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| Titel |
A three-dimensional phase-field study of grain boundary tracking behavior in crack-seal microstructures |
| VerfasserIn |
Kumar Ankit, Britta Nestler, Michael Selzer |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250073064
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| Zusammenfassung |
| The mechanism by which vein formation occurs is a widely debated topic with chief
assertions related to growing crystals-fracture wall surface interaction, degree of
super-saturation and fluid-flow pathways. Amidst the debate, an important question is
what causes the grain boundaries to curve/bend, a feature commonly observed in
natural crack-seal microstructures. Therefore, with a view to amend the current
understanding of the vein-growth mechanism, we present a 3D multi-phase-field model to
explain the dynamics of crystals precipitating from a super-saturated solution in a
progressively widening fracture. Since the present model equations are derived on the
basis of general thermodynamic and kinetic principles and relies on interfacial
energy minimization, complicated moving boundary problems such as microstructure
evolution on a large scale, can be dealt with ease [1,2]. A systematic simulation study
of the influence of different boundary conditions (free growth and crack-sealing)
on growing crystals highlights the importance of anisotropy in surface energy in
free-growth as well as crack-sealing conditions; a factor overlooked in the previous
models.
To define the crystal symmetry, we consider the anisotropy in surface energy to simulate
crystals (with flat facets and sharp corners) possessing different orientations and study the
resulting growth competition to deduce a consistent orientation selection rule in the
free-growth regime. From the crack-sealing simulations, we co-relate the grain boundary
tracking behavior and the relative rates of crack opening and trajectory, initial grain size and
wall roughness. Further, the formation of curved grain boundaries in crack-sealing conditions
as an imprint of anisotropy in surface energy of growing crystals and coupling with
wall rock is elucidated. We also identify the ‘mixed-mode’ growth of crystals in
crack-sealing conditions, characterized by formation of curved as well as straight
grain boundaries and decrease in grain boundary tracking behavior. Finally, it is
concluded that within the complete crack-seal regime, the propensity to form curved
boundaries is higher if wall roughness is not sufficiently high to suppress facet
formation.
References
[1]Â Â Â B. Nestler, H. Garcke, B. Stinner, 2005. Multicomponent alloy solidification:
Phase-field modeling and simulations. Phys. Rev. E 71, 041609.
[2]Â Â Â B. Nestler, M. Reichardt, M. Selzer, 2008. Massive multi-phase-field
simulations: methods to compute large grain system. In: Hirsch, J., Skrotzki,
B., Gottstein, G. (Eds.), Proceedings of the 11th International Conference on
Aluminium Alloys Aachen, Germany, pp. 1251-1255. |
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