Effect of micronsize-B4C dispersion on the sintering behavior and microstructures of SiC has been investigated for the SiC/B4C composite prepared by pressureless sintering technique. Especially relation between sintering additives and the sintering behavior of SiC/B4C composite was studied.
Nearly fully dense composites were obtained by the pressureless sintering technique in argon atmosphere at 2250-2300°C for lh of holding time. From SEM and TEM observations of the microstructure for these SiC/B4C composites, the dispersion of micronsize-B4C as the second phase into SiC matrix was found to inhibit SiC grain growth. In the case of SiC/B4C composite system prepared by the pressureless sintering technique, SiC matrix showed the rod-like grain up to 10 vol% of B4C addition. With the addition of 20% B4C, the morphology of SiC matrix grain was relatively round and fine. Furthermore, HREM observation showed no reaction phase at grain boundary of SiC matrix grain and B4C dispersion. The hardness was also evaluated for these SiCB4C composite system.
