Mechanical properties and deformation mechanisms of a dual-phase Mg-Sc alloy: Effects of strain rate and temperature

Abstract

The compressive mechanical behavior and deformation mechanisms of a dual-phase Mg-Sc alloy consisting of hexagonal close-packed (HCP) and body-centered cubic (BCC) phases are systematically investigated over a wide temperature range (133–473 K) at two representative strain rates (0.001 and 3000 s${}^{-1}$). The mechanical response strongly depends on both deformation temperature and strain rate. An excellent strength-ductility synergy is achieved at 133 K and 3000 s${}^{-1}$, with a yield strength of 364 MPa and a fracture strain of 32%. Microstructural analyses reveal that twinning in the HCP phase is significantly suppressed at 298 K and 0.001 s${}^{-1}$ due to the relatively high Sc content. Decreasing temperature and increasing strain rate both promote twinning activity, with strain rate playing a more pronounced role. At 133 K and 3000 s${}^{-1}$, $\left\{11\overline{2}1\right\}$ and $\left\{10\overline{1}2\right\}$ twins dominate, accompanied by $\left\{10\overline{1}1\right\}$ twin and secondary twins such as $\left\{11\overline{2}1\right\}-\left\{11\overline{2}1\right\}$ and $\left\{10\overline{1}1\right\}-\left\{10\overline{1}2\right\}$. Plastic deformation in the BCC phase is mainly governed by dislocation slip, and only a small amount of deformation-induced HCP martensite is observed. These results provide novel insight into the temperature- and strain-rate-dependent deformation mechanisms in dual-phase Mg-Sc alloys.