Abstract
Grain boundary migration of poly- and bi-crystalline silver under compression at 500°C was observed by means of a high temperature microscope. The results for the polycrystalline specimen are as follows; Thermal etching of grain boundaries took an impractically long time under the stress-free condition, while the boundaries could be detected within about one second under applied stress. One grain was absorbed by the surrounding grains. Twin boundaries intersecting a grain boundary restrained the grain boundary migration.
When a bicrystalline specimen with a curved grain boundary was subjected to strain gradient compression, the grain boundary migrated at first toward the low strain side (center of curvature) and then toward the high strain side. The driving force of the grain boundary migration was thought to arise from the grain boundary energy in the early stage and from the stored energy of deformation in the later stage. The increase in the mobility of a grain boundary under applied stress was interpreted as due to strain enhanced self-diffusion in the grain boundary.
