Фазовая диаграмма системы Be-Ti

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Be-Ti (Beryllium-Titanium) J.L. Murray The equilibrium solid phases of the Ti-Be system are (1) the high-temperature bcc (bTi) and (bBe) and low-temperature cph (aTi) and (aBe) solid solutions, with limited mutual solid solubilities; (2) TiBe2, a C15 Laves phase; (3) TiBe3; (4) two polymorphs, aTi2Be17 at the Be-rich side of stoichiometry and bTi2Be17 at the Ti-rich side (because there are no quantitative data on the homogeneity ranges and no data available on the temperature ranges of stability, the two forms are not distinguished in the assessed phase diagram); and (5) TiBe12. There is considerable interest in glass formation in Ti-Be alloys and in Be- rich alloys for high-temperature applications. The only previous assessment of the diagram is that of [Elliott], which is based on a limited amount of experimental work. The present assessment incorporates a somewhat larger set of experimental work and thermodynamic calculations, but is not a substantial improvement, particularly on the Be-rich side. Further experimental work is needed. The major experimental investigations of the Ti-Be system were conducted by [ 60Bed], [62Obi], and [66Hun]. [62Obi] examined the range 0 to 60 at.% Be at 775 to 1000 C by microscopy, X-ray diffraction, and electrical and magnetic properties. [66Hun] investigated the range 0 to 22 at.% Be at 800 to 1150 C. The master Ti-Be alloy contained 1.05 wt.% Fe. The eutectic composition was bracketed between 21 and 28.9 at.% Be; the eutectoid composition was placed at 2.6 at.% Be, and the maximum solubility of Be in (bTi) was placed at 5 at.%. [ 60Bed] examined alloys between 60 and 100 at.% Be and reported invariant temperatures involving the liquid, with uncertainties of 50 to 60 C. The topology of the assessed diagram is the same as that shown by [Elliott], except that the melting point of TiBe3 is interpreted as a peritectic reaction. This interpretation is based on previous and present thermodyamic calculations of the diagram, which give this topology for any reasonable choice of compound Gibbs energies. For the Ti-rich eutectic temperature, the lower value of [62Obi] is preferred, based on sample purity. The solubility of Be in (bTi) is placed midway between the determinations of [62Obi] (10 at.%) and [66Hun] (5 at.%). Other invariant temperatures are taken from [60Bed] or lie between the determinations of [60Bed] and [65Bea]. [79Tan] produced amorphous structures from 37 to 41 at.% Be by rapid solidification (107 to 108 C/s). The solubility of Be in (bTi) was extended to about 15 at.%. Other phases were TiBe2 and a metastable TiBe phase with the CsCl structure. The glass-forming range lies between the intermetallic compound and the eutectic point. During quenching, (bTi) transforms martensitically to the cph structure (a›Ti) in the range 0 to 15 at.% Be. 60Bed: R.G. Bedford, U.S. At. Energy Comm., UCRL-5991-T, 8 (1960). 62Obi: I. Obinata, K. Kurikar, and M. Simura, Titanium, 10(7), 160-166 (1962) in Japanese. 65Bea: W.W. Beaver, A.J. Stonehouse, and R.M. Paine, Plansee Proceedings ( Metals for the Space Age), Metallwerk Plansee AG, Reutte/Tirol, 682-700 (1965). 66Hun: D.B. Hunter, Trans. AIME, 236, 900-902 (1966). 79Tan: L.E. Tanner and R. Ray, Acta Metall., 27, 1727-1747 (1979). Published in Phase Diagrams of Binary Beryllium Alloys, 1987, and Phase Diagrams of Binary Titanium Alloys, 1987. Complete evaluation contains 1 figure, 4 tables, and 18 references. Special Points of the Ti-Be System