Фазовая диаграмма системы V-Yb

К оглавлению: Другие диаграммы (Others phase diargams)

V-Yb (Vanadium-Ytterbium) J.F. Smith and K.J. Lee Except for a cursory note in [Elliott] indicating liquid immiscibility in V- rich V-Yb alloys, experimental data pertinent to the phase relationships in the V-Yb system are lacking. However, theoretical considerations [76Mie1, 76Mie2, 79Deb, 81Mie, 83Nie] allow calculations to be made for approximation of the phase diagram. Calculations were based on a subregular-solution model for liquid, bcc, and fcc phases and an ideal gas model for the vapor phase. Eu and Yb are atypical when compared with the rest of the lanthanide elements, because their outer electron configurations can change with ligand environment. In Yb, this change is from a 4f146s2 divalent configuration to a 4f135d16s2 trivalent configuration at an energy cost of 41 kJ/mol [83Nie]. The estimated value of this energy cost has varied slightly from one evaluation to another [ 69Gsc, 76Mie1, 76Mie2, 79Deb, 81Mie, 83Nie], but the most recent value is that given above, and it has been used for the present calculations of the phase diagram. Data for the melting of V were taken from [81Smi], for the hypothetical fcc to bcc transition in V from [70Kau], for the temperatures of transition and melting of Yb from [Gschneidner], for the enthalpies of transition and melting of Yb from [83Cha], and for the enthalpy and temperature of boiling of Yb from [Gschneidner]. These data were combined with estimates of the interaction parameters derived with the Miedema model. The assessed (calculated) diagram shows that there is no significant solubility of Yb in V nor of V in Yb at ambient pressure. However, under pressure, sufficient Yb dissolves in liquid V to produce a 2 C depression in the melting point of V to result in a monotectic reaction with liquid containing 0.3 at.% Yb decomposing to (V) containing 0.2 at.% Yb and liquid containing 99.9 at.% Yb. 69Gsc: K.A. Gschneidner, Jr., J. Less-Common Met., 17, 13-24 (1969). 70Kau: L. Kaufman and H. Bernstein, Computer Calculation of Phase Diagrams, Academic Press, New York, 184 (1970). 76Mie1: A.R. Miedema, J. Less-Common Met., 46, 167-173 (1976). 76Mie2: A.R. Miedema, Philips Tech. Rev., 36, 217-232 (1976). 79Deb: F.R. DeBoer, W.H. Dijkman, W.C.M. Mattens, and A.R. Miedema, J. Less- Common Met., 64, 241-253 (1979). 81Mie: A.R. Miedema, F.R. DeBoer, and R. Boom, Physica B, 103, 67-81 (1981). 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). 83Nie: A.K. Niessen, F.R. DeBoer, R. Boom, P.F. DeChatel, W.C.M. Mattens, and A.R. Miedema, Calphad, 7, 51-70 (1983). Published in Phase Diagrams of Binary Vanadium Alloys, 1989. Complete evaluation contains 2 figures, 1 table, and 10 references. 1