Role of δ-ferrite in fatigue crack growth of AISI 316 austenitic stainless steel

•δ-ferrite could introduce a deflected crack path at δ/γ interface in the solution treated sample, which significantly increases the fatigue crack growth resistance.•The reticular M23C6 precipitated in decomposed δ-ferrite after accelerated aging process is responsible for the microcrack nucleation in the crack tip plastic zone.•The preexisting microcracks at M23C6/δ interfaces within decomposed δ-ferrite ahead of the crack tip provide viable path for crack propagation, thus the fatigue crack growth resistance of δ-ferrite decreases.