual strength by adding 1.0 wt.% yttrium into an AZ91D magnesium alloy
The influence of yttrium on the corrosion residual strength of an AZ91D magnesium alloy was investigated detailedly. Scanning electron microscope was employed to analyze the microstructure and the fractography of the studied alloys. The microstructure of AZ91D magnesium alloy is remarkably refined due to the addition of yttrium. The electrochemical potentiodynamic polarization curve of the studied alloy was performed with a CHI 660b electrochemical station in the three-electrode system. The result reveals that yttrium significantly promotes the overall corrosion resistance of AZ91D magnesium alloy by suppressing the cathodic reaction in corrosion process. However, the nucleation and propagation of corrosion pits on the surface of the 1.0 wt.% Y modified AZ91D magnesium alloy indicate that pitting corrosion still emerges after the addition of yttrium. Furthermore, stress concentration caused by corrosion pits should be responsible for the drop of corrosion residual strength although the addition of yttrium remarkably weakens the effect of stress concentration at the tip of corrosion pits in loading process.
Wang Qiang [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun, 130025 (China); Liu Yaohui, E-mail: firstname.lastname@example.com [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun, 130025 (China); Fang Shijie [Department of Mechanical and Electrical Engineering, Luoyang Institute of Science and Technology, Luoyang 471023 (China); Song Yulai; Zhang Dawei; Zhang Lina; Li Chunfang [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun, 130025 (China)
Thermoelectric properties of Mg2Si-based compounds synthesized partially using magnesium alloy
Mg2Si compounds are promising eco-friendly thermoelectric materials because both constituent elements of Mg and Si have no toxicity and exist richly in earth crust. We have a plan to use the compounds in the applications that convert waste heat in the temperature range (600-900 K) into electric power. However, the thermoelectric performance of the compounds has not yet reached to the practical use level. In addition, the compounds don't have durability in the thermoelectric performance under atmospheric circumstances in the temperature range of 750-900 K. These issues have to be solved for the practical use. In our previous work, we obtained knowledge that Al doping in Mg2Si lower the electrical resistivity and improved the thermoelectric performance. We newly attempted to use a magnesium alloy (AZ61) that includes the main three elements of aluminum (5.8-7.2 wt%), zinc (0.4-1.5 wt%) and manganese (0.15-0.35 wt%) in order to synthesize the Mg2Si-based compounds. The Mg2Si-based compound powders were synthesized from the mixture of silicon powder, AZ61 chips and Mg powder by the liquid-solid phase reaction method. The compound powders were sintered by the pulse discharge sintering method. The influence of mixing ratio of two metals of AZ61 and pure Mg on the thermoelectric properties was investigated. Addition of AZ61 greatly decreased the electrical resistivity as well as Al-doped Mg2Si and the thermoelectric performance had improved most in the 50wt%AZ61 sample.
Itoh, Takashi; Hagio, Kento
Microstructure and second-phase particles in low- and high-pressure die-cast magnesium alloy AM50
The microstructure and phase composition of low-pressure die-cast (LPDC) and high-pressure diecast (HPDC) magnesium alloy\\u000a AM50 were examined by transmission electron microscopy (TEM) techniques in combination with optical microscopy, scanning electron\\u000a microscopy (SEM), and electron-probe microanalysis (EPMA). It has been established that the dimensions and morphology of the\\u000a constituent phases (?-Mg solid solution, Mg17Al12, and Al8Mn5) depend on the processing
Val Y. Gertsman; Jian Li; Su Xu; James P. Thomson; Mahi Sahoo
A first-principles study of elastic and diffusion properties of magnesium based alloys
In this thesis, the influence of alloying elements on the elastic and diffusion properties of Magnesium (Mg) has been studied based on first-principles density functional theory. The stress-strain method has been used to predict the elastic constants of the Mg based alloys studied herein. This method involves calculating the resultant change in stress due to application of strain. The validity of this method has been successfully tested for both 0K as well as at finite temperatures. The elastic constants predicted in this work have been correlated to ductility, fracture toughness, stiffness, elastic anisotropy and bond directionality, thus providing a better understanding of the influence of alloying elements on the mechanical and physical properties of Mg. Elastic constants, as a function of temperature have been predicted using first-principles quasi-static approximation. In this approach elastic stiffness coefficients calculated with respect to volume (cij( V)) have been correlated to the equilibrium volume as a function of temperature V(T) from phonon calculations to obtain temperature dependence of elastic stiffness coefficients cij(T). To compare our calculated temperature dependent elastic constants with that of experiments an isentropic correction term has been introduced. It is seen that the influence of this isentropic correction term on the elastic constants becomes significant at high temperatures. The quasi-static approximation has been primarily applied to calculate temperature dependent elastic constants of Mg2Ge, Mg2Si, Mg 2Sn and Mg2Pb. In the case of dilute Mg alloys, a 36 atom supercell with 35 atoms of Mg and one atom of the alloying impurity has been used for calculating the corresponding elastic constants. It is seen that there is a direct correspondence between the trends in the elastic constants and the lattice parameters of all the Mg based alloys studied herein. Elements that cause a decrease (increase) in the lattice constants result in an increase (decrease) in the bulk modulus. Self-diffusion calculations of Mg have been performed within both LDA and GGA. It is seen that, in the absence of surface corrections, while results of the two approximations (i.e. LDA and GGA) bound experimental data, better agreement is seen with respect to results from LDA, in comparison with experimental measurements. The effect of thermal expansion on the diffusivity of Mg has been studied using both HA and QHA. It is seen that the influence of anharmonicity on the diffusivity of Mg is negligible. Self-diffusion of Mg is faster in the basal plane than between adjacent basal planes. Partial correlation factors corresponding to the diffusion of a Mg atom from one basal plane to the adjacent basal plane, i.e. fBx and fBz, decrease with temperature whereas the partial correlation factor corresponding to the diffusion of Mg atom within the basal plane, i.e. fAx , increases with temperature. The ratio of jump frequencies w?/w? for self-diffusion of Mg increase with increase in temperature. The method used to calculate self-diffusion coefficients has been extended to compute impurity diffusion coefficients of Al, Ca, Sn and Zn in Mg. For these calculations, a 36 atom supercell with 1 vacant site and 1 impurity has been used. The 8-frequencey model has been implemented to obtain the different atom jump frequencies in order to calculate impurity diffusion coefficients in Mg. The trend in the impurity diffusion coefficients, with the exception of DZn-Mg is as follows: D Mg-Ca>DMg>DMg-Sn> DMg-Al. For impurity diffusion of Zn in Mg, at high temperatures DMg-Zn overlaps with that of DMg-Al , while at low temperatures it overlaps with that of D Mg-Sn. The different atom jump frequencies computed during the diffusion calculations are seen to be temperature dependent, increasing with increase in temperature. The correlation factors for all the alloy systems considered herein, is close to 1. This is expected to be due to the close packing of Mg lattice. (Abstract shortened by UMI.)
Ganeshan, Swetha
Influence of the grain size on the in vivo degradation behaviour of the magnesium alloy LAE442.
The aim of this study was to investigate the differences in the in vivo degradation behaviour of magnesium implants with various grain sizes and damaged surfaces. For this purpose, three different LAE442 magnesium implants were produced: cast, single and double extruded implants, in order to obtain different grain sizes. Furthermore, defects were positioned on the surfaces of some of the single extruded implants. The initial stability was determined. Four pins of each implant material were implanted into rabbits' tibiae and regularly clinically, radiologically and micro-computed tomographically investigated over a period of 27 weeks. Following explantation, investigations were carried out using stereo and scanning electron microscopy including energy-dispersive X-ray analyses. Weight and strength changes were measured. The double extruded implants possessing the finest grains exhibited the highest initial stability (179.18 N). These implants demonstrated the lowest in vivo corrosion rates (0.0134 mm/year) and the least radiologically visible changes. The highest corrosion rate was computed for the implants possessing damaged surfaces. Radiologically discernible bone changes occurred at almost the same time as implant changes for all groups. Based on these results, the aim should be to produce fine-grained magnesium-based alloys for resorbable implants and to avoid any surface damage. PMID:23662348
Ullmann, Berit; Reifenrath, Janin; Seitz, Jan-Marten; Bormann, Dirk; Meyer-Lindenberg, Andrea
Dynamic behavior and constitutive modeling of magnesium alloys AZ91D and AZ31B under high strain rate compressive loading
The dynamic stress-strain characteristics of magnesium alloys have not been sufficiently studied experimentally. Thus, the present work investigated compressive dynamic stress-strain characteristics of two representative magnesium alloys: AZ91D and AZ31B at high strain rates and elevated temperatures. In order to use the stress-strain characteristics in numerical simulations to predict the impact response of components, the stress-strain characteristics must be modeled. The most common approach is to use accepted constitutive laws. The results from the experimental study of the response of magnesium alloys AZ91D and AZ31B under dynamic compressive loading, at different strain rates and elevated temperatures are presented here. Johnson-Cook model was used to best fit the experimental data. The material parameters required by the model were obtained and the resultant stress-strain curves of the two alloys for each testing condition were plotted. It is found that the dynamic stress-strain relationship of both magnesium alloys are strain rate and temperature dependent and can be described reasonably well at high strain rates and room temperature by Johnson-Cook model except at very low strains. This might be due to the fact that the strain rate is not strictly constant in the early stage of deformation.
Xiao, Jing; Ahmad, Iram Raza; Shu, D. W.
