Compressive behavior of ultrafine-grained Mg-Zn-Y-Zr alloy containing quasicrystalline phase

An ultrafine-grained (UFG) Mg-5.0wt%Zn-0.9wt%Y-0.2wt%Zr magnesium alloy with a rain size of about 0.8 mu m was produced by subjecting the extruded alloy to equal channel angular pressing (ECAP) for 8 passes at 473 K. Compressive testing was performed on the ECAPed alloy in a temperature range from 423 K to 523 K and under strain rates from 1.67 x 10(-3) to 1.67 x 10(-1) s(-1). The ultrafine grains of the ECAPed alloy were stable during compression because of the presence of the dispersion of a fine quasicrystal I-phase and of precipitates in the alloy, which restricted grain Growth. The activation energy for the compression at the temperature range from 423 K to 523 K is close to the value for grain boundary diffusion in magnesium, indicating that the compressive deformation is mainly controlled by grain-boundary sliding.