Study on Microstructure and Mechanical Properties of Aluminum–Copper Dissimilar Metals Joints by Nanosecond Laser Spiral Welding

Aluminum–copper dissimilar metals were successfully welded by nanosecond laser and optical galvanometer scanning. The joint formation, microstructure characteristics, and mechanical properties under different lap forms were studied. The results showed that when the joint was Al (upper)/Cu (under), the metal on the aluminum side melted completely. Part of the aluminum intruded into the copper base material to form a “V”-shaped weld. When the joint was Cu (upper)/Al(under), the weld consisted of multiple "nail"-shaped welds. In the two overlapping forms, the welds were mainly composed of four structures: γ2-Cu9Al4 phase region, hypereutectic region, eutectic region, and hypoeutectic region. The weld penetration formed by the Cu/Al joint was greater than that of the Al/Cu weld.