A Comparative Study on Stationary-Shoulder and Conventional Friction-Stir-Processed Al-6061 Alloy

Al-6061 sheets of 3 mm thickness were subjected to stationary-shoulder friction stir processing (S-FSP) and conventional friction stir processing (C-FSP) using similar processing parameters. The results showed that sound C-FSP samples could be obtained by all the selected parameters, while only high rotational (or low traverse) speed was suitable for S-FSP. The surface of S-FSP sample became smooth in comparison with C-FSP sample; moreover, the application of stationary-shoulder refined the grains further in the stir zone and inhibited the coarsening of precipitates in the heat-affected zone. For defect-free FSP samples, the tensile strength of S-FSP sample was a bit lower (about 10%) than that of C-FSP sample; however, the elongation of S-FSP sample increased due to the fine microstructures of fracture location.