Recovery of heavily cold-rolled aluminum: Effect of local texture
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I. INTRODUCTION
RECOVERY and recrystallization of deformed metals are driven by the energy stored in the deformed state. In many studies the recrystallization behavior has been analyzed based on the characteristics of the deformed state, while the structural changes taking place during recovery after deformation and prior to recrystallization have been studied to a far less extent.[1–10] However, at present there is a growing interest in this area, partly inspired by a drive to model and refine industrial annealing processes but also driven by the current interest in the deformation and thermal behavior of nanostructured metallic materials produced by plastic deformation to large strains.[11–16] The objective of the current study is to examine the structural evolution during recovery of cold-rolled commercialpurity aluminium (AA1200), an important industrial material that has been studied extensively.[2,3,5,6,15] The research will be focused on relations between local texture and microstructure after a large-strain deformation followed by recovery. This is because previous studies of low strains have shown for both single crystals and polycrystals that the grain orientation significantly affects the morphology, the structural parameters, and the stored energy of the deformed structure.[17–20] To study such an effect after a large strain, a true rolling strain of 2 has been chosen for a material that had an initial grain size of about 75 m. At this strain, rolling texture components with typical large-strain lamellar deformation structures have developed, but the width of structural features with a given orientation may still be sufficient to allow an examination of a correlation of the local deformation microstructure with a given texture component. Temperature was chosen as the variable to study the microstructural changes preceding the formation of recrysQ. XING, formerly Postdoctoral Researcher, was with the Centre for Fundamental Research: Metal Structures in Four Dimensions, Materials Research Department, Risø National Laboratory, Roskilde, Denmark, and is now with College of Sciences, University of New Orleans, New Orleans, LA 70148, U.S.A. (current mailing address: Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, U.S.A.). X. HUANG and N. HANSEN, Senior Scientists, are with the Centre for Fundamental Research: Metal Structures in Four Dimensions Materials Research Department, Risø National Laboratory DK-4000 Roskilde, Denmark. Contact e-mail: [email protected] Manuscript submitted June 26, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS A
tallization nuclei. The structures to be characterized were therefore on a very fine scale, and consequently transmission electron microscopy (TEM) was chosen as the investigation tool due to the high resolution of this technique under both imaging and diffraction conditions. In this paper the extended boundaries in the lamellar microstructure are termed “geometrically necessary boundaries” (GNBs), which are the original grain boundaries, def
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