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The Effect of Sensitization on Corrosion Fatigue and Threshold Stress Intensity of AA5083-H131 Used for Marine Applications

Bay, Rebecca Marie
http://orcid.org/0000-0001-5284-9397
http://rave.ohiolink.edu/etdc/view?acc_num=osu149261363924202

Abstract Details

2017, Master of Science, Ohio State University, Materials Science and Engineering.
AA5xxx series Al-Mg alloys with greater than ~3.5% Mg experience an acceleration in fatigue crack growth rate (da/dN) as the level of sensitization increases and fatigue loading frequency (f) decreases when loaded in 3.5 wt% NaCl. AA5xxx series alloys, commonly used in naval applications, are known to exhibit decreased resistance to intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) due to the formation of the active Al3Mg2-ß phase on grain boundaries. ß phase is metallurgically undesirable and forms on grain boundaries when slightly elevated in-service temperatures are experienced for prolonged periods of time, a phenomenon known as sensitization. Previous studies on AA5083-H131 corrosion fatigue (CF) show that da/dN is accelerated by an order of magnitude in the Paris regime for degrees of sensitization greater than or equal to 30 mg/cm2 at a f of 10 Hz and an R of 0.85, however, practical in-service naval ship fatigue loading occurs at 0.15 Hz and below. The results of this work show that, for sensitization levels examined above 33 mg/cm2, previous high-f results cannot be applied to low-f loading. High resolution fracture mechanics based experiments conducted at constant ¿K and R-ratio under full immersion in 3.5% NaCl show that da/dN for heavily sensitized material is highly f-dependent and increases with decreasing f by as much as three orders of magnitude over the as-received unsensitized condition. The result of this work suggests that high-f (10 Hz) testing severely underestimates da/dN for service-type loading of heavily sensitized material. Specifically, for sensitization levels of 37 mg/cm2 and above, da/dN increases with decreasing f by 2 to 3 orders of magnitude for 0.01 Hz loading over 1 Hz loading. Results from this study can enable advancement of service ship structural life prediction by generating data necessary to inform on safe versus unsafe sensitization levels.
Jenifer Locke, PhD (Advisor)
Gerald Frankel, PhD (Committee Member)
125 p.
Engineering; Materials Science
aluminum; corrosion fatigue; sensitization; IGSCC; AA5083

Recommended Citations

Citations

  • Bay, R. M. (2017). The Effect of Sensitization on Corrosion Fatigue and Threshold Stress Intensity of AA5083-H131 Used for Marine Applications [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu149261363924202

    APA Style (7th edition)

  • Bay, Rebecca. The Effect of Sensitization on Corrosion Fatigue and Threshold Stress Intensity of AA5083-H131 Used for Marine Applications. 2017. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu149261363924202.

    MLA Style (8th edition)

  • Bay, Rebecca. "The Effect of Sensitization on Corrosion Fatigue and Threshold Stress Intensity of AA5083-H131 Used for Marine Applications." Master's thesis, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu149261363924202

    Chicago Manual of Style (17th edition)

osu149261363924202
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This open access ETD is published by The Ohio State University and OhioLINK.