The in situ formation of sialon composite phases

The in situ formation of four sialon composites alpha-beta, alpha-15R, beta-15R and beta-12H in part of the system Y-Si-Al-O-N was investigated. The densification behavior of the alpha-beta materials differs from that of those containing polytypes. The alpha-based materials exhibit a unique composite microstructure where elongated grains of beta or plates of polytypes are embedded in an equiaxed matrix of alpha-sialon. This is important for the development of the strength and roughness of hard alpha-sialon ceramics. The properties of the composite phases are compared to those of the corresponding monolithic materials. (C) 1997 Elsevier Science Limited