Deformation Structure of Chromium-free High-nitrogen Austenite in Fe–N Binary Alloys

Planar slips have been frequently recognized in nitrogen-added austenitic stainless steels, and often discussed in terms of stacking-fault energy (SFE). On the other hand, nitrogen addition promotes the formation of N-Cr short-range order (SRO), which has been proposed to cause the planar slips. In this study, a chromium-free Fe-N binary austenite with 2.4 mass% of fully solid-solutioned N was fabricated to simplify the relationship among deformation structures, SFE and N-Cr SRO. The Fe-N alloy was found to exhibit wavy slips and possess almost the same SFE as a nitrogen-added austenitic stainless steel with planar slips. TEM results indicate the formation of modulated structures along <001> in the nitrogen-added austenitic stainless steels, which should be attributed to the presence of N-Cr SRO, as reported previously in the literature. These results indicate that the planar slips are primarily caused by N-Cr SRO rather than by SFE.