Atsushi Yamamoto, Masaaki Tsukamoto and Daisuke Okai
Department of Materials Science and Synchrotron Radiation Engineering, Graduate School of Engineering, University of Hyogo, Himeji 671-2201
Previously we have reported that dislocation cells which are formed by cold-rolling grew into recrystallized grains with other dislocation cells formed via the recovery of microstructures. There are not any differences between these cells after deformation and similar microstructural changes would occur in both cell types at an early stage of annealing. Intermittent observations via SEM-EBSD were performed during annealing on the same areas in the specimens of 1050 aluminum cold-rolled at 28, 45 and 73% and then annealed at 673 K. Dislocation cells were formed in all the specimens except in an area of the specimen cold-rolled at 28% in which dislocation tangles were formed. These tangles did not migrate or anneal out. Changes in the microstructure did not occur in area of annealing, and recrystallized grains which were formed through the SIBM mechanism invaded the area. In the specimen cold-rolled at 45%, dislocation cells with orientations that deviated from the circumference were observed, which shrank and disappeared at the early stage of annealing, resulting in formation of regions composed of sub-grains having a similar orientation. These sub-grains were surrounded with low angle boundaries and exhibited suppressed growth. In the case of the specimen cold-rolled at 73%, the orientation of the original grains split into two due to cold-rolling, and dislocation cells that had each orientation were formed via dispersion with each other. Dislocation cells grew into sub-grains, and sub-grain boundaries migrated with areas of low dislocation density forming. At this stage, the sub-grain was composed of areas with low and high dislocation densities. The latter was invaded by other sub-grains via subgrain boundary migration, and the remaining area that had a low dislocation density being surrounded by high angle boundaries formed a recrystallized grain. This effect was due to the neighboring sub-grains having other orientations. Growth of dislocation cells into recrystallized grains depends on misorientation between the neighboring grains.
1050 aluminum, recovery, recrystallization, strain induced grain boundary migration (SIBM), dislocation cell, scanning electron microscope-electron backscatter diffraction (SEM-EBSD), same area observation
Please do not copy without permission.