Role of the microstructure on fatigue properties of 475°C aged duplex stainless steels

This paper deals with the role of microstructure, nitrogen content and α/γ phases volume fraction, on fatigue properties of duplex stainless steels (DSS) aged at 475°C. The results obtained from this study show that the α/γ volume fraction plays an important role on fatigue lives. The fatigue resistance is not deteriorated in an aged DSS with 70% of austenite. The stress response to strain cycling is strongly affected by the difference of hardness between ferrite and austenite. A 475°C aged DSS containing 0.4% nitrogen and 70% of ‘hard austenite’ lead to interesting fatigue properties which do not strongly differ from that obtained in annealed DSS.