Formation of very large ‘blocky alpha’ grains in Zircaloy-4

Tong, Vivian; Britton, T. Ben

doi:10.1016/j.actamat.2017.03.002

Cited by 50 publications

(29 citation statements)

References 30 publications

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“…. The alloy was heat treated at 800 ˚C for two weeks to form large 'blocky-alpha' grains with a typical grain size larger than 200 μm, as described in Tong and Britton (Tong & Britton, 2017). Samples were electrochemically charged with hydrogen or deuterium using galvanostatic charging at a current density of 2 kA/m 2 , using a solution of 1.5 wt.…”

Section: Introductionmentioning

confidence: 99%

Quantification Challenges for Atom Probe Tomography of Hydrogen and Deuterium in Zircaloy-4

et al. 2019

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Analysis and understanding of the role of hydrogen in metals is a significant challenge for the future of materials science, and this is a clear objective of recent work in the atom probe tomography (APT) community. Isotopic marking by deuteration has often been proposed as the preferred route to enable quantification of hydrogen by APT. Zircaloy-4 was charged electrochemically with hydrogen and deuterium under the same conditions to form large hydrides and deuterides. Our results from a Zr hydride and a Zr deuteride highlight challenges associated to accurate quantification of hydrogen and deuterium, in particular associated to the overlap of peaks at low mass-to-charge ratio and of hydrogen/deuterium containing molecular ions. We discuss possible ways to ensure that appropriate information is extracted from APT analysis of hydrogen in a zirconium alloy systems that is important for nuclear power.

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Section: Introductionmentioning

confidence: 99%

Quantification Challenges for Atom Probe Tomography of Hydrogen and Deuterium in Zircaloy-4

et al. 2019

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“…%) was received as a rolled and recrystallized plate with a typical split basal texture and average grain size of ~ 11 μm. The sample was then heat treated at 800 ˚C for two weeks to form large 'blocky-alpha' grains > 200 μm similar to that recently reported by Tong and Britton [29]. The sample was then electrochemically charged with deuterium (galvanostatic charging, current density = 2 kA/m 2 ) using a solution of 1.5 wt.…”

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Atomic scale analysis of grain boundary deuteride growth front in Zircaloy-4

Breen

Mouton

et al. 2018

Scripta Materialia

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Zircaloy-4 (Zr-1.5%Sn-0.2%Fe-0.1%Cr wt. %) was electrochemically charged with deuterium to create deuterides and subsequently analysed with atom probe tomography and scanning transmission electron microscopy to understand zirconium hydride formation and embrittlement. At the interface between the hexagonal close packed (HCP) a-Zr matrix and a face centred cubic (FCC) d deuteride (ZrD 1.5-1.65 ), a HCP z phase deuteride (ZrD 0.25-0.5 ) has been observed. Furthermore, Sn is rejected from the deuterides and segregates to the deuteride/a-Zr reaction front.

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“…This motivates our study of the nucleation, growth and impact of hydrides, especially now that we can generate very large grain 'blocky alpha' [15] where we can vary the area fraction of easy hydride nucleation sites (i.e. grain boundaries) and reduce the interference from one nucleation event to the others by increasing the physical distances between their sites.…”

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The effect of cooling rate and grain size on hydride microstructure in Zircaloy-4

Birch

Wang

Tong

et al. 2019

Journal of Nuclear Materials

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We explore the distribution, morphology and structure of zirconium hydrides formed using different cooling rates through the solid state Zr+[H]  Zr + hydride transus, in fine and blocky alpha Zircaloy-4. We observe that cooling rate and grain size control the phase and distribution of hydrides. The blocky alpha (coarse grain, > 200 µm) Zircaloy-4, has a smaller grain boundary area to grain volume ratio and this significantly affects nucleation and growth of hydrides as compared to fine grain size (~11 µm) material. Main BodyZirconium alloys are used in the nuclear industry as fuel cladding, as it has a good strength to neutron absorption cross section ratio and reasonable corrosion resistance. One concerns when using zirconium alloys in high temperature water reactors is corrosion, as during service it can react with high temperature water to generate an oxide scale and pick up hydrogen [1]. For service conditions (~350°C) this hydrogen may exist in solution where it is highly mobile [2,3]. The hydrogen travels from hot to cold regions and from low to high hydrostatic stress. As the solubility of hydrogen in zirconium has a steep incline against temperature, and so excess hydrogen or changes in temperature may result in the precipitation of hydrides.

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Formation of very large ‘blocky alpha’ grains in Zircaloy-4

Cited by 50 publications

References 30 publications

Quantification Challenges for Atom Probe Tomography of Hydrogen and Deuterium in Zircaloy-4

Quantification Challenges for Atom Probe Tomography of Hydrogen and Deuterium in Zircaloy-4

Atomic scale analysis of grain boundary deuteride growth front in Zircaloy-4

The effect of cooling rate and grain size on hydride microstructure in Zircaloy-4

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