Effects of Natural Seawater and Electrochemical Potential on Fatigue-Crack Growth in 5086 and 5456 Aluminum Alloys
Abstract
Fatigue-crack growth in 5086-H116, 5086-H117, 5456-H116 and 5456-H117 aluminum alloys was measured in ambient air (R.H. approx. 50 percent) and in flowing natural seawater. Tests in seawater were conducted at the freely corroding (F.C.) potential (approx. -1.0 V) and at applied potentials of -0.75, -1.3, -1.4, and 1.5V. Results are presented in terms of cyclic crack-growth rate (da/dN) as a function of crack-tip stress-intensity range (delta K). Delta K values ranged from approximately 12 to 50 MPA(sq. root of m). In ambient air, all four alloys exhibited similar crack growth characteristics. Crack growth in the 5086 alloys was only slightly affected by either seawater or potential. However, crack growth in the 5456 alloys varied rather widely with seawater and potential. In particular, alloy 5456-H116 exhibited crack-growth rates which were significantly accelerated at the freely corroding potential, and both 5456 alloys exhibited crack-growth rates which were significantly retarded under cathodic potentials. Observations of electrochemically induced crack arrest were made in both 5456 alloys under cathodic potential.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 07, 1977
- Accession Number
- ADA047416
Entities
People
- F. D. Bogar
- Thomas W. Crooker
Organizations
- United States Naval Research Laboratory