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 similar to 3 mu m 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 degrees C. A maximum superplasticity of 3570% was achieved at 425 degrees C and a strain rate of 3 x 10(-2) s(-1). Such superior superplasticity is attributed to the thermally stable microstructure and good deformation compatibility. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.