Room temperature superelasticity in a lightweight shape memory Mg alloy

To realize a superelastic Mg-Sc lightweight alloy at room temperature, we investigated the stress-strain behavior of Mg-18.7 at.% Sc alloy sheets at room temperature with martensitic transformation starting temperature of approximately -90 degrees C. We found that the superelasticity of the alloy strongly depends on the grain size and a distinct room temperature superelasticity (similar to 3% superelastic strain) was obtained in the alloy with a large grain size. The obtained maximum superelastic strain was smaller than that expected from the orientation dependence of the transformation strain. This result suggests that the stress-induced martensite phase was stabilized because of the introduction of slip defects. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.