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Title The Effect of Sensitization on Corrosion Fatigue and Threshold Stress Intensity of AA5083-H131 Used for Marine Applications
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Publication Date
Degree MS
Discipline/Department Materials Science and Engineering
Degree Level masters
University/Publisher The Ohio State University
Abstract 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.
Subjects/Keywords Materials Science; Engineering; aluminum; corrosion fatigue; sensitization; IGSCC; AA5083
Contributors Locke, Jenifer (Advisor)
Language en
Rights unrestricted ; This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
Country of Publication us
Format application/pdf
Record ID oai:etd.ohiolink.edu:osu149261363924202
Repository ohiolink
Date Retrieved
Date Indexed 2017-09-11
Grantor The Ohio State University

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