Analysis of the fatigue dislocation structures in a duplex stainless steelalleged with nitrogen

The low cycle fatigue behaviour of a duplex stainless steel containing 0.15 % N is studied. TEM analysis of dislocation arrangements and determination of crack initiation are carried out according to the strain level. Two regi mes of cyclic response and fatigue damage have been determined. In the low strain regime (Delta epsilon(t) < 0.8%), the cyclic plasticity is carried b y the austenite while in the high strain regime (Delta epsilon(t) > 0.8%) b oth the austenite and the ferrite accommodate the plastic deformation.