Fourth CorroZoom Season 2 Webinar - Jenifer Locke
23 March 2022 at 0800 US Eastern
Recent Advances in Understanding Corrosion Fatigue, Stress Corrosion Cracking, and the Interaction of the Two
Jenifer (Warner) Locke
Materials Science and Engineering
The Ohio State University
Many structural metals are susceptible to both corrosion and environment assisted cracking (EAC, both stress corrosion cracking (SCC) and corrosion fatigue (CF)), which is a form of material degradation that occurs when a corrosive environment is concurrently present with external and/or internal mechanical stresses/strains. Research related to the interplay between corrosion fatigue and stress corrosion cracking to cause fast environmentally accelerated crack growth in Al-Mg alloys will be discussed. Al-Mg alloys are used widely in naval applications. In order to impart sufficient strength, Mg additions are typically higher than the solubility limit of ~3.5%. At room temperature, a Mg supersaturated solid solution is kinetically stable, but it has been well established that exposure to slightly elevated temperatures for extended periods of time leads to precipitation of a Mg rich β (Al3Mg2) phase on grain boundaries through a process known as sensitization. I will show that the resistance to CF is increasingly degraded as the fatigue loading frequency is decreased for heavily sensitized microstructures, i.e. there is a deleterious effect of grain boundary β phase and it is magnified as fatigue loading frequency decreases. Additionally, comparison of SCC resistance to literature reported K1SCC values, the threshold below which SCC does not occur, establishes that the severe degradation in CF resistance is triggered by loading conditions that promote SCC in addition to corrosion fatigue, a phenomenon known as superposition. Finally, the effect of cathodic polarization on CF will be discussed with results showing only limited protection for CF when full protection of SCC has been reported.
Jenifer (Warner) Locke is an assistant professor in the Department of Materials Science and Engineering and the Fontana Corrosion Center at The Ohio State University. Her research interests are in environment assisted cracking (EAC) and corrosion of metals and alloys. Particularly, she has interest in advancing laboratory EAC experimental capabilities to enable improved understanding of unique service environments, quantifying and understanding metallurgical and thermo-mechanical processing effects on occluded site electrochemistry in EAC of metals, and in inhibition of EAC. Before joining OSU in January 2015, Prof Locke held a position at the Alcoa Technical Center, the R&D facility for Alcoa Inc (now known as Arconic and Howmet), where she worked in alloy development, EAC, and corrosion of aerospace and automotive aluminum alloys.