Reactive Hot Pressing of ZrB ₂ –SiC Composites

Abstract

A ZrB 2 –SiC composite was prepared from a mixture of zirconium, silicon, and B 4 C via reactive hot pressing. The three‐point bending strength was 506 ± 43 MPa, and the fracture toughness was 4.0 MPa·m 1/2 . The microstructure of the composite was observed via scanning electron microscopy; the in‐situ ‐formed ZrB 2 and SiC were found in agglomerates with a size that was in the particle‐size ranges of the zirconium and silicon starting powders, respectively. A model of the microstructure formation mechanism of the composite was proposed, to explain the features of the phase distributions. It is considered that, in the reactive hot‐pressing process, the B and C atoms in B 4 C will diffuse into the Zr and Si sites and form ZrB 2 and SiC in situ , respectively. Because the diffusion of Zr and Si atoms is slow, the microstructure (phase distributions) of the obtained composite shows the features of the zirconium and silicon starting powders.