Characterization of high cycle fatigue behavior of a new generation aluminum lithium alloy

The high cycle fatigue life characteristics of an Al–Li alloy were studied as a function of microstructure. While for the parent microstructure fatigue life decreased as grain size increased, no such effect was noted at high stresses. This decrease in fatigue life was correlated with lower crack initiation life due to small crack effect. Under multiaxial stress conditions, the alloy exhibited intergranular cracking. The cross-linking of intergranular cracks (in the T8 condition) caused a further deterioration in fatigue life. Additionally, planar slip movements (in the T3 condition) in stage I crack propagation were observed. Slip planarity depended on both the sample texture and the nature of the precipitates. Fractographic and textural evidence is presented.

► Effect of microstructure on fatigue fracture of an advanced Al–Li alloy was studied in detail.
► Preferential crack propagation in T3 state at specific orientations was analyzed.
► Fatigue crack propagation difference between T3 and T8 tempers and friction stir welded condition was rationalized.
► The effect of grain size on fatigue life for T3 and T8 tempers was justified based on current theories.
► Delamination in T3 and T8 tempers was rationalized using microstructural analysis and FEA simulation.