Фазовая диаграмма системы Fe-Ta

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Fe-Ta (Iron-Tantalum) L.J. Swartzendruber and E. Paul The equilibrium phases of the Fe-Ta system are (1) the liquid, L; (2) the bcc solid solution, (Ta); (3) the m phase intermetallic compound FeTa, with a composition range of 49 to 54 at.% Ta at 1300 C; (4) the e phase intermetallic compound Fe2Ta, with a Laves structure and a composition range of 28 to 36 at.% Ta at 1300 C; (5) the bcc (dFe) phase; (6) the fcc (gFe) phase; and (7) the bcc (aFe) phase. The assessed phase diagram is based primarily on the work of [36Gen], [66Abr], [67Sin], and [70Fis]. Temperatures have been corrected to the IPTS-68 temperature scale and to agree with a value of 1538 C for the melting temperature of pure Fe. The phase boundaries in the assessed diagram have been obtained by thermodynamic modeling, with the exception of the g loop, the a/a + e, the liquidus, and the eutectic temperature. The melting temperature of the m phase has not been measured. The Ta-rich portion of the system has not been studied extensively. A 66.7 at.% Ta alloy clearly showed an equilibrium between the m phase and the (Ta) solid solution and had a near-eutectic structure [66Ram]. From a 90 at.% Ta alloy, it was also estimated that the solubility of Fe in (Ta) might be as much as 7 at.%. The Ta-rich portion of the diagram is based on these estimates. On water quenching from 1400 C, (dFe) was retained in alloys with hypereutectoid compositions (>1.4 at.% Fe), whereas hypoeutectoid alloys appeared to undergo the d<259>g<259>a transition. In an investigation of the magnetic properties of the m phase, [83Ahm] found a N‚el temperature that varied from 63 C for 50 at.% Ta to 47 C for 53 at.% Ta, with an apparent moment per Fe atom of 2.65 to 2.78 Bohr magnetons. M”ssbauer effect measurements revealed that a substantial portion of the Fe atoms remain magnetically unpolarized below the N‚el temperature. In Fe2Ta, [64Nev] did not observe an Fe magnetic hyperfine field down to 4 K. Magnetic susceptibility measurements confirmed that stoichiometric Fe2Ta is paramagnetic and showed the existence of weak ferromagnetism for nonstoichiometric compositions. The effect of Ta on the Curie temperature of aFe has not been measured. However, it is likely that Ta additions cause a slight increase in Curie temperature for small amounts of Ta. 36Gen: R. Genders and R. Harrison, J. Iron Steel Inst., 134, 173-209 (1936). 64Nev: M.V. Nevitt, C.W. Kimball, and R.S. Preston, Proc. Int. Conf. Magnetism, Nottingham, England, 137-140 (1964). 66Abr: E.P. Abrahamson and S.L. Lopata, Trans. AIME, 236, 76-87 (1966). 66Ram: A. Raman, Trans. Indian Inst. Met., 19, 202-205 (1966). 67Sin: A.K. Sinha and W. Hume-Rothery, J. Iron Steel Inst., 205, 671-673 (1967) . 70Fis: W.A. Fischer, K. Lorenz, H. Fabritius, and D. Schlegel, Arch. EisenhЃttenwes., 41, 489-498 (1970) in German. 83Ahm: M.S. Ahmed, G.C. Hallam, and D.A. Read, J. Magn. Magn. Mater., 37, 101- 109 (1983). Published in Bull. Alloy Phase Diagrams, 7(3), Jun 1986. Complete evaluation contains 2 figures, 5 tables, and 34 references. 1