Mechanochemical spinodal decomposition: a phenomenological theory of phase transformations in multicomponent, crystalline solids
Here, we present a phenomenological treatment of diffusiondriven martensitic phase transformations in multicomponent crystalline solids that arise from nonconvex free energies in mechanical and chemical variables. The treatment describes diffusional phase transformations that are accompanied by symmetrybreaking structural changes of the crystal unit cell and reveals the importance of a mechanochemical spinodal, defined as the region in straincomposition space, where the freeenergy density function is nonconvex. The approach is relevant to phase transformations wherein the structural order parameters can be expressed as linear combinations of strains relative to a highsymmetry reference crystal. The governing equations describing mechanochemical spinodal decomposition are variationally derived from a freeenergy density function that accounts for interfacial energy via gradients of the rapidly varying strain and composition fields. A robust computational framework for treating the coupled, higherorder diffusion and nonlinear strain gradient elasticity problems is presented. Because the local strains in an inhomogeneous, transforming microstructure can be finite, the elasticity problem must account for geometric nonlinearity. An evaluation of available experimental phase diagrams and firstprinciples free energies suggests that mechanochemical spinodal decomposition should occur in metal hydrides such as ZrH _{22c}. The rich physics that ensues is explored in several numerical examples in two and threemore »
 Authors:

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 Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Mechanical Engineering
 Univ. of California, Santa Barbara, CA (United States). Dept. of Materials
 Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Mechanical Engineering and Dept. of Mathematics
 Publication Date:
 Grant/Contract Number:
 SC0008637; CHE1027729; DMR 1105672
 Type:
 Accepted Manuscript
 Journal Name:
 npj Computational Materials
 Additional Journal Information:
 Journal Volume: 2; Journal Issue: 1; Journal ID: ISSN 20573960
 Publisher:
 Nature Publishing Group
 Research Org:
 Univ. of Michigan, Ann Arbor, MI (United States)
 Sponsoring Org:
 USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC22). Materials Sciences & Engineering Division; National Science Foundation (NSF)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; batteries; computational methods; mechanical properties; metals and alloys
 OSTI Identifier:
 1438027
Rudraraju, Shiva, Van der Ven, Anton, and Garikipati, Krishna. Mechanochemical spinodal decomposition: a phenomenological theory of phase transformations in multicomponent, crystalline solids. United States: N. p.,
Web. doi:10.1038/npjcompumats.2016.12.
Rudraraju, Shiva, Van der Ven, Anton, & Garikipati, Krishna. Mechanochemical spinodal decomposition: a phenomenological theory of phase transformations in multicomponent, crystalline solids. United States. doi:10.1038/npjcompumats.2016.12.
Rudraraju, Shiva, Van der Ven, Anton, and Garikipati, Krishna. 2016.
"Mechanochemical spinodal decomposition: a phenomenological theory of phase transformations in multicomponent, crystalline solids". United States.
doi:10.1038/npjcompumats.2016.12. https://www.osti.gov/servlets/purl/1438027.
@article{osti_1438027,
title = {Mechanochemical spinodal decomposition: a phenomenological theory of phase transformations in multicomponent, crystalline solids},
author = {Rudraraju, Shiva and Van der Ven, Anton and Garikipati, Krishna},
abstractNote = {Here, we present a phenomenological treatment of diffusiondriven martensitic phase transformations in multicomponent crystalline solids that arise from nonconvex free energies in mechanical and chemical variables. The treatment describes diffusional phase transformations that are accompanied by symmetrybreaking structural changes of the crystal unit cell and reveals the importance of a mechanochemical spinodal, defined as the region in straincomposition space, where the freeenergy density function is nonconvex. The approach is relevant to phase transformations wherein the structural order parameters can be expressed as linear combinations of strains relative to a highsymmetry reference crystal. The governing equations describing mechanochemical spinodal decomposition are variationally derived from a freeenergy density function that accounts for interfacial energy via gradients of the rapidly varying strain and composition fields. A robust computational framework for treating the coupled, higherorder diffusion and nonlinear strain gradient elasticity problems is presented. Because the local strains in an inhomogeneous, transforming microstructure can be finite, the elasticity problem must account for geometric nonlinearity. An evaluation of available experimental phase diagrams and firstprinciples free energies suggests that mechanochemical spinodal decomposition should occur in metal hydrides such as ZrH22c. The rich physics that ensues is explored in several numerical examples in two and three dimensions, and the relevance of the mechanism is discussed in the context of important electrode materials for Liion batteries and hightemperature ceramics.},
doi = {10.1038/npjcompumats.2016.12},
journal = {npj Computational Materials},
number = 1,
volume = 2,
place = {United States},
year = {2016},
month = {6}
}