Thermodynamic calculation of phase diagrams in the iron‐nitrogen system

On the basis of recent measurements of the equilibria between N 2 and NH 3 containing gas atmospheres, respectively, and of the nitrogen solved in the α, γ and ε iron phases a thermodynamic analysis of the Fe—N system has been carried out. The Gibbs free energy of the γ, ε transformation of pure iron was derived. The composition Fe 4.3 N was calculated concerning the γ’ phase above 593°C. The phase boundaries were stated as temperature functions of the N 2 equilibrium pressures. The resulting phase diagram shows the stability regions of the α, γ, γ’ and ε phases and an α/γ/ε triple point which corresponds to that of the pure iron.