The effect of ZrC on the mechanical response of ZrB2 ceramics has been evaluated from room temperature to 2000 °C. Zirconium diboride ceramics containing 10 vol% ZrC had higher strengths at all temperatures compared to previous reports for nominally pure ZrB2. The addition of ZrC also increased fracture toughness from ~3.5MPa√m for nominally pure ZrB2 to ~4.3MPa√m due to residual thermal stresses. The toughness was comparable with ZrB2 up to 1600 °C, but increased to 4.6MPa√m at 1800 °C and 2000 °C. The increased toughness above 1600 °C was attributed to plasticity in the ZrC at elevated temperatures. Electron back-scattered diffraction analysis showed strong orientation of the ZrC grains along the [001] direction in the tensile region of specimens tested at 2000 °C, a phenomenon that has not been observed previously for fast fracture (crosshead displacement rate = 4.0 mm min-1) in four point bending. It is believed that microstructural changes and plasticity at elevated temperature were the mechanisms behind the ultrafast reorientation of ZrC.
- Borides,
- Electron Backscattering Diffraction (EBSD),
- High-Temperature Mechanical Properties,
- Particulate Reinforced Composites,
- Ultra-High Temperature Ceramics (UHTC)
Available at: http://works.bepress.com/greg-hilmas/212/