Effects of Ti and Ta addition on microstructure stability and tensile properties of reduced activation ferritic/martensitic steel for nuclear fusion reactors

Kim, Han Kyu; Lee, Ji Won; Moon, Joonoh; Lee, Chang Hoon; Hocheng, H.

doi:10.1016/j.jnucmat.2018.01.008

Cited by 48 publications

(19 citation statements)

References 34 publications

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“…Reduced activation ferritic/martensitic steels (RAFMs) have been considered as the candidate structural materials for blanket module of nuclear fusion reactors [1][2][3] . The RAFM steel was derived from variants of modified 9Cr-1Mo heat resisting steel.…”

Section: Introductionmentioning

confidence: 99%

“…The RAFM steel was derived from variants of modified 9Cr-1Mo heat resisting steel. The RAFM steel involved the replacement of Mo in the modified 9Cr-1Mo steel by W (1-2 wt.%) and/or V (0.2 wt.%) 3,4) . Nb was substituted by Ta (0.02-0.18 wt.%).…”

Section: Introductionmentioning

confidence: 99%

“…Since the blanket is exposed to high flux of neutron and complex periods of fluctuating mechanical and thermal stresses, the RAFM steels are expected to experience stress/irradiation-induced non-equilibrium phases formation as well as coarsening of precipitates because of its high contents of Cr, W, V, Ta, which can affect high-temperature properties. Accordingly, the chemical composition optimization has been extensively studied to assure the excellent properties of RAFM steels based on the research programs in European Union, USA, Japan, China, India and Korea [2][3][4][5][6][7][8][9] . The blanket is an important device trapping the core plasma under extremely high heat load and neutron irradiation environment.…”

Section: Introductionmentioning

confidence: 99%

“…The blanket is an important device trapping the core plasma under extremely high heat load and neutron irradiation environment. This blanket provides multiple-functions to convert kinetic energy of neutrons generated in the fusion reaction into heat energy (heat exchange), to shield neutrons, and to multiply tritium from lithium in the coolant [1][2][3] . The blanket is composed of about 400 to 500 boxes to form an outer wall which is in primary contact with the plasma.…”

Section: Introductionmentioning

confidence: 99%

“…Typical microstructures of RAFM steel: (a) SEM micrograph and corresponding boundary angle map by EBSD, (c) TEM micrograph showing lath structure3) …”

mentioning

confidence: 99%

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Technical Issues in Fusion Welding of Reduced Activation Ferritic/Martensitic Steels for Nuclear Fusion Reactors

Jun

Moon

et al. 2020

Journal of Welding and Joining

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Reduced activation ferritic/martensitic steels (RAFMs), which are the modified variants of 9Cr-1Mo heat resisting steels, have been recognized as candidate structural materials for the blanket module of nuclear fusion reactors. Since the blanket is exposed to a high flux of neutrons and complex periods of fluctuating mechanical and thermal stresses, evaluation of the high-temperature mechanical properties of both the RAFM steel and welds, and understanding of their degradation behaviors, are needed to provide feedback for the development of better RAFM steels and welding processes. In this review article, first, several welding processes used to fabricate the blanket modules are introduced. Microstructural evolution during fusion welding of the RAFM steel and its subsequent degradation during creep and/or irradiation are reviewed. The thermal stability of the RAFM steel originates from solid solution strengthening, sub-grain hardening and precipitation hardening. The degradation of the RAFM steel is discussed in terms of matrix recovery associated with lath widening and reduction of dislocation density, coarsening of precipitates and the formation of Laves and Z phases. This work helps provide insight on how to mitigate the microstructural degradation, and design optimal welding technology.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Typical microstructures of RAFM steel: (a) SEM micrograph and corresponding boundary angle map by EBSD, (c) TEM micrograph showing lath structure3) …”

mentioning

confidence: 99%

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Technical Issues in Fusion Welding of Reduced Activation Ferritic/Martensitic Steels for Nuclear Fusion Reactors

Jun

Moon

et al. 2020

Journal of Welding and Joining

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Effects of Ti Addition on the Microstructure and Tensile Properties of China Low Activation Martensitic Steel for Nuclear Fusion Reactors

Zhan

Qiu

et al. 2019

steel research int.

