α-Sialon/SiC_(w) Composites Sintered in Different Atmosphere

The microstructures of two α-Sialon/SiC(w) composites sintered in N2 and N2＋CO atmosphere respectively, were studied by using TEM, HREM and EDS. TEM observations revealedquite different interface stuctures in-between those two composites. A strong interfacial bond between α-Sialon matrix and SiC whisker was observed in the composite sintered in N2, while for thecomposite prepared in N2＋CO, a thick layer of glass was found to be formed at the matrix/whiskerinterface. The glass was produced by the reaction between CO gas and the SiC whisker surface.Albeit different interface structures, both composites decreased mechanical properties because thecracks progressed directly across the whisker rather than circumferentially. Possible processeswere proposed in order to improve the mechanical properties of SiC whisker reinforced a-Sialoncomposites by tailoring the interface microstructures of the composite.