Dislocation Structures Formed During Hot and Cold Working

摘要

During many types of deformation, grains are subdivided into smaller regions by dislocation boundaries. The classification of structures formed by grain subdivision has differed between structures observed following cold deformation and hot deformation. Cold deformed microstructure are characterized by grain subdivision at two size scales. Grain subdivision occurs at the larger scale by geometrically necessary boundaries that delineate differently deforming blocks that contain nearly equiaxed cells. In contrast hot deformed structures have been described with a single level of subdivision by equiaxed subgrains. Infrequently an occasional long boundary provides subdivision at a larger level. However, new findings in warm to hot deformed alloys show that there are closer ties between the cold and hot deformed structures. Specifically, two levels of grain subdivision are observed following some types of high temperature deformation when large areas are surveyed in the TEM. Furthermore, the probability densities of boundary disorientation angles at high temperature show the same universal scaling as those at low temperature.