Фазовая диаграмма системы Fe-Ti

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Fe-Ti (Iron-Titanium) J.L. Murray The equilibrium solid phases of the Ti-Fe system are (1) the cph (aTi) solid solution, based on pure Ti below 882 C; (2) the bcc (bTi) and (aFe) solid solutions, of which the bcc phase is the stable solid phase of pure Ti above 882 C, and the stable solid phase of pure Fe below 912 C and above 1394 C; ( 3) the fcc (gFe) solid solution, based on the stable form of pure Fe between 912 and 1394 C, and where the (aFe)/(gFe) phase boundaries take the form of a g loop; (4) the compound TiFe, with the CsCl structure, which forms from the melt by the peritectic reaction L + TiFe3=TiFe at 1317 C; and (5) the compound based on TiFe2 stoichiometry, the MgZn2-type Laves phase, which melts congruently at 1427 C. The (aTi) solvus is retrograde in form, and the maximum solubility of Fe in (aTi) is 0.05 at.% Fe at about 700 C [67Rau]. The maximum solubility of Ti in (gFe) is 0.8 at.% at approximately 1150 C. The assessed Ti-Fe diagram is topologically the same as those of [Shunk] and [ Hultgren,B]. The major changes made in the present evaluation concern the homogeneity ranges of (gFe), TiFe2, and (aTi). [78Kau] modeled the thermodynamics of the system; the calculation is in qualitative agreement with the experimental diagram. Alloys of composition near TiFe2 are very reactive. [57Hel] reported that such alloys were contaminated by alumina crucibles and that thoria crucibles had to be used. High melting temperatures observed by [54Nis], for example, were probably due to contamination. The invariant and congruent melting temperatures are based on the thermal analyses of [57Hel]. The (aFe) solvus was determined by [66Abr] using lattice parameter data and by [79Ko] and [81Tak] using lattice parameters and microprobe analyses of equilibrated samples. Based on metallographic work, [56Kor] and [65Bor] reported higher solubilities. The lower solubilities are preferred, because equilibrium was more likely to have been achieved. The g loop is based on magnetic susceptibility data [66Fis], thermal analysis data [57Hel], and dilatometry [63Wad]. The maximum solubility of Ti in (gFe) is 0.8 at.% at about 1100 to 1150 C, and the (gFe) + (aFe) field is about 0.6 at.% wide at that temperature [57Hel, 63Wad, 66Fis]. The maximum extent of the outer loop is about 0.8 at.% Ti, based on dilatometric measurements [52Roe]. Quenching of (bTi) produces martensite in alloys of less than about 3 to 4 at.% Fe. With greater Fe content, (bTi) can be retained after quenching. The w phase forms from the metastable (bTi) phase either during quenching or during aging between 300 and 450 C [76Stu]. During aging, the w phase composition approaches 4 to 5 at.% Fe; the (bTi) composition approaches 10 to 14 at.% Fe [ 69Hic]. By splat cooling of the liquid, [72Ray] produced extended (bTi) solutions containing up to 35 at.% Fe and TiFe from 35 to 50 at.% Fe. The lattice parameters of the ordered and disordered phases followed a single linear trend with composition, from which [72Ray] concluded that the metastable ordering transition may be second order. Using cooling rates of 107 to 108 C/s, [73Pol] produced amorphous alloys from 28 to 30 at.% Fe. 52Roe: W.P. Roe and W.P. Fishel, Trans. ASM, 44, 1030-1041 (1952). 54Nis: H. Nishimura and K. Kamei, Bull. Eng. Res. Inst., Kyoto Univ., 6, 38-42 (1954) in Japanese. 56Kor: I.I. Kornilov and N.G. Boriskina, Dokl. Akad. Nauk SSSR, 108(6), 1083 ( 1956) in Russian. 57Hel: A. Hellawell and W. Hume-Rothery, Philos. Trans. Roy. Soc., London, 249, 417-459 (1957). 63Wad: T. Wada, J. Jpn. Inst. Met., 27(3), 119 (1963) in Japanese; TR: Trans. Nat. Research Inst. Met. (Tokyo), 6(2), 43-46 (1963). 65Bor: N.G. Boriskina and I.I. Kornilov, Sb. Nouyve Issled. Titanovykh Splavov, Moscow, Izd. Nauk, 6, 61-75 (1965) in Russian. 66Abr: E.P. Abrahamson and S.L. Lopata, Trans. AIME, 236, 76-87 (1966). 66Fis: W.A. Fischer, K. Lorenz, H. Fabritius, A. Hoffman, and G. Kalwa, Arch. Eisenhuttenwes., 37, 79-86 (1966) in German. 67Rau: E. Raub, Ch.J. Raub, and E. Roschel, J. Less-Common Met., 12, 36-40 ( 1967). 69Hic: B.S. Hickman, Trans. AIME, 245, 1329-1336 (1969). 72Ray: R. Ray, B.C. Giessen, and N.J. Grant, Metall. Trans., 3, 627-629 (1972). 73Pol: A.F. Polesya and L.S. Slipchenko, Izv. Akad. Nauk SSSR, Met., (6), 173- 178 (1973) in Russian; TR: Russ. Metall., (6), 103-107 (1973). 76Stu: M.M. Stupel, M. Ron, and B.Z. Weiss, J. Appl. Phys., 47(1), 6-12 (1976). 78Kau: L. Kaufman, Calphad, 2(2), 117 (1978). 79Ko: M. Ko and T. Nishizawa, J. Jpn. Inst. Met., 43(2), 118-126 (1979) in Japanese. 81Tak: T. Takayama, M.Y. Way, and T. Nishizawa, Trans. Jpn. Inst. Met., 22(5), 315-325 (1981). Published in Phase Diagrams of Binary Titanium Alloys, 1987. Complete evaluation contains 8 figures, 6 tables, and 117 references. Special Points of the Ti-Fe System