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Chloride Ion Activity and Susceptibility of Al Alloys 7075-T6 and 5083-H131 to Stress Corrosion Cracking

Published

Author(s)

Richard E. Ricker, Eun Lee, R. Taylor, C. Lei, B. Pregger, E. Lipnickas

Abstract

The influence of chloride ion activity on the susceptibility of aluminum alloys 5083-H131 and 7075-T6 to stress corrosion cracking was investigated by conducting slow strain rate tensile tests at a strain rate of 10-7 s-1 in naturally aerated aqueous solutions with varying NaCl mass fraction (0.001 % to 20 %) and in a 3.5 % mass fraction NaCl solution with varying strain rates (10-8 to 10-4 s-1). This study found that both alloys exhibited reduced strengths and failure strains (times) in the solutions compared to laboratory air. The extent of these reductions was greater in alloy 5083 for the conditions examined. The strength and ductility of both alloys decreased with chloride ion activity in a manner that indicates a chemical reaction is responsible. The strength and ductility of both alloys varied with strain rate in a sigmoidal manner that indicated cracking kinetics in alloy 7075 were about two orders of magnitude slower. It was deduced that the chloride ion interacts chemically with the passivated surface in the potential gradient at the crack tip to cause SCC. While no mechanism of cracking can be eliminated on the basis of these results alone, the results are consistent with the hypothesis that absorbed hydrogen causes cracking in alloy 7075 while cracking in 5083 is the result of a dissolution mechanism.
Citation
Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science
Volume
44A
Issue
3

Keywords

stress corrosion cracking, hydrogen embrittlement, aluminum alloys, slow strain rate testing

Citation

Ricker, R. , Lee, E. , Taylor, R. , Lei, C. , Pregger, B. and Lipnickas, E. (2013), Chloride Ion Activity and Susceptibility of Al Alloys 7075-T6 and 5083-H131 to Stress Corrosion Cracking, Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science, [online], https://doi.org/10.1007/s11661-1500-2 (Accessed March 4, 2024)
Created March 1, 2013, Updated November 10, 2018