HIGH-TEMPERATURE DEFORMATION OF FINE-GRAINED HIGH-PURITY ALUMINA

High-temperature deformation behavior of high-purity polycrystalline a lumina (the mean grain size is about 6 mu m) prepared with no additive was investigated. In the testing temperature range from 1400 to 1600 degrees C, ductile deformation is obtained at a low strain rate. The u ltimate compression stress in each test is decreased with the testing temperature and increased with the strain rate. The strain rate sensit ivity is about 0.6 and the apparent activation energy is almost consis tent with that of grain boundary diffusion of aluminum ion in the duct ile deformation. Stress-enhanced grain growth and nucleation of caviti es at grain boundary triple points were observed during the ductile de formation. The increase in area fraction of the cavity is proportional to the strain. It can be speculated that the cavities nucleate and gr owth at the triple point by nonaccommodated grain boundary sliding.