TIG welding of AZ31B magnesium alloy plates

TIG welding test of AZ31B magnesium alloy plates with the thickness of 5 mm was carried out.The microstructures,tensile fracture surfaces,and mechanical properties of welded joints were investigated by means of an optical microscope,a scanning electron microscopy,a universal tensile testing machine and a microhardness testing instrument.The effects of the welding current on the microstructure and mechanical properties of welded joints were discussed.The results show that when TIG welding was used to weld AZ31B magnesium alloy plates with the thickness of 5 mm,the welded joints with a smooth weld surface can be obtained at the welding current range from 130 to 145 A.When the welding current is 145 A,the maximum tensile strength of the welded joints is 248.6 MPa,approximately 84.0% of the strength of the base material.The microhardnesses of the weld zone(WZ) and the heat affected zone(HAZ) of AZ31B magnesium alloy plates are reduced,and the microhardness in HAZ is the lowest.When the welding current is 145 A,there are a large number of dimples on the tensile fracture surface of welded joint,and this fracture belongs to the tough fracture.