The thermodynamics of hydride precipitation: the importance of entropy, enthalpy and disorder

S.C. Lumley, R.W. Grimes, S.T. Murphy, P.A. Burr, Alexander Chroneos, P.R. Chard-Tuckey, M.R. Wenman

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    Abstract

    The precipitation of zirconium hydrides from Zr solid solution was investigated using first-principles lattice dynamics simulations. These included the temperature-dependent vibrational enthalpy and vibrational entropy combined with the configurational entropy terms. In contrast with previous approaches, it was found that the latent enthalpy alone is not sufficient to fully describe precipitation of hydrides; a full thermodynamic assessment is required. In particular, the vibrational enthalpy of precipitation assists in stabilizing hexagonal close-packed hydrides and is especially important in forming the metastable ζ phase. The configurational entropy change during precipitation favours face-centred cubic hydrides. Given this, at concentrations below 300. ppm H, no hydride precipitation is predicted, suggesting that when hydrides are seen in those materials it is because the local concentration of H is greater than that measured globally. While γ hydride is the most stable phase, it is very close in energy to the δ phase.
    Original languageEnglish
    Pages (from-to)351-362
    JournalActa Materialia
    Volume79
    Early online date16 Aug 2014
    DOIs
    Publication statusPublished - 15 Oct 2014

    Bibliographical note

    The full text is available free from the link given. The published version can be found at http://dx.doi.org/10.1016/j.actamat.2014.07.019.
    NOTICE: this is the author’s version of a work that was accepted for publication in Acta Materialia. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Acta Materialia [vol 79 (2014)] DOI: 10.1016/j.actamat.2014.07.019.

    Keywords

    • density functional theory
    • precipitation
    • thermodynamics
    • zirconium hydride

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  • Cite this

    Lumley, S. C., Grimes, R. W., Murphy, S. T., Burr, P. A., Chroneos, A., Chard-Tuckey, P. R., & Wenman, M. R. (2014). The thermodynamics of hydride precipitation: the importance of entropy, enthalpy and disorder. Acta Materialia, 79, 351-362. https://doi.org/10.1016/j.actamat.2014.07.019