Abstract
The liquid-phase sintered silicon nitride (Si3N4) based ceramics has glass phase at grainboundaries. The chemical composition, volume fraction, distribution of the glass phase strongly influence the mechanical properties of Si3N4-based ceramics at elevated temperatures. Three types of fine-grained β-Si3N4 which have nearly the same volume fraction and different chemical composition of glass phase were prepared . The Mean particle size and the aspect ratio of as-HIPed materials were almost the same. The XRD showed that the as-HIPed materials consisted of β-Si3N4 and Si2N2O. Compression tests were carried out at 1600 degree and at initial strain rate of 3×10-5 to 1×10-4 /s. The true-stress-true-strain curves were systematically changed with the difference of chemical composotion of glass phase. It is supposed that difference in flow stress is related to the difference in the melting temperature of glass. The stress exponent was 1, and was independent of the chemical composition of glass.
