Enhancement of high-temperature deformation in fine-grained silicon carbide with Al doping

Fine-grained SiC was hot-pressed with Al, B, and C additives under 150 MPa at 1850 °C. The grains had an equiaxed shape and the average grain size was 360 nm in as-sintered SiC. Al was detected at grain boundaries of Al, B, C-doped SiC by using energy-dispersive X-ray spectroscopy. The uni-axial compression tests were performed at constant crosshead speed at 1772 °C in He. The strain rates of Al, B, C-doped SiC in the low-stress region were ∼1 order of magnitude faster than those of B, C-doped SiC. The stress exponent of Al, B, C-doped SiC was 1.4 in the higher stress region, and increased to 2.6 with decreasing stress. The transition of the stress exponent, which is often observed in the superplasticity of metals and oxides, e.g., ZrO2, appeared in fine-grained SiC also.