Enthalpy change of the hcp/fcc martensitic transformation in the Fe-Mn and Fe-Mn-Si systems

An evaluation of enthalpy change of the hcp/fcc transformation in Fe-Mn and Fe-Mn-Si alloys, in the composition ranges from 0 to 12 at.% and from 17 to 32 at.% of Si and Mn, respectively, is performed. The calculation is based on a phenomenological description of the energy of Gibbs of the fcc- and hcp-phases and on the Redlich-Kister model. This result is compared with a systematic determination of the enthalpy change of transformation obtained by combining Differential Scanning Calorimetry experiments and the hcp-phase relative fractions extracted from Mössbauer spectroscopy, dilatometry and neutron diffraction measurements. The present calculation reproduces well the experimental data, reinforcing the validity of the previous thermodynamic description of the Gibbs energy of hcp- and fcc-phases.