1965. KÖRBER, F., AND OELSEN, W. [Thermodynamic Considerations on Some of the Equilibrium Curves in the Iron-Carbon Condition Diagram.] Arch. Eisenhüttenw., vol. 5, 1932, pp. 569-578; Chem. Abs., vol. 26, 1932, p. 5483.

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Literature Abstracts

Because of the uncertainty existing, the shape and coordinates of the saturation lines of γ-mixed crystals in a- and β-Fe (GOS) AND IN CEMENTITE (SE) were calculated thermodynamically from the heat-content curves of pure Fe given in the literature. The calculated GOS-line is convex to the concentration axis and the SE-line is straight, in agreement with numerous experimental results. Similar calculations, with the heat of fusion of γ-Fe for the beginning (BC) and the end (JE) of the separation of γ-mixed crystals from the melt, show that the JE-line is straight. They also show that in the melt, C is dissolved principally as Fe₃C molecules, and to a smaller extent as C atoms. On the basis of JE- and BC-lines, no definite statement can be made as to the molecular form of C in the γ-mixed crystals. The heat of solution of 1 gm. Fe₃C in γ-mixed crystals is –30.2 cal., the heat of transformation at 731° of 1 gm. of pearlite 20.5 cal., and the heat of formation of cementite –5 to –7 kcal. per mol. Bibliography.