Low cycle fatigue behavior of casting A319 alloy under two different aging conditions

To determine the influence of peak- and over-aging on low-cycle fatigue (LCF) behavior of casting A319 alloy, the strain controlled low-cycle fatigue tests was studied at room temperature under different total strain amplitudes. At lower total strain amplitudes (0.2-0.3%), the A319 alloy presented initial cyclic hardening and then, steady stage and cyclic softening; while at higher total strain amplitudes (0.35-0.4%), it presented continuous hardening in the peak-aged specimens and constant softening in the over-aged specimens. At a given total strain amplitude, the hysteresis loops in the peak-aged specimens were relatively narrower than those in the over-aged specimens. The fatigue life of the peak-aged samples was higher than that of the over-aged samples at any given total strain amplitude. Fractographic morphology indicated that the size of the fatigue crack propagation zone at peak-aged condition was larger than that at over-aged treatment. The crack characteristic in the propagation region and the fast fracture zone also showed some differences between two aging conditions.