FRACTURE TOUGHNESS AND FRACTURE OF ZrB_2 CERAMIC BASED COMPOSITES

摘要

Monolithic zirconium diboride (ZrB_2) and ZrB_2 based composites containing 2 wt% SiC and B4C particles were prepared from commercially available powders using High Pressure-High Temperature (HP-HT) method. The influence of the SiC and B4C addition on the microstructure development, hardness, fracture toughness and fracture characteristics was investigated. Materials with relativelly high relative density have been prepared with values approximately 96.3%, 96.8% and 97.9% for the systems ZrB_2, ZrB_2 + SiC and ZrB_2 + B_4C, respectively. The fracture toughness increased with addition of SiC and B_4C from 4.2 MPam~(0.5), which is characteristic for monolithis system, to 5.95 MPam~(0.5) for ZrB_2 + B_4C. Toughening mechanisms, mainly in the form of crack deflection were responsible for the toughenning of the composites.