Diffusion of chromium in nanocrystalline iron produced by means of surface mechanical attrition treatment |
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| Affiliation: | 1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China;2. LASMIS, University of Technology of Troyes, 10000, Troyes, France;1. Key Laboratory of Advanced Manufacturing Technology, Ministry of Education, Guizhou University, Guiyang Guizhou, 550025, PR China;2. College of Materials Science and Metallurgical Engineering, Guizhou University, PR China;3. Guizhou Key Laboratory for Mechanical Behavior and Microstructure of Materials, PR China;4. National & Local Joint Engineering Laboratory for High-Performance Metal Structure Materials and Advanced Manufacturing Technology, PR China;5. College of Mechanical Engineering, Guizhou University, Guiyang Guizhou, 550025, PR China;1. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;2. Department of Mechanical Engineering, Politecnico di Milano, Milan 20156, Italy;3. Center for Advanced Materials Technology (CAMT), Kookmin University, Seoul 136-702, Republic of Korea;1. School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, PR China;2. School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510641, PR China |
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| Abstract: | By means of surface mechanical attrition treatment (SMAT) to a pure iron plate, a nanometer-grained surface layer without porosity and contamination was fabricated. The average grain size in the top surface layer (of 5 μm thick) is about 10–25 nm, and the grain size stability can be maintained up to 653 K. Cr diffusion kinetics in the nanocrystalline Fe phase was measured by using second ion mass spectrometry within a temperature range of 573–653 K. Experimental results showed that diffusivity of Cr in the nanocrystalline Fe is 7–9 orders of magnitude higher than that in Fe lattice and 4–5 orders of magnitude higher than that in the grain boundaries (GBs) of α-Fe. The activation energy for Cr diffusion in the Fe nanophase is comparable to that of the GB diffusion, but the pre-exponential factor is much higher. The enhanced diffusivity of Cr may originate from a large volume fraction of non-equilibrium GBs and a considerable amount of triple junctions in the present nanocrystalline Fe sample processed by means of the SMAT technique. |
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