Hydride morphology and striation formation during delayed hydride cracking in Zr-2.5% Nb

Shek, Gordon K.; Jovanović, M.; Seahra, H.; Ma, Yongsheng; Li, D.; Eadie, R.L.

doi:10.1016/0022-3115(96)00370-4

Cited by 39 publications

(16 citation statements)

References 12 publications

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“…Previous workers [12][13][14][15][16] have investigated the morphology of DHC in Zr alloys, particularly Zr-2.5 pct Nb. The DHC models [17][18][19][20] are generally based on the formation of a single hydride platelet oriented parallel to the crack plane, as observed by Shek et al [15] for a Zr-Nb alloy.…”

Section: A Fractography Of Hementioning

confidence: 99%

Fractography of Stress Corrosion Cracking of Mg-Al Alloys

Winzer

Atrens

Dietzel³

et al. 2008

Metall Mater Trans A

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Mechanisms for the stress corrosion cracking (SCC) of Mg-Al alloys have been investigated by scanning electron microscopy (SEM) of the fracture surfaces, for the two-phase alloy AZ91 and the single-phase alloys AZ31 and AM30 in distilled water. The mechanism for crack initiation in AZ31 and AM30 involves localized dissolution. The mechanisms for crack propagation in AZ31 and AM30 involve microvoid coalescence and cleavage, respectively. The mechanism for crack initiation in AZ91 is unclear, but may involve the fracture of b particles near the surface. The mechanism for crack propagation at moderate strain rates in AZ91 is similar to that in AZ31, with b particles acting as sources of H for mobile dislocations. The fracture surface for AZ91 tested at the strain rate 3 · 10 -8 s -1 was similar to that for specimens precharged in gaseous H 2 . This fracture surface is the result of (1) the nucleation and growth of MgH 2 particles, (2) sudden fracture through the MgH 2 particles at some critical stress, and (3) decomposition of the MgH 2 particles after fracture.

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Section: A Fractography Of Hementioning

confidence: 99%

Fractography of Stress Corrosion Cracking of Mg-Al Alloys

Winzer

Atrens

Dietzel³

et al. 2008

Metall Mater Trans A

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“…As noted in Sect. 10.3, experimentally it has been found that the striation spacing is a good measure of L c [69]. A plot of the results of measurements of these striation lengths at different temperatures obtained in the recent IAEA tests [26] combined with those from earlier tests are reproduced in Fig.…”

Section: Limiting Values Of L C and K Ihmentioning

confidence: 95%

“…Direct confirmation of the stepwise sequence of events characterizing DHC was obtained in a limited number of TEM in situ experiments in different hydride forming metals [6,36,41,73], while indirect confirmation was obtained from metallographic and fractographic observations of hydrides at crack tips and from striation spacing length measurements, respectively [79]. In some favorable cases these observations could be correlated with corresponding stepwise intervals of acoustic emission and electrical resistivity signals [27,69,94] corroborating the metallographic and fractographic evidence of stepwise growth and fracture of the hydrided region. The rate of growth of the DHC crack suggests that the process is diffusion driven.…”

Section: General Features Of Dhcmentioning

confidence: 97%

“…However, the experimental results show that the crack tip hydrided region's thickness increases with temperature and with decreased supersaturation [69,70]. Therefore, a higher thickness value should have been chosen for the predictions at 350°C of the unirradiated and at 365°C of the pre-irradiated material, respectively.…”

mentioning

confidence: 96%

“…This effective normal transformation strain, which accounts for the elastic-plastic behavior of the matrix, varies with temperature (and whether or not the material has been pre-irradiated) because it depends on the yield strength of the matrix, which varies with temperature. These choices of adjusted uniaxial dilatational transformation strains in the present model calculations result in predicted values of L c and K The thickness of the hydrided region has also been chosen to have a temperature dependence, based roughly on the limited experimental observations for this parameter [69,70] with the thickness values modified from those obtained experimentally to roughly take account of the difference in the shapes of the hydrides between model and experimental observations (uniform thickness along its length and taper shaped, respectively). The values used and their temperature dependencies are listed in Table 10.1.…”

mentioning

confidence: 98%

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Delayed Hydride Cracking: Theory and Experiment

Püls¹

2012

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

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As noted in Chaps. 1 and 9, zirconium alloy components can fail by a time-dependent mechanism of cracking if hydrides can preferentially form and subsequently crack at locations of elevated tensile stress. This process of time-dependent hydride cracking, called delayed hydride cracking (DHC), is based on the mechanism of diffusion of hydrogen to a region of elevated tensile stress followed by nucleation, growth, and fracture of the hydrided region. By repeating these steps, a crack can propagate in a component at a rate that, above a threshold stress intensity factor, K IH ; is mainly dependent on temperature. In this chapter we present the status of the present state of understanding of DHC in zirconium alloys, emphasizing the connections between the models developed and the experimental data. The intent of this chapter is not to provide an exhaustive review of the literature but to focus on results that are deemed to have collectively advanced our understanding of this phenomenon. This chapter is divided into two main parts, the first part dealing with DHC propagation, the other with DHC initiation. Although it may appear backwards to start with DHC propagation rather than initiation, this approach is consistent with the historical development of the field and thus also helps somewhat in simplifying the exposition. Readers wishing to obtain a succinct recent overview of DHC and other aspects of the effects of hydrogen and hydrides on the integrity of zirconium alloys are referred to a recent review by Coleman [15]. In addition, an earlier review by Northwood and Kosasih [47] provides a comprehensive summary account of work published in this field up to the date of that publication.M. P. Puls, The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components, Engineering Materials,

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