Comparison on the Fatigue Crack Propagation of High‐Strength Aluminum Alloys

To investigate the fatigue crack propagation (FCP) behaviors of high‐strength 7075 and 2024 Al alloys, FCP experiments are conducted for the two alloys at different aging states (underaged [UA], peak aging, and overaged). It is found that strength and plasticity are the main factors influencing the FCP. For 7075 Al alloy, the FCP curves almost coincide for the three aging states that have similar tensile properties. However, 2024 Al alloy shows the lowest FCP rate at the UA state which has the strongest strength–plasticity match among the three aging stages. Based on the low‐cycle‐fatigue damage model, the effect of strength–plasticity balance on FCP rate of the two Al alloys at different aging states is quantitatively analyzed. It is found that the larger the strength–plasticity balance of the alloy, the smaller the FCP rate under the same stress intensity factor. This study indicates that the FCP rate of high‐strength Al alloys is mainly influenced by the strength–plasticity balance due to the difference in the aging states.