High-strain-rate superplasticity in nanocrystalline silicon nitride ceramics under compression

Dense nanocrystalline silicon nitride (Si3N4) samples were successfully fabricated at extremely low temperature of 1300 °C with high pressure 300 MPa by spark plasma sintering (SPS). The as-sintered sample consisted of equiaxed fine grains with an average grain size of 56 ± 13 nm. Nanocrystalline Si3N4 samples exhibited superplastic deformation at high strain rate ranging from 10−3 to 10−2 s−1 under compression. Significant microstructural development was not observed in the deformed samples. There was no cavity damage after large deformation.