Effect of Heat Input on the Microstructure and Mechanical Properties of 6060 Aluminum Alloy/Galvanized STEEL MIG Welding–Brazing Joints

In this paper, MIG welding–brazing was employed to join a 1.5-mm-thick 6060 aluminum alloy and a 2-mm-thick galvanized steel, using a 1.2-mm ER4043 welding wire as the filler. The microstructure, phase structure, and element distribution of the welded joint interface layer were analyzed using SEM, XRD, and EDS. The tensile strength of the joint and the hardness distribution of the interface layer were tested. The study found that when the welding current was around 60 A, the interface layer formed optimally, and the tensile strength of the welded joint reached a maximum value of approximately 200 MPa. During the welding process, an intermetallic compound (IMC) Fe₂Al₅ with lower free energy was formed at the joint interface. As aluminum atoms continuously diffused toward the steel side and reacted with iron, a compound FeAl₃ precipitated on the side closer to aluminum.