Microstructure and Properties Analysis of Laser Welding and Laser Weld Bonding Mg to Al Joints

Laser welding and laser weld bonding (LWB) Mg to Al joints were obtained in different welding parameters. The penetrations and microstructures of these kinds of joints changed with the increasing of pulse laser power density. Both laser welding and LWB Mg to Al joints with the best properties were obtained in conductive welding mode. In laser welding Mg to Al joint, several intermetallics formed at the bottom of the fusion zone, where some cracks were generated. In laser weld bonding Mg to Al joint, the decomposition of the adhesive caused a baffle effect on the diffusion between the Mg and the Al. The intermetallics formed in the middle of the fusion zone, and the thickness of Mg₁₇Al₁₂ layer was approximately 10 to 20 μm and the Mg₂Al₃ layer was less than 5 μm, which influenced the property of the joint less.