CO2 laser beam welding of dissimilar magnesium-based alloys

In this paper, dissimilar metals welding for butting magnesium alloys AZ31, AM60 and ZK60 was conducted by a 3 kW CO2 laser beam. The microstructure and mechanical properties of joints were analyzed by optical microscope (OM), energy dispersive spectrometer (EDS), scanning electron microscope (SEM), tensile machine and hardness machine. The experimental results show that the welding heat input and the chemical composition of base metal have great influences on the formation of weld bead. The results of tensile test show that the ultimate tensile strength (UTS) of the optimum joints for dissimilar metals welding is above 90% of the base metals and even higher than one of the base metals. Many precipitates distributed in the fusion zone, whose number is related to the alloy elements. The hardness test indicates that a sudden decrease of microhardness occurs in HAZ for sides of all the metals, and the hardness in the fusion zone of AZ31-AM60 joint is slightly higher than the others. The elements analysis reveals that there is an obvious compositional gradient only in the fusion zone of AM60-ZK60 joints.