The effect of impurities on stacking fault energy and dislocation properties in γ-TiAl

Abstract

The dislocation properties of γ-TiAl are systematically investigated under the effect of impurities with semi-discrete variational Peierls-Nabarro (SDVPN) model. The impurities prefer to locating at the first layer below the stacking fault plane along 1/2<112‾] which is attributed to the local effect between stacking fault and impurities by local energy scheme analysis. The dislocation dissociation width of γ-TiAl is 1.58 Å, which shows a compact core character and is well consistent with that by atomic simulation and experimental observation. Negligible changes occur in the dislocation dissociation width as C or O is doped, while the dislocation does not even dissociate with N or H addition. The Peierls stress is reduced and the dislocation mobility is improved by N, H, and O, while C takes an opposite effect. The improved dislocation mobility with H is consistent with the enhanced dislocation mobility by H in experiments, while the improved dislocation mobility with O in calculation excludes the dislocation pinning effect of oxygen in solution.