Recovery studies of cold rolled aluminum sheet using X-ray line broadening and activation volume determinations

The microstructure of cold rolled metals is highly complex, but characterization of its transformation to the recrystallized state is essential to design thermal–mechanical processing of sheet products. In this study recovery leading to continuous recrystallization was examined by both X-ray line broadening and measurement of activation volumes at 78 K as a function of isochronal anneals to characterize the recovered structure wherein non-conservative motion of defects is not possible. The statistically stored dislocation density recovered without a large reduction in the flow stress. On the other hand, the typical decrease in hardness associated with recrystallization was observed with the inception of discontinuous grain growth when the geometrically necessary dislocation arrays started to disintegrate. Activation distance determinations of pre-rolled structure during micro-strain correlate with the Burgers vectors of stair-rod dislocations, indicating that the controlling mechanism is the dragging of jogs.