Effect of Yttrium on High Temperature Strength of Magnesium

Abstract

The characteristics of high temperature deformation in Mg–Y alloys were investigated and compared with those of pure Mg. The effect of Y on slip and twinning deformations was also discussed in respect to the lattice parameter with temperature. Pure Mg displays a gradual decrease in proof stress with increasing temperature. However, the proof stress of as-quenched Mg–Y alloys remains unchanged until about 573 K . The strain rate sensitivity of pure Mg increases above 400 K, whereas in Mg–Y alloys, it becomes larger above 550 K . It is deduced that the increase of the m value is due to the dependence of non-basal slip on temperature. Single slip line and twinning were observed in pure Mg deformed at low temperature. Above 473 K, much cross slip and twinning occurs. In the case of Mg–8Y alloy, cross slip was observed at 673 K only and there was no twinning at any temperature. This is interpreted due to the observation that the c⁄a is constantly maintained by the addition of Y with increasing temperature, resulting in the restraint of the non-basal slip and twinning.