The Influence of Fatigue Loading on the Microstructure of an Austenitic Stainless Steel

Abstract The rotation of principal stress/strain axes, which takes place under conditions of non-proportional fatigue loading, may significantly worsen the fatigue life. An explanation of this phenomenon can be found through microstructure examination. In this paper, we present the results of a microstructure examination of a X5CrNi18-10 steel subjected to fatigue loading, both, proportional and non-proportional. The variability of the positions of the principal stress axes was controlled by a fatigue loading program that consisted of alternatively realised blocks of torsion and tension-compression. The microscopic investigations were carried out by X-ray structural analysis and the micro-hardness of the material was examined. The results revealed that the application of cyclic loading caused a plasticity-induced martensitic transformation. Comparative analysis showed that the transformation depended on intensity and the kind of applied loading.