The Kinetics of and the Microstructure Induced by the Recrystallization of Copper
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UCTION
RECRYSTALLIZATION of deformed materials is a process of high technological importance and, therefore, has been studied intensively for many decades.[1–3] Even though the kinetics of the recrystallization process is easily accessible through hardness, metallographic, or calorimetric measurements, its interpretation is a matter of on-going debate.[3] Simple models, e.g., based on the assumption that all *It must be recognized that nucleation in recrystallization is not the outcome of a fluctuation phenomenon as in heterogeneous phase transformations. Instead, the ‘‘nuclei’’ are already present in the deformed material (as subgrains[3]) and can become ‘‘activated’’ subject to instability criteria.[3–5] Nevertheless, the moment a (sub-) grain starts to grow is denoted ‘‘nucleation.’’
nuclei* are present at the beginning of the process and that the velocity of the interfaces between deformed and recrystallized material is constant (at constant temperature), were unable to correctly describe both the observed kinetics and the microstructure after recrystallization. Kinetic models have been proposed that are ERIC A. JA¨GLE, formerly Doctoral Student, Max Planck Institute for Intelligent Systems (formerly Max Planck Institute for Metals Research), 70569 Stuttgart, Germany, is now a Postdoctoral Researcher, with the Max Planck Institute for Iron Research, 40237 Du¨sseldorf, Germany. Contact e-mail: [email protected] ERIC J. MITTEMEIJER, Director, Max Planck Institute for Intelligent Systems (formerly Max Planck Institute for Metals Research), and Full Professor, with the Institute for Materials Science, University of Stuttgart, 70569 Stuttgart, Germany. Manuscript submitted April 26, 2011. Article published online December 21, 2011 METALLURGICAL AND MATERIALS TRANSACTIONS A
able to describe the experimentally determined recrystallization kinetics, e.g., by assuming that there exists a distribution of growth rates during recrystallization.[6] However, the assumptions made in such models need to be validated. One way to validate kinetic models is to compare the accordingly predicted microstructure, i.e., the grain morphology, the grain-size distribution, or the texture after completed recrystallization, with the experimentally determined microstructure. The microstructure, which follows the adoption of a certain kinetic model, can be determined by carrying out a mesoscopic simulation. Conversely, models have been proposed also that are able to describe experimentally observed microstructural parameters such as the grain-area distribution, e.g., by assuming that the nucleation rate accelerates during recrystallization.[7] They can be validated by comparing the recrystallization kinetics as predicted by mesoscopic simulations on the basis of these models with experiments. Recent recrystallization models use data on the microstructure of the material in the deformed state to calculate the nucleation rate (e.g., Reference 8) or the growth rate of recrystallizing grains (e.g., References 9 through 11). To this end, data abou
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