PREPARATION OF Mg-7Sn-1Ca MAGNESIUM ALLOY AND STUDY OF ITS RESISTANCE SPOT WELDING MICROSTRUCTURE AND MECHANICAL PROPERTIES

This paper investigated a 1.5-mm-thick Mg-7Sn-1Ca magnesium alloy through resistance spot welding, examining how the welding current affects the joint microstructure, nugget diameter and tensile strength. Various experimental techniques, including tensile tests, microhardness testing, optical microscopy, and scanning electron microscopy, were employed for a detailed analysis. The optimal mechanical performance was achieved under conditions of 14 kA current, 1 kN pressure, and 0.4 s welding time, with a tensile strength of 1.0295 kN and nugget diameter of 2.25 mm. The welded joints mainly consist of a nugget zone and a heat-affected zone. The nugget zone exhibits the highest microhardness, significantly exceeding that of the heat-affected zone and the base metal. The nugget zone is primarily composed of equiaxed dendrites and columnar dendrites, with grain coarsening observed in both the nugget and heat-affected zones. The microstructural features, fracture-surface morphology, and microhardness distribution of the joints were thoroughly investigated. These analyses provide valuable data on joint performance, aiding in the further understanding and optimization of the welding process.