Abstract
The thermodynamical functions (free energy, chemical potential and activity, etc) of the interstitial solid solutions were derived by the statistical thermodynamical methods. By comparing these functions with the experiment,mainly with the R.P.Smith’s activity data of carbon in γ- and α-iron,energy constants and the special characters of Fe-C interstitial solid solution were investigated.As the α-γ metastable equilibrium under A1 transformation point is important in the theory of heat treatment of carbon steel,these metastable equilibrium lines were calculated by using above functions and the physical constants.The result is as follows ; G P A line(solubility line of carbon in α-iron,) increases with temperature lowering,and has a tendency of conciding with Ar″ line.(Fig. 6).
