Interfacial microstructure formed by reactive metal penetration of Al into mullite

Abstract

Microstructures in the reaction interface between molten Al and dense mullite have been studied by transmission electron microscopy to provide insight into mechanisms for forming ceramic–metal composites by reactive metal penetration. The reactions, which have the overall stoichiometry 3Al6Si2O13 + (8 + x)Al → 13Al2O3 + xAl + 6Si, were carried out at temperatures of 900, 1100, and 1200 °C for 5 and 60 min and 1400 °C for 15 min. Observed phases generally were those given in the above reaction; their proportions and interfacial microstructures, however, were strongly dependent on the reaction temperature. Using previously measured reaction kinetics data, the observed temperature dependence of the interfacial microstructure has been modeled as three sequential steps, each of which is rate limiting in a different temperature range.