About this Abstract |
Meeting |
MS&T25: Materials Science & Technology
|
Symposium
|
Understanding Corrosion-Related Cracking
|
Presentation Title |
Influence of crack environment pH on Corrosion Fatigue Crack Growth in Aerospace Aluminum Alloys |
Author(s) |
Gabby Montiel, Jenifer Locke |
On-Site Speaker (Planned) |
Gabby Montiel |
Abstract Scope |
Studies on corrosion fatigue (CF) of Al-Cu and Al-Zn aluminum alloys show AA7075-T6 develops an acidic crack pH of ~4 at 0.1 Hz and AA2024-T8 is more alkaline at ~11.2 at 0.1 Hz. Both alloys shift toward the bulk solution pH with increasing frequency, this attributed to convective mixing; but the mechanism behind acidic and alkaline crack pH remains unknown. The leading hypothesis suggests corrosion of anodic Cu-rich precipitates within the crack cause redeposition of metallic Cu enhancing crack cathodic kinetics to increase crack pH. Two possible reasons of this could explain the decreased CF kinetics in AA2xxx: (1) the elevated pH stabilizes the native Al passive film reducing anodic dissolution and H uptake, (2) highly basic crack environments cause crack tip blunting slowing crack growth kinetics. Ongoing research focuses on alloys with varied Cu and Zn to isolate the role of strengthening precipitates and passivity versus blunting. |