Effects of Nanosecond Laser Scanning Paths on Weld Formation, Microstructure and Mechanical Properties of Dissimilar Ultra-Thin Al/Cu Foil Nanosecond Laser Welded Joints

A nanosecond laser is used to weld 35 μ m thickness copper and 100 μ m thickness aluminum foil. The influence of nanosecond laser scanning paths on the weld formation, microstructure and mechanical properties is investigated. The results show that the weld formation of the polygonal nanosecond laser scanning path presents obvious anisotropy. The microstructures of the nanosecond laser welded joints of the two scanning paths are similar, mainly composed of the columnar γ-Cu 9 Al 4 , blocky θ-CuAl 2 phase and reticular θ-CuAl 2 + α-Al eutectic phase. During the tension-shear test of the Al/Cu nanosecond laser welded joint, stress concentration and crack initiation begin to occur along the brittle intermetallic compounds (IMCs) of massive θ-CuAl 2 at the interface, and then, the crack propagates along the reticular θ-CuAl 2 and finally fracture failure occurs. Considering the welding efficiency and mechanical properties, a spiral scanning path is recommended.