SiC/combustion-synthesized β′-SiAlON composite

A composite of combustion-synthesized β′-SiAlON (Si₃Al₃O₃N₅) reinforced with SiC monofilaments (AVCO SCS-6) was hot-pressed at a temperature of 1600 °C for 2 h under a pressure of 34 MPa. The composite exhibited significant improvement in work of fracture (WOF) as well as in ultimate strength, in comparison to monolithic β′-SiAlON. Ultimate flexure strength values between 682 and 793 MPa for the composite and between 398 and 528 MPa for the monolithic β′ SiAlON were obtained. A work of fracture of 16.7 kJ m^-2 was obtained for the composite, compared to 2.7 kJ m^-2 for the monolithic material. Filament push-out tests revealed a moderate interfacial bonding strength of 26 MPa and a frictional sliding stress of 24 MPa. SEM observation of pushed-out filaments indicated that the debonding site was located at the interface between the outer carbon layer of the filament and the matrix. It appeared that the filament and the matrix were compatible with each other despite the fact that the matrix contained 20 wt% of Al₂O₃ as a secondary phase.