Solubility and diffusion of light elements and vacancies in α-Titanium: a first-principles study of site occupancy, migration and the effect of stress

In this work, we use first-principles calculations to investigate the incorporation and diffusion of carbon, hydrogen, oxygen, nitrogen, sulfur, and boron in α-Ti, while also revisiting the case of vacancies. Calculations show that, when occupying interstitial sites, all species prefer to reside in octahedral positions. However, boron and sulfur seem to prefer substitution sites to interstitial sites. With regard to diffusivity, we analyze in detail the migration mechanisms for C, H, O and N, and compare the diffusion coefficients obtained with experimental data. For B, S and vacancies, the diffusion coefficients are evaluated within the framework of the eight-frequency model. The influence of stress on the solubility and diffusivity of interstitial species is finally investigated using elastic and elastodiffusion theories. It is found that the effect is weak.