Optimizing Diffusion Bonding Parameters in AA6061-T6 Aluminum and AZ80 Magnesium Alloy Dissimilar Joints
The main difficulty when joining magnesium (Mg) and aluminum (Al) alloys by fusion welding lies in the formation of oxide films and brittle intermetallic in the bond region which affects the integrity of the joints. However, diffusion bonding is a suitable process to join these two materials as no such characteristic defects are produced at the joints. The diffusion bonding process parameters such as bonding temperature, bonding pressure, holding time, and surface roughness of the specimen play a major role in determining the joint strength. In this investigation, an attempt was made to develop empirical relationships to predict the strengths of diffusion bonded AZ80 magnesium and AA6061 aluminum alloys dissimilar joints from the process parameters based on central composite factorial design. Response surface methodology was applied to optimize the process parameters to attain the maximum shear strength and bonding strength of the joint. From this investigation, it was found that the bonds produced with the temperature of 405.87 °C, pressure of 7.87 MPa, holding time of 29.02 min and surface roughness of 0.10 ?m exhibited maximum shear strength and bonding strength of 57.70 and 76.90 MPa, respectively. The intermetallic formation at the interface was identified.
Joseph Fernandus, M.; Senthilkumar, T.; Balasubramanian, V.; Rajakumar, S.
The effect of high-intensity pulsed ion beam on surface structures of MAO film on magnesium alloy AZ31
Micro-arc oxidation (MAO) films on AZ31 magnesium alloy were modified by high-intensity pulsed ion beam (HIPIB) irradiation with ion energy of 300 keV at 200 A/cm2 with up to 10 shots. Scanning electron microscopy, X-ray diffractometry and micro-hardness testers were used to characterize the surface properties of the irradiated MAO films. The thickness of remelted layer increased and then decreased, and the maximal value of 10 ?m was obtained at 200 A/cm2 with 5 shots. The phase structure of the ablated surface still consisted of Mg2SiO4 and MgO, which are the same as that of the original ones. Surface roughness of the ablated surface increased and then decreased with the increase of shot number. The surface roughness for the original MAO film is about 2.10 ?m, it decreased to 1.18 ?m with 1 shot irradiation and then increased to 4.13 ?m with irradiation shots up to 10. Correspondingly, the surface energy of the ablated surface augmented, resulting in the tedious decrease of static contact angle from 145.9° for original film to 49.7° for the film with 10 shots. The ablation modification enhanced the continuity and compaction of the MAO films on AZ31 magnesium alloy.
Han, X. G.; Zhu, F.; Zhu, X. P.; Lei, M. K.; Xu, J. J.
A study of deformation twinning in magnesium alloy AZ31B
Crystals with a hexagonal close-packed crystal structure are inherently anisotropic, and have a limited number of independent slip systems, which lead to strong deformation textures and reduced formability in polycrystalline products. In magnesium (Mg), all of the easy slip systems have a Burgers vector in the direction making twinning necessary for arbitrary shape changes. The most common twinning system which allows extension along the c-axis is {1012}<1011>. A good predictor of slip is the global Schmid factor, which resolves the externally applied force onto the slip plane and direction of a crystal. The critically resolved shear stress (CRSS) at which a grain twins is not readily measured by experiment and the CRSS for twin initiation often appears larger than for twin propagation. In polycrystals, twin variants with both low and high Schmid factors have been observed indicating that this Schmid factor is inappropriate to predict twinning and more local effects play an important, though still uncertain role. In this work, experiments were devised to dynamically study extension twinning in a polycrystalline Mg alloy AZ31B with a strong basal rolling texture by tensile deformation parallel to the plate normal. Three-dimensional X-ray diffraction using a synchrotron source was used to map the centre-of-mass positions, orientations, and grain-resolved elastic strain tensors of over 1000 grains in-situ up to a true strain of 1.4%. The majority of twins formed in grains with a high local Schmid factor; however, low-ranked twin variants were common. The average grain-resolved stress did not always select the highest twin variant and resulted in some negative Schmid factors. The internal stress state of parent grains and twinned grains did not differ significantly within the large measurement uncertainties. The misorientations between grains ideally oriented for twinning and their nearest neighbours could not explain cases of no twin activity. Results suggest that the controlling factors for twin formation are much more local and not captured within the spatial resolution of the technique. Complimentary measurement of the strain rate sensitivity during twinning, by instantaneous strain rate change tests, suggest that basal slip is a part of this local process.
Majkut, Marta
Electroless nickel plating on ZM6 (Mg–2.6Nd–0.6Zn–0.8Zr) magnesium alloy substrate
To improve the corrosion resistance of ZM6 (Mg–2.6Nd–0.6Zn–0.8Zr) magnesium alloy, electroless nickel plating on ZM6 alloy with a new pretreatment process and nickel carbonate bath was investigated in this paper. The morphology, component, chemical composition and structure of the pretreatment layers and electroless nickel coating were analyzed using scanning electronic microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction
Yanrui Gao; Chuming Liu; Shengli Fu; Jing Jin; Xin Shu; Yonghao Gao
Organosilane self-assembled layers (SAMs) and hybrid silicate magnesium-rich primers for the corrosion protection of aluminum alloy 2024 T3
Although current chromate coatings function very well in corrosion protection for aircraft alloys, such as aluminum alloy 2024 T3, the U.S. Environmental Protection Agency is planning to totally ban the use of chromates as coating materials in the next decade or so because of their extremely toxic effect. For this purpose, both self-assembled layers and silicate magnesium-rich primers were tested
Duhua Wang
Thermodynamic investigation of the effect of alkali metal impuries on the processing of aluminum and magnesium alloys
Aluminum and magnesium alloys are widely used in the automobile and aerospace industries as structural materials due to their light weight, high specific strength and good formability. However, they suffer from the poor hot rolling characteristics due to undesired impurities like calcium, potassium, lithium and sodium. They increase the hydrogen solubility in the melt and promote the formation of porosity in aluminum castings. During fabrication of aluminum alloys, they cause the hot-shortness and embrittlement due to cracking. They also led to "blue haze" corrosion which promotes the discoloration of aluminum under humid condition. The removal of these elements increases overall melt loss of aluminum alloys when aluminum products are remelted and recast. Na is one of the common impurities in the Al and Mg alloys. In industry, primary Al is produced by the Hall-Heroult process, through the electrolysis of the mixture of molten alumina and cryolite (Al2O3+Na 3AlF6), the latter being added to lower the melting point. Therefore, Al inevitably contains some Na (>0.002%) without further treatment. The Na content in Al is influenced by the thermodynamics and kinetics of the electrolysis. Similarly, in the electrolytic production and subsequent processing of Mg, Mg is commonly in contact with molten salt mixtures of NaCl and MgCl 2. Consequently, 2--20 wt. ppm Na is often found in Mg alloys. Besides originating from the industrial production process, Na can be introduced in laboratory experiments from alumina crucibles by the reaction between the molten Al-Mg alloys and the Na2O impurity in the alumina crucible. The trace element K plays a similar role in Al alloys although it is seldom discussed. No systematic theoretic research has been carried out to investigate the behavior of these impurities during the processing of aluminum alloys. The thermodynamic description of the Al-Ca-K-Li-Mg-Na system is needed to understand the effects of Ca, K, Li and Na on phase stability of aluminum and magnesium alloys. As the first step of the thermodynamic description of the high-order system, the constitutive-binary systems were modeled in the present work using the CALPHAD technique combined with first-principles calculations. Then, ternaries and higher order systems can be modeled. For ternary systems without experimental data, the thermodynamic description is extrapolated by combining three constitutive-binary systems. Alkali-metal induced high temperature embrittlement (HTE) and loss of ductility were investigated in Al-Li, Al-Mg and Mg-Li alloys. It was discovered that the alkali-metal-rich liquid-2 phase is the cause of HTE and the loss of ductility is proportional to the mole fraction of the liquid phase and the grain size. The calculated results are consistent with experimental observations in the literature and were used to determine HTE safe and sensitive zones, maximum and critical hot-rolling temperatures and the maximum allowable Na content in alloys, which can be used to industrial processing of Al and Mg alloys. The degree of HTE is proportional to the mole fraction of the liquid-2 phase and the grain size.
Zhang, Shengjun
Precipitation of guinier- preston zones in aluminum- magnesium; a calorimetric analysis of liquid-Quenched and solid-Quenched alloys
A calorimetric analysis of precipitation in liquid-quenched (LQ; rapidly solidified) and solid-quenched (SQ; quenched after solution heat treatment) AlMg alloys was made. Nonisothermal annealing (constant heating rate) experiments (differential scanning calorimetry) were performed using specimens of various compositions (12 to 17 at. Pct Mg) aged at fixed temperatures (293 to 353 K) during variable times (up to 3 years). Constraints to be imposed on the heating rates to be applied were discussed. Attention was paid in particular to the formation on aging and dissolution on subsequent annealing of Guinier-Preston (GP) zones. Quantitative analysis of the heat of dissolution of GP-zones led to estimates for the GP-zone solvus and the enthalpy of formation of GP-zones. The kinetics of formation and dissolution of GP-zones can be interpreted in terms of nucleation and excess-vacancy enhanced diffusion of magnesium. Rates of formation and dissolution of GP-zones are higher for SQ-alloys than for LQ-alloys, which is caused by a higher amount of excess vacancies retained after drastic SQ as compared to LQ by melt spinning where cooling in the last part of the quench can be relatively slow. The activation energy of GP-zone dissolution is generally smaller than that of GP-zone formation, which is interpreted in terms of a precipitation model where vacancy voids/loops, formed during quenching and/or in the beginning of aging, become unstable at temperatures where the GP-zones dissolve. As compared to the precipitation of GP-zones, the precipitation of ?'/? particles showed an "opposite" kinetic behavior: it starts earlier in the LQ-alloys than in the SQ-alloys, which is ascribed to heterogeneous nucleation at structural heterogeneities (as grain boundaries) present with a higher density in the LQ-alloys.
van Rooyen, M.; Maartensdijk, J. A. Sinte; Mittemeijer, E. J.
