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Author: Publisher: ISBN: Category : Languages : en Pages : 13
Book Description
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 (
Author: Publisher: ISBN: Category : Languages : en Pages : 13
Book Description
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 (
Author: Publisher: ISBN: Category : Languages : en Pages : 14
Book Description
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.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
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 Dynamic Helium Charging Experiment (DHCE), and the results were compared with those from a non-DHCE in which helium generation and negligible. For specimens irradiated to [approx]18-31 dpa at 500--600 with a helium generation rate of 0.4--4.2 appm He/dpa, only a few helium bubbles were observed at the interface of grain matrices and some of the Ti(O, N, C) precipitates, and no microvoids or helium bubbles were observed either in grain matrices or near grain boundaries. Under these conditions, dynamically produced helium atoms seem to be trapped in the grain matrix without significant bubble nucleation or growth, and in accordance with this, density changes from DHCE and non-DHCE (negligible helium generation) were similar for comparable fluence and irradiation temperature. Only for specimens irradiated to [approx]31 dpa at 425 C, when helium was generated at a rage of 0.4--0.8 appm helium/dpa, were diffuse helium bubbles observed in limited regions of grain matrices and near [approx]15% of the grain boundaries in densities significantly lower than those in the extensive coalescences of helium bubbles typical of other alloys irradiated in tritium-trick experiments. Density changes of specimens irradiated at 425 C in the DHCE were significantly higher than those from non-DHCE irradiation. Microstructural evolution in V-4Cr-4Ti was similar for DHCE and non-DHCE except for helium bubble number density and distribution. As in non-DHCE, the irradiation-induced precipitation of ultrafine Ti[sub 5]Si[sub 3] was observed for DHCE at>500 C but not at 425 C.
Author: HM. Chung Publisher: ISBN: Category : Density change Languages : en Pages : 11
Book Description
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 (
Author: HM. Chung Publisher: ISBN: Category : Cleavage Languages : en Pages : 9
Book Description
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.
Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
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
Author: Publisher: ISBN: Category : Languages : en Pages : 10
Book Description
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: Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
Tensile properties of V-4Cr-4Ti (Heat BL-47), 3Ti-1Si (BL-45), and V-5Ti (BL-46) alloys after irradiation in a conventional irradiation experiment and in the Dynamic Helium Charging Experiment (DHCE) were reported previously. This paper presents revised tensile properties of these alloys, with a focus on the effects of dynamically generated helium of ductility and work-hardening capability at
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Author: HM. Chung
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Author: D. S. Gelles
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