Crack tip chemistry and electrochemistry of environmental cracks in AA 7050

Cooper, Kevin R.; Kelly, Robert G.

doi:10.1016/j.corsci.2006.12.001

Cited by 97 publications

(62 citation statements)

References 25 publications

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“…The environmental effect on the fatigue fracture of 25CrMo axle steel not only depends on the formation of corrosive pits and solution exposure time but also depends on the local deformation of the metal (stress level). The former involves the transformation of corrosion pits to stress corrosion cracks and the latter involves a electrochemical process (anodic dissolution) and hydrogen embrittlement due to the cyclic deformation on the surface [26,[31][32][33]. In addition, there is some scatter in the corrosive fatigue data, including the fatigue data for the samples tested in air, as shown in Figure 3.…”

Section: Resultsmentioning

confidence: 99%

“…This is because the fatigue fracture life depends primarily on the inside crack propagation length (a) in the environmental fatigue condition. A greater inside crack propagation length indicates a stronger stress-corrosion coupling effect [26,[31][32][33]35]. Therefore, the probability of the corrosion solution acting on the surface crack at the multi-crack initiation sites is lower than it acting on the single crack initiation sites.…”

Section: Fractography Analysismentioning

confidence: 99%

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High-Cycle Microscopic Severe Corrosion Fatigue Behavior and Life Prediction of 25CrMo Steel Used in Railway Axles

Wang

et al. 2017

Metals

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Abstract:The effects of environmental media on the corrosion fatigue fracture behavior of 25CrMo steel were investigated. The media include air, and 3.5 wt % and 5.0 wt % NaCl solutions. Experimental results indicate that the media induces the initiation of corrosion fatigue cracks at multiple sites. The multi-cracking sites cause changes in the crack growth directions, the crack growth rate during the coupling action of the media, and the stress amplitude. The coupling effects are important for engineering applications and research. The probability and predictions of the corrosion fatigue characteristic life can be estimated using the three-parameter Weibull distribution function.

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Section: Resultsmentioning

confidence: 99%

Section: Fractography Analysismentioning

confidence: 99%

High-Cycle Microscopic Severe Corrosion Fatigue Behavior and Life Prediction of 25CrMo Steel Used in Railway Axles

Wang

et al. 2017

Metals

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“…All fatigue data for the different environmental media are plotted in Figure 3 involves the transformation of corrosion pits to stress corrosion cracks and the latter involves a electrochemical process (anodic dissolution) and hydrogen embrittlement due to the cyclic deformation on the surface [23,[27][28][29]. In addition, there is some scatter in the corrosive fatigue data, including the fatigue data for the samples tested in air, as shown in Figure 3.…”

Section: Resultsmentioning

confidence: 99%

Section: Fractography Analysismentioning

confidence: 99%

High-Cycle Microscopic Corrosion Fatigue Behavior and Life Prediction of 25CrMo Steel Used in Railway Axle

Wang¹,

Wang²,

Wu³

et al. 2017

Preprint

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Abstract:The effects of environmental media on the corrosion fatigue fracture behavior of 25CrMo steel were investigated. The media include air, and a 3.5 wt.% and a 5.0 wt.% NaCl solutions.Experimental results indicate that the media induces the initiation of corrosion fatigue cracks at multiple sites. The multi-cracking sites cause the changes in the crack growth directions, the crack growth rate during the coupling action of the media and the stress amplitude. The coupling effects are important for engineering applications and research. The probability and predictions of the corrosion fatigue characteristic life can be estimated using the 3-parameter Weibull distribution function.

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“…12 In the theoretical section, it will be shown that one of the configurations well describes the experimental findings suggesting an explanation for the scattering of data under free corrosion conditions. 21,22 or artificial crevices 23 on aluminum alloys, chemical analyses of the electrolyte trapped in corroded grain boundaries have never been reported to our knowledge. As already discussed in the experimental section, the filter paper of the initial version of the foil penetration technique was replaced by a pH-indicator paper.…”

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confidence: 99%

Optical and Chemical Monitoring during Foil Penetration Experiments to Study Intergranular Corrosion in AA2024

Bonzom

Oltra

2018

J. Electrochem. Soc.

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A modified version of the foil penetration technique based on an optical detection of the full penetrating intergranular defects through thin foils was applied to AA2024 samples of various thicknesses in contact with a dilute chloride solution. As the rear side of the foil was free during the experiments, it was straightforward to measure the pH of the electrolyte trapped inside the grain boundary network leaking through the emerging defects on the rear side of the foils. The penetration regime in the longitudinal direction was determined for various exposure and electrochemical conditions confirming the decrease of the propagation kinetics as function of the depth of the intergranular defects. pH measurements were used to support mass transport simulation inside a pore electrode mimicking the propagation of the anodic head of grain boundaries. After validation under potentiostatic conditions, the same modelling approach was applied under free corrosion conditions, to discuss the location of cathodic areas during immersion and droplet exposures. Frankel and coworkers 1 considered the anisotropy of the intergranular corrosion process and performed foil penetration tests using various electrochemical conditions. They proposed that the propagation rate of intergranular corrosion followed a power law of the following type:where d is either the nominal thickness of the full penetrated foil or the resulting IG path length, a and n are constants (n is between 0 and 1) and t the time for the full penetration. To discuss these results in terms of IG propagation rate the raw data can be inverted and expressed as the depth of the fastest growing site as a function of time. However the physical meaning of the exponent and its value as function the nature of the alloy have not been discussed to our knowledge. Nevertheless, interesting work described in Ref. 2 illustrated application of such a law (relation 1) deduced from laboratory experiments to operational aircraft. In these practical cases there was a large variation in corrosion growth rates from one section of a wing to the next or from an aircraft to the next. But it was demonstrated that it was possible to provide a distribution for coefficients of relation (1), especially for coefficient a, which could be deduced from documented corrosion data collected, for example, from repair data.Relation (1) which means that the intergranular (IG) propagation rate on aluminum alloys (AA2024) is decreasing as function of the IG path length has been validated under potentiostatic conditions. 1 Moreover this trend has been also frequently discussed in other studies under free corrosion conditions. 3,4 Nevertheless, the origin of this feature has not been largely discussed quantitatively, especially as the inner surface of the "IG crevice" behind the active anodic head at the point of attack 5 can also suffer dissolution at a reduced rate and at long exposures as illustrated in different works showing a blunting of the IG path.6,7 Consequently the mass transport and/or the ohmic dr...

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Crack tip chemistry and electrochemistry of environmental cracks in AA 7050

Cited by 97 publications

References 25 publications

High-Cycle Microscopic Severe Corrosion Fatigue Behavior and Life Prediction of 25CrMo Steel Used in Railway Axles

High-Cycle Microscopic Severe Corrosion Fatigue Behavior and Life Prediction of 25CrMo Steel Used in Railway Axles

High-Cycle Microscopic Corrosion Fatigue Behavior and Life Prediction of 25CrMo Steel Used in Railway Axle

Optical and Chemical Monitoring during Foil Penetration Experiments to Study Intergranular Corrosion in AA2024

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