Fatigue crack growth in 2024 aluminum alloy with inhomogeneous solidification microstructure

This study reports the investigation of the fatigue crack growth behavior in 2024 aluminum alloy billets manufactured using the direct chill casting (DCC) and electromagnetic casting (EMC). It was expected that the billets produced from these different casting procedures would vary in terms of their microstructure. Therefore, they should exhibit different fatigue crack growth behavior. The results showed that, the structure of the middle center portion of both billets is not homogeneous and relatively coarse, while the structure of the center and edge portions is homogeneous compared with the structure of the middle center portion. As fatigue crack growth extended through many grains having different morphologies, it became unstable through the overall crack path, and the Paris zone almost disappeared. The effects of 5% rolling and commercially rolled DCC billets on the fatigue crack growth rate were also investigated. Striations were enhanced around Al₂Cu particles refined by commercial rolling, and fatigue crack growth was stable until large crack length.