Achieving high strain rate superplasticity in Mg–Zn–Y–Zr alloy produced by friction stir processing

Friction stir processing was applied to hot-rolled Mg–Zn–Y–Zr alloy to produce a fine-grained structure 4.5 μm in size with fine, uniformly distributed Mg3Zn3Y2 particles and predominant high-angle grain boundaries (HAGBs) of 91%. A maximum superplasticity of 1110% was achieved at a high strain rate of 1 × 10−2 s−1 and 450 °C. The superior superplasticity at this high strain rate is attributed to the excellent thermal stability of the fine-grained structure and the high percentage of HAGBs.