The Effect of Neutron Irradiation on the Tensile Properties and Microstructure of Several Vanadium Alloys. [Viewgraphs]. PDF Download

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Languages : en
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This paper contains viewgraphs describing the effects of neutron irradiation on the tensile properties and microstructure of vanadium alloys in first wall fusion reactors. A tritium trick experiment was used to study the helium embrittlement and the stresses and strains on these materials in a controlled environment. (LSP).

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Languages : en
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Specimens of V-15Cr-5Ti, VANSTAR-7, and V-3Ti-1Si were encapsulated in TZM tubes containing 7Li to prevent interstitial pickup and irradiated in FFTF (MOTA experiment) to a damage level of 40 dpa. The irradiation temperatures were 420, 520, and 600°C. For a better simulation of fusion reactor conditions, helium was preimplanted in some specimens using a modified version of the ''tritium trick.'' The V-15Cr-5Ti alloy was most susceptible to irradiation hardening and helium embrittlement, followed by VANSTAR-7 and V-3Ti-1Si. VANSTAR-7 exhibited a relatively high maximum void swelling of approx. 6% at 520°C while V-15Cr-5Ti and V-3Ti-1Si had values of less than 0.3% at all three temperatures. The V-3Ti-1Si clearly outperformed the other two vanadium alloys in resisting the effects of neutron irradiation.

Author: DN. Braski
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Category : Helium embrittlement
Languages : en
Pages : 20

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Specimens of V-15Cr-5Ti, VANSTAR-7, and V-3Ti-1Si were encapsulated in molybdenum alloy tubes containing 7Li to prevent interstitial pickup and irradiated in the Fast Flux Test Facility (FFTF), using Materials Open Test Assembly (MOTA) experiments, to a damage level of 40 displacements per atom (dpa). The irradiation temperatures were 420, 520, and 600°C. For a better simulation of fusion reactor conditions, helium was preimplanted in some specimens using a modified version of the "tritium trick." The V-15Cr-5Ti alloy was most susceptible to irradiation hardening and helium embrittlement, followed by VANSTAR-7, and V-3Ti-1Si. VANSTAR-7 exhibited a relatively high maximum void swelling of ~6% at 520°C while V-15Cr-5Ti and V-3Ti-1Si had values of

Author: DN. Braski
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ISBN:
Category : Fusion reactors
Languages : en
Pages : 18

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Tensile specimens of V-15Cr-5Ti, Vanstar-7, V-3Ti-lSi, and V-20TJ were irradiated at 420°C in FFTF-MOTA to a damage level of 82 dpa. Helium was preimplanted to levels up to 480 appm in selected specimens using a modified tritium trick. Irradiation hardeningwas the dominant effect influencing the post irradiation tensile properties, and it markedly increased the yield strength and reduced the total elongation. The V-15Cr-5Ti alloy was very sensitive to helium embrittlement, but Vanstar-7 and V-3Ti-lSi were only slightly affected. Without helium, negligible swelling was found in V-15Cr-5Ti and Vanstar-7, and only small values of swelling (

Author: BA. Loomis
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ISBN:
Category : Edema
Languages : en
Pages : 12

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The microstructures in V-15Cr-5Ti, V-10Cr-5Ti, V-3Ti-lSi, V-15Ti-7.5Cr, and V-20Ti alloys were examined by transmission electron microscopy after neutron irradiation at 600°C to 21 to 84 atom displacements per atom in the Materials Open Test Assembly of the Fast Flux Test Facility. The microstructures in these irradiated alloys were analyzed to determine the radiation-produced dislocation density, precipitate number density and size, and void number density and size. The results of these analyses were used to compute increases in yield stress and swelling of the irradiated alloys. The computed increase in yield stress was compared with the increase in yield stress determined from tension tests on these irradiated alloys. This comparison made it possible to evaluate the influence of alloy composition on the evolution of radiation-damaged microstructures and the resulting tensile properties.

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Languages : en
Pages : 28

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The microstructures in V-15Cr-5Ti, V-10Cr-5RTi, V-3Ti-1Si, V-15Ti-7.5Cr, and V-20Ti alloys were examined by transmission electron microscopy after neutron irradiation at 600°C to 21--84 atom displacements per atom in the Materials Open Test Assembly of the Fast Flux Test Facility. The microstructures in these irradiated alloys were analyzed to determine the radiation-produced dislocation density, precipitate number density and size, and void number density and size. The results of these analyses were used to compute increases in yield stress and swelling of the irradiated alloys. The computed increase in yield stress was compared with the increase in yield stress determined from tensile tests on these irradiated alloys. This comparison made it possible to evaluate the influence of alloy composition on the evolution of radiation-damaged microstructures and the resulting tensile properties. 11 refs.

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Languages : en
Pages : 15

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Vanadium-base alloys are candidates for use as structural material in magnetic fusion reactors. In comparison to other candidate structural materials (e.g., Type 316 stainless and HT-9 ferritic steels), vanadium-base alloys such as V-15Cr-5Ti and V-20Ti have intrinsically lower long-term neutron activation, neutron irradiation after-heat, biological hazard potential, and neutron-induced helium and hydrogen transmutation rates. Moreover, vanadium-base alloys can withstand a higher surface-heat, flux than steels because of their lower thermal stress factor. In addition to having these favorable neutronic and physical properties, a candidate alloy for use as structural material in a fusion reactor must have dimensional stability, i.e., swelling resistance, and resistance to embrittlement during the reactor lifetime at a level of structural strength commensurate with the reactor operating temperature and structural loads. In this paper, we present experimental results on the swelling and tensile properties of several vanadium-base alloys after irradiation at 420, 520, and 600°C to neutron fluences ranging from 0.3 to 1.9 x 1027 neutrons/m2 (17 to 114 atom displacements per atom (dpa)).

Author: ASTM International Symposium on Effects of Radiation on Structural Materials
Publisher: ASTM International
ISBN: 9780803103887
Category : Science
Languages : en
Pages : 502

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Author: R. Carlander
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ISBN:
Category : Elevated temperature
Languages : en
Pages : 16

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Fast-neutron-induced void formation in commercial pure vanadium is dramatically reduced by additions of titanium and/or chromium. As little as 1 percent by weight titanium decreases the void number density and void volume fraction by factors of 30 and 100, respectively, compared with pure vanadium after exposure at 525 C (977 F) to a fluence of 1.1 x 1022 n/cm2, En > 0.1 MeV. Additions of 3 percent by weight titanium or greater suppress void formation entirely under the same exposure conditions. Alloys of 10 and 15 percent by weight chromium have also been found beneficial in limiting swelling. Internal-friction measurements show that the reduction in void formation in the vanadium-titanium alloys may be partly related to the removal of interstitial impurities, oxygen, and nitrogen by the titanium to form a coherent precipitate of Ti3O2 or a complex oxynitride. Excess oxygen in the alloy after consumption of the available titanium as a precipitate results in increased void formation and also loss of precipitate coherency.

Author: John Moteff
Publisher: ASTM International
ISBN: 9780803103283
Category : Science
Languages : en
Pages : 560

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