Double-sided friction stir spot welding of steel and aluminum alloy sheets

Double-sided friction stir spot welding (FSSW) of dissimilar Al/steel alloy sheets was developed, and the effects of different tool rotational directions and plunge forces on the welding quality were investigated and compared with single-sided FSSW. Experimental results show that the fracture load increases with the increasing of plunge force, and double-sided FSSW can sustain higher fracture load than single-sided FSSW regardless of the plunge force. Two rotational directions result in similar fracture load of the welded part if the plunge force is less than 1.16 kN. If the plunge force is larger than 1.16 kN, opposite rotational direction achieves higher fracture load of the welding point. The formation of intermetallic compounds under different welding conditions at the welding joint was analyzed.