Partitioning and site occupancy of Ta and Mo in Co-base γ/γ′ alloys studied by atom probe tomography |
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| Affiliation: | 1. Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Materials Science & Engineering, Institute I, Martensstr. 5, 91058 Erlangen, Germany;2. Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Rd, Cambridge CB3 0FS, UK;1. Institute for Advanced Metallic Materials & School of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China;2. Computational Alloy Design Group, IMDEA Materials Institute, Getafe (Madrid) 28906, Spain;3. School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China;4. Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan;1. Northwestern University, Department of Materials Science & Engineering, 2220 Campus Drive, Evanston IL 60208, USA;2. Northwestern University Center for Atom-Probe Tomography (NUCAPT), 2220 Campus Drive, Evanston IL 60208, USA;1. Materials Science and Engineering Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899-8555, USA;2. Department of Materials Science and Engineering, Northwestern University, 2200 Campus Drive, Evanston, IL 60208-3108, USA;3. NanoAl LLC, Illinois Science & Technology Park, 8025 Lamon Ave, Suite 446, Skokie, IL 60077, USA;4. Northwestern University Center for Atom-Probe Tomography (NUCAPT), 2200 Campus Drive, Evanston, IL 60208-3108, USA |
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| Abstract: | The detailed understanding of solute partitioning and site occupancies of these solutes within the ordered γ′ (L12) precipitates holds a key role in the development of cobalt-base γ/γ′ alloys with optimized properties. The present atom probe tomography study utilizes both structural and compositional information to determine the partitioning behavior of transition elements like Ta and Mo between γ matrix and γ′ precipitates and their site occupancy within the γ′ phase. The addition of Ta, which enhances the formation of γ′, to a ternary Co–Al–W alloy with stoichiometric Co3(Al,W) precipitates, results in the substitution of only the W in the γ′ precipitates to form Co3(Al, W, Ta) precipitates. Interestingly, Mo, typically considered a γ solid solution strengthener in nickel-base alloys, also partitions strongly to γ′ precipitates when added to the Co–Al–W alloy and displaces only the W atoms. The experimentally observed equal atomic substitution of W by both Ta and Mo, without any change in the Al content within the γ′ precipitates, gives insights into the energetics of relative site substitutions in this ordered compound. |
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| Keywords: | A Aluminides miscellaneous A Ternary alloy systems B Precipitates B Diffusion D Site occupancy F Atom probe |
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