• DOI:10.1039/c6cp01899h
• Corpus ID: 19062940

A first-principles study of the diffusion coefficients of alloying elements in dilute α-Ti alloys.

@article{Xu2016AFS,
  title={A first-principles study of the diffusion coefficients of alloying elements in dilute $\alpha$-Ti alloys.},
  author={Wei Xu and Shunli Shang and B Zhou and Yanming Wang and L. J. Chen and C. P. Wang and X. J. Liu and Z K Liu},
  journal={Physical chemistry chemical physics : PCCP},
  year={2016},
  volume={18 25},
  pages={
          16870-81
        }
}

• W. Xu, S. Shang, +5 authors Z. K. Liu
• Published 22 June 2016
• Materials Science
• Physical chemistry chemical physics : PCCP

Using first-principles calculations accompanied by the transition state theory and an 8-frequency model, we present a comprehensive investigation of the diffusion coefficients of substitutional alloying elements X in dilute α-Ti alloys, where X denotes Al, V, Nb, Ta, Mo, Zr, and Sn. The alloying elements Mo and Al exhibit a maximum and a minimum diffusion rate in dilute α-Ti alloys, respectively. It is found that the nearest-neighbor solute-vacancy binding energies and activation energies are roughly inversely proportional to the volume changes induced by solute atoms. There are two exceptions to this trend: Al and Mo. Besides the physical effect (i.e., solute size), two other key factors governing solute diffusion in dilute α-Ti are clarified: the chemical bonding characteristics and vibrational features of X-Ti pairs. It verifies that the ultrafast diffusivity of Mo arises from the interactions with Ti atoms by metallic bonds and its low-frequency contributions to lattice vibration, while the more covalent bonding nature and the high-frequency contributions to the lattice vibration of Al lead to its ultraslow diffusivity. In addition, the correlation effects of diffusion coefficients are non-negligible for the large solutes Ta, Nb, and Zr, in which the direct solute-vacancy migration barriers are much smaller than the solvent-vacancy migration barriers.