Фазовая диаграмма системы Mg-Tb

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Mg-Tb (Magnesium-Terbium) A.A. Nayeb-Hashemi and J.B. Clark The Mg-rich region of the assessed Mg-Tb phase diagram is based on [78Dri1] ( see also [78Dri2]). The Tb-rich region is based on [64Mil], and the rest of the diagram is based on interpolation from other Mg-RE systems and the results of [64Kri1], [64Kri2], [65Ian], [67Kri], and [73Spe]. The four intermetallic compounds (Mg24Tb5, Mg3Tb, Mg2Tb, and MgTb) reported in the above literature are consistent with the homologous Mg-RE studies. [78Dri1] indicated that the Mg-rich region of the Mg-Tb system is the eutectic type, (L = (Mg) + Mg24Tb5), with the eutectic point "near" 9.25 at.% (40 wt.%) Tb and 559 с 3 C. [78Rok] showed the eutectic composition as 9.6 at.% Tb. The latter value is more consistent with the rest of the (Mg) liquidus data and is used in the assessed diagram. For alloys of more than 12 at.% Tb, the liquidus and solidus need to be determined, except for the Mg-80 at.% Tb alloy, for which [64Mil] placed the liquidus at slightly below 1185 C. The maximum solid solubility of Tb in (Mg) was placed at 4.6 at.% Tb by [ 78Dri1]. The solid solubility of Mg in (aTb) has not been determined. However, from a plot of the maximum solid solubility of Mg in other RE elements against atomic number [65Jos], maximum solid solubility of Mg in (aTb) is expected to be ~14 at.% Mg (86 at.% Tb) at 695 с 5 C, the eutectoid temperature of the ( bTb) = MgTb + (aTb) reaction. [64Mil] showed the existence of "bcc (Tb)," with a wide range of solid solubility of Mg, from which an allotropic transformation in pure Tb was deduced. [73Spe] confirmed the existence of bcc Tb and placed the transition temperature of allotropic transformation of pure cph aTb to pure bcc bTb at 1289 C. [64Mil] showed that (bTb) decomposes by a eutectoid reaction [(bTb) = MgTb + ( aTb)] at 695 с 5 C. The (bTb) eutectoid composition was not determined. [64Mil] showed that MgTb forms by a peritectic reaction (L + (bTb) = MgTb) at 857 с 5 C. The mechanisms of the formation of Mg24Tb5, Mg3Tb, and Mg2Tb are unknown. However, based on interpolation from other Mg-RE systems, probably these compounds also form by peritectic reactions. [86For] and [86Man] found the Mg-rich compound in the Mg-Gd system to be Mg5Gd stoichiometry; [Gschneidner] indicated that possibly the Mg-rich compound in other Mg-heavy lanthanide systems would be of Mg5RE stoichiometry. [73Bus] and [76Bus] studied the magnetic properties of MgRE and Mg3RE compounds in the temperature range 4.2 to 300 K with magnetic fields of up to 18 kOe. The Curie temperatures (TC) for MgTb and Mg3Tb were found to be 81 and 108 K, respectively. [75Ale] investigated the magnetic properties and magnetic structure of MgTb by neutron diffraction. The magnetic structure was reported as non-colinear, with a ferromagnetic component. [75Ale] reported the TC of MgTb as 83 K, in good agreement with that reported by [73Bus] (see also [66Cha] and [79Bur]). [78Bus1] studied the magnetic properties of Mg2RE compounds in the temperature range 1.5 to 300 K and the magnetic field of up to 18 kOe. According to [ 78Bus1], most of the Mg2RE compounds order ferromagnetically at temperatures " well below 100 K," except for Mg2La, Mg2Yb, and Mg2Y, which show Pauli paramagnetism; Mg2Sm and Mg2Eu order antiferromagnetically. The TC of Mg2Tb was found to be 88 K (see also [78Bus2]). 64Kri1: P.I. Kripyakevich, V.I. Evdokimenko, and E.I. Gladyshevskii, Kristallografiya, 9(3), 410-411 (1964) in Russian; TR: Sov. Phys. Crystallogr., 9(3), 330-331 (1964). 64Kri2: P.I. Kripyakevich and V.I. Evdokimenko, Problems of the Theory and Application of Rare Earth Metals, E. Savitskii and V.F. Terekhova, Ed., Nauka, Moscow, 191-194 (1964). 64Kri3: P.I. Kripyakevich, V.I. Evdokimenko, and I.I. Zalutzkii, Dop. Akad. Nauk Ukr. RSR, (6), 766-769 (1964) in Russian. 64Mil: A.E. Miller and A.H. Daane, Trans. AIME, 230, 568-572 (1964). 65Ian: A. Iandelli and A. Palenzona, J. Less-Common Met., 9, 1-6 (1965). 65Jos: R.R. Joseph and K.A. Gschneidner, Jr., Trans. AIME, 223, 2063-2069 ( 1965). 66Cha: C.C. Chao and P. Duwez, J. Appl. Phys., 37(7), 2631-2632 (1966). 67Kri: P.I. Kripyakevich and V.I. Evdokimenko, Z. Anorg. Allg. Chem., 355, 104- 112 (1967) in German. 73Bus: K.H.J. Buschow, J. Less-Common Met., 33, 239-244 (1973). 73Spe: F.H. Spedding, B. Sanden, and B.J. Beaudry, J. Less-Common Met., 31, 1- 13 (1973). 75Ale: R. Aleonard, P. Morin, J. Pierre, and D. Schmitt, Solid State Commun., 17, 599-603 (1975). 76Bus: K.H.J. Buschow, J. Less-Common Met., 44, 301-306 (1976). 78Bus1: K.H.J. Buschow, R.C. Sherwood, and F.S.L. Hsu, J. Appl. Phys., 49(3), 1510-1512 (1978). 78Bus2: K.H.J. Buschow, G. Will, and M.O. Bargouth, J. Phys. C, Solid State Phys., 11, 2405-2413 (1978). 78Dri1: M.E. Drits, L.L. Rokhlin, E.M. Padezhnova, and L.S. Guzei, Metallov, ( 9), 70-73 (1978) in Russian; TR: Russ. Metall., (9), 771-774 (1978). 78Dri2: M.E. Drits and L.L. Rokhlin, Engineering and Creep-Resistant Materials for the New Technology, Nauka, Moscow, 78-91 (1978) in Russian. 78Rok: L.L. Rokhlin, Probl. Metalloved. Tsvetn. Splavov, N.M. Zhavoronkov, Ed., Izd. Nauka, Moscow, 59-70 (1978) in Russian. 79Bur: P. Burgardt, S. Legvold, B.J. Beaudry, and B.N. Harmon, Phys. Rev. B, 20(9), 3787-3791 (1979). 85Gsc: K.A. Gschneidner, Jr., private communication, Ames Laboratory, Iowa State University, Ames, IA (1985). 86For: M.L. Fornasini, P. Manfrinetti, and K.A. Gschneidner, Jr., Acta Crystallogr., C42, 138-141 (1986). 86Man: P. Manfrinetti and K.A. Gschneidner, Jr., J. Less-Common Met., 123, 267- 275 (1986). Published in Phase Diagrams of Binary Magnesium Alloys, 1988. Complete evaluation contains 1 figure, 4 tables, and 25 references. Special Points of the Mg-Tb System