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ACTA AERONAUTICAET ASTRONAUTICA SINICA ›› 2014, Vol. 35 ›› Issue (10): 2834-2840.doi: 10.7527/S1000-6893.2014.0147

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Diffusion and Clustering of Oxygen Atom in Nb-based Alloys:A First-principles

ZHU Linggang1, HU Qingmiao2, SUN Zhimei1   

  1. 1. School of Materials Science and Engineering, Beihang University, Beijing 100191, China;
    2. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
  • Received:2014-04-16 Revised:2014-07-07 Online:2014-10-25 Published:2014-07-21

Abstract:

First-principles calculation is used to investigate the diffusion of oxygen atom under axial strain in Nb, as well as the clustering of oxygen in Nb-Ti and Nb-Zr alloys. It is found that with the increase of the axial-strain, the energy barrier in the direction parallel to the applied strain becomes lower, and when the strain is 10%, the energy barrier decreases from 0.92 eV to 0.5 eV. In the direction perpendicular to the strain, oxygen atom can diffuse into the elongated octahedral interstices more easily; therefore, oxygen atom tends to accumulate in the direction of applied strain which will lead to the stress concentration in real alloy. For the computations about the clustering of oxygen atom, it is found that in pure Nb, oxygen atom prefers to distribute uniformly in the system instead of forming atom pairs; however, when the alloying elements Ti and Zr are added, the formation of oxygen atom pairs becomes energy favorable, especially when the concentration of oxygen atom is relatively high. The result show that when one oxygen atom pair forms around Zr, the total energy of the system can be decreased by 0.29 eV.

Key words: Nb-based alloy, first-principles calculations, transition state theory, diffusion, oxygen atom clustering

CLC Number: