Growth and morphology of rod eutectics

TitleGrowth and morphology of rod eutectics
Publication TypeJournal Article
Year of Publication2008
AuthorsTeng J, Liu S, Trivedi R
Journal TitleActa Materialia
Volume56
Pages2819-2833
Date PublishedJul
Type of ArticleArticle
ISBN Number1359-6454
Accession NumberISI:000257600900016
Keywordsalloys, CRYSTALLIZATION, directional, directional solidification, eutectic solidification, microstructure, modeling, solidification
Abstract

The formation of rod eutectic microstructure is investigated systematically in a succinonitrile-camphor alloy of eutectic composition by using the directional solidification technique. A new rod eutectic configuration is observed in which the rods form with elliptical cylindrical shape. Two different orientations of the ellipse are observed that differ by a 90 degrees rotation such that the major and the minor axes are interchanged. Critical experiments in thin samples, where a single layer of rods forms, show that the spacing and orientation of the elliptic rods are governed by the growth rate and the sample thickness. In thicker samples, multi layers of rods form with circular cross-section and the scaling law between the spacing and velocity predicted by the Jackson and Hunt model is validated. A theoretical model is developed for a two-dimensional array of elliptical rods that are arranged in a hexagonal or a square array, and the results are shown to be consistent with the experimental observations. The model of elliptic rods is also shown to reduce to that for the circular rod eutectic when the lengths of the two axes are equal, and to the lamellar eutectic model when one of the axes is much larger than the other one. Published by Elsevier Ltd on behalf of Acta Materialia Inc.

DOI10.1016/j.actamat.2008.02.011
Alternate JournalActa Mater.