SiC-reinforcement of an Al2O3–γAlON composite

Three phase Al2O3–A1ON–SiC composites can be obtained by hot-pressing Al2O3–AlN–SiC mixtures under 40 MPa at temperatures around 1700°C. Silicon carbide can be added in the form of powders or platelets. In the case of powder, densification and aluminum oxynitride formation occur at higher temperatures than in the case of platelets, because of a steric and chemical hindrance by SiC on both Al2O3 densification and the Al2O3–AlN reaction. Composites containing powders present the highest values for rupture moduli of up to 800 MPa and toughnesses close to those of alumina (4 MPam). For platelets, a composite containing 20 vol.% SiC with a size of d50=8 μm produces a reinforcement effect (K1C=6–7 MPam).