A Study on Phase Evolutions and Tensile-Shear Performance of Dissimilar Resistance Spot Welds Formed Between AISI 430 Ferritic Stainless Steel and AISI 321 Austenitic Stainless Steel

This article addresses the phase evolutions and mechanical properties of dissimilar spot welds formed between AISI 430 stainless steel (FSS) and AISI 321 austenitic stainless steel (ASS). It was revealed that the fusion zone (FZ) microstructure consisted of three phases of ferrite, austenite, and martensite as well as precipitates. The heat-affected zone (HAZ) of 430 FSS had a dual-phase microstructure including coarse ferrite grains and martensite at the ferrite grain boundaries. Also, there are relatively large austenite grains, precipitates, and abundant twins in the HAZ microstructure of 321 ASS. The results of the tensile-shear test showed that peak load and failure energy were increased by enhancing the welding current from 1 to 4 kA. On the other hand, peak load and failure energy were firstly enhanced by an increase in the welding time from 1 to 2 s. Then, the peak load decreased by an enhancement in the welding time from 2 to 3 s. Finally, they improved by increasing the welding time from 3 to 4 s. In addition, it was found that the resistance spot welds failed by the pull-out failure (PF) mode in all welding currents of 1, 2, 3, and 4 kA and all welding times of 1, 2, 3, and 4 s.