Interfacial microstructure formed by reactive metal penetration of Al intomullite

Microstructures in the reaction interface between molten Al and dense mulli te have been studied by transmission electron microscopy to provide insight into mechanisms for forming ceramic-metal composites by reactive metal pen etration. The reactions, which have the overall stoichiometry 3Al(6)Si(2)O( 13) + (8 + x)Al --> 13Al(2)O(3) + xAl + 6Si, were carried out at temperatur es of 900, 1100, and 1200 degrees C for 5 and 60 min and 1400 degrees C for 15 min. Observed phases generally were those given in the above reaction; their proportions and interfacial microstructures, however, were strongly d ependent on the reaction temperature. Using previously measured reaction ki netics data, the observed temperature dependence of the interfacial microst ructure has been modeled as three sequential steps, each of which is rate l imiting in a different temperature range.