Application of the EBSD technique to describe the initiation and growth behaviour of microstructurally short fatigue cracks in a duplex steel

Up to 90% of the fatigue life of engineering alloys results from the initiation and propagation of microstructurally short cracks. Owing to their strong interactions with microstructural features, e.g. grain and phase boundaries, they exhibit substantially non-uniform propagation kinetics as compared with the growth rate of long cracks, which can be well described using a power-law function of the range of the stress-intensity factor DeltaK. In the present paper interactions between the crystallographic misorientation of grain and phase boundaries and microcracks in an austenitic/ferritic stainless steel are discussed and quantified by means of fatigue experiments in combination with the electron backscattered diffraction technique. In the second part a numerical model for the simulation of microcracks is introduced, which is capable of taking real microstructural arrangements into consideration.