Grain refinement mechanism during equal-channel angular pressing of a low-carbon steel |
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| Affiliation: | 1. Department of Metallurgy and Materials Science, Hanyang University, Kyunggi-Do, Ansan 425-791, South Korea;2. Division of Advanced Materials Science and Engineering, Taejon National University of Technology, Taejon 305-719, South Korea;1. School of Materials Science and Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai, 201418, PR China;2. School of Materials Engineering, Shanghai University of Engineering Science, 333 Longteng Road, Shanghai, 201602, PR China;1. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, PR China;2. School of Material Science and Engineering, Central South University, Changsha 410083, PR China;1. School of Materials Science and Engineering, University of Science and Technology, Beijing, Beijing 100083, China;2. Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801, USA;3. Nuclear Engineering Division, Argonne National Laboratory, Argonne, IL 60439, USA;4. X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA;1. Institute of Materials Design and Structural Integrity, Faculty of Engineering and Computer Science, University of Applied Sciences Osnabrück, 49009 Osnabrück, Germany;2. Institut für Werkstofftechnik, Universität Siegen, 57068 Siegen, Germany;3. Fraunhofer Institute for Mechanics of Materials IWM, Freiburg, Germany;4. Division of Materials Microstructure, Department of Physics, Chalmers University of Technology, 41296 Göteborg, Sweden;5. Instituto de Física Rosario – Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Rosario, 2000 Rosario, Argentina |
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| Abstract: | The grain refinement mechanism during equal-channel angular pressing of a plain low-carbon steel was explored by a careful analysis of the slip systems operating at each pass of repetitive pressing. The steel was subjected to one to eight passes of pressing, in which a single passage yielded an effective strain of ∼1, at 623 K. At the initial stage of pressing, submicrometer-order ferrite grains enclosed by serrated and low-angled boundaries were formed. Transmission electron microscopy examination revealed that these boundaries resulted from interaction between the slip systems that are typical in body-centered cubic structures. Further pressings mainly resulted in rotation of ultrafine subgrains rather than grain refinement, providing the formation of high-angle grain boundaries. Since the serrated boundaries restrict dislocation movement, the rotation of subgrains with the serrated boundaries is more favorable for accommodating further deformation than intragranular strain, and therefore boundaries become high-angled. |
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