Interfacial microstructural characterization and mechanical properties of inertia friction welding of 2219 aluminum alloy to 304 stainless steel

Aluminum alloy/steel hybrid components are receiving more and more attention in recent years due to their great potential in reducing weight while maintaining the mechanical properties of the structure. Inertia friction welding was performed to join 2219 aluminum alloy (Al alloy) bar to 304 stainless steel bar. The effects of welding parameters on the evolution of intermetallic compounds (IMCs) and tensile strength of the joints were investigated. High-quality welded joints can be obtained at the parameters combination of the medium friction pressure (120 MPa) and low rotational speed (1100 rpm) from the experimental study. Microstructural analyses indicated that the enrichment of Cu element at the friction interface formed Al2Cu IMCs instead of Fe-Al IMCs, which was usually reported to exist at the Al alloy/steel friction welded interface. The formation of the Al2Cu IMCs layer was mainly attributed to the accumulation of Al2Cu (precipitate in 2219 Al alloy base metal) at the wavy surface of the steel, significantly promoting the growth of Al2Cu by the subsequent precipitation process. However, cracks could easily occur in a thicker Al2Cu IMCs layer at a high heat input, which seriously deteriorated the mechanical properties of joints. Therefore, the massive formation of the Al2Cu IMCs layer should be suppressed by controlling the welding parameters to avoid any internal cracks at the weld interface.