Progression of Corrosion Damage in a 3rd Generation Aluminum Lithium Alloy 2060

Modeling of corrosion damage in aluminum lithium 2060-T8 alloy is an important step in inserting Al-Li alloys into the military aerospace applications.  Third generation Al-Li alloys are currently being used in commercial Boeing and Airbus aircraft due to superior properties and lower density compared to traditional aerospace alloys. First generation of these alloys was plagued with corrosion issues, but in this study the more recently developed 3^rd generation 2060 alloy was evaluated under the OSD funding. This alloy was characterized and mechanically tested both prior and post exposure to corrosive environment. The microstructure was evaluated to determine the effects of precipitates on corrosion and post-corrosion fatigue life under four-point bend loads. Corrosion was introduced into the alloy in a fog chamber, according to the cyclic Prohesion exposure protocol that combines a wet-dry cycle with an electrolyte that emulates the atmospheric environment that an aircraft will see in service. After the exposure, the samples were evaluated using a variety of analytical techniques to quantify damage. Samples exposed to corrosive environment were also evaluated using light microscopy to investigate corrosion-assisted damage and fatigue failure. Micro-tension samples were machined to test the individual grain boundaries for corrosion. This test methodology will be integrated into the larger picture of probabilistic approaches to realistically model corrosion effects in Al-Li alloys.