Relations between microstructure and mechanical properties of pressureless sintered SiC

Abstract

SiC green bodies with B4C and nano-scale carbon black as sintering aids were prepared by slip casting. After presintering at 2160°C for 10 min the samples were annealed at the same temperature for different times in order to obtain different microstructures. By this procedure the initial relative density of 0,981 was increased to 0,989 accompanied by grain growth and morphological changes. Samples annealed for 30 min possessed a fracture strength around 440 MPa, as determined by the double ring test. The maximum fracture toughness was 3.5 MPam0.5. Examination of the grain growth behaviour showed that the microstructure is up to relative densities of 0.985 stable against the accelerated grain growth.