Study of two-particle softening ZrB₂ ceramic matrix composites

The two-particle softening ZrB₂ ceramic matrix composites were prepared by means of mixing and hot pressing, their density, microhardness, mechanical properties, ablation resistance and microstructure have been studied. The results showed that the density of the composites possessed 99.5% of their theoretical density with a microhardness of 800 HV. The compressive strength of the composites at room temperature was 1.397 GPa and the relative compressibility was 21.8%. Those at high temperature decreased sharply, while the compressive strength still reached 649 MPa and the relative compressibility was 6.7% at 1100°C. After the composites had been burnt on the plasma-arc heater for 6 seconds, the temperature on the surface of the composites got 2800°C and the partial softening particles of the composites grew up, melt and spurted, remaining holes. After the composites had been burnt on the oxy-ethyne flame for 30 seconds, the temperature on the surface of the composites got 2000°C, a thin oxide film formed on the surface without crack, and the microstructure on the surface grew up slightly.