Limiting the development of Al4C3 to prevent degradation of Al/SiCP composites processed by pressureless infiltration

The presence of Al4C3 in Al/SiC composites may activate degradation of the material by its interaction with water; even moisture may cause its environmental degradation. It has been demonstrated that incorporation of 6 vol% SiO2 powders into SiCP preforms before processing by pressureless infiltration prevents formation of Al4C3. Analysis by electron back-scattered diffraction confirms that regardless of its crystal structure (alpha-quartz or alpha-cristobalite), SiO2 completely reacts to form MgAl2O4. The metal/composite interface microstructure condition of the specimens processed under the most severe conditions (1100 degrees C for 60 min), four months later confirms the effectiveness of the SiO2 powders. (c) 2005 Elsevier Ltd. All rights reserved.