Low-cycle fatigue behavior of austenitic stainless steels with gradient structured surface layer

Low-cycle fatigue behavior of gradient structured (GSed) 316L steels is investigated. The results show that both the homogeneous and gradient structures exhibit first cyclic hardening then cyclic softening. The GSed surface layer can, however, speed up cyclic hardening and extend cyclic softening processes. The analyses using hysteresis energy-based criterion indicates that the former phenomenon can be attributed to the reduced fatigue damage capacity, while the latter to the improved ability of damage defusing. This finding accordingly pinpoints that the retarded fatigue damage accumulation process has been acting as the main contributor to the enhanced fatigue performance of GSed 316L steels.