Dissimilar joining of aluminum alloy and stainless steel thin sheets by thermally assisted plastic deformation

Abstract Aluminum alloy/steel hybrid components are widely used in different industrial areas because of their high performance. However, the high importance of reducing the thickness of components to realize lightweight products requires the dissimilar joining of Al alloy and steel thin sheets (less than 1 mm in thickness), which is a major challenge using current joining technologies. In this paper, an alternative dissimilar joining process by thermally assisted plastic deformation is proposed for thin metallic sheets. The effects of various parameters on the joining performance were investigated. After exposure to an elevated temperature of 450 °C for 22 s, an optimized joint type was achieved by local plastic deformation using a punch-die pair. This joint type exhibited an average joint efficiency factor of 85.2%, and an average absorption energy of 1.69 kN mm in tensile shear tests, as well as satisfactory joining performance in peel tests. In addition to mechanical anchoring and surface enlargement, atomic interdiffusion at the interface activated by the elevated forming temperature was found to be critical for obtaining high joining quality. The thickness of the Fe-Al interdiffusion layer at the interface was positively correlated with the heat input and the locally distributed plastic strain. This study shows that the proposed dissimilar joining process for Al alloy and steel thin sheets is a promising joining method for Al alloy/steel lightweight structures owing to the excellent joining performance, weight effectiveness, simple operation and long tool lifetime.