The weldability in dissimilar joints of AA5052 and SPFC780DP steel by hybrid friction stir welding

The dissimilar welding of aluminum alloy and steel has become increasingly attractive in the automotive industry for achieve lightweight components. However, welding of these dissimilar materials is difficult when using conventional fusion welding due to differences in thermo-physical properties and the formation of intermetallic compounds (IMCs) at the Al–Fe joint interface. In this study, the dissimilar welding of 2.0-mm thick sheets of aluminum alloy (AA5052) and steel (SPFC780DP) sheets was carried out using hybrid friction stir welding (HFSW) with an additional heat source of gas tungsten arc welding (GTAW). Furthermore, the effects of process parameters on the mechanical and microstructure characteristics of joint were investigated. The results showed that the maximum tensile strength of the joint was 199 MPa, which exhibited a joint efficiency of about 90% of compared to the aluminum alloy base metal. A thin interfacial layer with a thickness of about 1.0 µm, consisting of Fe₃Al and FeAl₃ IMCs, was observed at the joint interface through SEM–EDS analysis, indicating an acceptable range for the thickness of IMCs.