Effect of Nitrogen on the Deformation Behaviour of High-Nitrogen Austenitic Stainless Steels

The deformation behaviour of high-nitrogen austenitic steels with the base composition of Fe-18Cr-10Mn containing various contents of nitrogen was investigated. Two deformation modes including deformation-induced martensitic transformation (DIMT) and deformation twinning (DT) were observed depending on the nitrogen content. In the alloys with lower nitrogen contents, gamma ->epsilon ->alpha' martensitic transformation sequentially occurred, whereas DT acted as a main deformation mode and DIMT was suppressed in the alloys with increasing nitrogen content. Both DIMT and DT showed strong crystallographic orientation dependence. The competing mechanism between them was discussed in terms of the variation of stacking fault energy with nitrogen content.