Enhanced fatigue crack propagation resistance of an Al-Cu-Mg alloy by artificial aging

The effect of artificial aging treatment on fatigue crack propagation (FCP) resistance of an Al-Cu-Mg alloy was investigated. It was shown that FCP rate of artificially aged alloy in the Paris region is lower than that of naturally aged alloy before and after thermal exposure. During the thermal exposure, tensile strength of artificially aged alloy remained unchanged. The results of three-dimensional atom probe (3DAP), transmission electron microscope (TEM) and differential scanning calorimeter (DSC) analysis showed that Cu-Mg co-cluster in artificially aged alloy are larger than that in natural aged alloy and can stably exist during thermal exposure. Size of Cu-Mg co-cluster was found to be the main factor influencing the thermal stability of Cu-Mg co-cluster and the FCP resistance.