Microstructure and Properties of Argon Tungsten Arc Welding Joints of AZ31B Magnesium Alloy Plates

The technical characteristics of argon tungsten arc welding for AZ31B magnesium alloy plates with 2 mm thickness were discussed.The microstructure,phase composition,mechanical properties and fracture morphology of welding joints were investigated using metalloscope,X-ray diffractometer,universal tensile testing machine and scanning electron microscopy.The results show that,at 50 A welding currents,the welded joint can get good weld formation and high welding quality,with no pore and crack inside.The tensile strength of the welded joint gets to 210 MPa,which is about 87% of the base materials.Fractures occurring in weld zones are ductile-brittle fractures.The microstructure is fine equiaxed grain in welded zone,which mainly consists of α-Mg and Mg17Al12.The microstructure of heat affected zones is coarser.The results of hardness test show that the hardness of the weld zone is higher than the base materials.