Microscopic phase-field simulation of Cr atom substitution character during formation of Ll₂ and DO₂₂ phases in Ni-Cr-Al alloy

The simulations of Cr atom substitution character during the formation of Ll₂ and DO₂₂ phases in Ni-Cr-Al alloy were performed at 873 K based on microscopic phase-field model. It is found that the substitution of Cr is affected by Cr and Al contents and limits of occupation probabilities of Cr atom in Ll₂ phase are present. The precipitate is single Ll₂ phase when the component is less than the limit, Cr atoms substitute the Al sublattices in Ll₂ phase, and both of atoms Al and Cr occupy the β-sites and complex phases Ni₃(Al_1-x Cr _x ) are formed; Cr atoms enter Ni sites when Al and Cr contents exceed the limit, and substitute β-sites or both of α-and β-sites. The DO₂₂ phase is formed at the boundary of Ll ₂ phase.