First-principles study of Nb and Ta on oxidation resistance of β phase in Ti-Al-Sn-Hf-Si high-temperature titanium alloy

Building on our previous insights into the oxidation resistance of the α phase in Ti-Al-Sn-Hf-Si-Ta alloy high-temperature titanium alloys, this study reveals that the β phase exhibits inferior oxidation performance. Through in situ high-temperature confocal microscopy and first-principles calculations, we demonstrate that oxidation in the Ti-Al-Sn-Hf-Si-Ta alloy initiates predominantly on β-Ti surfaces, where the energy barrier for oxygen diffusion is lower compared to α-Ti, rendering the β phase more susceptible to oxidation. Notably, doping with Nb and Ta reduces oxygen adsorption on the β-Ti (110) surface and increases the diffusion energy barrier, thereby suppressing oxygen uptake and hindering its penetration into the bulk. As a result, the incorporation of Nb and Ta significantly enhances the high-temperature oxidation resistance of the alloy. These findings offer theoretical guidance for the design of oxidation-resistant titanium alloys via strategic elemental doping for extreme-environment applications.