Microstructure characteristics of resistance spot welds of AZ31 Mg alloy

The experimental investigation was carried out to study the weld microstructure of resistance spot welding of AZ31 Mg alloy 1 mm thick. A fine and homogeneous non-equilibrium microstructure of globular alpha grains, surrounded by eutectic mixtures of alpha and beta (Mg17Al12), was achieved. The thermal - electrical - mechanical analysis model was employed to simulate the thermal history and the temperature gradient. It was found that a combination of the welding conditions and the particular thermophysical properties of the AZ31Mg alloy established a uniform temperature distribution throughout the weld pool and this thermal condition is ideal for nucleation throughout the melt metal and equiaxed grain structure forming.