Modeling and analyzing the effects of heat treatment on the characteristics of magnesium alloy joint welded by the tungsten-arc inert gas welding
The objective of this paper is to present the mathematical models for modeling and analysis of the effects of heat treatment on the characteristics of magnesium alloy joint welded by the tungsten-arc inert gas (TIG) welding. The process of heat treatment adopts the tempering process with varying processing parameters, including tempering temperature and tempering time. The microstructure and mechanical properties
Te-Chang Tsai; Chih-Chung Chou; Deng-Maw Tsai; Ko-Ta Chiang
In-Situ Scanning Electron Microscopy Comparison of Microstructure and Deformation Between WE43-F and WE43-T5 Magnesium Alloys.
In-situ tensile testing in the scanning electron microscope was used to investigate the quasi-static deformation behavior and fracture mechanism of WE43 magnesium alloys. The in-situ tensile experiments were conducted at room temperature at a constant cro...
B. Davis J. Yu K. Cho R. DeLorme T. San
A study on the effect of plasma electrolytic oxidation on the stress corrosion cracking behaviour of a wrought AZ61 magnesium alloy and its friction stir weldment
Friction stir weldments of a wrought AZ61 magnesium alloy produced in a robotic friction stir welder under optimised welding conditions were characterised for microstructure, mechanical properties, corrosion and stress corrosion cracking (SCC) behaviour. The effect of surface modification in the form of a plasma electrolytic oxidation (PEO) coating on the corrosion behaviour of the weldment was assessed. The weldment exhibited
P. Bala Srinivasan; R. Zettler; C. Blawert; W. Dietzel
In vivo assessment of the host reactions to the biodegradation of the two novel magnesium alloys ZEK100 and AX30 in an animal model
Background Most studies on biodegradable magnesium implants published recently use magnesium-calcium-alloys or magnesium-aluminum-rare earth-alloys. However, since rare earths are a mixture of elements and their toxicity is unclear, a reduced content of rare earths is favorable. The present study assesses the in vivo biocompatibility of two new magnesium alloys which have a reduced content (ZEK100) or contain no rare earths at all (AX30). Methods 24 rabbits were randomized into 4 groups (AX30 or ZEK100, 3 or 6 months, respectively) and cylindrical pins were inserted in their tibiae. To assess the biodegradation ?CT scans and histological examinations were performed. Results The ?CT scans showed that until month three ZEK100 degrades faster than AX30, but this difference is leveled out after 6 months. Histology revealed that both materials induce adverse host reactions and high numbers of osteoclasts in the recipient bone. The mineral apposition rates of both materials groups were high. Conclusions Both alloys display favorable degradation characteristics, but they induce adverse host reactions, namely an osteoclast-driven resorption of bone and a subsequent periosteal formation of new bone. Therefore, the biocompatibility of ZEK100 and AX30 is questionable and further studies, which should focus on the interactions on cellular level, are needed.
Comparison of electrochemical corrosion behaviour of MgO and ZrO 2 coatings on AM50 magnesium alloy formed by plasma electrolytic oxidation
Two types of PEO coatings were produced on AM50 magnesium alloy using pulsed DC plasma electrolytic oxidation process in an alkaline phosphate and acidic fluozirconate electrolytes, respectively. The phase composition and microstructure of these PEO coatings were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The corrosion behaviour of the coated samples was evaluated by open circuit potential
Evaluating the Superplastic Flow of a Magnesium AZ31 Alloy Processed by Equal-Channel Angular Pressing
Experiments show that the magnesium AZ31 (Mg-3 pct Al-1 pct Zn) alloy exhibits excellent superplastic properties at 623 K (350 °C) after processing by equal-channel angular pressing using a die with a channel angle of 135 deg and a range of decreasing processing temperatures from 473 K to 413 K (200 °C to 140 °C). A maximum elongation to failure of ~1200 pct was achieved in this alloy at a tensile strain rate of 1.0 × 10-4 s-1. Microstructural inspection showed evidence for cavity formation and grain growth during tensile testing with the grain growth leading to significant strain hardening. An examination of the experimental data shows that grain boundary sliding is dominant during superplastic flow. Furthermore, a comprehensive review of the present results and extensive published data for the AZ31 alloy shows the exponent of the inverse grain size is given by p ? 2 which is consistent with grain boundary sliding as the rate-controlling flow mechanism.
Figueiredo, Roberto B.; Langdon, Terence G.
Constitutive Behavior of Commercial Grade ZEK100 Magnesium Alloy Sheet over a Wide Range of Strain Rates
The constitutive behavior of a rare-earth magnesium alloy ZEK100 rolled sheet is studied at room temperature over a wide range of strain rates. This alloy displays a weakened basal texture compared to conventional AZ31B sheet which leads to increased ductility; however, a strong orientation dependency persists. An interesting feature of the ZEK100 behavior is twinning at first yield under transverse direction (TD) tensile loading that is not seen in AZ31B. The subsequent work hardening behavior is shown to be stronger in the TD when compared to the rolling and 45 deg directions. One particularly striking feature of this alloy is a significant dependency of the strain rate sensitivity on orientation. The yield strength under compressive loading in all directions and under tensile loading in the TD direction is controlled by twinning and is rate insensitive. In contrast, the yield strength under rolling direction tensile loading is controlled by non-basal slip and is strongly rate sensitive. The cause of the in-plane anisotropy in terms of both strength and strain rate sensitivity is attributed to the initial crystallographic texture and operative deformation mechanisms as confirmed by measurements of deformed texture. Rate-sensitive constitutive fits are provided of the tensile stress-strain curves to the Zerilli-Armstrong[1] hcp material model and of the compressive response to a new constitutive equation due to Kurukuri et al.[2
Kurukuri, Srihari; Worswick, Michael J.; Bardelcik, Alexander; Mishra, Raja K.; Carter, Jon T.
Calcium phosphate coatings on magnesium alloys for biomedical applications: A review
Magnesium has been suggested as a revolutionary biodegradable metal for use as an orthopaedic material. As a biocompatible and degradable metal, it has several advantages over the permanent metallic materials currently in use, including eliminating the effects of stress shielding, improving biocompatibility concerns in vivo and improving degradation properties, removing the requirement of a second surgery for implant removal. The
Shaylin Shadanbaz; George J. Dias
Effect of Rare-Earth Additions on the Texture of Wrought Magnesium Alloys: The Role of Grain Boundary Segregation
Magnesium alloys that contain certain rare-earth (RE) additions are known to have improved formability and this can be partly attributed to the different texture they display after recrystallization. Previous experimental work has identified segregation of RE to grain boundaries and dislocations as being potentially important in producing this change in behavior. In the present paper, two classical models (Langmuir-McClean and Cahn-Lücke-Stüwe) are used to explore the likely effect of RE additions on grain boundary solute concentration and drag. It is demonstrated that a wide range of RE elements are predicted to segregate strongly to grain boundaries due to the large atomic size misfit with magnesium. The maximum level of segregation is produced for elements such as Y or Gd that combine a high misfit and high bulk solubility. Segregated Y is predicted to produce a solute drag pressure on migrating boundaries several orders of magnitude greater than that obtained by Al or Zn additions. It is demonstrated that while this drag is predicted to be insufficient to strongly retard static recrystallization under typical annealing conditions, it is expected to suppress dynamic recrystallization by any mechanism requiring boundary migration.
Robson, Joseph D.
Study on the corrosion residual strength of the 1.0 wt.% Ce modified AZ91 magnesium alloy
The effect of corrosion on the tensile behaviour of the 1.0 wt.% Ce modified AZ91 magnesium alloy was investigated by the immersion of the test bar in 3.5 wt.% NaCl aqueous solution for 0, 12, 40, 108, 204, 372 and 468 h with the subsequent tensile tests in this paper. The fractography was analyzed by scanning electron microscopy. The results show that pitting corrosion should be responsible for the drop of the corrosion residual strength within the testing time. The depth of the corrosion pits was statistically and quantitatively obtained by an optical microscopy and the maximal value was recorded as the extreme depth of the corrosion pit. Furthermore, the corrosion residual strength is linearly dependent on the extreme depth of the corrosion pit, which can be attributed to the loss of cross-sectional area and the emergence of stress concentration caused by the initiation and development of corrosion pits.
Li Chunfang [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun 130025 (China); Liu Yaohui, E-mail: firstname.lastname@example.com [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun 130025 (China); Wang Qiang; Zhang Lina; Zhang Dawei [Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, College of Materials Science and Engineering, Jilin University, Changchun 130025 (China)
Influence of sodium borate concentration on properties of anodic coatings obtained by micro arc oxidation on magnesium alloys
The influence of sodium borate concentration on the formation and properties of anodic coatings obtained by micro arc oxidation (MAO) on magnesium alloys was systematically studied in an alkaline solution with addition of 0-40 g/L sodium borate. It is shown that sodium borate can decrease the solution conductivity, take part in the coating formation and increase the coating thickness. With the increase of sodium borate concentration, the boron content in the coatings increases in the range of 10-20 g/L but decreases within the range of 20-40 g/L. Sodium borate cannot further improve the corrosion resistance attributed to the development of porous or rough anodic coatings.
Zhang, R. F.; Zhang, S. F.; Shen, Y. L.; Zhang, L. H.; Liu, T. Z.; Zhang, Y. Q.; Guo, S. B.
