Abstract
The electronic mechanism of oxygen embrittlement of TiAl and the effect of vanadium on the ductility of TiAl have been investigated by the first-principles LDF DV embedded cluster method. According to the impurity formation energy, oxygen energetically prefers to occupy the Ti-rich octahedral interstitial site in TiAl compared with hydrogen. When O impurity is added to pure TiAl, a strong Ti - O bond forms due to Ti d/O p hybridization while no Al - O bond can be observed. The bonding character between Ti atoms changes from type to type. In V-doped TiAl, V greatly enhanced the intraplanar and interplanar bonds. The local environmental total bond order (LTBO) provides a reasonable description of the cohesive properties of the local impurity environment. The O impurity reduces the LTBO and partial LTBO of the pure TiAl, while V improves them greatly. Therefore, O should be regarded as an embrittler, and V as a ductilizer.
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