Microstructure and Composition of Al-Al₂O₃ Composites Made by Reactive Metal Penetration


The microstructure of Al-Al2O3 composites made by reactive penetration of Al (or Al alloy) into ceramic (mullite or kaolin) preforms has been investigated using transmission electron microscopy (TEM). The Al-Al2O3 composites were found to contain a mutually-interconnected network of Al and Al2O3. No crystallographic orientation was observed between the Al and Al2O3 phase. Impurities and pores in the ceramic preforms were found to have a strong effect on the microstructure of the composites. The impurities resulted in formation of small particles in the Al2O3 grains of Al-Al2O3 composites, whereas the porosity yielded a varied ratio of Al to Al2O2 in the composites. The growth rate of the Al-Al2O3 composites was found to depend on the microstructure and composition of the ceramic preforms as well as the composition of the reactive metals. Pure aluminium penetrated into a dense mullite faster than into a porous mullite at temperatures below 1200⁰C. Addition of Mg to Al reduced the growth rate, whereas a continuous phase of amorphous SiO2 in the ceramic preforms increased the growth rate.


Materials Science and Engineering

Keywords and Phrases

Addition reactions; Alumina; Aluminum; Composition effects; Impurities; Magnesium; Microstructure; Porosity; Silica; Transmission electron microscopy; Growth rate; Mutually interconnected network; Reactive metal penetration

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Document Type

Article - Journal

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© 1996 Springer Netherlands, All rights reserved.

Publication Date

01 Jan 1996