Improving local formability of 6xxx and 7xxx aluminum alloy sheets using friction stir processing

Friction stir processing (FSP) was performed on four different high-strength commercial aluminum sheets to improve local formability. FSP sheets were bend tested over a safe-to-fracture range by incrementally decreasing the bend radii to find the radius-to-thickness ratio (r/t) at fracture. The processed region showed a formability improvement of 20% in 7075, 37% in 7055, 41% in 7085, and 71% in 6111 compared to the base age-hardened conditions. Local formability improvement is retained even after 2 weeks of natural aging for processed 6111 and 7055 as evidenced elongation-to-fracture values from mini tensile testing. The top and bottom surfaces of the processed sheet were bend tested in tension and compression, and the results showed that specimens processed at higher spindle speeds results in higher formability on both sides. Finally, FSP was incorporated into a robotic platform to evaluate the feasibility of local FSP for commercial applications up to a processing speed of 5 m/min.

Automated summary

Friction stir processing (FSP) was used to improve the local formability of high-strength commercial aluminum sheets. The processed sheets showed significant improvements in formability compared to the base conditions. The formability improvement was retained even after natural aging, and higher spindle speeds during processing resulted in increased formability. FSP was successfully incorporated into a robotic platform for commercial applications.