Abstract
Influence of residual porosity on the flexural strength and fracture toughness of pressureless-sintered α-SiC ceramic with controlled microstructure, characterized by equiaxed-grain and a mixture of equiaxed/plate grains were investigated together with the trend of σ-KIC behavior. Both the flexural strength and the fracture toughness of the SiC ceramics showed an exponential decrease with porosity, but the extent of the porosity dependence was dependent on the microstructure; a higher porosity-dependent strength was seen for the equiaxed-grain microstructure, while the dependence became weak for the mixed one. The trend of flexural strength-toughness dependence appeared to be positive and became more pronounced for the SiC ceramics with mixed-grain morphology, suggesting a strengthening effect due to the presence of reinforced platelike phase. Crack deflection appeared to be the principal mechanism for toughness improvement in the SiC-Al2O3-Y2O3 ceramics.
