Фазовая диаграмма системы Ti-Zn

К оглавлению: Другие диаграммы (Others phase diargams)


Ti-Zn (Titanium-Zinc) J.L. Murray The Zn-rich portion of the Zn-Ti phase diagram has been studied extensively, because additions of Ti to Zn act as a grain refiner [75Leo, 76Leo] and promote creep resistance in rolled alloys. [44And] estimated the solubility of Ti in (Zn) as 0.01 to 0.02 at.% Ti at 300 C by metallographic examination. [62Hei] estimated it to be less than 0. 0006 at.% Ti by the same technique. The lower boundary is used in the assessed diagram. Reported eutectic compositions are between 0.16 and 0.63 at.% Ti [41Geb, 44And, 61Pel, 62Hei, 66Ren, 72Spi]. The reason for discrepancies in reported eutectic compositions is that this eutectic is of the faceted-nonfaceted type [76Leo]. The coupled eutectic zone (the composition and temperature range in which eutectic microstructures can appear) extends to the Ti-rich side of the equilibrium eutectic composition [72Spi, 73Got, 75Leo, 76Leo]. A value of 0.21 с 0.01 at.% Ti for the eutectic composition is preferred. The compounds that have been proposed as equilibrium phases include Zn15Ti, Zn10Ti, Zn5Ti, Zn3Ti, Zn2Ti, ZnTi, and ZnTi2. All investigators agreed that Zn15Ti is the most Zn-rich compound. [81Sai] found that the structure of Zn15Ti is a variant of the FeZn13 structure. The details of the structure are best described by the stoichiometry Zn16Ti. [54Pie] prepared Zn2Ti and Zn3Ti and determined their structures. The existence of Zn2Ti and Zn3Ti and the structure of Zn3Ti were verified by [ 62Hei] and [63Pio]. [62Hei] reported that Zn2Ti has hexagonal symmetry, rather than the C14 structure reported by [54Pie]. Between Zn15Ti and Zn3Ti at least one additional phase occurs; it has been identified not only as Zn10Ti [44And, 63Pio], but also as Zn5Ti [62Hei]. [ 62Hei] proposed the stoichiometry Zn5Ti based on the observation of two phases, Zn15Ti and Zn5Ti, in an 11.9 at.% Ti alloy. [63Pio] proposed the stoichiometry Zn10Ti based on chemical analysis of phases present in diffusion couples and X-ray analysis. [63Pio] related the structure of Zn10Ti to that of d1 phases in Fe-Zn and Co-Zn. At least three peritectic reactions occur in the composition range 0 to 20 at.% Ti. Each of the three reactions observed by [66Ren], at 446, 468, and 486 C, has also been observed by an independent investigation, although the interpretations differed greatly. The thermal analysis work of [66Ren] was used to construct the peritectic reactions. Liquidus data (primarily from thermal analysis experiments) fall into two groups. The data of [41Geb], [44And], and [66Ren] rise steeply, reaching 600 C at about 2.7 at.% Ti. The data of [62Hei] and [77Dob] lie considerably lower in temperature. The data of [62Hei] and [77Dob] are uncertain by at least с0.5 at.%, having been digitized from published figures, but it is clear that they are not consistent with the first set. The liquidus data of [44And] and [66Ren] have been chosen for this assessment, based on reinterpretation of a two-phase microstructure described in [62Hei]. The discrepancy, however, is not satisfactorily explained. 41Geb: E. Gebhardt, Z. Metallkd., 33, 355-357 (1941) in German. 44And: E.A. Anderson, E.J. Boyle, and P.W. Ramsey, Trans. AIME, 156, 278-286 ( 1944). 54Pie: P. Pietrokowsky, Trans. AIME, 200, 219-226 (1954). 61Pel: M.E. Pelzel, Metall., 15, 881-883 (1961) in German. 62Hei: W. Heine and U. Zwicker, Z. Metallkd., 53, 380-385 (1962) in German. 63Pio: W. Piotrowski, Zeszyty Nauk. Politech. Lodz. Mech., (10), 33-41 (1963). 66Ren: E.H. Rennhack, Trans. Metall. Soc. AIME, 236, 941-942 (1966). 72Spi: J.A. Spittle, Metallography, 5, 423-447 (1972). 73Got: S. Goto, K. Esashi, S. Koda, and S. Morozumi, J. Jpn. Inst. Met., 37(4), 466-473 (1973) in Japanese. 75Leo: G.L. Leone, P. Niessen, and H.W. Kerr, Metall. Trans. B, 6, 503-511 ( 1975). 76Leo: G.L. Leone and H.W. Kerr, J. Crystal Growth, 32, 111-116 (1976). 77Dob: R. Dobrev, V. Dimova, and I. Georgiev, Materialozn. Teknol., 5, 40-44 ( 1977) in Russian. 81Sai: M. Saillard, G. Develey, and C. Becle, Acta Crystallogr., B37, 224-226 ( 1981). Published in Phase Diagrams of Binary Titanium Alloys, 1987, and Bull. Alloy Phase Diagrams, 5(1), Feb 1984. Complete evaluation contains 3 figures, 4 tables, and 16 references. Special Points of the Zn-Ti System