Abstract
Thermal defect formation in γ-TiAl was studied in the framework of a simple nearest-neighbour bond model neglecting the tetragonal distortion of the L1 0 lattice. An activation enthalpy for preferential vacancy formation on the Ti sublattice of 1.27 eV at 1300 K and an atomic concentration of vacancies on the Ti sublattice at the melting temperature of 4-10 -4 , similar to a value found recently in high-temperature studies, were obtained. The thermal concentration of antisite atoms is calculated to be by several orders of magnitude higher than the vacancy concentration. The large differences in thermal vacancy concentrations experimentally observed between the B2 or L1 2 phases can be understood within the present simple model by the different coordination numbers in the two phases
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