Effect of the UFG structure on the fatigue properties of ferritic/martensitic steel

This paper presents the results of investigation of the effect of an ultrafine-grained structure on the fatigue properties of ferritic/martensitic steel. Special attention is paid to the study of structural changes after fatigue tests. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to study the features of fatigue fracture and microstructural evolution, depending on the distance from the fracture surface. Using X-ray diffraction, we determined the lattice parameter, coherent scattering region, dislocation density, the volume fraction and size of carbide particles. The paper discusses the effect of the ultrafine-grained structure, as well as the volume fraction and size of carbides on the mechanism of fracture during fatigue tests. (paper)