THE INFILTRATION OF ALUMINUM INTO SILICON-CARBIDE COMPACTS

Although liquid-metal processing of metal matrix composites offers economic advantages, problems related to the nonwetting nature of the ceramic discontinuous reinforcement create obstacles to its ready implementation. Infiltration can occur only if a threshold pressure is applied to overcome the unfavorable interfacial forces in the system. The research reported in this paper has been devoted primarily to experiments on infiltrating silicon carbide compacts with pure aluminum, aluminum-1 wt pet magnesium, and aluminum-1 wt pet silicon. The major finding has been that an incubation time is necessary before infiltration can proceed, even though the threshold pressure is exceeded. Thus, while the model equations available for predicting the infiltration rate of compacts appear to be adequate, the incubation time can represent the rate-determining step in the process. It is suggested that the mechanism responsible for the incubation phenomenon may be related to a surface modification produced by either reaction of liquid aluminum with an oxide film on the surface of the particles or coverage of the surface by a capillarity-induced aluminum condensate. © 1990 The Minerals, Metals & Material Society.