Abstract: High efficiency and quality fusion-brazing joining between 5A02 aluminium alloy and zinc-coated steel sheet, based on laser-MIG hybrid welding, is successfully done. The seam appearance and the mechanical properties as well as the microstructures of the joints are analyzed. The results indicate that a high speed fusion-brazing joining can be achieved with this welding method, and the highest welding speed is up to 5 m/min. A brazed joint between the aluminium alloy and the steel is formed, and the steel sheet under the seam is not melted. The top tensile strength of the joint is 153.1 MPa, about 75.7% of that of the aluminium alloy base metal. It is almost as high as that of the aluminium alloy’s fusion joint. In tensile test, the specimen fracture is in the heat-affected zone of aluminium aside. It can be sure that the main fracture form of the joint is ductile fracture, but has the trace of brittle fracture. The analysis on the microstructure of joint shows that a thin intermetallic compound layer is generated on the brazing interface, but its average thickness is only about 1.51 μm. It’s confirmed that the compound layer is composed of Fe3Al, FeAl2, Fe2Al5 and FeAl3, and the zone of these intermetallic compounds abounds in silicon.

Key words: Dissimilar metals, Fusion-brazing joining, Hybrid welding, Laser, MIG arc