AFM evidence of surface relief formation and models of fatigue crack nucleation

Atomic force microscopy and high resolution scanning electron microscopy were used to find the true surface relief corresponding to persistent slip markings emerging from persistent slip bands on fatigued polycrystalline austenitic and ferritic stainless steels. The persistent slip markings are formed by extrusions and intrusions. The shape of extrusions and intrusions was documented and the kinetics of the extrusion growth was studied in both steels. The experimental data were discussed and compared with the predictions of the recent models of fatigue crack nucleation.