The thermal cycle during the dissimilar friction spot welding of aluminum and magnesium alloy

The thermal cycle during dissimilar friction spot welding of Al alloy AA5754 to Mg alloy AZ31 was measured by thermocouples located in the weld region. The results revealed that the weld is exposed to a non-equilibrium solidus temperature induced by rapid heating and cooling. Microstructural analyses showed that the grain structure development in the stir zone was affected by grain boundary diffusion, interfacial diffusion and dynamic recrystallization, which resulted in fine equiaxed grains of Al12Mg17 in the weld center.