Journal
ACTA MATERIALIA
Volume 181, Issue -, Pages 262-277Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2019.09.047
Keywords
Metal-hydrogen interactions; Hydride formation; Polycrystals; Zirconium hydrides; Phase-field model
Funding
- U.S. Department of Energy [DE-AC52-07NA27344]
- Laboratory Directed Research and Development Program at LLNL [18-SI-001]
- Hydrogen Materials -Advanced Research Consortium (HyMARC) of the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (FCTO) [DE-AC52-07NA27344]
- Materials World Network Grant from the National Science Foundation [DMR-0710616]
- DOE NEUP Integrated Research Project [IRP17-13708]
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We report a phase-field model for simulating metal hydride formation involving large volume expansion in single- and polycrystals. As an example, we consider delta-hydride formation in a-zirconium (Zr), which involves both displacive crystallographic structural change and hydrogen diffusion process. Thermodynamic Gibbs energy functions are extracted from the available thermodynamic database based on the sublattice model for the interstitial solid solutions. Solute-grain boundary interactions and inhomogeneous elasticity of polycrystals are taken into consideration within the context of diffuse-interface description. The stress-free transformation strains of multiple variants for hcp-Zr (alpha) to fcc-hydride (delta) transformation are derived based on the well-established orientation relationship between the alpha and delta phases as well as the corresponding temperature-dependent lattice parameters. In particular, to account for the large volume expansion, we introduced the mixed interfacial coherency concept between those phases-basal planes are coherent and prismatic planes are semi-coherent in computing the strain energy contribution to the thermodynamics. We analyzed the morphological characteristics of hydrides involving multiple structural variants and their interactions with grain boundaries. Moreover, our simulation study allows for the exploration of the possible hydride re-orientation mechanisms when precipitating under applied tensile load, taking into account the variation in the interfacial coherency between hydrides and matrix, their elastic interactions with the applied stress, as well as their morphology-dependent interactions with grain boundaries. The phase-field model presented here is generally applicable to hydride formation in any binary metal-hydrogen systems. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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