A phase field model to simulate competitive precipitation of Mg2Sn along the basal or pyramidal habit planes in Mg-2.2Sn-0.1Zn alloy

Abstract

We use a phase field model to simulate the competitive precipitation of the Mg2Sn phase along different habit crystal planes of the parent α-Mg phase in real time and industrial scale space at an aging temperature of 450K as a function of time. An expression of the local free energy density was established as a function of the concentration of the α-Mg matrix simplified by main alloy element Sn only and of the order parameters of different phases for the Mg-2.2Sn-0.1Zn alloy during the aging process. Furthermore, a numerical phase transformation tensor method was cautiously introduced for Mg2Sn precipitation based on theoretical transformation atom displacement analysis. The simulations eventually can meet the experimental microstructure observation successfully. It is suggested that random distribution of dissolved Sn atoms in the α-Mg promotes favorite formation of pyramidal Mg2Sn precipitates.