Effects of welding speed on the microstructures and mechanical properties of laser welded AZ61 magnesium alloy joints

In this paper, the effects of welding speed on the microstructures and mechanical properties of laser welded AZ61 magnesium alloy plates were investigated by microstructural observations, microhardness tests and tensile tests. The results show that the microstructure in the fusion zone consisted of fine α-Mg equiaxed dendrite crystals and dispersed β-Mg17Al12 particles. With an increase in welding speed, the sizes of α-Mg grains and β-Mg17Al12 particles in the fusion zone decreased and the volume fraction of β-Mg17Al12 particles increased. The ultimate tensile strength, yield strength and elongation of welded joint increased when the welding speed increased from 1800 mm min−1 to 2800 mm min−1. In addition, the average hardness value of fusion zone and heat-affected zone increased with the increase in welding speed.