Low-temperature superplasticity of friction stir processed Al–Zn–Mg–Cu alloy

Friction stir processing was used to produce ultrafine-grained Al–Zn–Mg–Cu alloy. Low-temperature superplasticity of 350–540% was achieved at 200–350 °C. Increasing the temperature resulted in an increased optimum strain rate for maximum elongation. At 350 °C, the optimum strain rate shifted to a high strain rate of 1 × 10−2 s−1. A strain rate sensitivity of 0.33–0.42 was observed for maximum elongation at the investigated temperatures. Grain boundary sliding was observed even at 200 °C.