Effect of Multilayer and Multi-pass Welding on Microstructure and Properties of Al–Mg Alloy Welding Joint

Three-layer and four-pass metal inert gas welding tests were carried out on 5A01 alloy sheet by using 5B01 wires as filler material. The research results showed that the thermal cycle of the next weld would affect one or even more welds that have been welded. The short-term high-temperature thermal cycling made different weld regions go through different peak temperatures and cooling times, which made the structure and properties of the weld show some inhomogeneity. The fine-grained layer was formed in the fusion zone due to the great degree of supercoiling, and fine Al 3 Zr particles had become the nucleating center of the inhomogeneous nucleation. Grain boundary remelting caused by high welding temperature resulted in the appearance of coarse grain at the interface of weld beads. In addition, the grain growth direction was affected by the heat dissipation direction, and the center of each weld bead was typical rapidly cooled casting structure.