Search

High temperature low cycle fatigue tests at various strain amplitudes (±0.5%, ±0.6%, ±0.8%, ±1.0%) and strain rates (0.5%/s, 0.05%/s, 0.005%/s) were performed at 550 °C. The stress decomposition method and microstructure characterization were used to analyze cyclic hardening and softening behavior. Results showed that increased back stress and the combined action of back and friction stresses were responsible for the pronounced cyclic hardening at the early and late stages of initial hardening, respectively. The decrease in friction stress resulted in cyclic softening until final fracture. Moreover, the evolution behavior of dynamic strain aging (DSA) activity was discussed, which showed a clear dependence on loading cycles and directions. Specifically, the DSA activity was firstly attenuated and then gradually intensified from the late stage of cyclic hardening, and it was stronger in the compressive plastic deformation regime of hysteresis loops than in the tension part. • The increase in intergranular back stress and friction stress causes cyclic hardening. •The decrease in friction stress contributes to the cyclic stress softening. •The DSA activity attenuates firstly and then gets enhanced during cyclic loading. •The DSA activity under compression loading is stronger than that under tension part. [ABSTRACT FROM AUTHOR]