Effect of the Pulse Duty Cycle on Characteristics of Plasma Electrolytic Oxidation Coatings Formed on AZ31 Magnesium Alloy
Ceramic coatings are synthesized on AZ31 magnesium alloy in alkaline silicate solution by the method of plasma electrolytic oxidation. The effect of two different duty cycles (10% and 50%) on the structure and corrosive properties of the coatings is investigated. It is found that the coatings are mainly composed of MgO, Mg2SiO4 and MgF2 through XRD analysis. SEM images indicate that coatings formed at 50% duty cycle have a relatively coarse surface with larger pore size and fewer pores, and have a slower growth rate than those formed at 10% duty cycle with the same treatment time. However, the results of potentiodynamic polarization tests demonstrate that coatings formed at 50% duty cycle exhibit better corrosion resistance as a result of more compact microstructure.
Chen, Huan; Lv, Guo-Hua; Zhang, Gu-Ling; Pang, Hua; Wang, Xing-Quan; Zhang, You-Wei; Lee, Heon-Ju; Yang, Si-Ze
Preparation and characterization of HA microflowers coating on AZ31 magnesium alloy by micro-arc oxidation and a solution treatment
Magnesium and its alloys are potential biodegradable implant materials due to their attractive biological properties. But the use of magnesium is still hampered by its poor corrosion resistance in physiological fluids. In this work, hydroxyapatite microflowers coating is fabricated by micro-arc oxidation and a solution treatment on AZ31 magnesium alloy. The microstructure and composition are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The potentiodynamic polarization and electrochemical impedance spectroscopy are studied in simulated body fluid (SBF) solution, and the apatite-forming ability is studied also. The results show that the corrosion resistance of the magnesium alloy has been enhanced by MAO coating. And the solution treatment can improve the corrosion resistance of the MAO sample, by forming a barrier layer on the surface of the MAO coating, and by penetrating into the outer layer of the MAO film, sealing the micropores and micro-cracks existed in the MAO coating. In addition, the MAO-ST coating also exhibits a high ability to form apatite.
Tang, Hui; Yu, Dezhen; Luo, Yan; Wang, Fuping
Investigation of corrosion behavior of biodegradable magnesium alloys using an online-micro-flow capillary flow injection inductively coupled plasma mass spectrometry setup with electrochemical control
The development of biodegradable metallic materials designed for implants or medical stents is new and is one of the most interesting new fields in material science. Besides biocompatibility, a detailed understanding of corrosion mechanisms and dissolution processes is required to develop materials with tailored degradation behavior. The materials need to be sufficiently stable as long as they have to fulfill their medical task. However, subsequently they should dissolve completely in a controlled manner in terms of maximum body burden. This study focuses on the elemental and time resolved dissolution processes of a magnesium rare earth elements alloy which has been compared to pure magnesium with different impurity level. The here described investigations were performed using a novel analytical setup based on a micro-flow capillary online-coupled via a flow injection system to a plasma mass spectrometer. Differences in element-specific and time-dependent dissolution were monitored for various magnesium alloys in contact with sodium chloride or mixtures of sodium and calcium chloride as corrosive media. The dissolution behavior strongly depends on bulk matrix elements, secondary alloying elements and impurities, which are usually present even in pure magnesium.
Ulrich, A.; Ott, N.; Tournier-Fillon, A.; Homazava, N.; Schmutz, P.
Polishing-assisted galvanic corrosion in the dissimilar friction stir welded joint of AZ31 magnesium alloy to 2024 aluminum alloy
Galvanic corrosion of a dissimilar friction stir welded 2024-T3 Al/AZ31B-H24 Mg joint prepared using a water-based and a non-water-based polishing solution was characterized. Microstructure and the distribution of chemical elements were analyzed using optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The stir zone polished using water-based solution was observed to be much more susceptible to galvanic corrosion attack than that obtained using non-water-based polishing solution. The location of corrosion attack was observed in the narrow regions of AZ31 Mg alloy adjacent to Al2024 regions in the stir zone. The occurrence of galvanic corrosion was due to the formation of Mg/Al galvanic couples with a small ratio of anode-to-cathode surface area. The corrosion product was primarily the porous magnesium hydroxide with characteristic microcracks and exhibited a low microhardness value.
Liu, C. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada); Chen, D.L. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada)], E-mail: email@example.com; Bhole, S. [Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 (Canada); Cao, X.; Jahazi, M. [Aerospace Manufacturing Technology Centre, Institute For Aerospace Research, National Research Council Canada, 5145 Decelles Avenue, Montreal, Quebec H3T 2B2 (Canada)
Extraction of second phases from magnesium and aluminum alloys for analytical electron microscopy.
Techniques are described for the extraction onto carbon replicas of precipitates and inclusions from Mg and Al-based alloys for analytical transmission electron microscopy. EDX analysis of Mn precipitates from a Mg-Mn alloy illustrates the problems that can arise from spurious X-rays, caused by the use of a 3mm disc specimen. PMID:7919529
Carpenter, G J; Ng-Yelim, J; Phaneuf, M W
Spray forming of silicon added AZ91 magnesium alloy and its workability
Si was added to AZ91 Mg alloy to improve the mechanical properties of the AZ91 Mg alloy. Spray forming was employed to refine the primary phases during solidification by means of rapid solidification generated at atomization and droplet flight stages. The process parameters of spray forming were varied to reduce the porosity level and improve the morphology of the billet
C. Y. Chen; Chi Y. A. Tsao
Tensile and Fracture Properties of Cast and Forged Composite Synthesized by Addition of Al-Si Alloy to Magnesium
Cast Mg-Al-Si composites synthesized by addition of Al-Si alloy containing 10, 15, and 20 wt pct of Si, in molten magnesium, to generate particles of Mg2Si by reaction between silicon and magnesium during stir casting has opened up the possibility to control the size of these particles. The microstructure of the cast composite consists of relatively dark polyhedral phase of Mg2Si and bright phase of ?-Al12Mg17 along the boundary between dendrites of ?-Mg solid solution. After hot forging at 350 °C, the microstructure has changed to relatively smaller sizes of ?-Al12Mg17 and Mg2Si particles apart from larger grains surrounded by smaller grains due to dynamic recovery and recrystallization. Some of the Mg2Si particles crack during forging. In both the cast and forged composite, the Brinell hardness increases rapidly with increasing volume fraction of Mg2Si, but the hardness is higher in forged composites by about 100 BHN. Yield strength in cast composites improves over that of the cast alloy, but there is a marginal increase in yield strength with increasing Mg2Si content. In forged composites, there is significant improvement in yield strength with increasing Mg2Si particles and also over those observed in their cast counterpart. In cast composites, ultimate tensile strength (UTS) decreases with increasing Mg2Si content possibly due to increased casting defects such as porosity and segregation, which increases with increasing Mg2Si content and may counteract the strengthening effect of Mg2Si content. However, in forged composite, UTS increases with increasing Mg2Si content until 5.25 vol pct due to elimination of segregation and lowering of porosity, but at higher Mg2Si content of 7 vol pct, UTS decreases, possibly due to extensive cracking of Mg2Si particles. On forging, the ductility decreases in forged alloy and composites possibly due to the remaining strain and the forged microstructure. The initiation fracture toughness, J IC , decreases drastically in cast composites from that of Mg-9 wt pct. alloy designated as MA alloy due to the presence Mg2Si particles. Thereafter, J IC does not appear to be very sensitive to the increasing presence of Mg2Si particles. There is drastic reduction of J IC on forging of the alloy, which was attributed to the remaining strain and forged microstructure, and it is further lowered in the composites because of cracking of Mg2Si particles. The ratio of the tearing modulus to the elastic modulus in cast composites shows a lower ratio, which decreases with increasing Mg2Si content. The ratio decreases comparatively more on forging of cast MA alloy than those observed in forged composites.
Nanjunda Swamy, H. M.; Nath, S. K.; Ray, S.
Investigation into the hot workability of the as-extruded WE43 magnesium alloy using processing map.
The research concerned the characterization of the hot-working behavior of the as-extruded WE43 magnesium alloy potentially for biomedical applications and the construction of processing maps to guide the choice of forming process parameters. Isothermal uniaxial compression tests were performed over a temperature range of 350-480°C and strain rate range of 0.001-10s(-1). Flow stresses obtained were used to construct processing maps. Domains in processing maps corresponding to relevant deformation mechanisms, i.e., dynamic recrystallization (DRX), dynamic recovery (DRV) and flow instability, were identified, according to power dissipation efficiency and flow instability parameter values. Microstructures of compression-tested specimens were examined to validate these deformation mechanisms. Two mechanisms of DRX nucleation, i.e., particle-stimulated nucleation (PSN) and grain boundary bulging, were found to be operative at the low-temperature and high-temperature DRX domains, respectively. Flow instability was related to adiabatic shear bands and abnormal grain growth. An optimum condition for the hot working of this alloy was determined to be at a temperature of 475°C and a strain rate of 0.1s(-1). PMID:24508713
Wang, Lixiao; Fang, Gang; Leeflang, Sander; Duszczyk, Jurek; Zhou, Jie
Effect of laser power and specimen temperature on atom probe analyses of magnesium alloys.
