Synthesis and processing of ceramic-metal composites by reactive metal penetration

Molten aluminum reduces and penetrates silicate ceramics to produce a metal -ceramic composite which yields an Al2O3 Skeleton infiltrated with a solidi fied Al-Si alloy. Penetration experiments have been used to study the influ ence of p(O-2), temperature and substrate composition on penetration kineti cs and composite microstructure. The Limiting kinetic step for Al penetrati on is the chemical reaction between Al and the ceramic. For dense substrate s the maximum reaction rates are observed between 1000-1200 degrees C and a re independent of p(O-2). For porous substrates it is necessary to reach a critical temperature or p(O-2), before infiltration starts. Increasing the Si concentration in the molten Al results in the reduction of the reaction rates. (C) 1999 Elsevier Science Ltd. All rights reserved.