The energies of conservative and non-conservative antiphase boundaries on {11▪0} and (00▪1) planes of stoichiometric Ti3Al were calculated ab initio in order to shed light on the reason for the enormous strengthening by antiphase domains. The energy of the {1¯1▪0} non-conservative antiphase boundaries, which has never before been estimated either experimentally or theoretically, was found to be between those of the two types of {1¯1▪0} conservative antiphase boundaries, and therefore, the great strengthening could not be attributed to the energy of the non-conservative antiphase boundary. On the other hand, large differences were found between the calculated energies of conservative energies and those estimated from dissociation distances of super-dislocations. This was similar to the differences seen in the case of the antiphase boundary energies of TiAl, which were probably due to the equilibration of antiphase boundaries by rearrangements of atoms in the vicinity of antiphase boundaries. The calculated antiphase boundary energies in Ti3Al were significantly larger than those estimated experimentally, and the antiphase boundaries size dependences of the critical resolved shear stress estimated by substituting these calculated values into the previously proposed equations were in better agreement with the actual dependence than those obtained using the experimental values. This implied that the enormous strengthening by antiphase domains could be attributed to the quite large energy of the antiphase boundaries created by the shearing of antiphase domain boundaries.

Energies of Conservative and Non-Conservative Antiphase Boundaries in Ti3Al - a First Principles Study. Y.Koizumi, S.Ogata, Y.Minamino, N.Tsuji: Philosophical Magazine, 2006, 86[9], 1243-59