Фазовая диаграмма системы Ce-V

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Ce-V (Cerium-Vanadium) J.F. Smith and K.J. Lee The assessed phase diagram for the Ce-V system is a calculated diagram incorporating all of the reactions reported by [67Efi], but with the temperatures of the elemental transitions changed to current values. There are also minor differences in the temperatures and compositions associated with the invariant reactions. The number of experimental investigations of the Ce-V system is limited. The investigation of [62Sav] for the range 0 to 50 at.% Ce corroborated other reports including the absence of intermediate phases, the occurrence of a monotectic reaction at a temperature in close proximity to the melting temperature of V, and limited solubility of Ce in both liquid and solid V. Indeed, [62Sav] reported the solubility of Ce in solid (V) did not exceed 0.04 at.% at any temperature, with the solubility of Ce in liquid V at the monotectic reaction being 0.07 to 0.11 at.%. Unfortunately, the V used in the investigation was reported as only 99.77 wt.% pure and the Ce 98.8 wt.% pure. Because the impurities are most likely to be of lower atomic weight, the purities of the two components in at.% are likely to be much lower. Because the melting point of V was found near 1885 с 15 C, which is nearly 25 C below the currently accepted value of 1910 C, there is little doubt that a significant concentration of impurities was present in the V. The observation by [62Sav] that the melting point of V and the monotectic reaction were at essentially the same temperature, plus the observation that the lattice parameter of V was not measurably changed by Ce additions does, however, indicate very low solubility of Ce in both liquid and solid V. [62Sav] found transitions in the two-phase field at 705 с 5 C and 810 с 5 C; these are respectively 21 C below the currently accepted value [Gschneidner] for the fcc = bcc transition of Ce and 12 C above the currently accepted value [Gschneidner] for the melting of Ce. The first value implies a eutectoidal depression of the fcc = bcc transition, and the second implies a peritectic elevation of the melting of Ce. These are comparatively large shifts and may be due in part to impurities, but these shifts do indicate some solubility of V in Ce. No attempt was made to calculate the effect of V on the dcph = fcc transition of Ce, because any effect should be quite small in analogy with the negligible effect calculated for the fcc = bcc transition. Although the temperature scale in the assessed diagram does not extend to low enough temperatures to show the transformation, it is anticipated that the dcph = fcc transition temperature of 61 C for pure Ce [Gschneidner] would be negligibly affected by alloying with V. Transformations that occur in Ce below room temperature have not been considered in the present assessment. Studies of ternary equilibria in the Ce- V-Al [74Zar] and the Ce-V-N [73Bar] systems showed concurrence with the binary studies with regard to extensive immiscibility in solid Ce-V alloys, but the ternary studies added no additional detail. 62Sav: E.M. Savitskii, V.V. Baron, and Yu.V. Efimov, Zh. Neorg. Khim., 7(3), 701-703 (1962); TR: Russ. J. Inorg. Chem., (3), 359-360 (1962). 67Efi: Yu.V. Efimov, Izv. Akad. Nauk SSSR, Met., (6), 163-167 (1967); TR: Russ. Metall., (6), 86-89 (1967). 73Bar: O.M. Barabash, A.K. Shurin, and Yu.E. Yakovchuk, Izv. Akad. Nauk SSSR, Met., (1), 212-215 (1973); TR: Russ. Metall., (1) 154-158 (1973). 74Zar: O.S. Zarechnyuk and R.M. Rikhal, Visn. L'visk. Derzh. Univ., Ser. Khim., (16), 5-8 (1974) in Russian. Published in Phase Diagrams of Binary Vanadium Alloys, 1989, and Bull. Alloy Phase Diagrams, 8(6), Dec 1987. Complete evaluation contains 1 figure, 2 tables, and 21 references. Special Points of the Ce-V System