The role of orientation pinning in statically recrystallized oxygen-free high-conductivity copper wire
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INTRODUCTION
TWO physical processes characterize recrystallization: the formation of viable nuclei and their subsequent growth into the deformed matrix. The nature of the recrystallization texture is determined primarily by the orientation of the new grains or the relative nucleation and growth rates of these grains. For many years, two competing theories of “oriented nucleation” (ON) and “oriented growth” (OG) have been used to interpret the manner in which these factors operate to produce a unique recrystallization texture from a particular deformed texture.[1–4] The schematic in Figure 1 depicts the two types of recrystallization, for a case where the final recrystallization texture is predominantly Cube. This process can be realized by either “ON,” in which the nucleation texture is Cube dominated, or “OG,” in which the nucleation texture is random. “ON” assumes that the preferred nucleation of some special orientations (e.g., the cube component, {001}100, in rolled fcc metals) determines the final recrystallization texture. “OG” assumes that, starting from a randomly oriented array of nuclei, those with the best growth conditions with respect to the deformed matrix (e.g., grains with 40 deg 111 boundaries in aluminum) grow fastest and, therefore, dominate the recrystallization texture. The theory is based on the principle that a certain orientation grows more rapidly than other orientations. Although the two theories have been independently used to explain recrystallization D.R. WARYOBA, Postdoctorate Research Associate, and P.N. KALU, Associate Professor, Mechanical Engineering, are with the FAMU-FSU College of Engineering, Tallahassee, FL 32310. Contact e-mail: waryoba@ magnet.fsu.edu A.D. ROLLETT, Professor, is with the Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213. Manuscript submitted April 16, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS A
texture, the present trend is toward accepting both theories. Thus, the dominance of the cube orientation in the recrystallization texture of aluminum is thought to be due to its rapid nucleation and optimum growth conditions.[4] Recrystallization studies have been carried out using various techniques and approaches. The advent of computerassisted techniques such as orientation imaging microscopy (OIM) (e.g., Reference 5) has even provided additional dimensions to how recrystallization studies are pursued. It is now possible to address recrystallization phenomena from the viewpoint of grain boundary character distribution and grain-to-grain orientation, as opposed to grain size distribution. In recent years, the role of special coincidence site lattice (CSL) boundaries, high-energy grain boundaries (HEGBs), and orientation pinning have been used to explain recrystallization models. In Fe-Si steels, for example, two models have been proposed to explain the mechanism of abnormal grain growth. One model[6,7,8] suggests that certain CSL boundaries have high mobilities and are responsible for the abnormal grain growt
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