The influence of laser power, wave length, and specimen temperature on laser assisted atom probe analyses for Mg alloys was investigated. Higher laser power and lower specimen temperature led to improved mass and spatial resolutions. Background noise and mass resolutions were degraded with lower laser power and higher specimen temperature. By adjusting the conditions for laser assisted atom probe analyses, atom probe results with atomic layer resolutions were obtained from all the Mg alloys so far investigated. Laser assisted atom probe investigations revealed detailed chemical information on Guinier-Preston zones in Mg alloys. PMID:21269771
Oh-ishi, K; Mendis, C L; Ohkubo, T; Hono, K
Fabrication and characterization of AZ91\\/CNT magnesium matrix composites
Carbon Nano Tube (CNT) reinforced AZ91 metal matrix composites (MMC) were fabricated by the squeeze infiltrated method. Properties of magnesium alloys have been improved by impurity reduction, surface treatment and alloy design, and thus the usage for the magnesium alloys has been extended recently. However there still remain barriers for the adaption of magnesium alloys for engineering materials. In this
Yong-Ha Park; Yong-Ho Park; Ik-Min Park; Jeong-Jung Oak; Hisamichi Kimura; Kyung-Mox Cho
Effect of heat treatments on oxidation kinetics in AZ91 and AM60 magnesium alloys
The effect of heat treatments on a non protective atmosphere (air) on the morphology and composition of the oxide in AM60 and AZ91 alloys has been evaluated. With the aim of evaluating the loss of alloying elements during heat treatment, a study of these alloys has been carried out using thermogravimetric analysis (TGA). In order to determine the nature of the oxides the reaction products generated were evaluated by scanning electron microscopy and X-ray diffraction. Results show that the nature and morphology of the oxides generated are related to the temperature and the time of the heating conditions applied. - Highlights: {yields} The effect of heat treatments on the oxide growth in Mg-Al alloys has been evaluated. {yields} The nature and morphology of the oxides have been characterized. {yields} These oxides are associated to the time and the temperature conditions.
Barrena, M.I., E-mail: firstname.lastname@example.com; Gomez de Salazar, J.M.; Matesanz, L.; Soria, A.
Effect of processing environment on laser-induced darkening evolution in magnesium alloy
Laser-induced darkening effect is an important phenomenon for Mg alloys to provide potential engineering applications in product identification, photocatalysts, and bio-optical implants. This work reports darkening evolution on Mg alloy by KrF excimer laser irradiation. Effort was made to study how processing environment influence morphological evolution and chemical variation of laser-irradiated surface. All irradiated surfaces were characterized using Talysurf surface profiler, atomic force microscope, scanning electron microscope and energy dispersive X-ray spectrometer. The results showed that oxygen content played a critical role in determining darkening effect on the Mg alloy, and surface morphology transferred from network structures to granular structures and protruding oxide particles when darkening occurred. Mechanism of laser-induced darkening in Mg alloy was further discussed.
Guan, Y. C.; Zhou, W.; Li, Z. L.; Zheng, H. Y.
Creep deformation mechanisms in high-pressure die-cast magnesium-aluminum-base alloys
Creep of die-cast Mg alloys is described as an integral part of their plastic deformation behavior in terms of stress-strain-rate-strain\\u000a relations. Creep tests yield information on yield stress, work hardening, maximum deformation resistance (minimum creep rate),\\u000a and work softening. Testing in compression avoids influences by fracture. Data on the alloy AJ52 (5Al, 2Sr) in the temperature\\u000a range between 135 °C
W. Blum; Y. J. Li; X. H. Zeng; P. Zhang; B. von Großmann; C. Haberling
The chemical behaviour of carbon fibres in magnesium base Mg-Al alloys
The chemical interaction between carbon fibres and Mg-rich Mg-Al alloys was studied at 723–1273 K using optical metallography, scanning electron microscopy and electron probe microanalysis. In a first stage, carbon fibres were heated at 723, 1000 and 1273 K with Mg-Al alloys of different compositions. Two carbide phases were identified at 1000 and 1273 K: an Al4C3 type phase with
J. C. Viala; G. Claveyrolas; F. Bosselet; J. Bouix
Hydrogen-environment-assisted cracking of an aluminum-zinc-magnesium(copper) alloy
There is strong evidence to indicate that hydrogen embrittlement plays a significant, if not controlling, role in the environmentally assisted cracking of 7XXX series aluminum alloys. In order to better understand hydrogen environment assisted cracking (HEAC), crack growth rate tests in the K-independent stage II crack growth regime were conducted on fracture mechanics specimens of an Al-6.09Zn-2.14Mg-2.19Cu alloy (AA 7050)
George Aloysius Young Jr.
The high-strength alloy Al- Zn-Mg-Cu 0.5 is insensitive to continued ; loading at room temperature. At 100 and 150 deg C however a distinct drop of the ; time-rupture strength occurs which is characteristic also for other high-strength ; aluminum alloys. This drop may be connected to overaging phenomena. The ; results, according to E. J. Dorn, could approximately be
Microstructure and mechanical properties of Si and Sb added AZ91 magnesium alloy
The effect of Si (individual and combined) with 0.2 pct Sb additions on the microstructure and mechanical properties of permanent\\u000a mold AZ91 alloy has been studied. The results indicate that Si addition introduces a Chinese script Mg2Si phase at the grain boundary along with the Mg17Al12-? phase and reduces ductility and strength of the alloy both at room and high
A. Srinivasan; U. T. S. Pillai; B. C. Pai
Influence of rapid solidification on the mechanical properties of Mg-Zn-Ce-Ag magnesium alloy
This paper presents the differences in microstructure and mechanical properties between the conventional casting and rapidly solidified Mg-Zn-Ce-Ag alloy. The experimental results showed that the mechanical properties of rapidly solidified alloy are enhanced, which can be attributed to the changes of the microstructure significantly. The grain was refined and homogeneously distributed ?-Mg12Ce phase was obtained. High cooling rate refined the
J. Cai; G. C. Ma; Z. Liu; H. F. Zhang; A. M. Wang; Z. Q. Hu
Effect of ?-Al 2O 3 on the properties of cold sprayed Al/?-Al 2O 3 composite coatings on AZ91D magnesium alloy
Composite coatings using pure Al powder blended with ?-Al 2O 3 as feedstock were deposited on AZ91D magnesium alloy substrates by cold spray (CS). The content of ?-Al 2O 3 in the feedstock was 25 wt.% and 50 wt.%, respectively. The effects of ?-Al 2O 3 on the porosity, microhardness, adhesion and tensile strength of the coatings were studied. Electrochemical tests were carried out in neutral 3.5 wt.% NaCl solution to evaluate the effect of ?-Al 2O 3 on the corrosion behavior of the coatings. The results showed that the composite coatings possessed lower porosity, higher adhesion strength and tensile strength than cold sprayed pure Al coating. The corrosion current densities of the composite coatings were similar to that of the pure Al coating and much higher than that of bare AZ91D magnesium alloy.
Tao, Yongshan; Xiong, Tianying; Sun, Chao; Jin, Huazi; Du, Hao; Li, Tiefan
Heat-Transfer Coefficient and In-Cavity Pressure at the Casting-Die Interface during High-Pressure Die Casting of the Magnesium Alloy AZ91D
The present article deals with the application of a new measurement method to determine the heat-transfer coefficient (HTC)\\u000a and the heat flux density at the casting-die interface during high-pressure die casting (HPDC) and solidification of the magnesium\\u000a AZ91D alloy. The main measurements during the trial included velocity and the position of the piston that delivers the metal\\u000a into the die,
A. Hamasaiid; G. Dour; M. S. Dargusch; T. Loulou; C. Davidson; G. Savage
Constitutive prediction and dependence of tensile properties of high-pressure die-cast AM60B and AZ91D magnesium alloy on microporosity
The effect of micro-voids on the tensile property of high-pressure die-cast AM60B and AZ91D magnesium alloy was investigated\\u000a through systematic experimental approaches, with a constitutive prediction on the load carrying capacity and strain-related\\u000a factors. The strain rate sensitivity was measured through the incremental strain rate change test, and the microporosity was\\u000a measured from a comparison between the area of the
Choong Do Lee
Study on the interface of PVDF coatings and HF-treated AZ31 magnesium alloy: Determination of interfacial interactions and reactions with self-healing properties
In this paper the interface of poly(vinylidene fluoride) coatings prepared by the dip coating method and HF-treated AZ31 magnesium alloy was evaluated. The best performance of this system in corrosion tests compared to ground, as-received and acetic acid cleaned substrates is related to an acid–base interaction at the interface and to interfacial reactions which resulted in a self-healing process. The
Thiago F. da Conceicao; N. Scharnagl; W. Dietzel; D. Hoeche; K. U. Kainer
Effect of pulse frequency on the microstructure, phase composition and corrosion performance of a phosphate-based plasma electrolytic oxidation coated AM50 magnesium alloy
An AM50 magnesium alloy was plasma electrolytic oxidation treated using a pulsed DC power supply at three different pulse frequencies viz., 10Hz, 100Hz and 1000Hz with a constant pulse ratio for 15min in an alkaline phosphate electrolyte. The resultant coatings were characterized by X-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy for their phase composition and microstructural features. The
P. Bala Srinivasan; J. Liang; R. G. Balajeee; C. Blawert; M. Störmer; W. Dietzel
Effect of (NaPO 3) 6 concentrations on corrosion resistance of plasma electrolytic oxidation coatings formed on AZ91D magnesium alloy
Different plasma electrolytic oxidation (PEO) coatings were prepared on AZ91D magnesium alloy in electrolytes containing various concentrations of (NaPO3)6. The morphologies, chemical compositions and corrosion resistance of the PEO coatings were characterized by environmental scanning electron microscopy (ESEM), X-ray diffractometer (XRD), energy dispersive analysis of X-rays (EDAX), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) test. The results showed that the
