High temperature deformation of fine grained high purity alumina

High-temperature deformation behavior of high-purity polycrystalline alumina (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 ultimate compression stress in each test is decreased with the testing temperature and increased with the strain rate. The strain rate sensitivity is about 0.6 and the apparent activation energy is almost consistent with that of grain boundary diffusion of aluminum ion in the ductile deformation. Stress-enhanced grain growth and nucleation of cavities at grain boundary triple points were observed during the ductile deformation. The increase in area fraction of the cavity is proportional to the strain. It can be speculated that the cavities nucleate and growth at the triple point by nonaccommodated grain boundary sliding.