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The dynamics of coarsening in highly anisotropic systems: Si particles in Al–Si liquids


Shahani, A J; Gulsoy, E B; Roussochatzakis, V J; Gibbs, J W; Fife, J L; Voorhees, P W (2015). The dynamics of coarsening in highly anisotropic systems: Si particles in Al–Si liquids. Scripta Materialia, 97:325-337.

Abstract

The coarsening process of an Al–29.9wt%Si alloy is studied using four-dimensional phase contrast X-ray tomography. This alloy is composed of highly anisotropic, primary Si particles in an eutectic matrix. We analyze the morphology of the primary Si particles during coarsening by determining the interface normal distribution and the interface shape distribution. The inverse surface area per unit volume increases with the cube root of time despite the lack of microstructural self-similarity and highly anisotropic particle morphology. More specifically, over the time frame of the experiments, the Si particles evolve from mostly faceted domains to a more isotropic structure that is not given by the Wulff shape of the crystal. These trends can be rationalized by the presence of twin defects that intersect particle edges and that may provide the kink sites necessary for interfacial propagation, thus leading to a more isotropic structure. While in many cases the interfacial velocity of Si solid–liquid interfaces is highly anisotropic, the presence of many defects leads to a highly mobile interface and diffusion-limited coarsening.

Abstract

The coarsening process of an Al–29.9wt%Si alloy is studied using four-dimensional phase contrast X-ray tomography. This alloy is composed of highly anisotropic, primary Si particles in an eutectic matrix. We analyze the morphology of the primary Si particles during coarsening by determining the interface normal distribution and the interface shape distribution. The inverse surface area per unit volume increases with the cube root of time despite the lack of microstructural self-similarity and highly anisotropic particle morphology. More specifically, over the time frame of the experiments, the Si particles evolve from mostly faceted domains to a more isotropic structure that is not given by the Wulff shape of the crystal. These trends can be rationalized by the presence of twin defects that intersect particle edges and that may provide the kink sites necessary for interfacial propagation, thus leading to a more isotropic structure. While in many cases the interfacial velocity of Si solid–liquid interfaces is highly anisotropic, the presence of many defects leads to a highly mobile interface and diffusion-limited coarsening.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Biomedical Engineering
Dewey Decimal Classification:170 Ethics
610 Medicine & health
Language:English
Date:2015
Deposited On:09 Feb 2016 11:24
Last Modified:08 Dec 2017 17:59
Publisher:Elsevier
ISSN:1359-6462
Publisher DOI:https://doi.org/10.1016/j.actamat.2015.06.064

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