The Application of a first-order Quasichemical theory to Transformations in Steels

H. K. D. H. Bhadeshia

Abstract

A quasichemical thermodynamic model for interstitial solutions is used to show that the carbon-carbon interaction energy in ferrite is large and positive, indicative of repulsion between neighbouring carbon atoms.

The provided documents examine the application of first-order quasichemical theory to understand how carbon behaves within the different phases of steel. By utilising a mathematical model that accounts for the interaction energy between neighboring atoms, the author attempts to predict the thermodynamic properties of carbon in both ferrite and austenite. A key focus of the research involves correcting previous errors regarding the number of available interstitial sites in the iron lattice to ensure the model aligns with experimental data. Through detailed calculations of activity and free energy, the work demonstrates that carbon atoms experience a repulsive force that prevents them from occupying adjacent sites. Ultimately, these findings help clarify the phase boundaries and transformation behaviors essential for accurately modeling metallurgical processes.

Metal Science, Vol. 16, 1982, pp. 167-169.

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