Low-Cycle Fatigue Behaviour of 2205 Duplex Stainless Steel After High-Temperature Treatment

This study examines strain-controlled low-cycle fatigue (LCF) of 2205 duplex stainless steel after 1100 °C solution annealing and 1300 °C ferritization/post-weld simulation. Tests at total strain amplitudes of 0.5, 1.0, and 1.5% (triangular waveform, R = −1) show initial hardening followed by softening and stabilization at lower strains, and rapid hardening with accelerated failure at 1.5%. Optical microscopy/XRD confirm balanced α/γ at 1100 °C and ferrite dominance at 1300 °C. Mid-life hysteresis loops indicate non-Masing tendencies; cyclic stress–strain curves exceed static, evidencing cyclic hardening. Coffin–Manson fits capture strain–life behaviour and reveal a crossover near εT ≈ 0.92%, where the 1300 °C condition outperforms. SEM identifies overload dimples and fatigue striations whose spacing increases with strain amplitude, consistent with reduced life. Results link high-temperature microstructural changes to LCF performance for thermally affected DSS applications.