Microstructures and properties of laser-MIG arc hybrid brazed-fusion welded joint of Al alloy to galvanized steel

• 1、Institute for Material Joining, Shandong University, Jinan 250061

Abstract：According to the differences in melting point between Al alloy and steel, 5A02 Al alloy was jointed to galvanized steel by laser-MIG arc hybrid brazing-fusion welding with ER4043(AlSi5) filler wire, the effect of welding heat input on weld appearance, microstructures and mechanical properties of the brazed-fusion welded joint was analyzed. The welded joint can be divided into fusion welded joint and brazed joint. The microstructures of the fusion weld are α-Al solid solution equiaxed grains and short rod-like Al-Si eutectic at grain boundary. The zinc-rich zone in fusion weld toe is consisted of α-Al-Zn solid solution and Al-Zn eutectic. The brazed seam is the Fe-Al intermetallic compounds (IMCs) layer, whose thickness is 2μm-4μm. The IMCs include FeAl2, Fe2Al5 and Fe4Al13 in the real interface. FeAl2 and Fe2Al5 are located in reaction layer near the steel side, and Fe4Al13 with tongue shape or sawtooth shape grows towards the fusion weld. The tensile strength of brazed-fusion welded joint firstly increases and then decreases with the welding current and laser power being increased, and the highest tensile strength can be up to 247.3MPa. The fracture usually occurs at fusion zone of the fusion weld, which belongs to a ductile fracture. ?????

Keywords： Brazed-fusion welding welding of dissimilar metal Hybrid welding Al alloy/Steel；Mechanical properties Intermetallic compounds