Continuous Observation of Annealing Processes in Cold-Worked Aluminum by High-Voltage Electron Microscopy

Recovery and recrystallization processes have been continuously observed with a 500 kV electron microscope on cold-worked aluminum foils which are sufficiently thick to cause the same phenomena as in bulk specimens. When the specimens are annealed, many of tangled dislocations become loose and form sub-boundaries at different portions from the cell walls in general. Subsequently, the subgrains grow one after the other. In these processes, attractive force of dislocation arrays on each individual composite-dislocation of other sub-boundaries plays an important role, so that the composite-dislocations of sub-boundaries with low dislocation density are generally absorbed into the neighboring sub-boundaries with higher dislocation density. At the same time, the sub-boundaries migrate by the line-tension of neighboring sub-boundaries. Through these processes, new high-angle boundaries, i.e. , so-called recrystallization boundaries, are formed.