Microstructure evolution and statistical analysis of Al/Cu friction-stir spot welds

In this paper, friction-stir spot welding (FSSW) is performed on 3 mm thick AA1060 and C11000 using different process parameters and tool geometries. The microstructure- and the microhardness-profile analyses were conducted and the probability distribution function (PDF) of the obtained microhardness values was determined. Optical images showed a good material mixing in most of the spot welds produced, whereas the energy-dispersive-spectroscopy (EDS) analysis showed the presence of intermetallic compounds. Microhardness results revealed that process parameters and tool geometries have significant effects on the distribution of microhardness values in different locations of the produced spot welds. Furthermore, goodness-of-fit values showed that most of the R² values ranged between 0.8842 and 0.9999, which indicated how well the model fits with the experimental data. On the other hand, the residuals comprised positive and negative runs which also indicated the existence of a certain correlation with the experimentation.