Фазовая диаграмма системы Cu-Mg

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Cu-Mg (Copper-Magnesium) A.A. Nayeb-Hashemi and J.B. Clark The assessed Mg-Cu phase diagram is based primarily on the work of [31Jon] and [34Sed], with modifications from [78Bag]. There are three eutectics and two congruently melting compounds. The cph terminal solid solution, (Mg), has restricted solubility of Cu in Mg (maximum 0.013 at.% Cu). The stoichiometric compound Mg2Cu, of orthorhombic structure, melts congruently at 568 C. The nonstoichiometric compound MgCu2, of fcc C15-type structure, has a maximum composition range of about 64.7 to 69 at.% Cu (at stoichiometry, the MgCu2 phase melts congruently at 797 C), and the fcc terminal solid solution, (Cu), has a maximum solid solubility of 6.93 at.% Mg (93.07 at.% Cu). The intermediate phase Mg2Cu has no measured composition range, whereas MgCu2 has a narrow range of homogeneity that extends on both sides of the stoichiometric composition. X-ray powder diffraction has suggested the possibility of 3 to 4 at.% solubility on either side of the stoichiometric compound MgCu2. The extent of solubility on both sides of MgCu2 at 500 C does not exceed 2.55 at.% (from 64.55 to 67.20 at.% Cu) and is considerably less at lower temperatures. The maximum solid solubility occurs at the eutectic temperatures on both sides of the MgCu2 phase at 64.7 and 69 at.% Cu, which indicates that the maximum width of the solid solution does not exceed 4.3 at.% . No metastable variants of the two intermediate phases have been reported over the temperature and composition ranges of their existence. Metallic glasses have been obtained in Mg-Cu alloys from 9 to 42 at.% Cu (20.5 to 65.4 wt.% Cu). However, the region of complete glass formation is 12 to 22 at.% Cu (26.3 to 42.4 wt.% Cu) [80Som]. 31Jon: W.R.D. Jones, J. Inst. Met., 46, 395-419 (1931). 34Sed: V.G. Sederman, Philos. Mag., 18, 343-352 (1934). 78Bag: P. Bagnoud and P. Feschotte, Z. Metallkd., 69, 114-120 (1978) in French. 80Som: F. Sommer, G. Busher, and B. Predel, J. Phys. Colloque C8, 41, 563-566 ( 1980). Published in Phase Diagrams of Binary Magnesium Alloys, 1988, and Bull. Alloy Phase Diagrams, 5(1), Feb 1984. Complete evaluation contains 1 figure, 12 tables, and 43 references. Special Points of the Mg-Cu System