Effect of Rolling Temperature on Martensitic Transformation and Strain Hardening of Fe–21.2Mn–0.68C Steel

In this work, the temperature dependence of the stacking fault energy (SFE) of Fe–21.2Mn–0.68C steel was calculated using the thermodynamic model. The obtained dependence showed a decrease in the SFE with temperature and a saturation below the austenite Néel temperature. To demonstrate the effect of the SFE on the deformation-induced martensite transformations and strain hardening of Fe–21.2Mn–0.68C steel, the rolling was performed at different temperatures: close to the liquid nitrogen temperature, at room temperature, and at 473 K. The microstructure studies using electron backscatter diffraction, transmission electron microscopy, X-ray diffraction, and magnetization measurements revealed ε-martensite and a small amount of α′-martensite in samples rolled at two lower temperatures that correlated with their strain-hardening behavior. The calculated values of the SFE for these rolling temperatures were equal to 2 and 14 mJ/m², respectively, confirming the plasticity mechanism’s dependence on the SFE.