The nucleation of hydrides in a Zr-2.5 wt% Nb alloy

Perovic, V.; Weatherly, G. C.

doi:10.1016/0022-3115(84)90086-2

Cited by 55 publications

(29 citation statements)

References 14 publications

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“…Compared with the HPT sample without prior annealing treatment, the recrystallized sample exhibited the enhanced resistance to hydride formation at hydriding pressure of 15 atm. It is reported that dislocations are favorable sites for hydride nucleation, which can effectively accommodate the misfit strain associated with the hydride precipitation [18]. During the prior recrystallization annealing, the annihilation of dislocations in the HPT samples is initiated, inducing the lack of preferred nucleation sites for hydrides and resultant limited hydride formation after hydriding (Fig.…”

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confidence: 99%

Hydrogen-induced microstructure, texture and mechanical property evolutions in a high-pressure torsion processed zirconium alloy

Wang

Garbe

et al. 2012

Scripta Materialia

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confidence: 99%

Hydrogen-induced microstructure, texture and mechanical property evolutions in a high-pressure torsion processed zirconium alloy

Wang

Garbe

et al. 2012

Scripta Materialia

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“…A qualitative mechanistic explanation for the observed hydride precipitation behavior given by Perovic and Weatherly [35] is that the dislocation arrays at the interface (i.e. the epitaxial dislocations and the virtual or DSC dislocation arrays at steps) represent sites where the H content would be higher as a result of the interaction energy term given by the product of the tensile stress at these sites with the molar volume of the H atom in solution.…”

Section: Hydride Precipitation In A/b Zr Microstructuresmentioning

confidence: 97%

“…3.41. By using dark field techniques to identify the different phases, Perovic and Weatherly [35] find that the hydride plates are arranged in stacks filling the channels between the x cuboids which are produced by transformation of the retained b Zr phase. A careful indexing of the associated diffraction pattern (Fig.…”

Section: Hydride Precipitation In A/b/x Microstructuresmentioning

confidence: 99%

“…These studies showed the importance that the state of the b phase has on the choice of nucleation sites and how this choice influences the subsequent mode of growth of the hydrides. To understand this better in pressure tube alloys used in CANDU reactors, a follow-up study by Perovic and Weatherly [35] focused on a more detailed analysis of the state of the b phase in such pressure tube material. 4 Two thermo-mechanical states were studied.…”

Section: Hydride Precipitation In A/b-zr Alloysmentioning

confidence: 99%

“…The orientation relationship between the two phases was Pitsch-Schräder (Perovic and Weatherly [35]) as follows: ð1 0 1 0Þ aÀZr jjð1 1 0Þ bÀZr ; ½1 2 1 0 aÀZr jj½0 0 1 bÀZr . The authors used the matrix of transformation between the hcp and bcc crystal lattices given by Kelly and Groves [20] for these orientation relationships, viz., relative to the axes ½0 1 1 0; ½2 1 1 0 and ½0 0 0 1 as the basis of the description of the interface between the two phases.…”

Section: Microstructure Of Zr-25nb Alloysmentioning

confidence: 99%

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Hydride Phases, Orientation Relationships, Habit Planes, and Morphologies

Püls¹

2012

The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components

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Most of the studies on this topic were carried out from the early 1960s to the mid 1980s. As is described in Chap. 2, hydrides can form as one of three phases, each of which has a different crystal structure and composition. A broad consensus had emerged by the 1980s that the fct c-hydride (c/a [ 1) is a metastable phase while the stable hydride phases are the face-centered-cubic (fcc) d-hydride and the face-centered-tetragonal (fct) e-hydride (c/a \ 1) phases, the stoichiometric compositions of these phases being, respectively, ZrH, ZrH 1.5 , and ZrH 2 . However, recent experimental results have reinvigorated an earlier suggestion that the c-hydride phase could be the stable phase below a peritectoid transformation temperature of *286°C. This issue concerning which phase is the stable one when the solvus concentration is exceeded below the a/b Zr eutectoid temperature of *550°C is not specifically addressed in this book. However, the issue has not been entirely ignored as various aspects of its role in fracture and phase relationships are raised in various places throughout this book, specifically in Chaps. 2, 6, 7, 8 and 9. Regarding the hydride habit planes, a consensus had emerged by the mid 1980s that the predominant habit of d-and c-zirconium hydrides in Zircaloy-2 and Zr-2.5Nb is on the near-basal, hexagonal-close-packed (hcp) a-Zr {1 0 1 7} planes (14°from the basal plane [6], carried out detailed examinations using transmission electron microscopy of the morphology, orientation, dislocations generated, and strain fields in and around hydride precipitates formed in high purity Zr, Zircaloy-2, Zr-1 % Al, and Zr-1 % Cr. All the hydrides observed by Carpenter et al. [12] in these low-H-containing materials were of the c-hydride phase. Figure 3.1 shows dislocations that had been generated by two needle-shaped hydrides nucleated in close proximity of an intermetallic particle. The dislocations around the hydrides were in the form of loop segments attached to the ends of the needles with Burgers vectors of type \1120 [ lying on or near the basal plane. Figure 3.2 shows schematically in a projection on the (0 0 0 1) plane the hydride orientations, dislocation loops, and their Burgers vectors observed. Large strain fields were associated with these small hydrides as seen in Fig. 3.3 which also shows how this strain field made it difficult to reveal the dislocations generated closest to the hydride's interface. Similar strong strain contrast was observed along the basal pole (c) axis direction, but none along the needle direction. Similar results for hydride shapes and dislocations emitted were obtained for the Zr-1 % Cr and Zr-1 % Al materials except that the orientations of the c-hydrides in the latter material were in the \1 0 1 0 [ aÀZr directions. Less regular features for the dislocations generated by hydrides in Zr were found as shown in Figs. 3.4 and 3.5 examined in electron microscopes at 100 kV and 1 MeV, respectively. Nevertheless, these dislocations had similar Burgers vectors as those found attache...

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