Effect of Gd solutes on the micromechanical response of twinning and detwinning in Mg

Abstract

An investigation of the effect of solutes on the migration of a single {1012} Gd decorated twin boundary in a Mg-4wt.% Gd binary alloy in terms of the corresponding stress-strain response and the defect structure in the wake of (de)twinning was undertaken in this work. The results were benchmarked against those of a pure Mg sample that was tested under same conditions. We established that the critical stresses for both twinning and detwinning increased by 29% and 10%, respectively, due to the addition of Gd. We showed that the latter is mediated by the pinning effect of Gd atoms that decorated the pre-existing twin boundaries in the alloy. Conversely, a 68% decrease in the detwinning stress was recorded in pure Mg. We attributed the decrease to the nucleation-free nature of detwinning along with the absence of solutes atoms at the pre-existing twin boundaries. Unlike previous investigations, the work does not just highlight how twinning and detwinning affects the concurrent slip activity in pure Mg and Mg alloys, it establishes a direct link between these activities and the magnitude of the observed mechanical response.