Mechanical properties and microstructure of β-SiAION-β-SiC composites by pressureless sintering

β-SiAION-β-SiC composites containing up to 12 wt% β-SiC were prepared by pressureless sintering. The strength of composites at room temperature remained relatively unchanged, whereas strength at 1200 °C increased for composites. The fracture toughness (KIC) for composites was higher than that for β-SiAION ceramics. The maximum value was 5.4 MPa m1/2 for 6 wt% β-SiC, and this was an improvement of 15% in comparison with β-SiAION ceramics. From SEM observations, an improvement inKIC values was attributed to crack deflections and branching-off of cracks. Intra-granular fractures were frequently observed in β-SiAION. From TEM observations, β-SiAION crystals were nanocomposites, within which existed the fine crystals in β-SiAION crystal. For composite, β-SiAION and β-SiC crystals were directly in contact. The mismatching zone was observed in β-SiC.