Фазовая диаграмма системы B-Mo

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B-Mo (Boron-Molybdenum) K.E. Spear and P.K. Liao The assessed phase diagram for the Mo-B system is taken from [Molybdenum], who used experimental data from [65Rud] and [77Sto], with supporting information from [67Por]. The equilibrium solid phase of the Mo-B system are (1) the terminal solid solutions of bcc (Mo) metal and rhombohedral (bB) and (2) the intermediate compounds Mo2B, aMoB, bMoB, MoB2, Mo2B5, and MoB4 (Mo1-xB3). It is extremely doubtful that the phase reported as Mo3B2 [53Gil] exists as a thermodynamically stable binary compound. The compositions of the three B-rich solid phases vary considerably from those indicated by their respective ideal chemical formulas. The composition data for the liquid phases involved in peritectic reactions are not well established. A ternary phase (Mo2BC) is produced when Mo2B reacts in the presence of excess carbon [63Rud]. MoB, MoB2, and Mo2B5 are stable in the presence of carbon, but not Mo2B or MoBn (MoB4) [62Rud]. B is only slightly soluble in (Mo). [Molybdenum] chose a value of 0.8 с 0.4 at. % B as a reasonable value to assume for the solubility of B in solid (Mo) at the 2175 C equilibrium temperature of the eutectic reaction [65Rud]. The solubility of Mo in (bB) has not been established. The data of [65Rud] clearly illustrate the lack of accurate data for the liquidus curves of bMoB and the resulting peritectic liquid compositions. Thermochemical optimization [81Spe] yielded peritectic liquid compositions that were consistent with the available thermody-namic and phase diagram data, as well as being well within the uncertainty limits of the experimental values. The B-rich eutectic liquid compositions of 94 с 4 at.% B are much less reliable, leading to the conclusion that the reported 94 at.% B is probably an upper limit on the B content of the eutectic liquid in equilibrium with (bB) and Mo2B5. A value of 90 с 5 at.% B may be a more realistic composition, which would include the value of 88 at.% B obtained by the thermochemical opti- mization process reported by [81Spe]. 47Kie: R. Kiessling, Acta Chem. Scand., 1, 893-916 (1947). 50Kie: R. Kiessling, Acta Chem. Scand., 4, 209-227 (1950). 52Ste: R. Steinitz, I. Binder, and D. Moskowitz, J. Met., 4, 983-987 (1952). 53Gil: P.W. Gilles and B.D. Pollock, J. Met., 5, 1537-1539 (1953). 63Rud: E. Rudy, F. Benesovsky, and L. Toth, Z. Metallkd., 54(6), 345-353 (1963) . 65Rud: E. Rudy and St. Windisch, AFML-TR-65-2, Air Force Materials Lab, Wright- Patterson Air Force Base, Ohio (1965). 67Por: K.I. Portnoi, Y.V. Levinski, V.M. Romashov, O.A. Mordovin, and M.K. Levinskaya, Izv. Akad. Nauk SSSR, Met., (4), 171-176 (1967) in Russian; TR: Russ. Metall., (4) 92-94 (1967). 68Gal: F. Galasso and J. Pinto, Trans. AIME, 242, 754-755 (1968). 73Lun: T. Lundstrom and I. Rosenberg, J. Solid State Chem., 6, 299-305 (1973). 77Cal: B. Callmer, Acta Crystallogr. B, 33, 1951-1954 (1977). 77Sto: E. Storms and B. Mueller, J. Phys. Chem., 81, 318-324 (1977). 81Spe: K.E. Spear and M.S. Wang, Calphad, 5(2), 109-113 (1981). Published in Bull. Alloy Phase Diagrams, 9(4), Aug 1988. Complete evaluation contains 3 figures, 6 tables, and 31 references. Special Points of the Mo-B System