3570. VOGEL, R., AND DÖRING, W. [Iron-Cementite-Manganese Carbide-Manganese.] Arch. Eisenhüttenw., vol. 9, 1935, pp. 247-252; Chem. Abs., vol. 30, 1936, p. 710. Former investigations of this system and parts of it were enlarged and completed by establishing the constitutional diagrams on the basis of heats of reaction and structure. Mn and Mn3C do not form, as indicated previously, an uninterrupted series of solid solutions with a maximum temperature, a transition equilibrium occurs at solidification between 1.5 and 2.9% C, which leads toward higher C contents, to a minimum temperature. A new transformation of Mn carbide was observed at 1,050°. Four kinds of crystals were found in the system Fe-Fe3C-Mn3C-Mn: Ternary solid solutions of a(δ)-Fe with C and Mn, which are restricted to a small range in the Fe-corner; ternary solid solutions of γ-Fe with C and Mn with a very extended range; ternary solid solutions of γ-Fe with C and Mn with a very extended range; ternary solid solutions of γ-Mn with C and Fe (area +β4v3); and solutions Fe3C and Mn3C (area C β4v3v1). The cementite does not form solid solutions with the excess Fe but the Mn3C does with excess Mn. The conditions are explained in detail by the diagram. A table shows the location of the characteristic points a, β, γ, δ, and ε for the equilibria of the Fe-Mn-C alloys in solid state. Various structures illustrated in photomicrographs. |