Papers by Keyword: Stored Energy

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Authors: Anne Laure Etter, Marie Helene Mathon, Thierry Baudin, Richard Penelle
Authors: Hua Long Li, Jong Tae Park, Jerzy A. Szpunar
Authors: Satyam Suwas, André Eberhardt, László S. Tóth, Jean-Jacques Fundenberger, Thierry Grosdidier
Abstract: The amount of stored energy of cold work for the processing routes A and Bc of Equal Channel Angular Extrusion (ECAE) process has been measured using differential scanning calorimetry. The study is preceded by the effect of amount of ECAE deformation on materials of different stacking fault energies, namely Cu and Ag. The results indicate that the different processing routes have significant effect on the stored energy, which is likely to affect the grain refinement process.
Authors: Yoshimasa Takayama, Jerzy A. Szpunar, Hajime Kato
Abstract: Intragranular misorientation reflects strain generated during deformation with dislocation glide. The SEM/EBSP (scanning electron microscope/ electron back scatter diffraction pattern) technique provides is “kernel average misorientation (KAM)” as the most appropriate quantity to evaluate the strain or the stored energy for a given point. The KAM is defined for a given point as the average misorientation of that point with all of its neighbors. In the present paper two analyses of the intragranular misorientation using the SEM/EBSP technique for a cyclic deformation at room temperature and a high temperature deformation in an Al-Mg-Mn alloy are reviewed.
Authors: Naoki Takata, Kousuke Yamada, Kenichi Ikeda, Fuyuki Yoshida, Hideharu Nakashima, Nobuhiro Tsuji
Abstract: The recrystallization behavior and texture development in copper accumulative roll-bonding (ARB) processed by various cycles (2, 4 and 6 cycle) were studied by differential scanning calorimetry (DSC) analysis and SEM/EBSP method. The exothermic peaks caused by recrystallization appeared at 210 ~ 253 􀍠 in each sample. The peak positions shifted to lower temperature as the number of ARB cycles increased. This result indicated that the evolution of finer microstructure with increasing number of the ARB cycles enhanced the occurrence of recrystallization at lower temperature. The stored energy calculated from the DSC curve of the ARB processed copper increased with the increasing strains. During an annealing, the preferential growth of cube-oriented grains ({100}<001>) occurred in each sample. The recystallization behavior of ARB processed copper having low stacking fault energies was distinguished from that of so-called “recovery type” materials, i.e. aluminum and low carbon steels, which shows rather continuous changes in microstructure during annealing. The accumulated strains provided the driving force for the preferential growth, which was the same mechanism as the preferential growth in normally rolled copper. The sharpest cube texture developed in ARB processed copper by 4 cycles. The difference of cube texture development between 2 cycles and 4 cycles was caused by the distribution of cube-oriented regions which corresponded to the nucleation sites of recrystallized grains before annealing. More nanocystalline layers in the vicinity of bonded interfaces were distributed in ARB processed copper by 6 cycles than 4cycles. The nanocystalline structure could grow faster than the cube-oriented grains and led to the inhibition of sharp cube texture in the ARB processed copper by 6 cycles.
Authors: H. Ahmed, Mary A. Wells, Daan M. Maijer, Menno van der Winden
Abstract: A mathematical model has been developed and validated to predict deformation, temperature and microstructure evolution during multi-pass hot rolling of an AA5083 aluminum alloy. The validated model was employed to examine the effect of changing the number of rolling passes and the strain partitioning during multi-pass rolling on the material stored energy and the resulting microstructure. Results indicate that the number of rolling passes has a significant effect on the material stored energy. In addition, the way the strain is partitioned in two-pass rolling cases affects the material stored energy with decreasing strain/pass providing the highest stored energy in the material after rolling and vice versa. The reason behind these results was further investigated indicating that the thermal evolution during rolling may significantly influence the material stored energy and subsequent recrystallization kinetics.
Authors: Chao Fang, C. Isaac Garcia, Shi Hoon Choi, Anthony J. DeArdo
Abstract: Stored energy in deformed metals plays an important role during the annealing process by providing the initial driving force for recovery and recrystallization. Many direct or indirect measurement and calculation methods have been used to evaluate the amount and distribution of the stored energy in the past decades. The advent of relatively new analytical techniques such as Electron Back-Scattered Diffraction (EBSD) has permitted the development of mathematical models such as Sub-grain Method, Image Quality (IQ) Method and Taylor Factor Method etc., these new techniques have permitted a much better understanding of the annealing behavior of cold rolled steels. The sub-grain method based on the level of sub-grain structure is used in our study to quantify the stored energy distribution prior to and its evolution during the batch annealing process of cold rolled HSLA steels. Orientation dependent stored energy distribution maps at different annealing stages have been constructed and analyzed. The results of this study show that the stored energy increases with cold rolling reduction ratio and its distribution through the thickness of the steel sample is not uniform due to the inherit inhomogeneous deformation process. The stored energy was continuously consumed during annealing. The amount of γ-fiber was relatively lower than the α-fiber in the specific steel sample, which can have a strong effect on the available driving force for recovery and recrystallization. Hence other structural factors such as precipitation and/or solute drag might become more important in controlling the kinetic behavior of the steel during annealing.
Authors: K. Piękoś, Jacek Tarasiuk, Krzysztof Wierzbanowski, Brigitte Bacroix
Abstract: The recrystallization process in polycrystalline material was studied using the newly developed two–dimensional model based on the vertex concept. In the model presented below the microstructure of polycrystalline material is represented by two-dimensional network of grains. The initial microstructure is characterized by topology, crystal orientations and stored energy values of the grains. The boundary energies and mobilities are anisotropic in general. Additional driving forces in recrystallization, are exerted on vertices and are derived from the stored energy gradients between adjacent grains. The nucleation mechanism of a given type is selected at the start of the calculations. Two different nucleation types were tested. Deformation texture, stored energy distribution and initial microstructure are input parameters of the model. The goal of the calculations is the prediction of texture and microstructure modification during recrystallization. A comparison of predicted and experimental characteristics enables the verification of the model assumptions.
Authors: Jan Kuśnierz, M. Kurowski, Marie Helene Mathon, Thierry Baudin, Zdzislaw Jasieński, Richard Penelle
Authors: Kyoo Young Lee, Gyo Sung Kim, Leo Kestens
Abstract: By applying a double cold rolling and annealing treatment, the evolution of the α and γ fiber components differed from the ones observed in conventional processing. This is attributed to the difference of the initial texture. An increased reduction of stored energy of the {111}<112> component was found by monitoring the change of the stored energy during annealing, indicating that the onset of the nucleation stage of recrystallization by relaxation and annihilation of dislocations occurred mainly on the {111}<112> component with its higher stored energy. The detailed texture evolution of the double cold rolled specimen during 2nd annealing is described by coupling the theory of oriented nucleation and orientation pinning, which is experimentally confirmed by OIM scan.
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