Elucidation of fatigue crack propagation behavior in dissimilar aluminum alloy and steel joints from resistance spot welding

Abstract The resistance spot welding of steel and aluminum alloys was developed to achieve multimaterial structures in the automotive industry. A layer of intermetallic compounds is produced at the joint interface, but dissimilar joints with high strength can be achieved by optimizing the welding conditions and selection of electrodes. This study clarified the fatigue crack propagation behavior of resistance spot welds of steel and aluminum alloys for structural parts of vehicle bodies. Consequently, dissimilar joints with aluminum alloys and steel sheets achieved a similar level of fatigue strength compared to those with same-material aluminum alloy and steel joints. In terms of fatigue crack propagation behavior of the dissimilar joints, a fatigue crack initiated on the aluminum alloy loaded side of the joint interface in the early stage of fatigue life and then propagated unstably in the intermetallic compound layer. The fatigue fracture mechanism was influenced by the thickness and distribution of the intermetallic compound layer and the indentation shape of the joined area on the aluminum alloy.