The formation of thermal vacancies in the  phase was studied by using positron lifetime spectroscopy at temperatures between ambient and 1400K. An estimate of the atomic concentration of thermal vacancies yielded a value which was similar to that for face-centered cubic pure metals, and the estimated effective vacancy formation enthalpy of 1.41eV was in good agreement with nearest-neighbor bond model calculations. A comparison of these data with the results of self-diffusion studies suggested that a low vacancy mobility was typical of ordered intermetallic compounds. No evidence of structural vacancies was found at room temperature.

Thermal Formation of Vacancies in TiAl. U.Brossmann, R.Würschum, K.Badura, H.E.Schaefer: Physical Review B, 1994, 49[10], 6457-61