Age-hardening effect by phase transformation of high Sc containing Mg alloy

The effect of aging treatment on microstructure and hardness in a Mg-16.8 at%Sc alloy with a bcc phase (β-Sc) was investigated. The hardness increased dramatically upon aging, owing to the formation of a fine hcp phase (α-Mg) in the bcc phase. The width of the hcp phase was below 50 nm. The crystal orientation of each phase was related by the Burgers orientation relationship. The maximum Vickers hardness was 231.5 Hv after aging treatment at 473 K for 18 ks. This significant age-hardening could be explained by the solid-solution hardening of Sc in Mg and the grain refinement hardening by the hcp precipitates.