The novel two-step spot FSW technique was applied to dissimilar welding of 6061 Al to SPCC steel. After welding, the Al upper plate exhibits greatly refined grain structure, while the SPCC lower plate exhibits slightly refined grain structure. At the interface of the Al/SPCC welds, a few submicro-sized intermetallic compounds can be observed. The Al/SPCC welds show high tensile strength. The effect of welding parameters on the mechanical properties was also investigated.
