Effect of Boron and Carbon Addition on High Temperature Deformation Behavior of β-Silicon Carbide

摘要

β-Silicon carbides (SiC) sintered without any sintering aids and with B and C addition were deformed by compression at high temperatures and observed by transmission electron microscopy to reveal the effect of B and C addition on the high temperature deformation behavior of β-SiC. The main results obtained are as follows.rnIt was found that addition of B and C resulted in remarkable change in high temperature deformation behavior of β-SiC; flow stress was markedly decreased and stress oscillation took place on the stress-strain curves. The effect of B and C addition was likely to occur owing to decrease in the stacking fault energy. That is, change in the magnitude of stacking fault energy must have affected the characteristics of glide motion for partial dislocations. Furthermore, since the contribution of the effective stress to flow stress would be high during high temperature deformation of SiC because of its high Peierls' barrier, the flow stress oscillation probably resulted from the combination of the work-softening due to Johnston-Gilman mechanism and the work-hardening due to dynamic recrystalliza-tion (DRX). It is evident that the addition of B and C increases the ability of plastic deformation governed by dislocation motion. Therefore, superplasticity would be expected to occur by homogeneous plastic deformation without a contribution of such heterogeneous deformation as grain boundary sliding.