Grain Morphology Contribution to Stress Corrosion Susceptibility in 7075-T651 Aluminum Alloy

Geschwind, Gary; Soltz, G. C.; Adler, P. N.

doi:10.5006/0010-9312-26.7.265

Cited by 2 publications

(1 citation statement)

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“…AA7xxx alloys are known to be susceptible to intergranular stress corrosion cracking (IGSCC) when subjected to a tensile stress in an aggressive environment [20,21,[31][32][33][34][35]. However, in this study the sharp IGC fissures grew in samples that were unstressed.…”

Section: Sharp Igc Fissure Mechanismmentioning

confidence: 80%

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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