Characterization of fatigue behavior of Al-Li alloy 2099

Abstract Experiments and modeling were performed to quantify the microstructure-fatigue properties relationship of wrought aluminum-lithium alloy 2099 (AA2099) plate. Microstructural morphology was examined via optical microscopy, SEM, and TEM techniques. The mechanical properties were determined through monotonic tensile and fully reversed fatigue testing. The rolled AA2099 was shown to have large elongated columnar grains several millimeters long. Metastable secondary phases, T 1 and δ′, were observed and provided strength to the material. Fractography determined fatigue cracks initiate from copper-rich constituent particles. These particles ranged from 1 to 25 μm in size, with an average size of 12 μm. The size of these intermetallic Cu-rich particles influenced the fatigue life of AA2099. Lastly, a microstructure-sensitive fatigue model was used to correlate the various effects of intermetallic particle sizes on the fatigue life of AA2099.