Spark plasma sintering of ZrB2-based composites co-reinforced with SiC whiskers and pulverized carbon fibers

Abstract Spark plasma sintering (SPS) process was used to preparation of ZrB2-based composites co-reinforced with SiC whiskers as well as various amounts of pulverized carbon fibers. The effects of CF content on microstructure and mechanical characteristics of ZrB2–SiCw–CF composites were scrutinized. Although all composites approached high densification, a fully-dense sample was fabricated by the addition of 2.5 wt% CF. The growth of ZrB2 grains was remarkably inhibited in CF-reinforced composites. No in-situ formed phase was detected by XRD; however, trace of nano-ZrC clusters was observed in SEM fractographs of ZrB2–SiCw–CF samples. The formation of such nano-sized ZrC refractory phase was also proved by thermodynamics. The hardness of composites slightly decreased from 21.9 to 19 GPa with increasing the CF content. Reversely, the fracture toughness values enhanced from 4.7 to 6 MPa.m½ with increasing the amount of pulverized carbon fibers.