Effects of VC additives on densification and elastic and mechanical properties of hot-pressed ZrB₂–SiC composites

In this study, highly dense ZrB₂-20 vol% SiC composites with 3–10 wt% VC additives were prepared by hot-pressing at 1750 °C for 1 h under a pressure of 20 MPa in a vacuum. The densification behavior and elastic and mechanical properties of the obtained composites were examined, and the effect of the VC content on the densification and the properties is analyzed. The addition of VC promotes the activation of densification mechanism at a lower temperature and inhibits the growth of ZrB₂ and SiC grains during the sintering. In addition, the elastic moduli, hardness and fracture toughness that measured in the obtained composites are constant and independent of the VC content, with a shear modulus of ~ 220 GPa, Young’s modulus of ~ 500 GPa, hardness of ~ 20 GPa and fracture toughness of ~ 4.4 MPa m^1/2. On the other hand, the flexural strength of the composites decreased as the VC content increased from 3 to 7 wt% and then it increased with further increasing the VC content to 10 wt%, with strength values of 620–770 MPa.