Microstructure and Mechanical Properties of Welded Joint of AZ61 Magnesium Alloy Plates by TIG Welding

AZ61 plates with 3 mm thickness were welded by TIG welding with AZ31 and AZ61 welding wires,respectively.The influences of welding wires on the strength of the welded joints of AZ61 magnesium alloy plates were investigated.By OM,SEM,X-ray diffraction and etc.,the morphology,microstructure,deposited phase and mechanical properties were analyzed.The results show that the good appearance of the welded joint can be obtained with both AZ31 and AZ61 welding wires,the morphology of the welded joint with AZ61 welding wire is better than with AZ31 welding wire.The microstructure of the welded zone is fine equiaxed grain,which consists of α-Mg and β-Mg17Al12,and the microstructure of the heat affected zone is coarser.The microhardness of the weld zone and heat affected zone is lower than the base metal with AZ31 welding wire.With AZ61 welding wire,the microhardness of the weld zone is higher than base metal,while that of the heat affected zone is lower.The tensile fracture always occurs in the coarse grain of heat affected zone.