Structure and Property of Aluminum-Steel Dissimilar Metal Joint by Laser Fusion Brazing with Addition of Different Alloy Powders

5A06 aluminum alloy and ST04Z galvanized steel plates with different thicknesses were joined by laser fusion brazing after precoating with five alloy powders enriched with Si, Mg, Mn, B, Zn elements, respectively. The microstructure, tensile properties and corrosion resistance of the welded joint were studied. The results show that an intermetallic compound layer was formed at the interface of the joint; the intermetallic compound formed near the galvanized steel side was mainly composed of Fe₂Al₅ and near the aluminum alloy side was mainly composed of FeAl₃. The intermetallic compound layer obtianed by precoating with B-rich alloy powder was the thickest. All the joints fractured at the weld in a mixed mode that was dominated by ductile fracture and supplemented by brittle fracture. The tensile strength of the joint obtained by precoating Si-rich alloy powder was the largest. The corrosion resistance of the joint was the best after welded by precoating with Mn-rich alloy powder, and decreased when precoating with Mg-rich, Si-rich, and Zn-rich alloy powders in turn. The corrosion was likely to occur at the interface between intermetallic compound layer and alumium alloy.