Effect of sintering temperature and holding time on the microstructure and mechanical properties of ZrB2-SiCw composites

ZrB2-based ceramic composites containing 20 vol.% Sic whiskers were prepared through hot-pressing. Effect of sintering temperature (1650-1950 degrees C) and holding time (30-60 min) on the microstructure and mechanical properties of ZrB2-SiCw Composites were investigated. Relative density and grain size increased with increasing temperature, from 93% and 3.0 mu m for 1650 degrees C to 99.5% and 5.6 mu m for 1950 degrees C. Similarly, relative density and grain size increased when the holding time prolonged from 30 min to 45 min, and then showed a little increment with further increase of time. Flexural strength and fracture toughness were improved with hot-pressing temperature increased, except 1950 degrees C. Analysis suggested that mechanical properties were limited by the thermal instability of Sic whiskers at such high temperature. Meanwhile, flexural strength increased as the increase of holding time. However, no obvious increment was found for fracture toughness, which was probably attributed to the residual pores. (C) 2009 Elsevier B.V. All rights reserved.