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ISRN Metallurgy
Volume 2012 (2012), Article ID 631096, 7 pages
http://dx.doi.org/10.5402/2012/631096
Research Article

Effect of Isothermal Holding on Semisolid Microstructure of Al–Mg2Si Composites

1School of Metallurgy and Materials Engineering, University of Tehran, P.O. Box 14395-731, Tehran, Iran
2Center of Excellence for Advanced Materials and Processing (CEAMP), School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran 16846-13114, Iran

Received 5 February 2012; Accepted 3 April 2012

Academic Editors: A. Chrysanthou, C.-G. Kang, D. V. Louzguine-Luzgin, G. Purcek, J. M. Rodriguez-Ibabe, and A. Squillace

Copyright © 2012 A. Malekan et al. 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

Effect of heat treatment and isothermal holding has been investigated on the microstructure and degree of globularity of Al–Mg2Si composites. Different contents of reinforcement, 15, 20, and 25% have been used in this study. Isothermal holding experiments were conducted at 585 °C for 140 min. Results showed that, upon heat treatment, grain size of dendrites was reduced while the degree of nodularity was increased. Results of nodularity were obtained using an image-analyzing software which gives the distribution of radius of curvature for different phases of particles. According to the results, in contrast to Al–15 and 25% Mg2Si, isothermal holding significantly influenced the microstructure of Al–20% Mg2Si composites. Two companion mechanisms have been proposed for the generation of globular grains. SEM investigations were also employed to confirm the optical observations.