Compressive deformation of Mg–Zn–Y–Zr alloy processed by equal channel angular pressing

An ultrafine-grained (UFG) Mg–Zn–Y–Zr magnesium alloy with a grain size of about 0.8 μm was produced by subjecting the extruded alloy to equal channel angular pressing (ECAP) for eight passes at 473 K. Compressive testing was performed on the as-extruded and on the further ECAP-processed Mg–Zn–Y–Zr alloy at a temperature of 423 K and under strain rates from 1.67 × 10−3 to 1.67 × 10−1 s−1. In the UFG ECAP-processed magnesium alloy, the strain hardening rate was extremely low, in contrast to that of the extruded alloy. The ultrafine grains of the ECAP-processed alloy were stable in compression because of the presence of the dispersion of a fine I-phase and of precipitates in the alloy, which restricted grain growth. The ECAP-processed alloy exhibited a higher strain rate sensitivity exponent than the as-extruded magnesium alloy, which may have contributed to its enhanced ductility.