Martensite transformation behavior and mechanical properties of cold-rolled metastable Cr-Mn-Ni-N austenitic stainless steels

In order to understand the mechanism of substitution for nickel with manganese in metastable austenitic stainless steels 14Cr10Mn and 16Cr6Mn, the transformation behavior of ε- and α′- martensite and the corresponding mechanical properties were investigated in this study. The microstructures and tensile and hardness properties of the cold-rolled steels under different rolling reductions at ambient temperature were measured using X-ray diffraction (XRD), scanning electron microscope (SEM) together with an electron back scatter diffraction (EBSD) and transmission electron microscope (TEM). The results show that α′- martensite is not easy to be transformed from austenite, and the martensite transformation γ → ε → α′ in 14Cr10Mn and 16Cr6Mn metastable stainless steels is found during cold rolling. The results also reveal that ε- martensite acts as an hardness reinforcing phase, and high total martensite volume fraction and ratio of ε- and α′- martensite content are helpful to achieve higher tensile strength with sigmoidal shape stress-strain curves. In addition, a model considering cold rolling reduction was developed to predict the contents of ε- and α′- martensite in the steels.