Fatigue softening of X10CrAl24 ferritic steel

Cyclic plastic response of X10CrAl24 ferritic stainless steel in a wide domain of plastic strain amplitude was measured. Cyclic hardening–softening curves show important cyclic softening during most of the fatigue life. Cyclic stress-strain curves have different slopes in the domain of low and high strain amplitudes. These two domains in cyclic stress–strain curve correspond to two types of internal structure as observed by transmission electron microscopy (TEM). The areas of condensed dislocation structure in the interior and the bands of extrusions and intrusions on the surface indicate the localization of cyclic strain. Fatigue softening was discussed in terms of properties of dislocations in b.c.c. structure and localization of the cyclic plastic strain.