An investigation was made of the site preference and bonding properties of alloying elements including Nb, Mo, Ni and Ag in TiAl with O impurity using a first-principles method based upon density functional theory. It was found that the preferable sites for O were the Ti-rich octahedral interstitial ones, while those for the alloying elements were the substitutional ones. Among these elements which were beneficial to improve the mechanical properties of TiAl, Ni and Ag occupy the Al sites, while Nb and Mo occupy the Ti sites. It was demonstrated that the presence of O alters the site preference of these alloying elements in TiAl, making these elements prefer to substitute Al that was the first nearest neighbour of O, because O prefers to bond with Ti rather than Al. It was suggested that, according to the local density of states results, O could be deleterious to the ductility of TiAl with Nb and Mo, but has little effect on that of TiAl with Ni and Ag.

First-Principles Investigation of Site Preference and Bonding Properties of Alloying Element in TiAl with O Impurity. H.B.Zhou, Y.Wei, Y.L.Liu, Y.Zhang, G.H.Lu: Modelling and Simulation in Materials Science and Engineering, 2010, 18[1], 015007