Effect of process parameters on tensile strength and morphology of friction stir spot welds of aluminium and copper

Friction stir spot welding (FSSW) is a solid-state welding process used for joining similar and dissimilar materials. AA1060 and C11000 sheets were joined using different process parameters and tool geometries. The presence of a copper rings also called hooks were observed in all the produced spot welds and their length increases with the tool shoulder plunge depth; whereas the spot welds produced at 1200 rpm for the two tool geometries exhibited a decrease and a slight increment in the length of the copper ring using a flat pin/flat shoulder and conical pin/concave shoulder, respectively. Furthermore, the mapping of the produced spot weld using energy dispersive spectroscopy (EDS) exhibited different microstructures with the presence of copper fragments and particles in the aluminium matrix. It was also observed that, the shoulder plunge depth had an effect on the shear tensile results, except for the weld produced at 800 rpm when using a conical pin and a concave shoulder.