Microstructure,grain growth,and hardness during annealing of nanocrystalline Cu powders synthesized via high energy mechanical milling |
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| Affiliation: | 1. Department of Materials Engineering, University of Maragheh, Maragheh, P.O. Box 83111-55181, Iran;2. Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, South Korea;1. School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, PR China;2. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore;3. State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, PR China;1. Structural Integrity Group, Escuela Politécnica Superior, Avenida Cantabria s/n, 09006 Burgos, Spain;2. Civil Engineering Department, University of Burgos, Calle Villadiego s/n, 09001 Burgos, Spain;1. Department of Materials Physics, Eötvös University, Budapest, H-1518, P.O. Box 32, Budapest, Hungary;2. Physics of Nanostructured Materials, Faculty of Physics, University of Vienna, A-1090 Vienna, Boltzmanngasse 5, Austria;1. National Core Research Center, Pusan National University, Busandaehak-ro 63 beon-gil, Geumjeong-gu, Busan 609-735, Republic of Korea;2. Department of Metallurgical Engineering, Pukyong National University, Sinseon-ro 365 beon-gil, Nam-gu, Busan 608-739, Republic of Korea;1. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China;2. Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA |
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| Abstract: | In this paper, the microstructure and hardness evolutions of commercially pure Cu subjected to high energy mechanical milling and subsequent annealing treatments in the temperature range of 400–700 °C are investigated. The results demonstrated the simultaneous occurrence of recovery, recrystallization, and grain growth during annealing of the nanocrystalline Cu. The volume fraction of the recrystallized grains estimated using the grain orientation spread exhibits lower values as a result of its dynamic recovery at higher temperatures. The normal grain growth in the range of 400–600 °C and significant abnormal grain growth at higher temperatures are observed during annealing. As a result of the abnormal grain growth, the microhardness value rapidly decreases for the sample annealed at 700 °C. An analysis of the grain growth kinetics using the parabolic equation in the temperature range of 400–600 °C reveals a time exponent of n ≈ 2.7 and an activation energy of 72.93 kJ/mol. The calculated activation energy for the grain growth in the nanocrystalline Cu is slightly less than the activation energy required for the lattice diffusion. This low activation energy results from the high microstrain as well as the Zener-pinning mechanism that arises from the finely dispersed impurities drag effect. |
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| Keywords: | Nanocrystalline Grain growth Kinetics Microhardness Electron back scattering diffraction |
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