Effects of heating process on the microstructures and tensile properties of friction stir spot welded AZ31 magnesium alloy plates

In this paper, the effects of heating process on the microstructures and tensile properties of a friction stir spot welding (FSSW) welded AZ31 magnesium alloy were investigated by microstructural observations and tensile tests. The results shown that compared with the FSSW welded joint, the width of the bonded zone of the heating FSSW welded AZ31 magnesium alloy joint increased remarkably, while the width of the partial metallurgical zone and the number of the voids formed in it reduced. The tensile test results indicated that the increase of the heating temperature improved the tensile shear load (TSL) of the heating FSSW welded joint greatly when the heating temperature was lower than 573 K. However, the TSL of the heating FSSW welded joint decreased when the heating temperature was more than 573 K due to the coarsening of the grains.