The Role of Ordered Phases in Enhanced Ductility of RE-Based Mg Alloys

Various experimental and modelling efforts do confirm that low concentrations of rare earth (RE) solutes in Mg enhance the room temperature ductility and weaken the deleterious basal texture that occurs during sheet forming of classical wrought Mg alloys. However, the mechanistic origin(s) of the improved ductility and texture weakening are still been debated. In order to gain insights into the underlying governing mechanisms, we carried out in-depth dislocation-strength characterization of micropillars made in single crystals of pure Mg and a Mg–0.75 at% Gd alloy oriented for basal, prismatic and pyramidal slip. We postulate that the remarkable differences in dislocation slip activity observed between these two systems, along with significant decreases in non-basal/basal CRSS slip ratios, strongly suggest that the improved formability of the RE-based Mg alloys is a consequence of ordered domains and precipitates that lie mainly on the basal planes of the alloy.