The transport and fate of helium in nanostructured ferritic alloys at fusion relevant He/dpa ratios and dpa rates

Yamamoto, Takuya; Odette, G.R.; Miao, Pifeng; Hoelzer, David T.; Bentley, J.; Hashimoto, Naoyuki; Tanigawa, Hiroyasu; Kurtz, Richard J.

doi:10.1016/j.jnucmat.2007.03.047

Cited by 113 publications

(81 citation statements)

References 18 publications

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“…YTiO clusters in ODS steels 22 . Another may be to synthesize materials containing interfaces with increased resistance to He-assisted degradation.…”

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confidence: 99%

The effect of excess atomic volume on He bubble formation at fcc–bcc interfaces

Demkowicz

Bhattacharyya

Usov

et al. 2010

Applied Physics Letters

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Atomistic modeling shows that Cu-Nb and Cu-V interfaces contain high excess atomic volume due to constitutional vacancy concentrations of ~5%at. and ~0.8%at., respectively. This finding is supported by experiments demonstrating that a ~5-fold higher He concentration is required to observe He bubbles via throughfocus transmission electron microscopy at Cu-Nb interfaces than in Cu-V interfaces.Interfaces with structures tailored to minimize precipitation and growth of He bubbles may be used to design damage-resistant composites for fusion reactors.Unlike pure metals 1 , some materials contain constitutional vacancies that are thermodynamically stable at arbitrarily low temperature, for example grain boundaries (GBs) in ceramics 2 and semiconductors 3 , compounds with wide phase fields like NiAl 4 , and certain metal hydrides 5 . We use atomistic modeling to show that Cu-Nb and Cu-V interfaces contain high constitutional vacancy concentrations.Indirect experimental verification of this prediction is obtained by measuring the critical He concentration at which bubbles become detectable at these interfaces in transmission electron microscopy (TEM).

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“…YTiO clusters in ODS steels 22 . Another may be to synthesize materials containing interfaces with increased resistance to He-assisted degradation.…”

mentioning

confidence: 99%

The effect of excess atomic volume on He bubble formation at fcc–bcc interfaces

Demkowicz

Bhattacharyya

Usov

et al. 2010

Applied Physics Letters

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“…Much higher patterning temperatures are experimentally obtained by using highly NFAs are distinguished from more traditional oxide dispersion steels by a higher number density and smaller size of precipitates, which produce much greater interfacial area available for trapping and recombining point defects [45,[47][48][49][50].…”

Section: Stable Microstructuresmentioning

confidence: 99%

“…These alloys have indeed demonstrated outstanding high temperature properties and remarkable tolerance to irradiation-induced displacement damage [45,[49][50][51].…”

Section: Stable Microstructuresmentioning

confidence: 99%

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Atomic-scale design of radiation-tolerant nanocomposites

2010

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Recent work indicates that materials with nanoscale architectures, such as nanolayered Cu-Nb composites and nanoscale oxide dispersion-strengthened steels, are both thermally stable and offer improved performance under irradiation.Current understanding of the atomic-level response of such materials to radiation yields insights into how controlling composition, morphology and interface-defect interactions may further enable atomic-scale design of radiation tolerant nanostructured composite materials. With greater understanding of irradiationassisted degradation mechanisms, this bottom-up design approach may pave the way for creating the extreme environment-tolerant structural materials needed to meet the world's clean energy demand by expanding use of advanced fission and future fusion power.2

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“…Because NC may promote point defect recombination and trap transmutation-produced He in small clusters, NFA have the potential to be highly resistant to radiation damage in fission and fusion environments [1,2], and thus are being characterized following neutron and ion irradiation. Energy-filtered transmission electron microscopy (EFTEM) performed at 300 kV on a LaB 6 Philips CM30 equipped with a Gatan imaging filter (GIF) has been especially beneficial for imaging NC.…”

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confidence: 99%

TEM Characterization of Crept and Irradiated Nano-structured Ferritic Alloys

Bentley¹,

Hoelzer²,

Busby³

et al. 2009

Microsc Microanal

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The past ten years or so have seen the development of an exciting new class of mechanically alloyed (MA) nano-structured ferritic alloys (NFA) with outstanding mechanical properties that are mostly due to the presence of high concentrations (>10 23 m -3 ) of Ti-, Y-, and O-enriched nano-clusters (NC). Because NC may promote point defect recombination and trap transmutation-produced He in small clusters, NFA have the potential to be highly resistant to radiation damage in fission and fusion environments [1,2], and thus are being characterized following neutron and ion irradiation. Energy-filtered transmission electron microscopy (EFTEM) performed at 300 kV on a LaB 6 Philips CM30 equipped with a Gatan imaging filter (GIF) has been especially beneficial for imaging NC. In particular, Fe-M jump-ratio images produced from component images recorded with 10-eV slits at energy losses of 46 and 62 eV reliably reveal NC in dark contrast. Such images are insensitive to surface oxide films or modest surface contamination and for sufficiently thin regions (<50 nm) 2-nm diameter NC are visible [3]. Additional EFTEM elemental mapping (e.g. O, Ti-L 23 , Cr-L 23 ) has also been usefully applied to NFA, and focused-ion-beam (FIB) lift-out specimens have been used to good advantage [2]. Fabrication of an Fe-14.2wt.%Cr-1.95%W-0.22%Ti-0.25%Y 2 O 3 NFA, designated 14YWT, has been described elsewhere, as have the contributions of TEM to help optimize material processing parameters [3,4]. It was also previously shown that NC in 14YWT are not detectably changed by tensile testing at 25 and 700°C with total strains of up to 39% [5] and that in MA957 (an INCO-patented Fe-14wt%Cr-1%Ti-0.3%Mo-0.27%Y 2 O 3 NFA) neutron irradiated at 500°C to 9 displacements per atom (dpa) and with ~380 appm He, the diameter (~3 nm) and concentration (~4 x 10 23 m -3) of the NC differ little from those of unirradiated MA957 [1,2].The NC in MA957 also appear to be unchanged after creep testing in air for a remarkable 38,555 h at 800°C and 100 MPa (Fig. 1). Cavities of >1 m diameter present in the crept specimen may have formed from the release of gases entrained during the original material processing (a potential problem for all MA materials) and may have initiated specimen rupture after a uniform strain of <0.4%. In TEM specimens prepared by electropolishing these cavities caused premature perforation with little or no thin regions, so it was necessary to use FIB lift-out specimens. A Japanese 9Cr oxide-dispersion-strengthened (ODS) steel .%Cr-1.95%W-0.23%Ti-0.27%Y-0.14%O) was irradiated at 525°C with 2.6 MeV protons at ~5 x 10 -6 dpa/s to 1 dpa at the University of Wisconsin [6]. EFTEM results showed that the mean diameter (~3.2 nm) and concentration (~1 x 10 23 m -3) of NC were approximately the same in irradiated and unirradiated material. However, the NC were heterogeneously distributed with factors of >2.5 (unirradiated) and >5 (irradiated) variation in the mean concentration over 6 mapped regions in each sample and with a ~2-fold variation in mean dia...

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The transport and fate of helium in nanostructured ferritic alloys at fusion relevant He/dpa ratios and dpa rates

Cited by 113 publications

References 18 publications

The effect of excess atomic volume on He bubble formation at fcc–bcc interfaces

The effect of excess atomic volume on He bubble formation at fcc–bcc interfaces

Atomic-scale design of radiation-tolerant nanocomposites

TEM Characterization of Crept and Irradiated Nano-structured Ferritic Alloys

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