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Herein, the effects of Ti, a low activation alloying element, in the range of 0.01–0.11 wt% on the microstructure, mechanical properties, and impact toughness of China low activation martensitic steel are studied. Fine prior austenite grains and some δ‐ferrite phases are observed for alloys with a Ti content of 0.05 and 0.11 wt%, respectively. The 0.05Ti alloy exhibits a higher yield strength (YS) compared with the 0.01Ti and 0.11Ti alloys because of the additional precipitation hardening by the fine MX particles and small grain size. When the samples are tempered at 650 °C, nanosized (Ti, W) C MX carbides with a size of approximately 20 nm precipitate, leading to an increase in the ultimate tensile strength (UTS) and YS of the 0.05Ti alloy. The ductile‐to‐brittle transition temperature (DBTT) decreases when the Ti content increases to 0.05 wt%. However, the DBTT of the 0.11Ti alloy increases with the precipitation of the δ‐ferrite phase. On the basis of the performance of the steels, the optimal Ti content is found to be approximately 0.05 wt% and the optimal tempering temperature is found to be 650 °C.

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Strengthening Effect of Multiscale Second Phases in Reduced Activation Ferrite/Martensitic Steel

Qiu

et al. 2021

steel research int.

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Owing to their excellent resistance to irradiation, good creep property, and extraordinary structural and chemical stability in harsh, high-temperature environments, oxide dispersionstrengthened (ODS) reduced activation ferritic martensitic (RAFM) steels are considered prime candidates for advanced structures, including nuclear fusion reactors. [1,2] The excellent properties of ODS RAFM steel can be attributed to the fine grain size of the steel and the dispersed nano strengthening phases, such as Y 2 O 3 , MX (M ¼ Ta, V, X ¼ C, N), and M 23 C 6 (M ¼ Fe, Cr). [3,4] Dispersed Y 2 O 3 particles can not only effectively block dislocation movements but also absorb the vacancies produced by irradiation and the helium generated by transmutation in the nuclear fusion reactor, thereby improving the radiation resistance of the alloy. [5] Y 2 O 3 particles could be refined by the addition of Ti and Zr to the Fe matrix to form Y-Ti-O and Y-Zr-O clusters. [6,7] Ti and Zr elements could also form TiC, (Ti, W) C, (Ti, Ta) C, and V 3 Zr 3 C, which have strengthening effects similar to that of MX with Ta/V, to improve the high-temperature mechanical properties of steel alloys. [8,9] Ti and Zr are important alloying elements often used to prepare ODS steel. ODS RAFM alloys are commonly manufactured via powder metallurgy (PM), which involves mechanical alloying, hot powder consolidation (e.g., hot isostatic pressure, hot extrusion, or sparking-plasma sintering), and heat treatment. However, PM presents several inherent defects for the preparation of ODS alloys; for example, the technique could introduce impurities (e.g., O 2 ) to its complex processes, thereby inducing anisotropy in the microstructure and mechanical properties of the resulting alloys. [10] The technology also requires large amounts of energy and, at present, cannot be scaled up to industrial production.A demonstration nuclear fusion reactor requires over 11 000 tons of ODS RAFM steel as its structural material, [11] but PM technology for fabricating large-scale ODS steels has not yet been developed. This shortcoming is a basic defect of ODS RAFM steel production. Research on alternative preparation technologies for ODS steel is ongoing globally.Shi and Han directly added micron Y 2 O 3 powders to molten Fe alloy to prepare ODS steel by vacuum casting, forging, and heat treatment. [12] Analysis of the resulting alloys revealed complicated oxides containing Cr, Ti, Ta, Mn, V, Y, and O, which could prevent dislocations from gliding to improve the yield strength of the steel. Zhan et al. prepared 9Cr-ODS alloys by adding Y and Ti alloys to 9Cr steel through vacuum induction melting (VIM). [13] A large number of Y-Ti-O particles smaller than 0.5 μm were found in the steel, and the density of these particles reached 2.69 Â 10 19 m À3 ; this value is close to the density reported for 9Cr-ODS steel prepared by chemical reduction and mechanical milling (i.e., 5.7-8.1 Â 10 20 m À3 ). Oxygen carrier casting technology has been adopted to prepare ODS RAFM alloys by introducin...

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Effects of Ti and Ta addition on microstructure stability and tensile properties of reduced activation ferritic/martensitic steel for nuclear fusion reactors

Cited by 48 publications

References 34 publications

Technical Issues in Fusion Welding of Reduced Activation Ferritic/Martensitic Steels for Nuclear Fusion Reactors

Technical Issues in Fusion Welding of Reduced Activation Ferritic/Martensitic Steels for Nuclear Fusion Reactors

Effects of Ti Addition on the Microstructure and Tensile Properties of China Low Activation Martensitic Steel for Nuclear Fusion Reactors

Strengthening Effect of Multiscale Second Phases in Reduced Activation Ferrite/Martensitic Steel

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