Abstract:

      Argon tungstenarc welding (TIG) is the most popular welding method for magnesium alloys. AZ31 extruded plates with thickness of 6.0 mm were welded by DC-TIG welding. Microstructure and mechanical properties of welded joint of AZ31 magnesium alloy were studied by optical microscopy, scanning electron microscopy and tensile test machine. The microstructure analysis shows that the welded joint is composed of base material, heat affected zone and weld zone. A transition zone appears near the groove between the heat affected zone and the weld zone, which is the mix-fusion zone. The average tensile strength and the elongation of the welding joint is 241.0 MPa and 13.8% respectively, which arrives to 86.0% and 13.8% respectively of the base material. The fracture of welding joints is located in heat affected zone and the fracture surface presents mix fracture characteristics.

Key words: magnesium alloys;argon tungstenarc welding;microstructure;mechanical properties