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The characteristic of interface microstructure for aluminum-steel butt joint by arc assisted laser welding-brazing

An arc-assisted laser welding-brazing technique was used to join 5A06 aluminum alloy to galvanized steel. The result shows that a layer of intermetallic compounds (IMC) consisting of Fe4Al13 and Fe2Al5 are formed along the interface between the Al alloy and the steel. Both the shape and thickness of the IMC layer vary spatially, and there is a significant portion of Fe2Al5 IMC near the galvanized steel. The interface morphology of Fe2Al5 and steel changes from tongue-like shape to straight with the increase of laser power, and the Fe4Al13 IMC from dotted-like shape to needle like shape. The weld joint with straight Fe2Al5-steel interface morphology exhibits low tensile strength from 65Mpa to 92 MPa. The tongue-like Fe2Al5-steel interface morphology may play a role of ‘nailing’, which can inhibit the rapid propagation of cracks and improve the bonding strength. The Fe2Al5 IMC show the highest hardness of 8.39 GPa and low dissipation of plastic energy for the nanoindentation test.