Theoretical Analysis of Binary Fe-N Phase Diagrams at Low Temperatures

The binary Fe-N phase diagrams at the low temperatures were calculated by using a two-sublattice version of the Compound Energy Model (CEM). The phase equilibrium of α-Fe(N) and 7'-Fe4N, and 7'-Fe4N and e-Fe2N1-x was respectively obtained in the temperature range of 25-350℃. Theα-Fe(N), γ'-Fe4N, and e-Fe2N1-x phases are thermodynamically stable at the low temperatures. The calculated binary Fe-N phase diagram by using the Guillermet and Du's parameters describing the thermodynamic properties of Fe-N phases was confirmed from the available experimental data at the low temperatures.