Фазовая диаграмма системы C-La

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C-La (Carbon-Lanthanum) K.A. Gschneidner, Jr. and F.W. Calderwood The assessed phase diagram for the La-C system is based primarily on the work of [59Spe]. They reported that the solubility of C in (La) lies between 1.6 to 3.4 at.% at 775 C and slightly below 1.6 at.% at 695 C. C has no effect on the a = b transformation of La, which occurs at 310 C on heating and 260 C on cooling. A eutectic occurs between (La) and La2C3 at 806 с 2 C at a composition of 20. 6 at.% C. The maximum solubility of C in (La) at the eutectic temperature is 3. 4 с 0.6 at.% C. An addition of C raises the b = g transformation temperature of La from 865 to 875 C. The solid solubility range of La2C3 at room temperature extends from 56.2 to 60.2 at.% C. The C content at the (La)-La2C3 phase boundary varies from 54 с 2. 5 at.% at 800 C to 57.1 с 5 at.% at 1000 C. La2C3 forms peritectically at 1415 с 3 C on cooling from the melt and LaC2. The melting point of LaC2 is 2360 с 25 C. This compound is dimorphic, with a tetragonal CaC2-type structure at room temperature. The LaC2 polymorphic transformation temperature is 1060 C [67Kir]. A eutectic occurs between LaC2 and (C) at 2250 C and an undetermined composition. [59Spe] found that aLaC2 contains less than the stoichiometric amount of C at room temperature, but reaches the stoichiometric dicarbide composition at higher temperature. At room temperature, the lattice spacing of alloys around the LaC2 composition varies slightly with C content, indicating a solid solubility range of ~3 at.%. Microscopic examination of a 64.4 at.% specimen revealed a single-phase structure at 1385 с 25 C, from which La2C3 precipitated during furnace quenching at room temperature. A 62.5 at.% sample that was quenched from 1400 с 25 C consisted of two phases, but on slow cooling the amount of the La2C3 phase increased at the expense of the LaC2 phase. 59Spe: F.H. Spedding, K.A. Gschneidner, Jr., and A.H. Daane, Trans. AIME, 125, 192 (1959). 67Kri: N.H. Krikorian, T.C. Wallace, and M.G. Bowman, in Propri‚ti‚s Thermodynamiques Physiques et Structurales des D‚riv‚ Semi-Metalliques, Centre National Recherche Scientifique, Paris, 489 (1967). Published in Bull. Alloy Phase Diagrams, 7(5), Oct 1986. Complete evaluation contains 1 figure, 1 table, and 55 references. 1