THE CONCENTRATION AND TEMPERATURE DEPENDENCES OF ANTIPHASE-BOUNDARY ENERGIES IN GAMMA-TIAL - A FIRST-PRINCIPLES STUDY

The dependences of antiphase-boundary (APE) energetics upon temperatur e and concentration in gamma-TiAl have been studied from first princip les. Total energies for idealized APBs and various ordered Ti-Al compo unds have been calculated ab initio and used as a basis for thermodyna mic computations. Finite-temperature APB energies have been calculated for both thermally equilibrated and unequilibrated {100} and {111} bo undaries as a function of Al concentration. It is found that the effec t of temperature and Al-rich compositions is to reduce significantly t he calculated APB energies, bringing the theoretical values into bette r agreement with estimates based upon experimental measurements.