Kinetics of Metal‐Ceramic Composite Formation by Reactive Penetration of Silicates with Molten Aluminum

Wetting and reactions between molten Al and silicate substrates (particularly mullite) are studied to determine both how substrate tensity and p (O 2 ) influence wetting behavior, reaction rates, composition, and reaction product microstructure and what key steps control penetration kinetics. Guidelines are provided for using reactive penetration or infiltration when fabricating metal/ceramic composites. For dense substrates, a reactive penetration process occurs. For a certain range, the chemical reaction between Al and the ceramic is a limiting kinetic step resulting in fast reaction rates. Maximum dense mullite substrate reaction rates are between 1000° and 1200°C independent of p (O 2 ), unlike fused silica, which has faster penetration rates at higher temperatures. For mullite, reaction layer microstructure evolution halts reaction at higher temperatures. For porous substrates, reactive infiltration alone occurs. Either a critical temperature or p (O 2 ) must be reached before infiltration starts.