Swelling and Structure of Vanadium-base Alloys Irradiated in the Dynamic Helium Charging Experiment PDF Download

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Languages : en
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Author: HM. Chung
Publisher:
ISBN:
Category : Density change
Languages : en
Pages : 11

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Combined effects of dynamically charged helium and neutron damage on density change, void distribution, and microstructural evolution of V and V-4Cr-4Ti alloys have been determined after irradiation to 18-31 dpa at 425-600°C in the Dynamic Helium Charging Experiment (DHCE). The results were compared with those from a non-DHCE in which helium generation was negligible. For V-4Cr-4Ti specimens irradiated to ?18-31 dpa at 425, 500, or 600°C with a helium generation rate of 0.4-4.2 appm helium/dpa, only limited number of helium bubbles were observed either at some Ti(O,N,C) precipitate interfaces, in localized regions of grains, or near grain boundaries. Neither extensive coalescences of helium bubbles on grain boundaries, typical of some alloys irradiated in tritium-trick experiments, nor dense helium bubbles within grains, typical of unalloyed V or alloys not containing Ti, were observed. Under the conditions of DHCE, most of dynamically produced helium atoms seem to be trapped by irradiation-induced defects and defect clusters within grains or fine Ti5Si3 precipitates, which prevents significant bubble nucleation or growth. Density changes measured on specimens irradiated in DHCE or non-DHCE were low (

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Languages : en
Pages : 13

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One property of vanadium-base alloys that is not well understood in terms of their potential use as fusion reactor structural materials is the effect of simultaneous generation of helium and neutron damage. In the present Dynamic Helium Charging Experiment (DHCE), helium was produced uniformly in the specimen at linear rates of (almost equal to) 0.4 to 4.2 appm helium/dpa by the decay of tritium during irradiation to 18--31 dpa at 425--600 C in Li-filled capsules in a sodium-cooled fast reactor. This paper presents results of postirradiation examination and tests of microstructure and mechanical properties of V-5Ti, V-3Ti-1Si, V-8Cr-6Ti, and V-4Cr-4Ti (the latter alloy has been identified as the most promising candidate vanadium alloy). Effects of helium on tensile strength and ductility were insignificant after irradiation and testing at> 420 C. However, postirradiation ductilities at 250 C were higher than those of the non-DHCE specimens (

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Languages : en
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Languages : en
Pages : 8

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Helium effect of neutron irradiated vanadium alloys, containing titanium, has been studied using Dynamic Helium Charging Experiment (DHCE) in FFTF. Cavity formation was observed only in pure vanadium irradiated at 430 to 600 C and in V-5Ti irradiated at 600 C. No apparent cavity formation was obtained in V-3Ti-1Si and V-4Cr-4Ti. The precipitation of titanium oxide in V-5Ti, V-3Ti-1Si and V-4Cr-4Ti occurred in all irradiation conditions in this study and the precipitates of Ti5Si3 only appeared in V-3Ti-1Si irradiated at 600 C up to 15 dpa with helium generation rate of 4 appmHe/dpa. It is suggested that titanium oxide plays an important role for suppression of cavity formation and swelling from early stage of irradiation. Detail characterization of precipitates and He effect for neutron damages in vanadium alloys are discussed here.

Author: D. S. Gelles
Publisher: ASTM International
ISBN: 0803120168
Category : Materials
Languages : en
Pages : 1169

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Languages : en
Pages : 5

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Combined effects of dynamically charged helium and neutron damage on density decrease (swelling) of V-4Cr-4Ti, V-5Ti, V-3Ti-1Si, and V-8Cr-6Ti alloys have been determined after irradiation to 18-31 dpa at 425-600°C in the Dynamic helium Charging Experiment (DHCE). To ensure better accuracy in density measurement, broken pieces of tensile specimens ≈ 10 times heavier than a transmission electron microscopy (TEM) disk were used. Density increases of the four alloys irradiated in the DHCE were

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Languages : en
Pages : 14

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One property of the vanadium-based alloys that is not well understood for the purpose of application as fusion reactor structural material is the effect of simultaneous generation of helium and neutron damage under conditions relevant to fusion-reactor operation. In the present dynamic helium charging experiment (DHCE), helium was produced uniformly in the specimen at linear rates ranging from (approximately)0.4 to 4.2 appm helium/dpa by the decay of tritium during irradiation to 18-31 dpa at 425-600°C in the Li-filled DHCE capsules in the Fast Flux Test Facility. This paper presents results of postirradiation tests of mechanical properties of V-4Cr-4Ti alloy which has been identified as the most promising candidate alloy on the basis of its superior baseline and irradiation properties. Effects of helium on tensile strength and ductility were insignificant for test temperatures>420°C. However, room-temperature ductilities of the DHCE specimens were higher than those of the non-DHCE specimens (negligible helium generation) whereas strengths were lower, indicating that different types of hardening centers are produced during the DHCE and non-DHCE irradiation. Ductile-brittle transition behavior of the DHCE specimens was also determined from bend tests on TEM disks and broken tensile specimens. No brittle behavior was observed at temperatures>-150°C for DHCE specimens. Predominantly brittle-cleavage fracture morphologies were observed only at -196°C in some specimens that were irradiated to 31 dpa at 425°C during DHCE. In strong contrast to tritium-trick experiments in which a large amount of helium is produced in absence of displacement damage, no intergranular fracture was observed in any tensile or bend-tested specimens that were irradiated in the DHCE.

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Category :
Languages : en
Pages : 10

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The objective of this work is to determine void structure, distribution, and density changes of several promising vanadium-base alloys irradiated in the Dynamic Helium Charging Experiment (DHCE). Combined effects of dynamically charged helium and neutron damage on density change, void distribution, and microstructural evolution of V-4Cr-4Ti alloy have been determined after irradiation to 18-31 dpa at 425-600°C in the DHCE, and the results compared with those from a non-DHCE in which helium generation was negligible.

Author: HM. Chung
Publisher:
ISBN:
Category : Cleavage
Languages : en
Pages : 9

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One property of vanadium-base alloys that is not well understood in terms of their potential use as fusion reactor structural materials is the effect of simultaneous generation of helium and neutron damage under conditions relevant to fusion reactor operation. In the present Dynamic Helium Charging Experiment (DHCE), helium was produced uniformly in the specimen at linear rates ranging from?0.4 to 4.2 appm helium/dpa during irradiation to 18-31 dpa at 425-600°C in the Li-filled capsules. Results of postirradiation tests of mechanical properties of V-4Cr-4Ti, an alloy identified to be most promising, are presented. Effects of helium on tensile strength and ductility at 420-600°C were insignificant for irradiation at these temperatures. However, postirradiation ductilities measured at 20-200°C were higher than those of the non-DHCE specimens (negligible helium generation), whereas strengths were lower, indicating that different types of hardening centers were produced during DHCE and non-DHCE. Ductile-brittle transition behavior of the DHCE specimens was determined from multiple bend tests on TEM disks and broken tensile specimens. No brittle behavior was observed at temperatures >-175°C. In contrast to tritium-trick experiments in which grain-boundary coalescence of helium is pronounced in the absence of displacement damage, no intergranular fracture was observed in tensile or bend-tested DHCE specimens.