Phase Stability of bcc MgScY via Cluster Expansion and Monte Carlo Methods

The MgSc disordered bcc lattice has the potential for light weight, high strength applications, but is only stable far above room temperature. It is thought that the addition of ternary or quaternary components to the binary system could stabilize this phase at accessible lower temperatures. However, the search space for possible ternary candidates is too large to fully explore experimentally. Thus, to guide the physical alloy development, computational methods are applied to determine the relative phase stability of the MgSc binary to the model ternary, MgScY. A lattice cluster expansion model is developed based on density functional calculations, and finite temperature thermodynamic behavior is computed from Monte Carlo simulations. The method may be applied to further ternary components, elucidating elements that best lower the stable temperature regimes of the bcc phase.