Haihe Luo; Qizhou Cai; Bokang Wei; Bo Yu; Dingjun Li; Jian He; Ze Liu
Study on the microstructure and corrosion resistance of ZrO 2-containing ceramic coatings formed on magnesium alloy by plasma electrolytic oxidation
ZrO2-containing ceramic coatings were prepared on AZ91D magnesium alloy by plasma electrolytic oxidation (PEO) technique in three different zirconate electrolytes. The morphology and phase composition of the ceramic coatings were characterized by environmental scanning electron microscopy (ESEM) and X-ray diffractometer (XRD). The corrosion properties of the coatings were examined by immersion test and electrochemical corrosion test in 3.5wt.% NaCl solution
Haihe Luo; Qizhou Cai; Bokang Wei; Bo Yu; Jian He; Dingjun Li
Effects of current frequency on the structural characteristics and corrosion property of ceramic coatings formed on magnesium alloy by PEO technology
Plasma electrolytic oxidation (PEO) process was carried out on magnesium alloy with a pulsed direct current (dc) power source at high and low frequencies. The morphology and phase composition of the coatings were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion performances of the different coatings were evaluated via a three-electrode system in a 3.5-wt.% NaCl
Guo-Hua Lv; Huan Chen; Wei-Chao Gu; Li Li; Er-Wu Niu; Xian-Hui Zhang; Si-Ze Yang
Effect of additives on structure and corrosion resistance of plasma electrolytic oxidation coatings on AZ91D magnesium alloy in phosphate based electrolyte
Plasma electrolytic oxidation (PEO) coatings were prepared on magnesium alloy AZ91D in a phosphate based electrolyte with different additives such as sodium fluoride (NaF) and sodium aluminate (NaAlO2). The effects of F? and AlO2? additives on the morphology, phase structure and corrosion resistance of PEO coatings were examined by scanning electron microscopy (SEM\\/EDX), X-ray diffraction (XRD) and potentiodynamic polarization. The
Guo-Hua Lv; Huan Chen; Xing-Quan Wang; Hua Pang; Gu-Ling Zhang; Bin Zou; Heon-Ju Lee; Si-Ze Yang
Serrated flow and enhanced ductility in coarse-grained aluminum-magnesium alloys
Aluminum 5XXX alloys are of industrial importance and interest as they combine a wide range of desirable strength, forming and welding characteristics with a high resistance to corrosion. The presence of Mg in these alloys ensures favorable mechanical properties. However, the room temperature stretching performance of these alloys is limited. Moreover, Al-Mg alloys are known for being susceptible to the Portevin-LeChatelier effect when deformed at room temperature. Nevertheless, improvements in ductility can be achieved through warm forming, especially when the ductility approaches superplastic levels. The aim of this study was to test for enhanced ductility in three coarse-grained Al-Mg alloys namely, super-pure Al-3%Mg and Al-5%Mg, and commercial AA 5056 alloy. The temperature-dependent flow stress and rate sensitivity behavior of these alloys was investigated by means of tensile testing using ASTM E8M-04 standard samples. Samples were deformed to 10% strain to allow enough deformation to occur such that serrations in the dynamic strain aging (DSA) temperature/strain rate range would be rendered visible on a stress-strain curve. Using this information, the regions of negative and higher-than-normal strain rate sensitivity ('m') were plotted and tensile tests to failure were performed in the vicinity of maximum 'm'. ASTM E2448-06 standard samples for superplasticity tensile testing were used in this case. A maximum ductility of 170% was recorded with these samples and this was found to increase to nearly 300% when the gage length was shortened. It was observed that the DSA serrations were more prominent at lower strain rates, higher temperatures and higher Mg contents. The results of this study show clearly that if the rate sensitivity is high enough, then enhanced ductility in coarse-grained materials is possible at temperatures well below the maximum test temperature.
Samuel, Ehab
Quasi-Static and Shock Induced Mechanical Response of an Aluminium-Zinc-Magnesium Alloy as a Function of Heat Treatment
Samples of an aluminium-zinc-magnesium alloy, typical of high strength weldable aluminium alloys, have been heat treated to produce two different microstructural conditions, these being peak-aged and under-aged. Mechanical tests have been performed, both at quasi-static strain rates and under shock loading conditions to determine how the mechanical properties change with heat treatment. Results indicate that the material has its highest strength when peak aged. Properties are discussed in relation to observed features within the microstructure, as recorded by optical and scanning electron microscopy.
Edwards, M. R.; Millett, J. C. F.; Bourne, N. K.
Development and compatibility of magnesium matrix fuel plates clad with 6061 aluminum alloy.
Aluminum (Al) is a commonly used matrix for research reactor fuel plates. It has been found that a reaction between the fuel and the aluminum matrix may reduce or increase the irradiation stability of the fuel. To further understand the contribution of the reaction to the irradiation stability, experiments to develop a non-reacting matrix were performed. The work focused on magnesium (Mg), which is an excellent non-reacting matrix candidate and has a neutron absorption coefficient similar to Al. To avoid the formation of a liquid Al/Mg phase, improvements were made to the roll bonding process to achieve acceptable bonding at 415 C. After these methods were developed, fuel plates were produced with two fuels, uranium (U)-2 w/o molybdenum (Mo) and U-10-w/o Mo with two matrices, Al and Mg. A reaction between the magnesium and the 6061 Al cladding was discovered to take place during the processing at 415 C. To minimize the amount of reaction, methods were successfully developed to roll bond the fuel plates at 275 C. No reaction zone was observed in fuel plates processed at 275 C. Using this method, fuel plates with a Mg matrix are planned to be fabricated and included in the next irradiation matrix for the RERTR high density fuel development program.
Wiencek, T. C.
Cyclic deformation of extruded AM30 magnesium alloy in the transverse direction
Cyclic deformation characteristics of a recently developed AM30 Mg extrusion alloy in the transverse direction were evaluated under strain-controlled tests at different strain amplitudes. The alloy exhibited strong cyclic hardening especially at higher strain amplitudes. While the initial tensile Young's modulus was essentially the same in both transverse and longitudinal directions, the hysteresis loops were asymmetric in the longitudinal direction, but nearly symmetric in the transverse direction. This tension-compression asymmetry was associated with the presence of strong texture in the extruded Mg alloy. With increasing strain amplitude the mid-life hysteresis loops showed a clockwise rotation which was related to nonlinear or pseudoelastic deformation behavior. Fatigue crack initiation occurred at the specimen surface, and multiple initiation sites were observed at higher strain amplitudes. Crack propagation was basically characterized by the formation of characteristic fatigue striations.
Chen, D. L.; Emami, A. R.; Luo, A. A.
Grain Refinement of Magnesium Alloys: A Review of Recent Research, Theoretical Developments, and Their Application
This paper builds on the "Grain Refinement of Mg Alloys" published in 2005 and reviews the grain refinement research on Mg alloys that has been undertaken since then with an emphasis on the theoretical and analytical methods that have been developed. Consideration of recent research results and current theoretical knowledge has highlighted two important factors that affect an alloy's as-cast grain size. The first factor applies to commercial Mg-Al alloys where it is concluded that impurity and minor elements such as Fe and Mn have a substantially negative impact on grain size because, in combination with Al, intermetallic phases can be formed that tend to poison the more potent native or deliberately added nucleant particles present in the melt. This factor appears to explain the contradictory experimental outcomes reported in the literature and suggests that the search for a more potent and reliable grain refining technology may need to take a different approach. The second factor applies to all alloys and is related to the role of constitutional supercooling which, on the one hand, promotes grain nucleation and, on the other hand, forms a nucleation-free zone preventing further nucleation within this zone, consequently limiting the grain refinement achievable, particularly in low solute-containing alloys. Strategies to reduce the negative impact of these two factors are discussed. Further, the Interdependence model has been shown to apply to a broad range of casting methods from slow cooling gravity die casting to fast cooling high pressure die casting and dynamic methods such as ultrasonic treatment.
StJohn, D. H.; Easton, M. A.; Qian, M.; Taylor, J. A.
Since the 1940's Mg-alloys have been used for military applications, from aircraft components to ground vehicles. The drive for usage was primarily availability and lightweighting of military systems. But the promise of widespread military usage was not met largely based on corrosion and flammability concerns, poor mechanical behavior and inferior ballistic response. This review paper will cover historical, current and potential future applications with a focus on scientific, engineering and social barriers relevant to integration of Mg-alloy. It will also present mechanical and physical property improvements solutions which are currently being developed to address these issues.
Mathaudhu, Suveen N.; Nyberg, Eric A.
Explosion bonding: aluminum-magnesium alloys bonded to austenitic stainless steel
The explosion bonding of 5000 series aluminum alloys to 300 series stainless steel alloys is summarized. The process technique involves a parallel gap arrangement with copper or aluminum bonding aids. Successful bonds have been achieved using either a single shot process for joining the trilayer clad or a sequential shot technique for each metal component. Bond success is monitored through a combined metallographic and tensile strength evaluation. Tensile properties are shown to be strongly dependent upon process parameters and the amount of intermetallic formation at the aluminum bond interface. Empirical data has been compared with experimental and destructive test results to determine the optimum procedures.
Patterson, R.A.
