Hybrid laser welding and brazing for controlling intermetallic compounds in Al/Cu dissimilar joint

Micro-welding of Al and Cu foils is increasing used in various industries, particularly in the production of battery components for electric vehicles. However, direct fusion welding of Al and Cu may compromise joint mechanical properties due to the formation of brittle intermetallic compounds (IMC). Consequently, strategies for controlling IMC to enhance joint mechanical properties have received significant research attention. In this study, lap welds of 1050 Al foil and T2 Cu foil (both 200 μm thick) are achieved using a single-mode fiber laser equipped with a scanning galvanometer. This setup enables spatial power modulation for laser spot welding via beam spiral scanning. Notably, laser fusion welding occurs along the laser beam scanning path, while laser weld-brazing is achieved through heat conduction in the spiral spacing between the adjacent scanning paths, resulting in a hybrid joint with alternated fused and brazed areas. The laser weld-brazing areas expand the effective connection area of the joint, improving its load-bearing capacity while effectively controlling IMC compared to fusion joints. The screw-type hybrid joints exhibit excellent mechanical properties, with a maximum tensile strength of 140 MPa. Experimental and simulation results indicate the mechanism for hybrid joint formation and improvement in mechanical properties. This study provides an effective strategy for regulating joint microstructure to mitigate the negative influence of IMC.