Abstract
Two kinds of silicon carbide ceramics were fabricated with Al 2 O 3 -Y 2 O 3 -CaO additives by hot-pressing using different SiC powders. The small pieces of these SiC were deformed by compression at 1650°C and 1700°C under constant cross-head speed, respectively. The specimen which was sintered with very fine powder (90nm) at 1750°C showed superplasticity, but the specimen sintered with less fine powder (280nm) at 1900°C did not. The microstructure of both the superplastic and the non-superplastic SiC ceramics was observed by transmission electron microscopy and scanning electron microscopy. After the deformation at 1650°C, liquid phase in the superplastic specimen redistributed and made large pockets. The orientation relation between adjacent two grains was observed by means of a microdiffraction techniquc. There was no significant difference in percentage of both coincidence site lattice boundary and low angle boundary between superplastic SiC and non-superplastic SiC.
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