Coupling Binary and Ternary Information in Assessing the Fcc/Hcp Relative Phase Stability and Martensitic Transformation in Fe-Mn-Co and Fe-Mn-Si Alloys

This paper presents a study of the composition dependence of the fcchcp martensitic transformation temperatures and relative phase stability of these structures in Fe-Mn-Co and Fe-Mn-Si alloys. The approach combines new experimental determinations of M, and A, in the binary systems Fe-Mn and Fe-Co, and in both ternary systems with a critical analysis of the previously published experimental data, and thermodynamic calculations. It is shown how this combination of binary and ternary information with various methods of analysis can be used to establish the To-temperatures in the Fe-Mn-Co system and to refine the thermodynamic description of the metastable hcp structure of the Fe-Co system. The present methods also help to detect possible inconsistencies in the previously reported M, and As data for Fe-Mn-Si alloys, which is used as a basis for discussing the most recent calculation of M, temperatures in this system.