Influence of aging on high cycle and low cycle fatigue behavior of AA2024

In this study natural aging (T4) and artificial aging (T6) were performed on fatigue, tensile and witness specimens of AA2024 alloy using water as the quenching media. Hardness tests of T4 and T6 witness samples showed 137.5 HV and 123.4 HV, respectively. Obtained tensile results stated higher ultimate tensile and yield stresses for T4 which can be due to microstructural evolutions and precipitations formed during natural aging. Fatigue tests were carried out at both high cycle and low cycle fatigue regimes where T4 had higher fatigue resistance at high cycle, while at low cycle it was opposite. Scanning electron microscope (SEM) images of fatigue fracture surfaces displayed dimples in T4 specimens and gray fibers in T6 ones which can be related to the intrinsic differences in natural an artificial aging.

Keywords:

Fatigue , T4 , T6 , heat treatment , Low and high cycle , fracture