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Observations of temperature stability of γ-zirconium hydride by high-resolution neutron powder diffraction
Malmö högskola, Faculty of Technology and Society (TS). Malmö högskola, Faculty of Culture and Society (KS), Medea.
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2016 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 661, p. 55-61Article in journal (Refereed) Published
Abstract [en]

The phase evolution in a zirconium–50 deuterium (Zr–50D, at.%) alloy system during thermal cycling has been investigated using in situ high-resolution neutron powder diffraction. The results showed that the peritectoid reaction α-Zr + δ-ZrD → γ-ZrD previously suggested to occur at high temperatures does not take place in the system. Slow cooling, from high temperatures (≥520 K) to room temperature at a rate of 5 K min–1, promoted the γ-hydride formation rather than fast cooling as reported earlier. In contrast to the observation that the δ-hydride present in the system remained at temperatures up to 740 K, the produced γ phase transformed to δ-hydride in the temperature range of 370 K to 559 K, with the transformation completing at approximately 559 K. It is confirmed that the formation of the γ-hydride was reproducible with slow cooling, and a diffusion-controlled sluggish δ-to γ-hydride transformation is suggested to be responsible for the favorable development of γ-hydride during slow cooling.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 661, p. 55-61
Keywords [en]
Metal hydrides, Phase transitions, Neutron diffraction, Zirconium hydride, Zirconium, Nuclear materials
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:mau:diva-15994DOI: 10.1016/j.jallcom.2015.11.187ISI: 000367521200009Scopus ID: 2-s2.0-84949783111Local ID: 19775OAI: oai:DiVA.org:mau-15994DiVA, id: diva2:1419516
Available from: 2020-03-30 Created: 2020-03-30 Last updated: 2024-11-19Bibliographically approved
In thesis
1. Phase transformation and stability studies of the Zr-H system
Open this publication in new window or tab >>Phase transformation and stability studies of the Zr-H system
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Zirconium alloys are widely used in the nuclear industry because of their high strength, good corrosion resistance and low neutron absorption cross-section. Zirconium has a strong affinity for hydrogen, however, and if hydrogen concentration builds up, the material will gradually degrade. In one class of such hydrogen caused degradation, called hydride induced embrittlement, hydrogen chemically reacts with zirconium forming one, or several, crystal phases of zirconium hydride. These hydrides play a primary, but sometime not fully understood, role in crack initiation and propagation within these materials. Despite the fact that hydride induced embrittlement in zirconium have been studied for several decades, there are still some unresolved issues. It has been the aim of the research presented in this thesis to provide the research community with new and updated data of the hydrides themselves in order to aid further studies within the field of hydride induced embrittlement in general, and the mechanism of delayed hydride cracking in particular. To that end, the research presented here proceeded, in short, as follows: First, zirconium hydride powder, of well defined hydrogen concentration, was produced from commercial grade zirconium. This powder was subjected to heat treatment and the hydride phases were characterized both in situ and ex situ using neutron, synchrotron X-ray, and conventional laboratory X-ray based diffraction techniques. Next, most of the low-pressure zirconium hydride phases were produced under hydrogen/argon atmosphere from commercial grade zirconium powder. This process was simultaneously monitored and recorded in real time using synchrotron X-ray diffraction. These experiments have produced new data of the behavior of different hydride phases during thermal treatment and in situ hydrogenation. For the first time all commonly reported zirconium hydride phases and the complete transformation between two different hydride phases were recorded with a single experimental arrangement. The phase transformation between δ and ε zirconium hydride was recorded in detail and presented. Finally, the controversial γ zirconium hydride was observed both in situ and ex situ and the preparation route, its crystal structure, and formation mechanisms were analyzed and presented.

Place, publisher, year, edition, pages
Institute for Educational Sciences, Lund University, Sweden, 2015. p. 65
Keywords
Zirconium hydride, synchrotron X-ray diffraction, Nuclear materials, phase transformation, in-situ hydrogen charging, hydrogen related degradation, neutron diffraction, powder diffraction, Rietveld analysis, γ-ZrH, hydrogen embrittlement
National Category
Natural Sciences
Identifiers
urn:nbn:se:mau:diva-7770 (URN)19765 (Local ID)978-91-7623-552-2 (ISBN)978-91-7623-553-9 (ISBN)19765 (Archive number)19765 (OAI)
Public defence
2015-12-03, M:E LTH, Lund University, Lund, 10:15 (English)
Opponent
Note

Paper III in thesis as manuscript with title "The phase transformation between the δ and ε Zr hydrides"

Available from: 2020-02-28 Created: 2020-02-28 Last updated: 2024-03-15Bibliographically approved

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Maimaitiyili, TuerdiBlomqvist, JakobBjerkén, Christina

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