Microstructure Evolution and Precipitation Strengthening in Ca-Containing Mg-Rare Earth Alloys

Abstract

The significant precipitation strengthening during aging provides Mg-rare earth (RE) alloys with exceptional strength. The low density and reasonable cost of Ca could favor Mg alloys for commercial use with improved properties. In order to investigate the potential interaction effect of Ca for improving the aging response and strength of Mg–RE alloys, this study was performed. 0.5 wt% and 1.0 wt% Ca were added to the ternary alloy Mg–2 wt%Nd–4 wt%Y. The microstructures of different processing conditions were examined by a series of experimental characterization techniques. The microstructure evolution and phase transformations were also calculated by commercial CALPHAD software. Vickers hardness tests were performed to characterize the aging response of the quaternary Mg–2 wt%Nd–4 wt%Y–0.5 wt%Ca alloy. Current results showed that 0.5 wt% Ca addition accelerated the peak aging, as compared to the previously studied ternary Mg–Nd–Y alloy. The initial APT analysis on the aged samples indicated that Ca segregated with Nd and Y in the precipitates in Mg–RE alloys.