Computation of Ni-Cr phase diagramvia a combined first-principles quantum mechanical and CALPHAD approach

A first-principles quantum-mechanical computational code has been used to compute the energy of formation for selected ordered and topologically close-packed (TCP) phases in a Ni-base alloy. The thermodynamic data are incorporated into an existing database for Ni alloys and used in conjunction with the CALPHAD approach to compute the binary Ni-Cr phase diagram. In addition, a thermodynamic model is used to treat long-range ordering and the formation of the Ni₂Cr. The phase field for ordering is compared against that predicted by the Thermo-Calc to elucidate possible implications on the long-term phase stability of Ni-base alloys in a nuclear waste repository environment.