On the modelling of the point defects in the ordered B2 phase of the Ti-Al system: Combining CALPHAD with first-principles calculations

First-principles calculations are performed in order to calculate the energies of formation of different point defects in the ordered B2 phase of the Ti-Al system. The dominant point defects in the sublattice of the B2-TiAl structure are determined to be either substitutional vacancies or anti-site defects. Based on the results of first-principles calculations, substitutional vacancies are considered in the sublattice for the CALPHAD assessment (Al,Ti,Va) 0.5:(Al,Ti,Va) 0.5. A self-consistent set of thermodynamic parameters is obtained. Phase equilibria in the Ti-Al binary system are reproduced using these thermodynamic parameters. © 2012 Elsevier Ltd. All rights reserved