Analytical model for estimating calcium solution strengthening in single-crystal Mg-Ca alloys at finite temperatures

Abstract

Mg is the lightest structural metal and a suitable replacement for heavy steel and Al alloys. However, Mg exhibits poor plastic formability at room temperature, and the strength of conventional Mg alloys is less than that of most Al alloys. Its low formability at room temperature is attributed to the lack of slip systems because of the extremely large gap in the critical resolved shear stress (CRSS) between the lowest basal system and the other slip and twin systems. This low CRSS of the basal slip usually limits the strength of Mg alloys. Therefore, strengthening the basal slip is important to improve the strength and deformability of Mg alloys and enhance their ductility. In this study, we construct an analytical model for predicting the CRSS in single-crystal Mg–Ca alloys at finite temperatures by quantitatively investigating the CRSS for the 〈a〉 dislocation gliding on the basal plane at temperatures from 1 to 500 K through molecular-dynamics computations. The prediction results agree well with our simulation results and the micropillar compression test results of Mg–0.3at.%Ca and Mg–0.6at.%Ca alloys at room temperature.