Reversible Characteristics and Cycling Effects of the ε ↔ γ Martensitic Transformations in Fe-Mn-Cr Twip/TRIP Steels

The hcp  ε ↔ fcc γ martensitic transformation is the base of the TWinning Induced Plasticity (TWIP effect) in FeM steels. In some aspects this transformation is similar to the thermoealstic martensitic transformations of the shape memory alloys, whereas it differs in other aspects. The aims of the present work are to examine the similarities between the ε ↔ γ transformations compared to the thermoelastic martensitic transformations and the effect of chromium content on the investigated transformations. The reversibility and the thermal cycling effects on the transformation temperatures of the ε ↔ γ transformations were examined using Differential Scanning Calorimetry (DSC) and dilatometric measurements, the microstructural changes during the thermally induced ε ↔ γ transformations were examined using in situ optical microscopy with Differential Interference Contrast (DIC) imaging.