Effects of vacancy-solute clusters on diffusivity in metastable Fe-C alloys
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Kabir-2010-Effects of vacancy-s.pdf
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Author(s)
Kabir, Mohammad Mukul
Lau, Timothy T.
Yip, Sidney
Van Vliet, Krystyn J
Lin, Xi, 1973-
Date Issued
October 2010
Journal
Physical Review B
Publisher
American Physical Society
Citation
Kabir, Mukul et al. “Effects of vacancy-solute clusters on diffusivity in metastable Fe-C alloys.” Physical Review B 82.13 (2010): 134112. © 2010 The American Physical Society.
Version
Final published version
Abstract
Diffusivity in defected crystals depends strongly on the interactions among vacancies and interstitials. Here we present atomistic analyses of point-defect cluster (PDC) concentrations and their kinetic barriers to diffusion in ferritic or body-centered-cubic (bcc) iron supersaturated with carbon. Among all possible point-defect species, only monovacancies, divacancies, and the PDC containing one vacancy and two carbon atoms are found to be statistically abundant. We find that the migration barriers of these vacancy-carbon PDCs are sufficiently high compared to that of monovacancies and divacancies. This leads to decreased self-diffusivity in bcc Fe with increasing carbon content for any given vacancy concentration, which becomes negligible when the local interstitial carbon concentration approaches twice that of free vacancies. These results contrast with trends observed in fcc Fe and provide a plausible explanation for the experimentally observed carbon dependence of volume diffusion-mediated creep in ferritic (bcc) Fe-C alloys. Moreover, this approach represents a general framework to predict self-diffusivity in alloys comprising a spectrum of point-defect clusters based on an energy-landscape survey of local energy minima (formation energies governing concentrations) and saddle points (activation barriers governing mobility).
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
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DOI of Published Version
https://doi.org/10.1103/PhysRevB.82.134112
