The Effect of Stress on Hydride Precipitation

Flanagan, Ted B.; Mason, N.B.

doi:10.1016/b978-0-08-034813-1.50072-3

Cited by 4 publications

(6 citation statements)

References 10 publications

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“…64 The relative strength of these effects has been experimentally observed to vary amongst hydride-forming metals. For example, the first mechanism has been determined to be negligible for Nb and Zr due to nearly identical values of hydrogen partial molar volume in the hydride and metal.…”

mentioning

confidence: 99%

The Hydrogen Corrosion of Uranium: Identification of Underlying Causes and Proposed Mitigation Strategies

Loui¹

2012

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mentioning

confidence: 99%

The Hydrogen Corrosion of Uranium: Identification of Underlying Causes and Proposed Mitigation Strategies

Loui¹

2012

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“…As discussed in detail in Chap. 10 dealing with DHC, and also previously pointed out by Flanagan et al [7] and, recently, by Puls [32], this statement is only true when the increase in hydrogen concentration at the crack tip is insufficient to reach the solvus concentration for hydride formation.…”

Section: Theories Of Solvus Hysteresis Based On Accommodation Energymentioning

confidence: 65%

“…From this analysis, the authors concluded that tensile stress at the crack tip could result in a substantial increase in the temperature at which hydride formation and dissolution could occur. However, as was later demonstrated by Flanagan et al [7] and noted by Oates and Flanagan [23], the ''thermodynamic arguments offered by Birnbaum and Grossbeck [13] in support of the mechanism of stress induced hydride precipitation are difficult to understand because of their failure to clearly differentiate between the effects of uniform and non-uniform stress on the solvus behaviour.'' Using the expression for the effect of stress on chemical potential of hydrogen in solution given by Li et al [19], Birnbaum and Grossbeck [13] concluded that the increase with tensile stress of the hydrogen concentration in solution would not be large.…”

Section: Theories Of Solvus Hysteresis Based On Accommodation Energymentioning

confidence: 93%

Characteristics of the Solvus

Püls

2012

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

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The solvus is defined as the hydrogen concentration in the dilute phase that is in equilibrium with the hydride phase at a given temperature. It is sometimes also referred to as the terminal solubility of hydrogen or, particularly in the zirconium literature, as the Terminal Solid Solubility (TSS). In a closed system with constant hydrogen content, it represents the temperature during a temperature scan at which the last remaining hydrides have dissolved or have just started to precipitate for a given value of total hydrogen content. The most striking and important characteristic of the solvus in metal-hydrogen systems is the large and reproducible hysteresis between the dissolution and formation stages of the hydride phase. Depending on the direction of the transformation this hysteresis manifests itself in closed systems of constant hydrogen content as a difference in temperature at which the transformation occurs during a temperature scan and in systems open to an external source of hydrogen gas as a difference in the plateau pressures of the gas. Although all first-order phase transformations exhibit hysteresis to some extent because of the finite differences in extensive physical properties between the transforming phases, the greater magnitude of these differences in metal-hydrogen systems appears to be a associated with the disparity between the high mobility of hydrogen relative to that of the metal component. This allows the phase transformation to rapidly proceed at temperatures at which the lack of mobility of the underlying metal lattice could force the crystal into a metastable state.In early experimental determinations of the solvus relationships in hydride forming metals and, particularly in zirconium and its alloys, it was at first not appreciated that there were in fact at least two reproducible, apparently stable, phase relationships, and that neither of these represented a true equilibrium state of the thermodynamic system even though each was highly reproducible. To some extent this lack of understanding (or appreciation of its importance, particularly for DHC) has persisted to this day. As an example, a widely quoted source of the literature M. P. Puls, The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components, Engineering Materials,

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“…10.15 and 10.16, either aid or impede the stress-gradient-driven flux depending on the sign of the volume difference. An alternative interpretation of the foregoing result-which implicitly supports the foregoing explanation-has been provided by Flanagan et al [23].…”

Section: Theory Of Dhc Growth Ratementioning

confidence: 81%

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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The Effect of Stress on Hydride Precipitation

Cited by 4 publications

References 10 publications

The Hydrogen Corrosion of Uranium: Identification of Underlying Causes and Proposed Mitigation Strategies

The Hydrogen Corrosion of Uranium: Identification of Underlying Causes and Proposed Mitigation Strategies

Characteristics of the Solvus

Delayed Hydride Cracking: Theory and Experiment

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