Фазовая диаграмма системы La-V

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La-V (Lanthanum-Vanadium) J.F. Smith and K.J. Lee Only the general form of the La-V diagram is well defined. Details such as the invariant reaction temperatures and terminal solubilities are highly questionable because the published diagrams are based on work with component elements of questionable purity. On this basis, a calculation of the phase diagram was undertaken. In calculating the diagram, no attempt was made to consider the effect of V on the dcph = fcc transition that is known to occur at 310 C in pure La [Gschneidner]. In support of the calculated diagram, the calculated value for the maximum terminal solubility of 99.97 at.% V (0.03 at.% La) at the monotectic temperature is in close accord with the report [64Obr] of 0.04 at.% La as the upper limit of the La content before the appearance of a second phase in solidified alloys. Also in support of the calculated diagram is the van't Hoff compatibility of the 7 C melting depression with the 99.56 at.% V composition of the monotectic liquid and the 99.97 at.% V composition of the V terminal solution at the monotectic temperature. The calculated 0.7 C peritectic elevation of the melting of La by V addition is considerably less than that reported by [60Sav] and differs from the rest of the rare earth-vanadium series in being peritectic rather than eutectic. However, if the temperature difference between the rare earth melting temperature and the calculated invariant reaction temperature is plotted, with appropriate sign, against the atomic number of the rare earth, the trend extrapolates to a very small value for La with either a positive or negative sign being acceptable. The calculations indicate that V additions to La result in a eutectoidal decrease of 0.5 C in the bcc g = fcc b transformation with the compositions of the bcc eutectoid and the fcc terminal solution very close to each other near 0.1 at.% V. Decrease in temperature below the eutectoid results in decreasing terminal solubility of V in fcc La to below at. ppm level at the temperature of the fcc b = dcph a transformation whose temperature is insignificantly affected by this low concentration. 60Sav: E.M. Savitskii, V.V. Baron, and Yu.V. Efimov, Trudy Inst. Met. im A.A. Baikova, Akad. Nauk SSSR, (5), 166-173 (1960) in Russian. 61Gsc: K.A. Gschneidner, Jr., Rare Earth Alloys, D. Van Nostrand Co., Inc., New York, 331-332 (1961). 64Obr: W.L. O'Brien and E.A. Rowe, U.S. Bur. Mines Rep. 6553, 18 p (1964). 66Gib: J.A. Gibson and G.S. Harvey, U.S. Govt. Report AFML-TR-65-430, 48 (1966) . 67Efi: Yu.V. Efimov, Izv. Akad. Nauk SSSR, Met., (6), 163-167 (1967); TR: Russ. Metall., (6), 88-89 (1967). 70Kau: L. Kaufman and H. Bernstein, Computer Calculation of Phase Diagrams, Academic Press, New York, 184 (1970). 81Smi: J.F. Smith, Bull. Alloy Phase Diagrams, 2(1), 40-41 and 2(2), 172 (1981) . 83Cha: M.W. Chase, Bull. Alloy Phase Diagrams, 4(1), 124 (1983). Published in Phase Diagrams of Binary Vanadium Alloys, 1989. Complete evaluation contains 1 figure, 2 tables, and 16 references. Special Points of the La-V System