Development of Mg-Based Superelastic Alloy Through Aging Heat Treatment

Abstract

The effect of aging heat treatment on microstructure, hardness, and superelasticity at room temperature was investigated herein for Mg-18.8 at.% Sc alloy. The hardness of the alloy is increased via aging heat treatment at temperatures between 423 and 523 K, from ~ 90 Hv (as-quenched condition) to a maximum of 180 Hv. Aging heat treatment at a higher temperature reduces the incubation time before the onset of age hardening. Scanning electron microscopy observations and X-ray diffraction analysis showed that the precipitation of hexagonal close-packed (α) phases within the body-centered cubic (β) matrix phase causes age hardening and the hardness value almost depends linearly on the volume fraction of α precipitates. Furthermore, the α precipitates formed via aging heat treatment can be deformed along with β matrix phase upon stress-induced martensitic transformation in a sample with ~ 10% volume fraction of α precipitates, resulting in a slight reduction in stress hysteresis and a minor increase in superelastic recovery compared with the as-quenched condition.KeywordsBcc-magnesium alloyShape memory alloyAgingSuperelasticity