Superplasticity of a fine-grained Mg–9Gd–4Y–0.4Zr alloy evaluated using shear punch testing

The superplasticity of an extruded fine-grained Mg–9Gd–4Y–0.4Zr alloy was investigated by measuring the strain rate sensitivity using shear punch testing (SPT). Shear punch tests were conducted at shear strain rates in the range of 3×10−3–2×10−1s−1 and at temperatures in the range of 573–773K. The results indicate the strain rate sensitivity, m, increases from about 0.11 at 573K to about 0.40 at 723K and then decreases to 0.32 with a further increase in test temperature. A strain rate sensitivity of 0.40 and an activation energy of 140kJ/mol are indicative of a superplastic deformation behavior dominated by grain boundary sliding accommodated by lattice diffusion at temperatures above 673K