高純度微細多結晶粒アルミナの高温変形

Abstract

High-temperature deformation behavior of high-purity polycrystalline alumina (the mean grain size is about 6 μm) prepared with no sintering additives has been investigated through a series of compression tests. In the testing temperature range from 1400 to 1600°C, the alumina can be deformed plastically at a lower strain rate, while it fails without plastic deformation at a higher strain rate. The ultimate stress decreased with the testing temperature and increased with the strain rate. The strain rate sensitivity of the flow stress is about 0.6 and the apparent activation energy is almost consistent with that of grain boundary diffusion of aluminum ion in the plastic deformation at the lower strain rates. In the specimens deformed at low strain rates, stress-enhanced grain growth and nucleation of cavities at triple points of grain boundaries were observed during the plastic deformation. The increase in area fraction of the cavity is proportional to the strain. It may be considered that the cavities nucleate and grow at the triple point by grain boundary sliding without a sufficient accommodation process.