Abstract
Magnesium alloys are considered to be a valuable engineering material since they offer a great potential to reduce weight due to their low density, good thermal and fatigue properties, among others. However, problems appear when trying to apply conventional welding techniques to these alloys. The typical low weldability of magnesium alloys with traditional joining processes involving melting is expected to be improved with Friction Stir Welding (FSW) since it is a solid state joining process. Magnesium alloys also are very susceptible to the heat effects being an advantage for the FSW process since it works at lower temperatures than the conventional methods. The FSW process is applied in this work to AZ31 plates with 2mm thick and the samples were welded at 100mm/min and 800rpm with a constant applied force of 950kg and 0.5 0 tilt angle. These alloys have been described for being very susceptible to corrosion in saline environments [1] some authors have found that usually in magnesium alloys some particles are not dissolved in the magnesium matrix and will promote pitting corrosion [2] . When analyzing the base material it was observed the existence of undiluted particles (white) that were aligned with the material matrix. After the welding, there was an increase of these particles in the heat affected zone (HAZ) while the nugget that suffers both mechanical and thermal stresses have promoted the decrease of the grain size and also reduced the number of undiluted particles in this area (Figure 1 ). After performing an EDS analysis in one of these particles it was observed that it was an AlMn particle which has not been dissolved in the magnesium matrix (Figure 2) . After a corrosion test it was observed that there was the existence of pitting corrosion promoted by these alloys (Figure 3) where the particles would act as a cathode corroding the magnesium matrix around it. While this was expected for the exposed particles it was also observed that the interior particles promote corrosion when in close vicinity of the corrosion front. The reduction of the AlMn particles will improve the corrosion properties therefore the usage of the FSW process can be effective since the nugget displayed a great reduction of these particles. It was also observed that there is an increase of particles in the heat affected zone increasing the corrosion in this area. Using higher advancing speeds will reduce the heat releases in this process and can effectively reduce the heat influence over the existing particles. The FSW process presents itself as a process that can effectively join the magnesium alloys and further studies should focus the reduction of the heat released to improve the corrosion resistance of the magnesium alloys.

Email: davisalison@example.com Magnesium alloys are considered to be a valuable engineering material since they offer a great potential to reduce weight due to their low density, good thermal and fatigue properties, among others. However, problems appear when trying to apply conventional welding techniques to these alloys. The typical low weldability of magnesium alloys with traditional joining processes involving melting is expected to be improved with Friction Stir Welding (FSW) since it is a solid state joining process. Magnesium alloys also are very susceptible to the heat effects being an advantage for the FSW process since it works at lower temperatures than the conventional methods. The FSW process is applied in this work to AZ31 plates with 2mm thick and the samples were welded at 100mm/min and 800rpm with a constant applied force of 950kg and 0.5 0 tilt angle. These alloys have been described for being very susceptible to corrosion in saline environments [1] some authors have found that usually in magnesium alloys some particles are not dissolved in the magnesium matrix and will promote pitting corrosion [2] . When analyzing the base material it was observed the existence of undiluted particles (white) that were aligned with the material matrix. After the welding, there was an increase of these particles in the heat affected zone (HAZ) while the nugget that suffers both mechanical and thermal stresses have promoted the decrease of the grain size and also reduced the number of undiluted particles in this area (Figure 1 ). After performing an EDS analysis in one of these particles it was observed that it was an AlMn particle which has not been dissolved in the magnesium matrix (Figure 2) . After a corrosion test it was observed that there was the existence of pitting corrosion promoted by these alloys (Figure 3) where the particles would act as a cathode corroding the magnesium matrix around it. While this was expected for the exposed particles it was also observed that the interior particles promote corrosion when in close vicinity of the corrosion front. The reduction of the AlMn particles will improve the corrosion properties therefore the usage of the FSW process can be effective since the nugget displayed a great reduction of these particles. It was also observed that there is an increase of particles in the heat affected zone increasing the corrosion in this area. Using higher advancing speeds will reduce the heat releases in this process and can effectively reduce the heat influence over the existing particles. The FSW process presents itself as a process that can effectively join the magnesium alloys and further studies should focus the reduction of the heat released to improve the corrosion resistance of the magnesium alloys. 

{'paper_id': '31652823', 'title': 'Corrosion Behavior of the Friction Stir Welded AZ31 Magnesium Alloy', 's2_url': 'https://api.semanticscholar.org/CorpusID:31652823', 'source': 'S2ORC'}