Interfacial energies in two-phase TiAl-Ti3Al alloy

The intrinsic values of interfacial energies based on first-principles calculations, including atomic relaxation, were obtained for the three types of γ/γ interfaces and the α2/γ lamellar boundary in two-phase TiAl alloy. The pseudo-twin boundary energy is highest, ΓP = 270 mJ/m2, and the true-twin boundary energy is lowest, ΓT = 60 mJ/m2. Planar fault energies at pseudo-twin and 120°-rotational interfaces are markedly different from those in the bulk of the γ-phase, i.e., approximately, EAPB and ECSF decreases by more than 30% and ESISF increases by threefold. Enhanced mobility of ordinary dislocations along the γ/γ and α2/γ interfaces (except true twin boundaries) is predicted based on the reduced ECSF values at the interfaces.