Mechanical behaviours of reactive hot-pressed B 4 C-based composites with ZrB2-ZrC

Three B4C-based composites with 10, 20 and 30 vol% ZrB2-ZrC were prepared by reactive hot-pressing of Zr and B4C powders at 1900 degrees C for 2 h under 20 MPa in Ar. Relative density of similar to 96 % was obtained for 10 vol% ZrB2-ZrC, while relative density of >99 % was obtained for 20 and 30 vol% ZrB2-ZrC. The resulting composites were composed of B4C, ZrB2 and ZrC. The elastic moduli and hardness were insensitive to the ZrB2-ZrC content, whereas the fracture toughness increased with increasing ZrB2-ZrC content. In addition, the three compositions were fractured in four-point flexure at temperatures ranging from room temperature to 1600 degrees C. At or below 1500 degrees C, only linear stress-strain response was observed for each composition. Nonlinear response was observed in the stress-strain curves for temperature at 1600 degrees C. The strength displayed by the three compositions was closely associated with the amount and characterization of ZrB2 and ZrC phases formed during the sintering.