Low Cycle Fatigue Behavior and Failure Mechanism of Wire Arc Additive Manufacturing 16MND5 Bainitic Steel

In this study, the low cycle fatigue behavior and failure mechanism of WAAM 16MND5 bainitic steel, which is commonly used in the nuclear reactor, were investigated thoroughly via a series of strain-controlled and stress-controlled low cycle fatigue tests. Results show that the microstructure of WAAM 16MND5 steel is granular bainite with a certain number of banded pro-eutectoid ferrite. WAAM 16MND5 steel exhibits similar cyclic deformation behavior under different strain amplitudes, i.e., a long stage of continuous cyclic softening and rapid cyclic softening till failure. The fatigue life decreases with the increasing strain amplitude. Moreover, the persistent slip markings in ferrite grains, the interface of pro-eutectoid ferrite and large Al 2 O 3 inclusions are the preferred locations for microcrack initiation. The crack initiated from the edge of the specimen is observed to develop into a main crack. The main crack propagates mainly in transgranular mode and can also propagate along the pro-eutectoid ferrite interface.