The influence of Cr and N additions on the mechanical properties of FeMnC steels

The influence of Cr and N additions on the mechanical properties of austenitic Fe-Mn-Cr-C-N alloys was studied. The ductility and the strain-hardening behavior were investigated in detail, because these alloys may potentially be used for crash-relevant automotive body parts. It was found that Cr and low N additions to a Fe-18Mn-0.25C alloy resulted in a higher ductility and a reduced strain hardening. Increasing the N content up to 0.22 mass pct resulted in a further increase of ductility and a more favorable strain-hardening behavior. X-ray diffraction and transmission electron microscopy studies revealed that the strain-hardening behavior was linked to the presence of strain-induced martensite and mechanical twinning. The analysis of the mechanical properties and the microstructure clearly demonstrates that, in the Fe-Mn-Cr-C-N system, both N additions and combined N and Cr additions increase the stacking fault energy.