Absorption and Diffusion of Oxygen in Ti-Al Bulk Alloys

Abstract

The oxygen absorption and diffusion properties are studied in γ-TiAl and TiAl3 alloys within density functional theory using projector augmented wave method in the plane-wave basis. It is shown that the octahedral site inside the Ti-rich octahedron is preferable for oxygen in case of γ-TiAl alloy whereas the Al-rich octahedron is more favorable environment for oxygen in TiAl3. It is shown that the energy barriers for oxygen jumps between different sites in bulk alloys depend significantly on the local environments of oxygen and increase for its jump from Ti-rich sites. The trajectories with minimum energy barriers are determined for both Ti-Al alloys. It is shown that the increase of Al content in alloy leads to the decrease of barriers for oxygen jumps.

First-Principles Calculations of Oxygen Diffusion in Ti-Al Alloys

“…A technique that is an extension of the theory proposed in [23] was used to describe the oxygen diffusion in α-Ti. More details can be found in [22]. As is seen from Fig.…”

“…Finally, it is shown that in TiAl the oxygen diffusion through the Al-layer is almost barrierless, while the migration barrier through the Ti-layer is significantly higher (2.17 eV). In contrast to [21], in our previous work [22] the diffusion coefficient D = D 0 exp(-E a /k B T), where D 0 -the pre-exponential factor and E a -the activation energy, was calculated using a specific value of frequency (ν) for each elementary jump and the corresponding energy barriers along the considered paths. A technique that is an extension of the theory proposed in [23] was used to describe the oxygen diffusion in α-Ti.…”