抄録
Microstructures of columnar grains of uranium dioxide grown under the temperature gradient —sintered pellets, swaged compacts and vibratory compacts— below the melting point have been studied by optical and electron micrography.
The main results obtained are as follows:
1. The dominant mechanism in columnar grain growth varies with porosity. The columnar grains in high density sintered pellets of 97% theoretical density are considered to be grown by the migration of grain boundary. As the porosity increases, the migration of large voids plays a dominant role in the columnar grain growth.
2. In addition to lenticular voids, voids or gaps along the grain boundary of columnar grains are observed in porous specimens.
3. As for the powder compacts of the same composition and different compact densities, the size and number of lenticular voids increase with decreasing density.
