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TEM Characterization of Al/Al2O3 Composite Fabricated by Reactive Metal Infiltration

Published online by Cambridge University Press:  15 February 2011

Y. Gao ,
J. Jia ,
R. E. Loehman  and
K. G. Ewsuk
Y. Gao
Affiliation:
Dept. of Materials Eng., New Mexico Inst. of Mining and Technology, Socorro, NM 87801
J. Jia
Affiliation:
Dept. of Materials Eng., New Mexico Inst. of Mining and Technology, Socorro, NM 87801
R. E. Loehman
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185
K. G. Ewsuk
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185
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Abstract

The microstructure of Al/α-Al2O3 composites made by infiltrating into dense mullite preforms has been characterized using transmission electron microscopy. Observations revealed that the formation of the Al/Al2O3 composites involves three stages. Initially, infiltrates into a dense mullite preform through grain boundary diffusion, and reacts with mullite at grain boundaries to form a partial reaction zone. Then, a complete reaction takes place in the reaction region between the partial reaction zone and the full reaction zone to convert the dense mullite preform to a composite of α-Al2O3 (matrix) and an Al-Si phase (thin channels). Finally, the reduced Si from the reaction diffuses out of the Al/A2O3 composite through the metal channels, whereas from the molten pool is continuously drawn to the reaction region until the mullite preform is consumed or the sample is removed from the molten pool. Based on the observed microstructure, infiltration mechanisms have been discussed, and a growth model of the composites is proposed in which the process involves repeated nucleation of Al2O3 grains and grain growth.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 365: Symposium M – Ceramic Matrix Composites–Advanced High-Temperature Structural Materials , 1994 , 209
Copyright
Copyright © Materials Research Society 1995

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