Magnesium-lithium alloys in metal matrix composites — A preliminary report
Procedures are described for the fabrication of fibrous composites based on magnesiumlithium alloys as a matrix. Such composites have been produced containing planar random and aligned (continuous and discontinuous) fibres of carbon, alumina and silicon carbide. For all of these, except silicon carbide whiskers, significant fibre degradation occurred, during fabrication or subsequent heat treatments, either by chemical reaction or by
J. F. Mason; C. M. Warwick; P. J. Smith; J. A. Charles; T. W. Clyne
Evaluation of the delayed hydride cracking mechanism for transgranular stress corrosion cracking of magnesium alloys
This paper evaluates the important elements of delayed hydride cracking (DHC) for transgranular stress corrosion cracking (TGSCC) of Mg alloys. A DHC model was formulated with the following components: (i) transient H diffusion towards the crack tip driven by stress and H concentration gradients; (ii) hydride precipitation when the H solvus is exceeded; and (iii) crack propagation through the extent
N. Winzer; A. Atrens; W. Dietzel; G. Song; K. U. Kainer
Creep of die-cast Mg alloys is described as an integral part of their plastic deformation behavior in terms of stress-strain-rate-strain relations. Creep tests yield information on yield stress, work hardening, maximum deformation resistance (minimum creep rate), and work softening. Testing in compression avoids influences by fracture. Data on the alloy AJ52 (5Al, 2Sr) in the temperature range between 135 °C and 190 °C are presented and compared to those for AZ91 and AS21. Die-cast Mg-Al alloys consist of fine grains with a grain boundary region containing intermetallic precipitates. Transmission electron microscopic observations indicate that basal glide is the dominant mechanism of deformation being supplemented by nonbasal glide and twinning to maintain compatiblity between the grains. The deformation resistance can be modeled with a composite approach assuming that the grain boundary region is relatively hard due to precipitation of intermetallic phases. The differences in long-term creep resistance at low stress are explained in terms of different strength and stability of precipitates in the different alloys.
Blum, W.; Li, Y. J.; Zeng, X. H.; Zhang, P.; von Großmann, B.; Haberling, C.
Investigations on thermal fatigue of aluminum- and magnesium-alloy based composites
Both the KS1275® piston and AE42 alloys and their composites have realistic and\\/or potential applications as engine components in the automotive industry. Used as engine components, the dimensional stability is of great concern. Thermal cycling experiments can simulate the service conditions of the materials and give an evaluation how the dimension changes during their service in the changing temperature environments.
Y. D. Huang; N. Hort; H. Dieringa; P. Maier; K. U. Kainer
Surface integrity and process mechanics of laser shock peening of novel biodegradable magnesium-calcium (Mg-Ca) alloy.
Current permanent metallic biomaterials of orthopedic implants, such as titanium, stainless steel, and cobalt-chromium alloys, have excellent corrosive properties and superior strengths. However, their strengths are often too high resulting in a stress shielding effect that is detrimental to the bone healing process. Without proper healing, costly and painful revision surgeries may be required. The close Young's modulus between magnesium-based implants and cancellous bones has the potential to minimize stress shielding while providing both biocompatibility and adequate mechanical properties. The problem with Mg implants is how to control corrosion rates so that the degradation of Mg implants matches that of bone growth. Laser shock peening (LSP) is an innovative surface treatment method to impart compressive residual stress to a novel Mg-Ca implant. The high compressive residual stress has great potential to slow corrosion rates. Therefore, LSP was initiated in this study to investigate surface topography and integrity produced by sequential peening a Mg-Ca alloy. Also, a 3D semi-infinite simulation was developed to predict the topography and residual stress fields produced by sequential peening. The dynamic mechanical behavior of the biomaterial was modeled using a user material subroutine from the internal state variable plasticity model. The temporal and spatial peening pressure was modeled using a user load subroutine. The simulated dent agrees with the measured dent topography in terms of profile and depth. Sequential peening was found to increase the tensile pile-up region which is critical to orthopedic applications. The predicted residual stress profiles are also presented. PMID:20696413
Sealy, M P; Guo, Y B
Microstructural evolution and mechanical properties of high strength magneisum alloys fabricated by deformation processing
The goal of this research was to develop high strength Mg by thermo-mechanical processing. Several novel techniques were developed to impart large plastic strains on Mg alloys and Mg based composites. The main emphasis of this work was on investigating the effect of different processing schemes on grain-refinement and texture modification of processed material. The room-temperature and elevated-temperature mechanical behavior of processed-Mg was studied in detail. Biaxial corrugated pressing, also known as alternate biaxial reverse corrugation processing was applied to twin-roll cast AZ31 Mg and warm-extruded ZK60 Mg. Friction stir processing to partial depths was applied to thixomolded AM60 Mg and warm-extruded ZK60 Mg. A new process called "bending reverse-bending", was developed and applied to hot rolled AZ31-H24 Mg. A Mg/Al laminated composite was developed by hot pressing and rolling. In processed condition, Mg alloys exhibit enhancement in room-temperature strength and ductility, as well as elevated temperature formability. It was concluded that improvement in mechanical properties of processed-Mg is strongly influenced by grain size and precipitates; while ductility largely depends on resulting deformation textures.
Mansoor, Bilal
Magnesium Gluconate
Magnesium gluconate is used to treat low blood magnesium. Low blood magnesium is caused by gastrointestinal disorders, prolonged vomiting or ... disease, or certain other conditions. Certain drugs lower magnesium levels as well.This medication is sometimes prescribed ...
There is strong evidence to indicate that hydrogen embrittlement plays a significant, if not controlling, role in the environmentally assisted cracking of 7XXX series aluminum alloys. In order to better understand hydrogen environment assisted cracking (HEAC), crack growth rate tests in the K-independent stage II crack growth regime were conducted on fracture mechanics specimens of an Al-6.09Zn-2.14Mg-2.19Cu alloy (AA 7050) and a low copper variant (Al-6.87Zn-2.65Mg-0.06Cu). Crack growth rate tests were performed in 90% relative humidity (RH) air between 25 and 90°C to assure hydrogen embrittlement control. The underaged, peak aged, and overaged tempers were investigated. Hydrogen uptake in humid air, hydrogen diffusion, and hydrogen trapping were investigated for each temper. Lastly, near crack tip hydrogen concentration depth profiles were analyzed via nuclear reaction analysis (NRA) and secondary ion mass spectroscopy (SIMS) using a liquid gallium, focused ion beam sputtering source (FIB/SIMS). The results of this study help explain and quantify empirically known trends concerning HEAC resistance and also establish new findings. In the copper bearing alloy, overaged tempers are more resistant but not immune to HEAC. Humid air is an aggressive environment for Al-Zn-Mg alloys because water vapor reacts with bare aluminum to produce high surface concentrations of hydrogen. This occurs in all tempers. Hydrogen diffuses from the near surface region to the high triaxial stress region ahead of the crack tip and collects at the high angle grain boundaries. The combination of tensile stress and high hydrogen concentration at the grain boundaries then causes intergranular fracture. Crack extension bares fresh metal and the process of hydrogen production, uptake, diffusion to the stressed grain boundary, and crack extension repeats. One reason increased degree of aging improves HEAC resistance in copper bearing 7XXX series alloys is that volume lattice and effective hydrogen diffusion are slower. Overaging has little benefit on the stage II crack growth rate of low copper alloys because no such decrease in the diffusivity of hydrogen occurs.
Young, George Aloysius, Jr.
Experimental investigation on fiber and CO2 inert gas fusion cutting of AZ31 magnesium alloy sheets
The influence of processing parameters and laser source type on cutting edge quality of AZ31 magnesium alloy sheets and differences in cutting efficiency between fiber and CO2 lasers were studied. A first part of the cutting experiments compared a fiber and CO2 laser source when cutting 1 mm thick sheets in continuous wave mode and using Argon as an assist gas. The effects of cutting speed and assist gas pressure were investigated and optimal conditions were identified. In the second part of the experimental investigation, 3.3 mm thick sheets were cut using fiber laser. Focal position and cutting speed were varied in order to detect the optimal combination of processing parameters to obtain the best edge quality. For both sheet thicknesses investigated, surface roughness, dross height, and striation pattern inclination were measured. Cutting quality assessment and classification was carried out according to UNI EN ISO 9013 standard. Results showed that productivity, process efficiency and cutting edges quality obtained using fiber lasers outperform CO2 laser performances and therefore are considered suitable for application like sheet metal trimming.
Scintilla, L. D.; Tricarico, L.
Microstructure and Mechanical Properties of Fiber-Laser-Welded and Diode-Laser-Welded AZ31 Magnesium Alloy
The microstructures, tensile properties, strain hardening, and fatigue strength of fiber-laser-welded (FLW) and diode-laser-welded (DLW) AZ31B-H24 magnesium alloys were studied. Columnar dendrites near the fusion zone (FZ) boundary and equiaxed dendrites at the center of FZ, with divorced eutectic ?-Mg17Al12 particles, were observed. The FLW joints had smaller dendrite cell sizes with a narrower FZ than the DLW joints. The heat-affected zone consisted of recrystallized grains. Although the DLW joints fractured at the center of FZ and exhibited lower yield strength (YS), ultimate tensile strength (UTS), and fatigue strength, the FLW joints failed at the fusion boundary and displayed only moderate reduction in the YS, UTS, and fatigue strength with a joint efficiency of ~91 pct. After welding, the strain rate sensitivity basically vanished, and the DLW joints exhibited higher strain-hardening capacity. Stage III hardening occurred after yielding in both base metal (BM) and welded samples. Dimple-like ductile fracture characteristics appeared in the BM, whereas some cleavage-like flat facets together with dimples and river marking were observed in the welded samples. Fatigue crack initiated from the specimen surface or near-surface defects, and crack propagation was characterized by the formation of fatigue striations along with secondary cracks.
Chowdhury, S. M.; Chen, D. L.; Bhole, S. D.; Powidajko, E.; Weckman, D. C.; Zhou, Y.
Characterization of High Strain Rate Mechanical behavior of AZ31 magnesium alloy using 3D Digital Image Correlation
Characterization of the material mechanical behavior at sub-Hopkinson regime (0.1 to 1000 s{sup -1}) is very challenging due to instrumentation limitations and the complexity of data analysis involved in dynamic loading. In this study, AZ31 magnesium alloy sheet specimens are tested using a custom designed servo-hydraulic machine in tension at nominal strain rates up to 1000 s{sup -1}. In order to resolve strain measurement artifacts, the specimen displacement is measured using 3D Digital Image correlation instead from actuator motion. The total strain is measured up to {approx} 30%, which is far beyond the measurable range of electric resistance strain gages. Stresses are calculated based on the elastic strains in the tab of a standard dog-bone shaped specimen. Using this technique, the stresses measured for strain rates of 100 s{sup -1} and lower show little or no noise comparing to load cell signals. When the strain rates are higher than 250 s{sup -1}, the noises and oscillations in the stress measurements are significantly decreased from {approx} 250 to 50 MPa. Overall, it is found that there are no significant differences in the elongation, although the material exhibits slight work hardening when the strain rate is increased from 1 to 100 s{sup -1}.
