Table of Contents
Journal of Metallurgy
Volume 2013, Article ID 628495, 12 pages
http://dx.doi.org/10.1155/2013/628495
Research Article

Columnar-to-Equiaxed Transition in Metal-Matrix Composites Reinforced with Silicon Carbide Particles

1Faculty of Sciences, University of Misiones, 1552 Félix de Azara Street, 3300 Posadas, Misiones, Argentina
2Member of Scientific Research Career (CIC) of the National Council of Scientific and Technical Research (CONICET), 1917 Rivadavia Street, 1033 Buenos Aires, Argentina

Received 30 July 2013; Accepted 4 November 2013

Academic Editor: Menahem Bamberger

Copyright © 2013 Alicia E. Ares and Carlos E. Schvezov. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The present work is focused on the study of the effect of directional heat extraction on the silicon-carbide (SiC) distribution in zinc-aluminum matrix composites (MMCs) and on the columnar-to-equiaxed (CET) position in directionally solidified samples. To this end, a ZA-27 alloy matrix was reinforced with ceramic particles of SiC and vertically directionally solidified. The cooling rates, temperature gradients, and interphase velocities were then measured, and their influence on the solidification microstructure of the MMCs was analyzed. The recalescence detected and measured during the equiaxed transition was of the order of 3.5°C to 1.1°C. The values of the temperature gradients reached a minimum during the CET and were even negative in most cases (between −3.89 K and 0.06 K). The interphase velocities varied between 0.07 mm/s and 0.44 mm/s at the transition. Also, the presence of ceramic particles in ZA-27 alloys affected the thermodynamic local conditions and the kinetics of nucleation, producing a finer microstructure.