Effect of interfacial reaction layer continuity on the tensile strength of resistance spot welded joints between aluminum alloy and steels

We have joined aluminum alloy A5052 to cold-rolled steel SPCC and austenitic stainless steel SUS304 using resistance spot welding. The interfacial microstructures have been observed using scanning electron microscopy and the tensile strength of the joints have been examined by cross tension testing. We have investigated the effect of interfacial reaction layer on the tensile strength of the joints based on the analyses of the fracture surfaces and the distribution of reaction layer thickness in the welding interface for two types of dissimilar materials joints. The results reveal that the tensile strength of joint is related to the fraction of discontinuous reaction layer.