Abstract
The phase and chemical equilibria in the Fe – Si system at 298 K were considered. The comparison between the available thermodynamic information on the solid solubility of silicon in bcc-iron at low temperatures was performed with and without consideration of the α-phase long distance ordering. The standard Gibbs energy of formation for non-stoichiometric iron silicide was estimated. The possible maximum solid solubility of Si in bcc-Fe at 298 K was estimated. The thermodynamic activities of the components in this saturated solution were calculated. The state diagram of the Fe – Si – O system at 298 K was plotted and the characteristics of their invariant conditions were calculated. The solid solubility of Fe2SiO4 in Fe3O4 and of SiO2 in Fe2O3 at 298 K was estimated. The activity – pH diagrams for the aqueous Fe (II) and Fe (III) species were constructed. The potential – pH diagram of the Fe – Si – H2O system at 298 K, air pressure of 1 bar and activities of ions in solution, equal to 1 mol l–1 was plotted. Basic chemical and electrochemical equilibria in this system were considered. The thermodynamic analysis of chemical and electrochemical stability of the Fe – Si system alloys was performed.