2014 Fiscal Year Annual Research Report
酸化物分散強化鋼の高温照射環境下における強度劣化とその機構の解明
| Project/Area Number |
14F04903
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| Research Institution | Tohoku University |
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Principal Investigator |
阿部 弘亨 東北大学, 金属材料研究所, 教授 (40343925)
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| Co-Investigator(Kenkyū-buntansha) |
LI Yanfen 東北大学, 金属材料研究所, 外国人特別研究員
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| Project Period (FY) |
2014-04-25 – 2016-03-31
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| Keywords | nuclear materials / oxide dispersion / creep properties / irradiation effect / thermal stability / microstructure / nano-scale particles / ODS steels |
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| Outline of Annual Research Achievements |
Oxide dispersion strengthened (ODS) steels are considered as the advanced structural materials of fusion blanket and nuclear fuel cladding tube in fast breeder reactors due to their excellent tensile and creep strength and good irradiation resistance. In this work, the long-term creep properties and fracture mechanism were investigated to determine the maximum operation temperature of materials. Also, irradiation experiments by electron and ion were carried out to reveal the microstructural evolution especially the stability of nano-particles.
The creep test was carried out at the temperature of 773 to 973 K, the stress level of 120-600 MPa, and creep rate of 1E-6 - 1E-10/s. 12Cr-ODS steel exhibited excellent and unique behaviors, such as significantly longer second steady-state stage, smaller in minimum creep rate, and almost absence of tertiary accelerated creep stage. The creep stress exponent n was in the range of 10-50, which is much higher than the heat-resistant steels. The existence of a creep threshold stress, which associated with the interaction between dislocations and nano-scale oxide particles, is expected. SEM/EBSD observations showed a mixed ductile and brittle fracture mode. High density of defects and/or cavities, were formed along rolling direction or grain elongated direction and perpendicular to the tensile direction, and connected into cracks. The electron irradiation was performed at temperature ranging from 673 to 873 K and with the energy from 0.75 to 2 MeV, as well as ion irradiation, showed that nano-particles were unstable under irradiation.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
All the experiments and proposed research are going well as the schedule. The present researcher has carried out the research on ODS steels for the application in the fusion and fission reactor for several years, and already has the proficient skills and profound knowledge background. The creep machines and devices for microstructural observation are available in the institute of host professor. The irradiation equipments such as UHVTEM and HIT accelerator are available in the cooperated institutes and universities.
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| Strategy for Future Research Activity |
The remained creep property testing at lower testing temperatures, and long-term aging in 12Cr-ODS will be finished. The corresponding microstructural evolution, including the fractography, during will be analyzed by SEM, EBSD and TEM. The expected fracture model is evolution of grain and grain boundaries, precipitates and dislocation during the creep process. The creep deformation and fracture maps will be built for the prediction of the creep mechanisms at related temperature and stress condition. The longer-term creep performance in the typical fusion blanket limit condition and fission reactor will be predicted, which can provide the important reference for the design of advanced nuclear reactors. In-situ observation of the stability of nano-particles during the electron irradiation, as well as ion irradiation, will be continued to reveal microstructural evolution under irradiation.
Finally, all the experimental results will be summarized and a series of research reports will be completed. These results will be presented in domestic conference and 17th International Conference on Fusion Reactor Materials (ICFRM-17). Manuscripts will be prepared and expected to be published in scientific journals.
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[Journal Article] Effects of alloying elements (Sn, Nb, Cr, and Mo) on the microstructure and mechanical properties of zirconium alloys2015
Author(s)
Huilong Yang, Jingjie Shen, Yoshitaka Matsukawa, Yuhki Satoh, Sho Kano, Zishou Zhao, Yanfen Li, et al.,
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Journal Title
Journal of Nuclear Science and Technology
Volume: in press
Pages: in press
Peer Reviewed
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