Microstructure characteristics and mechanical properties of laser weld bonding of magnesium alloy to aluminum alloy

Weldability of magnesium alloy to aluminum alloy in laser weld bonded (LWB) joints was investigated. Results showed that magnesium/aluminum could be easily joined by LWB under proper technological parameters. The weld was characterized by complex vortex flow at the bottom, and there existed intermetallic compound layer between weld pool and lower sheet metal, which was composed of the brittle phases of Al3Mg2 and Al12Mg17, resulting in the formation of weld cracking. Adhesive in the weld was heated up and then escaped in the form of gas, which would not affect the microstructures of weld. However, Adhesive near the weld was oxidized and carbonized, leading to the formation of a failure zone. But this failure zone had little influence on load bearing capability of the joints. Besides, it was also found that the penetration of LWB joints was greater than that of laser welded joints alone. In tensile shear test and T-peel test, LWB samples gave both the highest shear resistance and the highest peel resistance compared to laser welded samples and adhesive bonded samples.