Zirconium Hydride Precipitation and Dissolution Kinetics in Zirconium Alloys

This work presents a detailed microstructure and texture study of various hydrided Zircaloy-4 materials by neutron diffraction and microscopy. The results show that the precipitated δ-ZrH1.66generally follows the δ(111)//α(0001) and δ[1{\overline 1}0]//α[11{\overline 2}0] orientation relationship with the α-Zr matrix. The δ-hydride displays a weak texture that is determined by the texture of the α-Zr matrix, and this dependence essentially originates from the observed orientation correlation between α-Zr and δ-hydride. Neutron diffraction line profile analysis and high-resolution transmission electron microscopy observations reveal a significant number of dislocations present in the δ-hydride, with an estimated average density one order of magnitude higher than that in the α-Zr matrix, which contributes to the accommodation of the substantial misfit strains associated with hydride precipitation in the α-Zr matrix. The present observations provide an insight into the behaviour of δ-hydride precipitation in zirconium alloys and may help with understanding the induced embrittling effect of hydrides.

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The metallography of zirconium hydride precipitation in a magnesium/0.5 wt % zirconium alloy

Journal of Nuclear Materials ◽

10.1016/0022-3115(72)90166-3 ◽

1972 ◽

Vol 45 (3) ◽

pp. 201-210

Author(s):

K. Nuttall ◽

K.J. Gradwell

Keyword(s):

Zirconium Alloy ◽

Zirconium Hydride ◽

Hydride Precipitation

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Zirconium hydride precipitation kinetics in Zircaloy-4 observed with synchrotron X-ray diffraction

Journal of Nuclear Materials ◽

10.1016/j.jnucmat.2015.04.025 ◽

2015 ◽

Vol 464 ◽

pp. 160-169 ◽

Cited By ~ 23

Author(s):

M.S. Blackmur ◽

J.D. Robson ◽

M. Preuss ◽

O. Zanellato ◽

R.J. Cernik ◽

...

Keyword(s):

Zirconium Hydride ◽

Precipitation Kinetics ◽

X Ray Diffraction ◽

X Ray ◽

Hydride Precipitation

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A Review of Hydride Precipitates in Titanium and Zirconium Alloys: Precipitation, Dissolution and Crystallographic Orientation Relationships

MATEC Web of Conferences ◽

10.1051/matecconf/202032111042 ◽

2020 ◽

Vol 321 ◽

pp. 11042

Author(s):

Egle CONFORTO ◽

Xavier FEAUGAS

Keyword(s):

Zirconium Alloys ◽

Zirconium Hydride ◽

Misfit Dislocations ◽

Orientation Relationships ◽

Ti Alloys ◽

Local Plastic Strain ◽

Bulk Scale ◽

Hydride Phases ◽

Zr Alloys

This work proposes a review of recent results on the formation and dissolution of hydrides in HCP alloys (Ti and Zr alloys) correlated to the nature of crystallographic hydride phases and their ORs. The crystallographic coherence observed between the surface hydride layer and the substrate is very important for many applications as for biomaterials devices. Five particular orientation relationships (OR) were identified between titanium/zirconium hydride precipitates and the oc-Ti and a-Zr substrates. In addition, the nature of hydrides have a large implication on the ductility, the strain hardening, and the local plastic strain accommodation in the Ti alloys. Our studies using XDR, TEM and SEM-EBSD have been demonstrating that the nature of the hydride phase precipitates depends on the hydrogen content. DSC has been used to obtain the hydride dissolution and precipitation energy values at the bulk scale, whose difference can be associated to misfit dislocations. Local in-situ TEM dissolution observations show the depinning of part of misfit dislocations during dissolution process. Hydride reprecipitation is thus possible only if hydrogen is not driven away during heating by misfit dislocations depinning.

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