Sub-stoichiometry-facilitated oxidation kinetics in a δ-TixC-doped Ti-based alloy

Titanium carbide has been widely considered as a stabilizer to alleviate the serious chemical activity of Ti-based alloys at elevated temperatures. However, a reverse effect may also take place: we show the sub-stoichiometry characteristic of δ-TixC can facilitate the oxidation kinetics of a Ti-6Al-4V alloy to a significant extent. In particular, oxygen atoms tend to preferentially occupy the vacant carbon sites within the Ti2C phase, giving rise to a higher oxidation rate. The intrinsic mechanisms were understood with a combination of ab initio simulation and experimental validation