| About this Abstract |
| Meeting |
MS&T23: Materials Science & Technology
|
| Symposium
|
Advanced Materials for Harsh Environments
|
| Presentation Title |
Crack Tip pH Measurements in Al-Cu-Mg and Al-Zn-Mg Alloys to Understand Differences In Corrosion Fatigue Behavior |
| Author(s) |
Gabby C. Montiel, Jenifer Locke |
| On-Site Speaker (Planned) |
Gabby C. Montiel |
| Abstract Scope |
2xxx series (Al-Cu) and 7xxx series (Al-Zn) are age-hardenable aluminum alloys widely used in aerospace applications. Multiple studies have reported differing corrosion fatigue (CF) crack susceptibilities with 2xxx alloys having greater resistance. It is hypothesized that the existence of a passive film at the crack tip in 2xxx alloys lowers thereby crack growth rate (da/dN). A possible reason for passivity in 2xxx alloys is the presence of Al-Cu-X precipitates redepositing Cu at the crack tip to increase pH allowing formation of a stable passive film. Crack tip pH measurements show 7075-T6 has a pH of 3.5-5.5 at f = 0.1 Hz, while a pH of 11-12 was found in 2024-T8 at f = 0.1 Hz. This work aims to quantify CF performance between alloy systems by varying copper and zinc content to better understand the role of these strengthening precipitates as a function of crack tip pH and frequency. |