Effects of substitutional impurity Au and Si atoms on antiphase boundary energies in Ti₃Al: A first principles study

Abstract

Effects of substitutional impurity atoms Au and Si on the energies of antiphase boundaries (APBs) on {1100} and (0001) planes in a Ti 3 Al intermetallic compound were examined using first principles calculations. Au additions reduce the energies of APBs on both {1100} and (0001) planes by up to more than 40%. The reduction tends to be more remarkable especially when the added Au atom has 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 APBs on (0001) planes, and no remarkable dependence of APB energies on the coordinating atoms was found even for APBs on (0001) planes. These results are crucial to both understanding of the effect of APBs on the impurity diffusivity and predicting the ability of impurity atoms to stabilize antiphase domain structure that increases the strength of Ti 3 Al dramatically.

Effects of Alloying Atoms on Antiphase Boundary Energy and Yield Stress Anomaly of L12 Intermetallics: First-Principles Study

“…where 110 is the Burgers vector of superdislocations in {111} and {010} planes which will be dissociated into two 110 /2 partials with an APB between them [19][20][21][22][23]. There may be other dissociation types like CSF (complex stacking fault) and SISF (superlattice intrinsic stacking fault).…”