Фазовая диаграмма системы Al-V

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Al-V (Aluminum-Vanadium) J.L. Murray The Al-V intermetallic phases have all been structurally well characterized, but the equilibrium diagram has not yet been determined accurately. On the V- rich side, high melting temperatures make the liquidus and solidus difficult to determine and also make equilibrium difficult to achieve in the solid state. Interest in the possibility that "AlV3" may have good superconducting properties has led to numerous investigations around 75 at.% V, with conflicting results. On the Al-rich side, there is a cascade of sluggish peritectic reactions, and it is most likely that metastable reactions have been interpreted as stable ones, leading to conflicting phase diagrams. The assessed phase diagram was obtained by thermodynamic modeling of the experimental data of [40Rot], [55Car], [55Ell], [59Bai], [63Var], [81Ere], and [86Sch]. It differs in some qualitative features from previous assessments [ Hansen, Elliott], and critical experiments are needed to test the validity of the hypotheses on which the present diagram is based. The equilibrium phases are (1) fcc (Al) and bcc (V) solid solutions, the former with a very narrow homogeneity range (0 to 0.3 at.% V), the latter with a wide (~50 to 100 at.% V) range; (2) the Al-rich compounds, including complex cubic Al21V2 (also sometimes designated Al11V or Al10V in the literature), monoclinic Al45V7 (also designated Al7V), and hexagonal Al23V4 (also designated Al6V), and Al3V with the D022 structure; and (3) Al8V5 with the cubic g-brass structure, which is thought to have some range of homogeneity at high temperature. Based on lattice parameter data, the solubility of V in (Al) at 620 C is about 0.2 at.% [40Rot]. [63Var] used the maximum in paramagnetic susceptibility to estimate that the maximum solubility of V in (Al) is 0.3 at.% ; this value is consistent with that reported by [40Rot] and with thermodynamic properties. Numerous attempts have been made to synthesize an A15 compound AlV3 because of its potential as a superconducting material. [63Hol] and [71Kod] reported A15 structures formed by annealing at 1000 C in quartz tubes. [68Kor] tried to duplicate these results, but found that the only A15 compound present was V3Si. They concluded that annealing in quartz tubes caused contamination by Si and that only the bcc phase is stable in the binary alloy. [71Har] performed vacuum evaporation experiments at substrate temperatures of 350 to 450 C and found an A15 phase. With increasing Al content, bcc + A15 and bcc phases were formed. The A15 phase decomposed at some temperature between 600 and 700 C. This suggests that other attempts to synthesize AlV3 were unsuccessful because too high annealing temperatures were used. The solubility of V in (Al) can be extended metastably to 0.6 at.% by solidification at rates of 5 x 104 C/s [63Var]. The quasicrystalline icosahedral phase has also been found in a 9 at.% V alloy rapidly solidified by melt spinning [86Sch]. 40Rot: A. Roth, Z. Metallkd., 32, 356-359 (1940). 43Bra: G. Brauer, Z. Electrochem., 49, 208-210 (1943). 55Car: O.N. Carlson, D.J. Kenney, and H.A. Wilhelm, Trans. ASM, 47, 1-20, ( 1955). 55Ell: R.P. Elliott, Trans. ASM, 47, 538-540 (1955). 57Smi: J.F. Smith and A.E. Ray, Acta Crystallogr., 10, 169-172 (1957). 59Bai: D.M. Bailey, O.N. Carlson, and J.F. Smith, Trans. ASM, 51, 1097-1102 ( 1959). 59Bro: P.J. Brown, Acta Crystallogr., 12, 995-1002 (1959). 60Ray: A.E. Ray and J.F. Smith, Acta Crystallogr., 13, 876-884 (1960). 61Geb: E. Gebhardt and G. Joseph, Z. Metallkd., 310-317 (1961). 63Hol: H. Holleck, F. Benesovsky, and H. Nowotny, Monatsh. Chem., 94, 447-481 ( 1963). 63Var: N.I. Varich, L.M. Burov, K.Ye. Kolesnichenko, and A.P. Maksimenko, Fiz. Metal. Metalloved., 15(2), 292-295 (1963); TR: Phys. Metal. Metallogr., 15(2), 111-113 (1963). 68Kor: I.I. Kornilov and N.M. Matveeva, Dokl. Acad. Nauk SSSR, 179(4), 870-871 (1968); TR: Dokl. Chem. Proc. Acad. Sci. USSR, 298-299 (1968). 71Har: L.D. Hartsough and R.H. Hammond, Solid State Comm., 9, 885-889 (1971). 71Kod: B.N. Kodess, V.I. Surikov, V.L. Zagryazhskii, A.K. Shtol'ts, and P.V. Gel'd, Izv. Akad. Nauk SSSR, Neorg. Mater., 7(5), 853-854 (1971); TR: Russ. J. Inorg. Mater., 7(5), 746-747 (1971). 73Leg: J.M. Leger and H.T. Hall, J. Less-Common Met., 32, 181-187 (1973). 77Bha: K.K. Bhandary and K. Girgis, Acta Crystallogr., A33, 903-913 (1977). 77Bra: J.K. Brandon, W.B. Pearson, and P.W. Riley, Acta Crystallogr., B33, 1088-1095 (1977). 81Ere: V.N. Eremenko, Ya.V. Natanzon, and V.P. Titov, Russ. Metall., (5), 34- 37 (1981). 86Sch: R.J. Schaefer, National Institute of Standards and Technology, private communication (1986). Published in Phase Diagrams of Binary Vanadium Alloys, 1989, and Bull. Alloy Phase Diagrams, 10(4), Aug 1989. Complete evaluation contains 3 figures, 5 tables, and 28 references. Special Points of the Al-V System