Behavior of Dislocations in Copper under Reverse Stress

Abstract

Movement of dislocations induced by unloading and reverse stressing have been directly observed in copper by the in-situ observation technique with a 3MV-class electron microscope.
By unloading, isolated dislocations in the interior of cells make backward movements after inverted their bowing direction.
When the stress is applied in the reverse direction, these isolated dislocations are swept away from the interior of cells, and dislocations in cell walls begin to move. In this case, both position and dislocation density of cell walls are scarcely changed during deformation until the reverse stress reaches the prestress level. In the stress range higher than the prestress level, the cell structure is developed around these pre-existing cell walls in the same way as in the case of forward deformation. These results are discussed in terms of the nature of cell walls.