Wang, Yanli [ORNL; Xu, Hanbing [ORNL; ERDMAN III, DONALD L [ORNL; Starbuck, J Michael [ORNL; Simunovic, Srdjan [ORNL
Abnormal distribution of microhardness in tungsten inert gas arc butt-welded AZ61 magnesium alloy plates
In this study, the effects of heat input on the distribution of microhardness of tungsten inert gas (TIG) arc welded hot-extruded AZ61 magnesium alloy joints were investigated. The results show that with an increase of heat input, the distributions of microhardness at the top and bottom of the welded joints are different because they are determined by both the effect of grain coarsening and the effect of dispersion strengthening. With an increase of the heat input, the microhardness of the heat-affected zone (HAZ) at the top and bottom of welded joints and the fusion zone (FZ) at the bottom of welded joints decreased gradually, while the microhardness of the FZ at the top of welded joints decreased initially and then increased sharply. The reason for the abnormal distribution of microhardness of the FZ at the top of the welded joints is that this area is close to the heat source during welding and then large numbers of hard {beta}-Mg{sub 17}(Al,Zn){sub 12} particles are precipitated. Hence, in this case, the effect of dispersion strengthening dominated the microhardness.
Xu Nan [College of Material Science and Engineering, Chongqing University, Chongqing 400044 (China); Shen Jun, E-mail: firstname.lastname@example.com [College of Material Science and Engineering, Chongqing University, Chongqing 400044 (China); Xie Weidong; Wang Linzhi; Wang Dan; Min Dong [College of Material Science and Engineering, Chongqing University, Chongqing 400044 (China)
Ductile Fracture Prediction in Rotational Incremental Forming for Magnesium Alloy Sheets Using Combined Kinematic/Isotropic Hardening Model
To predict the ductile fracture of a magnesium alloy sheet when using rotational incremental forming, a combined kinematic and isotropic hardening law is implemented and evaluated from the histories of the ductile fracture value ( I) using a finite element analysis. Here, the criterion for a ductile fracture, as developed by Oyane ( J. Mech. Work. Technol., 1980, vol. 4, pp. 65-81), is applied via a user material based on a finite element analysis. To simulate the effect of the large amount of heat generation at elements in the contact area due to the friction energy of the rotational tool-specimen interface on the equivalent stress-strain evolution in incremental forming, the Johnson-Cook (JC) model was applied and the results compared with equivalent stress-strain curves obtained from tensile tests at elevated temperatures. The finite element (FE) simulation results for a ductile fracture were compared with the experimental results for a (80 mm × 80 mm × 25 mm) square shape with a 45 and 60 deg wall angle, respectively, and a (80 mm × 80 mm × 20 mm) square shape with a 70 deg wall angle. The trends of the FE simulation results agreed quite well with the experimental results. Finally, the effects of the process parameters, i.e., the tool down-step and tool radius, on the ductile fracture value and FLC at fracture (FLCF) were also investigated using the FE simulation results.
Nguyen, Duc-Toan; Park, Jin-Gee; Kim, Young-Suk
Oxide matrix composite by directional oxidation of a commercial aluminum-magnesium alloy
Oxidation rates of a commercial Al-Mg alloy, Al-5083, were investigated to understand the synthesis of an oxide-based composite. In some experiments, the oxide layer was grown with several platinum wires embedded in the matrix to facilitate transport of electrons. The oxidation rate was not controlled by the rate of transport of the electrons and positive holes through the ceramic oxide layer. In the initial phase of the composite growth, an incubation period was observed due to formation of MgO on the alloy surface. At 1,273 K or higher, the incubation period was followed by a period of sustained oxidation after MgO was converted to a spinel layer. It is demonstrate that, after the initial incubation period, the rate of oxidation is influenced by the rate of transport of ions through the oxide matrix composite.
DebRoy, T.; Bandopadhyay, A.; Roy, R. (Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering)
Ignition and combustion of aluminum/magnesium alloy particles in O2 at high pressures
The ignition and combustion of Al, Mg, and Al/Mg alloy particles in 99 percent O2/1 percent N2 mixtures is investigated at high temperatures and pressures for rocket engine applications. The 20-micron particles contain 0, 5, 10, 20, 40, 60, 80, and 100 wt pct Mg alloyed with Al, and are ignited in oxygen using the reflected shock in a single-pulse shock tube near the endwall. Using this technique, the ignition delay and combustion times of the particles are measured at temperatures up to 3250 K as a function of Mg content for oxygen pressures of 8.5, 17, and 34 atm. An ignition model is developed that employs a simple lumped capacitance energy equation and temperature and pressure dependent particle and gas properties. Good agreement is achieved between the measured and predicted trends in the ignition delay times.
Roberts, Ted A.; Burton, Rodney L.; Krier, Herman
Fusion cutting of aluminum, magnesium, and titanium alloys using high-power fiber laser
The effects of cutting speed and assist gas pressure on laser cutting of 1-mm thick Al 1050, AZ31, and Ti6Al4V lightweight alloys are experimentally investigated. Fiber laser cutting of these materials is not broadly investigated and the acquisition of a new level of knowledge is of fundamental importance for applications like sheet metal trimming in automotive industry. The main process outputs are in depth compared with results reported in literature and obtained by cutting with CO2 and Nd?YAG lasers. The good cut quality, the high productivity, and the easy delivery of the beam obtained at the same time, corroborate the advantage of using fiber lasers for thin sheets lightweight alloys cutting.
Scintilla, Leonardo Daniele; Tricarico, Luigi
Hot compression behavior of the AZ91 magnesium alloy produced by high pressure die casting
The hot deformation behavior of a Mg–9Al–1Zn alloy produced by high pressure die casting has been investigated by means of compression tests in the temperature and strain rate ranges of 125–300°C and 1.6×10?5 to 10?1s?1, respectively. The samples were deformed in the high pressure die casting state or after an exposure at 415°C for 2h to evaluate any different response
E. Cerri; P. Leo; P. P. De Marco
Enhanced ductility in an aluminum-4 Pct magnesium alloy at elevated temperature
A considerable enhancement of the tensile ductility in a commercial Al-4 pct Mg alloy is observed during deformation at elevated\\u000a temperatures (up to 250?C) and slow strain rates. Total elongations of ?175 pct at 250?C were obtained compared to 27 pct\\u000a at ambient temperature. Much of this ductility was a result of large increases with temperature in the post uniform
Robert A. Ayres
Solidification modeling and experimental investigation of aluminum-rich aluminum-copper-magnesium-zinc alloys
The microstructure and microsegregation of two ternary Al-rich alloys, Al-3.9Cu-0.9Mg and Al-15Cu-1Mg, and a quaternary Al-rich Al-3.86Cu-0.89Mg-0.99Zn alloy were studied by using microscopic modeling coupled with the information of real phase diagram. The microscopic model calculations include Scheil conditions, back diffusion in the solid, dendrite arm coarsening, and undercoolings of dendrite tip and the formation of eutectic mixture. The modeling results were verified with experimental measurements in present study. The dendritic microstructure was found in all three alloys directionally solidified with cooling rates varying between 0.039 and 2 K/s. It was found that the area scan method is the best way for obtaining solute distributions in multi-component alloys with complex dendritic microstructure. The cylindrical geometry in the microscopic modeling was found to be the best for describing the dendrite arm growing. The model-calculated solute concentration profiles including the effects of back diffusion in the solid and dendrite arm coarsening were in good agreement with those experimental measurements. In contrast, the calculated results under the Scheil conditions were not satisfactory. For the cooling rates studied, the effect of undercoolings, of dendrite tip and eutectic can be neglected. It was found that the accuracy of phase diagram information for multi-component system had a significant influence on the calculation results. A weighted averaging procedure was used to get results in accord with experimental data for the model-calculated microsegregations of solute elements Mg and Zn when the remaining liquid reaches the region in which two solid phase form.
Xie, Fanyou
Realization of high strength and high ductility for AZ61 magnesium alloy by severe warm working
Extruded Mg–6%Al–1%Zn (AZ61) alloy bar was subjected to 4-pass Equal Channel Angular Extrusion (ECAE) processing at 448–573K. At the processing temperature of 448K, extremely fine grains with the average grain size of 0.5?m are formed as a result of dynamic recrystallization originated by fine Mg17Al12 (?) phase particles having 50–100nm diameter dynamically-precipitated during ECAE processing. The sizes of both ?
Yu Yoshida; Keita Arai; Shota Itoh; Shigeharu Kamado; Yo Kojima
Friction stir welding of AZ-91 and AM-Lite magnesium alloys
The objective of this paper was to report the results of butt joint quality of friction stir welding (FSW) of samples of alloys of MgAlZn group. Welding has been carried out with the FSW tool of welding speed ranging from 140 to 355 mm\\/min. In the stir zone and the surrounding, neither porosity nor cracks have been obtained. Microhardness in the
Lechos?aw Tuz; Pawe? Ko?odziejczak; Andrzej Kolasa
Effect of magnesium content on the semi solid cast microstructure of hypereutectic aluminum-silicon alloys
A comprehensive study of microstructural evolution of A390 hypereutectic aluminum-silico