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

W. W. Xu, S. L. Shang, B. C. Zhou, Y. Wang, L. J. Chen, C. P. Wang, X. J. Liu, Z. K. Liu

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19 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)16870-16881
Number of pages12
JournalPhysical Chemistry Chemical Physics
Volume18
Issue number25
DOIs
StatePublished - Jan 1 2016

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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