Phase transformations in Fe-Cr-Mn alloys for magnetocaloric applications

The sequence of phase transformations in a Fe-Cr-Mn alloy (known as an austenitic stainless steel) are investigated in order to explore the potential of this rare earth-free material for magnetocaloric applications at high temperature. In the lack of high temperature X-ray diffraction the magnetic response and transition temperatures of alloys have been determined by using a Faraday's Balance apparatus and an extraction vector magnetometer. These characterizations have been complemented by DCS and DTA measurements as well as thermodynamic calculations using Thermocalc. The retained nominal composition is Fe0.59Cr0.16Mn0.25 (referred to as FeCrMn 15/25) shows the targeted reversible transformation. Carbon addition is shown to shift the transition temperature to lower values. The effect of carbon addition on the phase transition and on the magnetocaloric response is discussed. A comparison is made with the chromium-poor Fe-Cr-Ni system.