Thermodynamical Phase Equilibrium of Iron Nitrides at Low Temperatures

The presence of α-Fe(N), γ'-Fe₄N, and ε-Fe₄N_1-x phases and the phase equilibrium between α-Fe(N) and γ'-Fe₄N, and γ'-Fe₄N and ε-Fe₄N_1-x have been studied at the low temperatures below 350°C, according to the binary Fe-N phase diagram calculated using the sublattice-compound energy model. The α-Fe(N), γ'-Fe₄N, and ε-Fe₄N_1-x phases would be thermodynamically stable at the low temperatures. Thermodynamic phase equilibrium of the iron nitrides is supported by the experimental results, explaining the phase formation and its stability in the Fe-N system at low temperatures.