Фазовая диаграмма системы Al-Co

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Al-Co (Aluminum-Cobalt) A.J. McAlister The equilibrium phases of the Al-Co system are (1) the (Al) solid solution, based on fcc Al; (2) the (aCo) solid solution, based on fcc paramagnetic aCo; magnetostriction produces a slight tetragonal distortion of the fcc lattice in the ferromagnetic state; (3) the (eCo) solid solution, based on cph eCo, stable below ~422 C; (4) Al9Co2, monoclinic with nil solubility range, formed peritectically from the melt and Al13Co4 at ~970 C; (5) Al13Co4, C-centered monoclinic with nil solubility range, formed peritectically from the melt and Al3Co at ~1093 C; (6) Al3Co, of undetermined structure and nil solubility range, formed peritectically from the melt and Al5Co2 at ~1135 C; (7) Al5Co2, hexagonal, with a solubility range of ~1 at.%, formed peritectically from melt and AlCo at ~1180 C; and (8) AlCo, with the CsCl structure, formed congruently from the melt at ~50 at.% Co, near 1640 C, with solid solubility extending from ~46 to ~78 at.% Co. In the assessed phase diagram, the temperature and liquid composition of the L = (Al) + Al9Co2 eutectic are from [32Fin]. The temperature and compositions of the L = AlCo + (aCo) eutectic are from [41Sch]. The composition and peritectic formation temperature of the phases Al9Co2, Al13Co4, Al3Co, and Al5Co2 are from [71Goe]. [32Fin] concluded that the solubility of Co in (Al) is less than 0.00090 at.% Co. No Al9Co2 particles could be optically detected in a sample containing 0. 00045 at.% Co. The maximum solubility of Al in (aCo) is ~16 at.% Al at ~1400 C [41Sch]. No solidus data appear to be available. In the absence of more reliable data, the provisional liquidus between 25 and 71 at.% Co has been drawn to agree with the data of [08Gwy], [33Koe], and [ 38Koe] as closely as possible, while joining smoothly with the data of [32Fin], [47Ray], [71Goe], and [41Sch]. The existence and structures of Al9Co2, Al13Co4, and Al5Co2 are well established. All but Al5Co2 appear to have negligible solubility ranges. Evidence for the existence of Al3Co is less extensive, but particularly on the basis of the [71Goe] study it is persuasive. It too has a negligible solubility range, and its structure is complex and as yet unknown. Although the existence and structure of AlCo has been confirmed many times, there is reason to distrust available data on its melting behavior. The phase remains ordered at stoichiometric composition to at least 1110 C [67Cli]. In an earlier study of the specific heat of near-stoichiometric AlCo samples variously heat treated in the range from 100 to 800 C, [59Tre] found a distinct peak at 740 C in all samples. This peak was tentatively attributed to disordering of the phase, but in the light of the [67Cli] result, it must be attributed to some other unknown effect. The Curie temperatures of (aCo) were obtained by magnetic saturation measurements as a function of temperature on both heating and cooling [38Koe, 41Sch]. These data are in good agreement in the single-phase (aCo) region. The saturation magnetizations of (aCo) and (eCo) are sufficiently different that measurement of this quantity has been used to study the a = e transformation [41Sch]. This transformation is extremely sluggish on both heating and cooling, and the true transformation temperatures cannot be determined. In the assessed diagram, the value of 300 C for the Curie temperature in the two-phase region is used [41Sch]. The low-temperature magnetic susceptibility of AlCo was studied by [73Wac], who found that for Co content less than 50 at.%, AlCo is paramagnetic. Above 50 at.% Co, it becomes ferromagnetic, with the Curie temperature increasing to about -153 C at 57.9 at.% Co. [63Luo] reported that by splat quenching metastable (aCo), solid solutions containing up to 17 at.% can be produced. [81Nik] reported observation of four multilayer martensitic phases (here labeled aI, aII, aIII, and aIV, containing about 126, 126, 84, and 48 close-packed {111} layers, respectively. The martensitic transformations occur when (aCo) single crystals containing 4 to 16 at.% Al are heat treated in the range 1100 to 1300 C, quenched, aged at 400 to 800 C, then cooled rapidly to 200 C. 08Gwy: A.G.C. Gwyer, Z. Anorg. Chem., 57, 113-153 (1908) in German. 30Ekm: W. Ekman, Z. Phys. Chem., B12, 57-78 (1930) in German. 32Fin: W.L. Fink and H.R. Freche, Trans. AIME, 99, 141-148 (1932). 32Koe: W. Koester, Arch. EisenhЃttenwes., 7, 263-264 (1933) in German. 38Koe: W. Koester, Z. Metallkd., 30, 281-286 (1938) in German. 41Sch: J. Schramm, Z. Metallkd. 33, 381-387 (1941). 47Ray: G.V. Raynor and P.C.L. Pfeil, J. Inst. Met., 73, 609-624 (1947). 50Dou: A.M.B. Douglas, Acta Crystallogr., 3, 19-24 (1950). 59Tre: Yu.D. Tretyakov and K.G. Khonyakov, Zh. Neorg. Khim., 4, 13-16 (1959) in Russian; TR: Russ. J. Inorg. Chem., 4, 5-6 (1959). 61New: J.B. Newkirk, P.J. Black, and A. Damjanovic, Acta Crystallogr., 14, 532- 533 (1961). 62Hud: R.C. Hudd and W.H. Taylor, Acta Crystallogr., 15, 441-442 (1962). 63Coo: M.J. Cooper, Philos. Mag., 89, 805-810 (1963). 63Luo: H.L. Luo, Can. J. Phys., 41, 758-761 (1963). 67Cli: H.E. Cline, Trans. AIME, 239, 1906-1916 (1967). 71Goe: T. Goedecke, Z. Metallkd. 62, 842-843 (1971). 73Wac: E. Wachtel, V. Linse, and V. Gerold, J. Phys. Chem. Solids, 34, 1461- 1466 (1973). 81Nik: B.I. Nikolin and N.N. Shevchenko, Fiz. Met. Metalloved., 51(2), 316-325 (1981) in Russian; TR: Phys. Met. Metallogr., 51(2), 74-82 (1981). Published in Bull. Alloy Phase Diagrams, 10(6), Dec 1989. Complete evaluation contains 2 figures, 3 tables, and 27 references. Special Points of the Al-Co System