MECHANICAL-BEHAVIOR AND MICROSTRUCTURE OF SIC AND SIC TIB2 CERAMICS/

Toughness characteristics and associated microstructural behavior in t wo kinds of SiC and TiB2 particulate-reinforced SiC composites were st udied. From indentation-strength tests, the Al2O3-doped, high volume f raction beta-SiC/TiB2 showed a distinctive flaw tolerance and a higher retained strength in the long-crack region, as compared with B-SiC al one. On the other hand, the boron-and carbon-doped, low volume fractio n, alpha-SiC/TiB2 exhibited a higher retained strength without an appa rent improvement in flaw tolerance, as compared with alpha-SiC. Crack bridging and sliding and pullout of TiB2 particulates toughened the be ta-SiC/TiB2, while only crack bridging by TiB2 occurred in alpha-SiC/T iB2 with difficulty in grain sliding and pullout. A quantitative evalu ation of the indentation-strength data revealed a sharp rising toughne ss curve for beta-SiC/TiB2. The enhanced long-crack toughness originat ed from the weak interface created by the TiB2 and sintering additives . (C) 1997 Elsevier Science Limited.