Thermomechanical Properties of Heat Treated ZrB2-SiC Composites with WC Additions

Mechanical properties of hot pressed, heat treated zirconium diboride – silicon carbide (ZrB₂-SiC) composites were tested at room temperature and at elevated temperatures.ZrB₂-SiC composites, containing 20-30 vol% SiC as a dispersed particulate phase and up to 4mol%WC additions, were hotpressed to near full density at 1900°C under an applied pressure of 32MPa in a flowing argon atmosphere.  The hotpressed billets were machined to ASTM standard test bars with the tensile surface polished to 1um. The test bars were heat treated at temperatures up to 1800°C for times up to 24 hours in an argon atmosphere. Young’s modulus, Vickers’ hardness, fracture toughness (chevron notch), and four-point bend strength were measured for the heat treated samples. Four-point bend tests, and fracture toughness from room temperature to 1800°C were performed in an air atmosphere. The influence of microstructure on the mechanical properties will be discussed.