Study on microstructure and mechanical properties of 5052 aluminum alloy MIG welded joint for high-speed train

Abstract In this paper, the MIG welding process is utilized to weld a 3 mm thick 5052 aluminum alloy plate by using ER5356 welding wire as filler. The effects of different welding speeds on the microstructure and mechanical properties of the weld are systematically studied utilizing a metallographic microscope, x-ray diffractometer, scanning electron microscope, room temperature tensile, and microhardness. It was found that there were pore defects in the samples at lower or higher welding speeds, and there was no penetration at the maximum welding speed. When the welding speed is 650 mm min −1 , the weld is well-formed, the surface is flat without pores, the fish scale is evenly distributed, and the weld shows good penetration. The intermetallic compounds of all the welds are mainly composed of α (Al), Mg 2 Si, Al 3 Fe, and Al 3 Mg 2 . The mechanical properties of the samples show that the hardness of the weld reaches the maximum value of 56.7HV at this welding speed, and the tensile strength and elongation are 210 MPa and 14.3%, respectively. The fracture is located at the junction of the base metal and the heat-affected zone, and the fracture type showed typical ductile fracture.