The role of peening processes as a pre-treatment to anodizing on fatigue behavior of aircraft aluminum alloy

In this work, the possibility of employing shot peening and laser peening as pre-treatments to a tartaric–sulfuric anodizing process on the fatigue behavior of 7050-T7451 aluminum alloy components was investigated. The surface modifications and stress fields induced by the combination of the peening and anodizing processes were evaluated by scanning electron microscopy and residual stress assessment methodologies based on diffraction techniques, respectively. It was found that the anodizing process alone results in a significant reduction in fatigue life compared to the as-machined condition especially in the high-cycle fatigue (HCF) region of the S-N diagrams due to the presence of defects within the anodic layer that act as stress concentrators facilitating the initiation of fatigue cracks. The application of both shot and laser peening treatments is demonstrated to offset the negative effects induced by anodizing, offering greater safety margins useful for the design of critical aeronautical structures.