PRESSURELESS SINTERING AND MECHANICAL-PROPERTIES OF ALUMINA-SIALON COMPOSITES

Compositions of Al2O3, Si3N4 and AIN were sintered to produce six different alumina-sialon composites. The composites reached the highest density at 1700-degrees-C in a nitrogen atmosphere. Sialon acted as a binder, promoting the densification and suppressing the grain growth of alumina. The composites had a bending strength of 450 MPa at room temperature and maintained high strength over 300 MPa at 1400-degrees-C. The composite with 30 wt % sialon had the maximum fracture toughness of 4.3 M Pa . m1/2 and exhibited good oxidation resistance even at 1400-degrees-C. Mullite was formed in the oxidation layer and little degradation in strength was observed after oxidation.