Application of ab initio electronic structure calculations for prediction of phase equilibria in superaustenitic steels

Our recent results of the application of ab initio electronic structure calculations to the modeling of phase equilibria in binary and ternary transition-metal systems containing complex intermetallic phases (Laves phase, sigma phase) are summarized. As examples, the application of total energy differences calculated by ab initio methods for the sigma phase included in the CALPHAD treatment of the Cr–Mo and Cr–Fe–Mo systems is presented. The description of the sigma phase, based on the above-mentioned total energy differences, for the systems Cr–Fe, Cr–Ni, Fe–Ni, Fe–Mo, Cr–Mo, and for Cr–Fe–Ni and Cr–Fe–Mo systems has been included in the thermodynamic database for the calculation of phase equilibria in steels, developed earlier by some of the authors. Theoretical results obtained by using the new and older models are compared with new experimental data for superaustenitic (high-nickel–chromium) steels.