An investigation was made of site occupancy and interfacial energetics of a TiAl–Ti3Al binary-phase system with O using a first-principles method. Oxygen was shown to energetically occupy the Ti-rich octahedral interstitial site, because O prefers to bond with Ti rather than Al. The occupancy tendency of O in TiAl alloy from high to low was α2-Ti3Al to the γ-α2 interface and γ-TiAl. It was demonstrated that O could largely affect the mechanical properties of the TiAl–Ti3Al system. Oxygen at the TiAl–Ti3Al interface reduces both the cleavage energy and the interface energy, and thus weakens the interface strength but strongly stabilizes the TiAl/Ti3Al interface with the O2 molecule as a reference. Consequently, the mechanical property variation of TiAl alloy due to the presence of O not only depends on the number of TiAl/Ti3Al interfaces but also was related to the O concentration in the alloy.

Effects of O in a Binary-Phase TiAl–Ti3Al Alloy: from Site Occupancy to Interfacial Energetic. Y.Wei, H.B.Zhou, Y.Zhang, G.H.Lu, H.Xu: Journal of Physics - Condensed Matter, 2011, 23[22], 225504