High Temperature Mechanical Properties of AZ91 Magnesium Alloy Weld Joint

Magnesium alloys are widely applied in aircraft and automotive industry, due to their low density and high specific strength. Welding methods can be used to join Mg alloy elements and to repair or regenerate defective or worn-out castings. Therefore the influence of weld joint’s microstructure on mechanical properties needs to be studied. In present paper high temperature mechanical properties of AZ91 Mg alloy weld joint was investigated. Tensile tests were conducted in temperature range between 20 and 200°C. Ultimate tensile strength decreased as the temperature increased from 50°C. At temperature up to 150°C rapture occurred in the base metal, at 200°C rupture location switched to the weld fusion zone. Based on metallographic and fractographic observation, the fracture mechanism was described. Macro crack formed from the merger of micro cracks occurring at massive β phase precipitates.