Effects of substitutional impurity atoms Au and Si on the energies of antiphase boundaries on {11•0} and (00•1) planes in a Ti3Al intermetallic compound were examined using first-principles calculations. Au additions reduced the energies of antiphase boundaries on both {11•0} and (00•1) planes by up to more than 40%. The reduction tends to be more remarkable especially when the added Au atom had larger number of Al atoms on its second-nearest neighbor sites rather than on first-nearest neighbor ones. In addition, in the case of Si addition, a significant energy reduction was found only for antiphase boundaries on (00•1) planes, and no remarkable dependence of antiphase boundary energies on the coordinating atoms was found even for antiphase boundaries on (00•1) planes. These results were crucial to both understanding of the effect of antiphase boundaries on the impurity diffusivity and predicting the ability of impurity atoms to stabilize antiphase domain structure that increased the strength of Ti3Al dramatically.

Effects of Substitutional Impurity Au and Si Atoms on Antiphase Boundary Energies in Ti3Al: a First Principles Study. Y.Koizumi, M.Mizuno, A.Sugihara, Y.Minamino, Y.Shirai: Philosophical Magazine, 2010, 90[29], 3919-34