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Effects of stress on intergranular corrosion and intergranular stress corrosion cracking in AA2024-T3

Liu, Xiaodong
http://rave.ohiolink.edu/etdc/view?acc_num=osu1133313637

Abstract Details

2005, Doctor of Philosophy, Ohio State University, Materials Science and Engineering.
High strength AA2024-T3 alloy has pronounced susceptibility to intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC), which seriously limits the lifetime as engineering materials. Conventional investigation methods constrained a single crack per specimen can not characterize and evaluate multiple IGC cracks exist in real structures. In this study, a number of specially designed approaches have been developed to allow better understanding of the effects of applied and residual tensile and compressive stresses on growth kinetics of IGC and IGSCC in AA2024-T3. The stressed foil penetration technique and microfocal x-ray radiography along with electrochemical measurements are primarily used in this study. The breakdown potential was lower and the passive current density was higher under tension compared to unstressed samples. Microfocal x-ray radiography analysis resulted in IGSCC kinetics and characterized the morphology of individual cracks and generated the kinetics of localized IGC growth, which is not limited to the formation of a single crack and the competition between SCC cracks can be studied. Tensile stress along the transverse direction promotes linking of the IGC on the edges of the elongated grains to form a fracture surface that is nominally perpendicular to the transverse stress. Arrest marks were observed on the fracture surface associated with the transition from IGC to IGSCC. The current oscillations suggest that the linking process is discontinuous in nature. A constant load setup along with x-ray radiography was used to monitor multiple IGSCCs grow and competition. Interestingly, it was found in every experiment that the crack that resulted in ultimate failure was not the longest crack at early stages of the experiment, and long cracks tended to stop growing. The stifling of cracks appeared to intersect triple points at grain ends. The local grain boundary composition, and interaction between the susceptible microstructure and local environment under tensile stress are associated with intermittent anodic dissolution of precipitates and the adjacent grain boundaries in AA 2024-T3. The application of compressive stress at a level halfway to yield significantly reduced the growth kinetics of IGC in the perpendicular direction, but did not eliminate it totally. The breakdown and repassivation potentials increased, and passive current density decreased for samples under compression or with compressive residual stress.
Gerald Frankel (Advisor)
293 p.
High Strength Aluminum Alloy; Intergranular Corrosion; Stress Corrosion Cracking; Environmental Induced Cracking; Non-Destructive Evaluation; X-ray radiography; In Situ Study SCC; Foil Penetration Technique; Multiple Intergranular Cracking.

Recommended Citations

Citations

  • Liu, X. (2005). Effects of stress on intergranular corrosion and intergranular stress corrosion cracking in AA2024-T3 [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1133313637

    APA Style (7th edition)

  • Liu, Xiaodong. Effects of stress on intergranular corrosion and intergranular stress corrosion cracking in AA2024-T3. 2005. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1133313637.

    MLA Style (8th edition)

  • Liu, Xiaodong. "Effects of stress on intergranular corrosion and intergranular stress corrosion cracking in AA2024-T3." Doctoral dissertation, Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1133313637

    Chicago Manual of Style (17th edition)

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© 2005, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.