Abstract
Replacing steel with aluminum alloy is appealing to realize the lightweight of ship structure, so it is inevitable to weld these two materials in products. When joining AA5083 aluminum alloy to FH36 steel with the thickness of 6 mm by tungsten inert gas (TIG) arc welding process, the liquid Zn-based filler metal reacted with steel matrix to form Fe-Zn intermetallic compounds (IMCs) and Fe-Al IMCs. A novel interface structure composed of spinous Г-Fe3Zn10, thinner η-Fe2Al5Zn0.4 and a small number of dispersed δ-FeZn10 with a relatively high bonding strength can be obtained at the weld seam/steel interface by optimizing the backing welding current. When the backing welding current was 120 A, the maximum tensile strength of joint could reach 98 MPa. Simulation indicated that a large stress concentration developed at the weld seam/steel interface, within crack active temperature range of Fe-Zn and Fe-Al IMCs, during the backing welding process. The lattice misfit of δ-FeZn10/η-Fe2Al5Zn0.4 and Г-Fe3Zn10/η-Fe2Al5Zn0.4 interfaces were 19.9% and 9.4%, which revealed that dislocations were more likely to accumulate around δ-FeZn10, providing the location of crack initiation in aluminum alloy/steel welded joints.
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