Model of dislocation sweep-in of hydrogen during fatigue crack growth

Tien, J. K.; Richards, R. J.; Buck, O.; Marcus, Harris L.

doi:10.1016/0036-9748(75)90287-2

Cited by 71 publications

(8 citation statements)

References 6 publications

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“…For the HELP mechanism to continue to operate, the dislocation velocity must not exceed some critical value, which can be calculated approximately from the following (Tien et al, 1975: respectively for the bcc and fcc metals were considered. The resultant dislocation velocities remain below the critical breakaway velocities.…”

Section: Effect Of Loading Ratementioning

confidence: 99%

“…Models for hydrogen transport by dislocations have been proposed by Tien et al (1975Tien et al ( , 1976 and Tien (1976). These dislocation transport models yield much faster diffusion rates than lattice diffusion and support the idea that dislocations can carry hydrogen deep into a specimen gage section or plastic zone even at ambient temperatures.…”

Section: Introductionmentioning

confidence: 98%

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Modeling hydrogen transport by dislocations

Dadfarnia

Martin

Nagao

et al. 2015

Journal of the Mechanics and Physics of Solids

198

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Section: Effect Of Loading Ratementioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Modeling hydrogen transport by dislocations

Dadfarnia

Martin

Nagao

et al. 2015

Journal of the Mechanics and Physics of Solids

198

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“…The different crack velocities for AZ91, AZ31 and AM30 may be due to a difference in the predominant mechanism for SCC propagation. H may be transported more rapidly with mobile dislocations than by diffusion [62]. Thus, HELP is associated with higher crack velocities than HEDE and DHC.…”

Section: The Influence Of Strain Ratementioning

confidence: 99%

Characterisation of stress corrosion cracking (SCC) of Mg–Al alloys

Winzer

Atrens

Dietzel³

et al. 2008

Materials Science and Engineering: A

164

106

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“…[18,19] HEDE and DHC involve stress-assisted diffusion of H ahead of the crack tip, which is slower than H transport by mobile dislocations (as per HELP). [20] Thus, HEDE and DHC are associated with relatively low V c s. …”

mentioning

confidence: 99%

Stress Corrosion Cracking (SCC) in Mg‐Al Alloys Studied using Compact Specimens

et al. 2008

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Our recent publications [1][2][3][4][5][6][7] showed that there exists a considerable body of research outlining the phenomenology of Transgranular Stress Corrosion Cracking (TGSCC) in Mg alloys. TGSCC is the inherent mode of SCC in Mg alloys. It is generally accepted that the mechanism for TGSCC of Mg alloys is a form of Hydrogen Embrittlement (HE) with the hydrogen coming from the cathodic partial reaction (hydrogen generation) of the Mg corrosion reaction, [8][9][10][11] however, the specific nature of the HE mechanism remains uncertain. The mechanisms that have been proposed are: Hydrogen Enhanced Decohesion (HEDE)Determination of the mechanism for TGSCC of Mg alloys is complicated by its dependence on microstructure, environment and mechanical loading. A key indicator of the predominant mechanism for an SCC system is the stress corrosion crack velocity, V c . AIDE involves enhanced microvoid coalescence due to emission of dislocations from the crack tip by adsorbed H atoms. Since AIDE does not involve transport of H into the matrix, it is associated with very high V c s. [12,17,18] HELP involves enhanced dislocation mobility due to H atmospheres at dislocations and obstacles to dislocations. Thus, HELP is associated with moderate V c s, at which H atmospheres can remain bound to mobile dislocations. [18,19] HEDE and DHC involve stress-assisted diffusion of H ahead of the crack tip, which is slower than H transport by mobile dislocations (as per HELP). [20] Thus, HEDE and DHC are associated with relatively low V c s. Experimental MethodThe test materials were the Mg-Al alloys AZ91 and AZ31. C(T) specimens were machined from as-cast ingots (in the case of AZ91) or large extrusions (in the case of AZ31). AZ31 specimens were machined such that the crack propagation direction was parallel with the extrusion direction. The alloys were the same as those used in the form of cylindrical tensile specimens in our previous research. [2,3,6] AZ91 consisted of an a-matrix and large interdendritic particles. The composition of the interdendritic particles was consistent with the b-phase Mg 17 Al 12 identified by previous workers. [8,9,16,[21][22][23] AZ31 consisted of an a-matrix with similar Al-concentration to that in AZ91 and a sparse distribution of small Al-Mn plate-like crystals (sometimes aligned collinearly in the extrusion direction). The specimens were 7.5 mm thick and were fatigue pre-cracked such that a/W ≈ 0.5 (where W is 40 mm) at the beginning of each SCC test. The SCC test environment was double-distilled H 2 0. Control tests were carried out in laboratory air (previously shown to be inert [2,3,6] ). The experimental setup for SCC tests is shown in Figure 1. The specimens were immersed in the environment to just above the machined notch. The fatigue crack was saturated with distilled water prior to each test by applying a small constant load (∼ 0.5 kN) to the immersed specimen for ∼ 24 h. The distilled water was slowly circulated between the environment cell and a remote reservoir. The applied tensile load ...

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Model of dislocation sweep-in of hydrogen during fatigue crack growth

Cited by 71 publications

References 6 publications

Modeling hydrogen transport by dislocations

Modeling hydrogen transport by dislocations

Characterisation of stress corrosion cracking (SCC) of Mg–Al alloys

Stress Corrosion Cracking (SCC) in Mg‐Al Alloys Studied using Compact Specimens

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