Enhancing Joint Performance of Dissimilar A6061 Aluminum and Galvanized Steel Using Dual-Beam Laser Brazing

A dual-beam laser brazing process was investigated to improve joint performance in dissimilar joining of A6061 aluminum alloy and GA steel. In this approach, a preheating beam was applied to control the interfacial condition prior to brazing, followed by a main laser beam for filler metal melting. Microstructural observations and tensile shear tests revealed that the dual-beam configuration suppressed blowhole formation and significantly enhanced wettability, leading to improved joint strength. Under the optimum condition (preheating: 200 W, main: 1.5 kW), base metal fracture occurred in both A6061/SPCC-GA and A6061/980DP-GA joints, demonstrating the superior performance of the dual-beam process. Numerical simulations were conducted to elucidate the underlying mechanisms, showing that increasing laser power increases the wetting width and decreases the bead wetting angle. Improved wettability in the dual-beam process was attributed to the elevated SPCC-GA interface temperature prior to filler metal spreading, which promotes melting of the galvanized coating and reduces interfacial resistance. These findings demonstrate that controlling the interfacial thermal condition via a dual-beam configuration is an effective strategy to enhance wettability and joint performance in dissimilar laser brazing.