Superplasticity of Silicon Carbide

Nanocrystalline silicon carbide that was doped with boron and carbon (B,C‐SiC) and contained 1 wt% boron additive and 3.5 wt% free carbon was fabricated using hot isostatic pressing under an ultrahigh pressure of 980 MPa and a temperature of 1600°C. The average grain size of the material was 200 nm. The tensile deformation behavior of this material at elevated temperature was investigated. The nanocrystalline B,C‐SiC exhibited superplastic elongation of >140% at a temperature of 1800°C. High‐resolution transmission electron microscopy observation and electron energy‐loss spectroscopy analysis revealed that this nanocrystalline SiC did not have a secondary glassy phase at the grain boundary and the grain boundary had a strong covalent nature, which means that an intergranular glassy phase was not necessary to obtain superplasticity of covalent materials.