炭化珪素の高温変形における流動応力の振動

抄録

In order to clarify the intrinsic nature of high temperature deformation of β-SiC without crack formation, pressureless sintered β-SiC with B+C additives as sintering aids has been deformed by compression at temperatures from 2070 to 2270 K and at strain rates from 6×10⁻⁶ to 7×10⁻⁵ s⁻¹. Microstructures were also examined by scanning electron microscopy (SEM) and X-ray diffraction.
It was found that the shape of stress-strain curves showed a regular oscillation. The oscillation depended markedly on strain rate; the period and the amplitude of the flow stress oscillation respectively tend to decrease and to increase with decreasing strain rate. A change in grain shape was observed from acicular grain, which is characteristic of pressureless sintered β-SiC, to almost equiaxed one after deformation. Furthermore, X-ray diffraction analysis revealed that there was no definite sign of structure change, that is, the β structure was maintained after deformation. The observed phenomena were discussed from the viewpoint of dynamic recrystallization.