Experimental evidence and thermodynamics analysis of high magnetic field effects on the austenite to ferrite transformation temperature in Fe–C–Mn alloys

The non-isothermal decomposition of austenite into ferrite and pearlite in Fe–xC–1.5 wt.% Mn steels with x = 0.1, 0.2 and 0.3 wt.% C is investigated by in situ dilatometry and microstructure characterization in magnetic fields up to 16 T. The global shift towards higher temperatures of the respective austenite, ferrite + austenite and ferrite + pearlite stability regions is experimentally quantified. A systematic increase in the ferrite area fraction and proportional reduction of the Vickers hardness values with the magnetic field intensity are also reported. Moreover, the steels’ magnetizations, measured up to 3.5 T and 1100 K, are used to calculate the magnetic contribution to the free energy of the transformation and to account thermodynamically for the field dependence of the transformation temperature. The impact of magnetic field is found to be greater with increasing carbon content in the steels.