Abstract. Metastable Fe-Mn alloys exhibit a non-thermoelastic martensitic transformation which is accompanied by a significant thermal effect (ca. 20 J/g). Among Fe-Mn alloys, the highest value of latent heat was registered in alloys with 17-18 wt. % Mn. In this work we investigate effects of carbon (up to 0.4 wt. %) and cold rolling (5-25% of thickness reduction) on the latent heat and the temperature hysteresis of the martensitic transformation. Changes in chemical and phase composition are analyzed based on the goal of enthalpy maximizing transitions are registered using differential scanning calorimetry and dilatometry. The phase composition is determined by means of X-ray diffraction. An effect of thermocycling is considered in connection with microstructural and enthalpy changes.

Fe-(17∼25)Mn alloys have been systematically investigated by means of X-ray diffraction, optical microscopy, differential scanning calorimetry and dilatometry. Such parameters of martensitic transformation as transformation temperatures, enthalpy, phase composition and microstructural changes are discussed taking into account the effect of thermocycling. A special focus is laid on the incompleteness of the γ → ∊ transformation that is attributed mainly to the antiferromagnetic → paramagnetic transition of austenite. The volume fraction of epsilon martensite has been determined using the results from X-ray diffraction and dilatometry tests.