Microstructural Effects on the Mechanical Properties of SiC-15 vol% TiB2 Particulate-Reinforced Ceramic Composites

The microstructures and mechanical properties were studied for two different SiC ceramics containing 15 vol% of TiB2 particulates. The first was prepared from commercially available spray‐dried granules and the second by blending individual SiC and TiB2 powders. The average TiB2 particle sizes were 2.7 μm for the ceramic prepared from blended powders, which had a uniform distribution of TiB2, and 2.3 μm for the ceramic prepared from spray‐dried granules, which had a nonuniform distribution of TiB2 agglomerates. Although the two ceramics had hardness values of 26 GPa, the other properties were different. For example, the fracture toughness was 4.3 MPa·m1/2 for the ceramic prepared from blended powders compared to 3.1 MPa·m1/2 for the ceramic prepared from spray‐dried granules. In contrast, the Weibull modulus for the ceramic prepared from spray‐dried granules was 21 compared to 12 for the other. Calculations predicted spontaneous microcracking in the ceramic prepared from spray‐dried granules, which was confirmed by analysis of the microstructure. The presence of microcracks accounted for the higher Weibull modulus, but lower flexural strength, Young's modulus and fracture toughness for the ceramic prepared from spray‐dried granules.