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Issue 25, 2016
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A first-principles study of the diffusion coefficients of alloying elements in dilute α-Ti alloys

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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.

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

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Publication details

The article was received on 22 Mar 2016, accepted on 25 May 2016 and first published on 25 May 2016


Article type: Paper
DOI: 10.1039/C6CP01899H
Citation: Phys. Chem. Chem. Phys., 2016,18, 16870-16881

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    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 and Z. K. Liu, Phys. Chem. Chem. Phys., 2016, 18, 16870
    DOI: 10.1039/C6CP01899H

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