Effect of applied tensile stress on intergranular corrosion of AA2024-T3

Liu, Xiaodong; Frankel, G. S.; Zoofan, B.; Rokhlin, S. I.

doi:10.1016/s0010-938x(03)00149-5

Cited by 69 publications

(42 citation statements)

References 20 publications

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“…Stressed L-T foil penetration data are also presented for comparison. 12 As was the case for the unstressed samples, the results from the L-T foil penetration experiments overlie those from the L-T radiography experiments. Also shown in Fig.…”

Section: Methodsmentioning

confidence: 82%

Transition from Intergranular Corrosion to Intergranular Stress Corrosion Cracking in AA2024-T3

Liu¹,

Frankel²,

Zoofan

et al. 2006

J. Electrochem. Soc.

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The transition of intergranular corrosion (IGC) to intergranular stress corrosion cracking (IGSCC) in AA2024-T3 was studied using microfocal X-ray radiography, scanning electron microscopy (SEM), and electrochemistry. A constant potential was applied in 1 M NaCl solution, and a fixed elastic tensile displacement was applied in the transverse direction using a modified ASTM G49 jig. In this orientation, IGC grows primarily along the elongated grain boundaries in the longitudinal and transverse directions, parallel to the applied stress. SEM and X-ray radiography provided insightful images of the transition to IGSCC. Linking of the individual IGC sites occurred at the edges of the elongated grains, resulting in transition of the IGC sites into IGSCC that was nominally normal to the applied stress. This coalescence process was discontinuous in nature, as evidenced by arrest marks on the fracture surface and oscillations in the measured current.High-strength aluminum alloys are susceptible to intergranular corrosion (IGC) and stress corrosion cracking (SCC). SCC in aluminum alloys is almost exclusively intergranular.1-3 The relationship between IGC and intergranular stress corrosion cracking (IGSCC) has been discussed for decades. [4][5][6][7] The combination of stress and electrochemical reactions can alter the local environment at the IGC tips, which can accelerate the growth rate. It has been suggested that an intergranular (IG) crack subjected to a normal tensile stress can develop into IGSCC. 8 However, the influence of tensile stress parallel to a crack tip on the subsequent growth is unclear, as are the details of how IGC transitions into IGSCC. In order to understand this transition, IGC and SCC need to be monitored in situ. Zhao et al. used X-ray radiography, a nondestructive evaluation (NDE) technique, to study IGC and exfoliation corrosion in AA2024 and AA7178. 9 We have described the use of X-ray radiography to image in situ the initiation and growth of multiple IGC sites in AA2024 growing in the longitudinal direction with an applied normal tensile stress in the short transverse direction. 10,11 A competition between the IG cracks was observed. The deepest crack at the beginning of the experiment was found to slow and stop growing, and was then surpassed by another crack that eventually penetrated through the sample. The results of the radiography technique were found to be in agreement with data generated using the stressed foil penetration method. 12 Although they are quite different, both approaches can accurately determine the rate of the fastest growing crack. In the current study, microfocal X-ray radiography was put to further use in the study of IGC and SCC in AA2024-T3. In

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Section: Methodsmentioning

confidence: 82%

Transition from Intergranular Corrosion to Intergranular Stress Corrosion Cracking in AA2024-T3

Liu¹,

Frankel²,

Zoofan

et al. 2006

J. Electrochem. Soc.

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“…Like exfoliation corrosion, the fissures could grow as a result of self-stressing by voluminous corrosion product formed at the grain boundary region. It has recently been shown that very low stresses (as low as 10% of the yield stress) normal to the elongated microstructure in wrought aluminum alloys can increase localized corrosion penetration rates significantly [36]. For the sharp fissures in this study, the wedging stress from the corrosion product is apparently sufficient to drive cracking despite the constraining effect of the unexposed surrounding material.…”

Section: Sharp Igc Fissure Mechanismmentioning

confidence: 52%

Kinetics of sharp intergranular corrosion fissures in AA7178

Huang

Frankel

2007

Corrosion Science

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During service in structural aircraft applications, AA7178 has been found to develop sharp intergranular corrosion (IGC) fissures, a special form of attack. A new laboratory approach to quantify the kinetics of sharp IGC fissure growth was developed in this work. Sharp IGC fissures, similar to those formed in service, grew in samples that were given an electrochemical pre-treatment and then exposed in a humid environment. The time for the first sharp IGC fissure to penetrate the thin sample was determined by visual observation of the back side of the sample. The depth of the sharp IGC fissure was determined by serial sectioning. The kinetics measured by this approach did not represent the fastest rates, but rather the rates of long sharp IGC fissures. Relative humidity had no measurable effect on fissure kinetics, indicating that there was little connection of the local sharp IGC fissure region with the outside environment. AA7178 in the as-received and T7 conditions exhibited slower sharp IGC fissure rates than in the T6 condition. The sharp IGC fissures were found to be filled with corrosion products, which possibly exert a stress that could play an important role in driving fissure growth. It is suggested that the sharp IGC fissure could be a form of SCC.

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“…First industrial tests show that this material may show some sensitivity to intergranular corrosion in specific conditions. Intergranular corrosion can depend on several parameters as precipitation [11], crystallographic orientations [12][13] or mechanical stress application [14]. In this document, corrosion tests are presented in order to underline some parameters effect (external stress, internal stress and microstructure).…”

Section: Materials Of the Studymentioning

confidence: 99%

Intergranular stress corrosion cracking of friction stir welded nugget on a 2050-T8 aluminum alloy

D’Hondt¹,

Aubert²,

Saintier³

et al. 2011

Advances in Materials Sciences

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Intergranular corrosion sensitivity is studied for the friction stir weld nugget of aluminum alloy 2050-T8. The weld nugget consists of fine equiaxed grains having average sizes from 4 to 20 µm, the grain size increases with decreasing of the distance from the weld surface. The weld nugget contains a particular microstructure called "onion rings" due to crystallographic orientations. The effect of the "onion rings" on stress corrosion cracks initiation is studied for stress corrosion cracking tests at a strain rate of 2.10 -6 s -1 . EBSD cartographies allow showing that the initiation site of the biggest cracks is located at boundaries between the texture bands. Corrosion and stress corrosion tests in 1.0 M NaCl are performed in order to show stress effect on intergranular corrosion. Pitting corrosion is observed during corrosion tests, whereas intergranular cracks appear during stress corrosion tests. The medium crack length is 20 µm and 168 cracks per mm 2 can be located. In these severe laboratory conditions, the order of magnitude of long crack growth rate is 5.10 -8 m.s -1 .

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Effect of applied tensile stress on intergranular corrosion of AA2024-T3

Cited by 69 publications

References 20 publications

Transition from Intergranular Corrosion to Intergranular Stress Corrosion Cracking in AA2024-T3

Transition from Intergranular Corrosion to Intergranular Stress Corrosion Cracking in AA2024-T3

Kinetics of sharp intergranular corrosion fissures in AA7178

Intergranular stress corrosion cracking of friction stir welded nugget on a 2050-T8 aluminum alloy

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