Low Cycle Fatigue of High Nitrogen Duplex Stainless Steels

Investigations on a DSS containing 0.15% nitrogen show that the plasticity is accommodated by the austenite at low strain amplitude and by both phases at high strain amplitude From TEM analysis, the dislocation arrangements are very different in the ferrite according to the strain level. In the austenite, arrangements resulting from planar slip of dislocations are observed as the effect of nitrogen concentrated in the austenitic phase Increasing the amount of nitrogen up to 0.25%N does not change drastically the behaviour However, when the austenite is supersaturated with nitrogen (DSS with 0.6%N), it appears to be unable to accommodate the plastic deformation which is now carried by the ferrite.