The influence of temperature on the cyclic behavior of aged and unaged super duplex stainless steels

The cyclic behavior of type UNS S32750 (super) duplex stainless steels (DSSs) in as-received and aged conditions was investigated between room temperature and 500 °C. The pronounced cyclic hardening observed in as-received samples between 200 and 475 °C is associated with the activation of dynamic strain aging (DSA) in the ferritic phase. On the other hand, during the entire fatigue life aged samples only show a cyclic softening behavior that could be related to the demodulation of the spinodal decomposition in the ferrite phase. It is worthwhile to point out that despite the manifestation of DSA in as-received samples at intermediate temperatures and the presence of spinodal decomposition in aged samples no influence of these phenomena on the fatigue lifetime was observed.