AN ASSESSMENT OF THE FE-C-SI SYSTEM

Precise knowledge of the Fe-C-Si system has been the subject of numerous previous studies because of the importance of this system for steelmaking processes and cast iron foundry. However, the most recent articles on this subject still reveal uncertainties or insufficient information. The purpose of this work was to assess this system and to give it a precise description, but one which was simple enough for practical applications. An evaluation of the parameters describing the thermodynamic properties of the phases involved in the binary Fe-Si system has been achieved, mainly based on values of the silicon activity in the body-centered cubic (bcc) phase and on knowledge of the phase diagram. The A2-B2 ordering reaction of the bcc phase has been included. It has been shown that this reaction is of paramount importance for the description of the thermodynamic properties of this phase and its field of stability. This preliminary work and previous similar studies of the Fe-C and Si-C systems were used as a base for the evaluation of the ternary stable and metastable Fe-C-Si systems. Optimization of the parameters describing the properties of the phases involved in both of these systems was achieved using experimental thermodynamic data and the critical assessment of the phase diagrams.