Microstructure and mechanical properties of 6061/galvanized steel laser-arc hybrid fusion-brazed welded joint: experiment and first-principles calculation

In this study, 6061 aluminum alloy and galvanized steel fusion-brazed lap joints were obtained using a laser-arc hybrid heat source, and the effects of laser power variation on the microstructure, mechanical properties, and fracture mechanism of the joints were analyzed. The results showed that the tensile shear load initially increases with rising laser power, followed by a decrease. At a laser power of 240 W, the maximum tensile shear load was 2479.8 N/cm and the weak section of joint was in the Al-Fe reaction layer consisting of Fe(Al,Si)₃, Fe₂(Al,Si)₅, and Fe(Al,Si) intermetallic compounds (IMCs). Computational results showed that the inherently high brittleness and hardness of Fe(Al,Si)₃ and the high mismatch rates of Fe(Al,Si)₃/Al interfaces were the key factor leading to the failure of the joints at lower heat input.