A study of vacancy-type defects in pure and boron-doped Ni3Al alloys |
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| Affiliation: | 1. Department of Applied Science, Brookhaven National Laboratory, Upton, NY 11973, USA;2. Physics Department, Brookhaven National Laboratory, Upton, NY 11973, USA;1. College of Chemistry and Chemical Engineering, State Key Laboratory for Physical Chemistry of Solid Surfaces, and National Engineering Laboratory for Green Chemical Productions of Alcohols-Ethers-Esters, Xiamen University, Xiamen 361005, China;2. College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, China;3. Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman 99164, USA;1. Division of Medical Oncology, Department of Medicine, University of British Columbia, Vancouver, BC, Canada;2. Centre for Lymphoid Cancer, BC Cancer, Vancouver, BC, Canada;3. UHN Division of Medical Oncology and Hematology, Princess Margaret Cancer Centre, Toronto, ON, Canada;4. Oncology Institute of Southern Switzerland, Bellinzona, Switzerland;5. Department of Diagnostic Imaging, BC Cancer, Vancouver Centre, BC, Canada;6. Department of Pathology, University of British Columbia, Vancouver, BC, Canada;1. The Laboratory of Data Science and Artificial Intelligence Innovation, Department of Computer Science, School of Engineering and Computer Science, Baylor University, Waco, TX 76798, USA;2. School of Computer Science and Engineering, South China University of Technology, Guangzhou, Guangdong 510641, China;3. Institute of Computational Science and Technology, Guangzhou University, Guangzhou, Guangdong 510006, China;4. Department of Computer Science and Software Engineering, Monmouth University, West Long Branch, NJ 07764, USA |
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| Abstract: | Positron lifetimes have been measured for two sets of pure and boron-doped Ni3Al alloys. The alloys were large-grain polycrystals and had compositions of Ni75+xAl25−x (x = −1, 0, + 1) with 0, 100 and 500 wt ppm boron added. Lifetime parameters for samples of composition Ni75+xAl25−x (x= ± 1) with 0 and 500 wt ppm boron added were measured after initial thermal conditioning and after a subsequent cold-work anneal treatment. Positron trapping (≈20%) was observed in all unprocessed alloys. The vacancy concentration was calculated to be ≈ 5 × 10−6 and showed little, if any, systematic dependence on either alloy composition or boron concentration. Cold-worked fully annealed samples contained no detectable vacancies, i.e. the trapped state intensity was observed to be zero. The results are at variance with previously published data. During the annealing procedure (> 350°C) carbon was observed to diffuse out of the cold-worked samples. It is therefore possible that carbon stabilizes vacancies in Ni3Al alloys. There is, however, no evidence to suggest that boron interacts with constitutional vacancies in Ni3Al. |
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