HRTEM Observation of Metastable Phases in a Mg–15%Gd–6.4%Sc Alloy

Abstract

The aging behavior of a ternary Mg-15%Gd-6.4%Sc (mass%) alloy was examined by high-resolution transmission electron microscopy. During the first stage of age hardening of the alloy, a contrast corresponding to a precursor of the 00 phase was observed predominantly. The 00 and 0 phases coexist in the second stage of hardening, up to the point of maximum hardness. In the over-aging stage, the spheroidal contrast of the 0 phase became longer along the h1 1 100i Mg direction. The addition of Sc to the Mg-Gd alloys is useful to clarify the precipitation behavior and contribution of the 00 and 0 phases to age hardening, as indicated by the two stage in the early stage of aging.

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

“…Several studies have reported the effect of a small Sc addition on high temperature strength [12][13][14][15][16], the age-hardening response of Mg-5wt%Sc alloy [17], Mg-3wt%Sc-3wt%Y as a biodegradable implant material [18], and the precipitate hardening behavior in Mg-15wt%Gd-6.4wt%Sc alloy [19]. However, the alloy matrices in these studies have an hcp structure.…”