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

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DOI：https://doi.org/10.1016/j.calphad.2012.06.007

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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. Highlights ▸ We have studied the formation of point defects in the ordered B2 phase in the Ti–Al system. ▸ Enthalpy of formation of vacancies and anti-site atoms was calculated using DFT. ▸ Concentrations of point defects at finite temperatures were calculated using first-principles. ▸ The Gibbs energy model of the B2 and A2 phases was revised to include vacancies. ▸ Ti anti-sites in the Al sublattice and vacancies in the Ti sublattice are the dominant point defects.