Mesoscopic analysis of fatigue strength property of a modified 2618 aluminum alloy

The existence of the fatigue limit and the effect of the generated texture in a modified 2618 aluminum alloy were investigated in this study. This alloy was fabricated by adding 1.0% excess Cu, 0.24% Mn, and 0.16% Zr to the standard composition. The fatigue limit was considered in terms of the fatigue crack initiation limit and fatigue crack propagation limit. To verify the former, the scatter of the fatigue crack initiation life in fatigue tests was discussed. To verify the latter, the results of a coaxing effect test and the scatter of the microstructural sensitive fatigue crack life were discussed. Moreover, the effect of texture on the fatigue strength property was studied by observing the initiation and growth behavior of cracks in a tensile test and a fatigue test by using the replica technique. The results showed that the fatigue crack propagation limit was absent in the modified alloy, whereas the fatigue crack initiation limit existed only in the material with un-textured microstructures. In addition, the distinct deviation in the mechanical properties of the modified alloy was attributed to the local stress-concentration at the boundary between the un-recrystallized and the recrystallized areas. Finally, a comparison with the 2618 alloy showed that the modified alloy had higher fatigue strength and lower notch sensitivity. (C) 2013 Elsevier Ltd. All rights reserved.