First-principles thermodynamic models based upon the cluster expansion formalism, Monte Carlo simulations, and quantum-mechanical total energy calculations were used to compute short-range order parameters and diffuse antiphase boundary energies in hexagonal close-packed based α-Ti-Al alloys. The calculations unambiguously revealed that a substantial amount of short-range order was present in α-Ti-6Al and that, at typical processing temperatures and concentrations, the diffuse antiphase boundary energies associated with a single dislocation slip could reach 25mJ/m2. It was found that there was very little anisotropy between the energies of diffuse antiphase boundaries lying in the basal and prism planes. Perfect antiphase boundaries in DO19-ordered Ti3Al were also investigated and their interfacial energies, interfacial stresses and local displacements were calculated from first principles via direct super-cell calculations.

First-Principles Investigation of Perfect and Diffuse Antiphase Boundaries in HCP-Based Ti-Al Alloys. A.van de Walle, M.Asta: Metallurgical and Materials Transactions A, 2002, 33[3A], 735-41