Boron Diffusion in Cerium Doped Alpha Titanium and Beta Titanium: First-principles Calculation

Abstract

The effects of Ce substitution on boron incorporation and the diffusion mechanisms of the α-Ti and β-Ti phases were studied by first-principles calculations. The interstitial formation energy, diffusion pathways, energy barriers, and diffusion coefficients of B in both Ti and Ce-doped Ti were calculated. The results indicate that the stable adsorption sites for individual B atoms in α-Ti are octahedral interstitial sites. In β-Ti, stable adsorption sites are octahedral interstitial and tetrahedral interstitial sites. The observed anisotropy in B diffusion within α-Ti reveals that diffusion is energetically more favorable along [000ī] direction, where the diffusion coefficient significantly exceeds that along [ī2ī0] direction. Furthermore, the diffusion energy barrier for B along the T-T pathway in β-Ti is 0.905 eV, which is lower than the corresponding value for B in α-Ti, indicating that the β phase is more favorable for B diffusion. Ce-doped reduces the energy barrier of B diffusion and enhances the B diffusion coefficient in both α-Ti and β-Ti. The calculated results indicate that Ce doping enhances the diffusion of B and facilitates the formation of boride layer in the Ti substrate, which is in line with the conclusions of experimental observations.