Exceptional high-strain-rate superplasticity in Mg–Gd–Y–Zn–Zr alloy with long-period stacking ordered phase

Friction stir processing (FSP) was applied to Mg–Gd–Y–Zn–Zr casting, producing a fine-grained structure of ∼3 μm with a long-period stacking ordered phase distributed within the grains and predominantly high-angle grain boundaries. This FSP alloy exhibited superior high-strain-rate superplasticity at 350–500 °C. A maximum superplasticity of 3570% was achieved at 425 °C and a strain rate of 3 × 10−2 s−1. Such superior superplasticity is attributed to the thermally stable microstructure and good deformation compatibility.