Fatigue mechanisms in an austenitic steel under cyclic loading: Experiments and atomistic simulations

Experimental investigations on the austenitic stainless steel X6CrNiNb18-10 (AISI – 347) and concomitant atomistic simulations of a FeNi nanocrystalline model system have been performed in order to understand the basic mechanisms of fatigue damage under cyclic loading. Using electron backscatter diffraction (EBSD) the influence of deformation induced martensitic transformation and NbC size distribution on the fatigue crack formation has been demonstrated. The martensite nucleates prevalently at grain boundaries, triple points and at the specimen free surface and forms small (~1 µm sized) differently oriented grains. The atomistic simulations show the role of regions of a high density of stacking faults for the martensitic transformation.