Фазовая диаграмма системы Cu-Pt

К оглавлению: Другие диаграммы (Others phase diargams)

Cu-Pt (Copper-Platinum) P.R. Subramanian and D.E. Laughlin The equilibrium phases of the assessed Cu-Pt diagram are (1) the liquid, L; (2) the fcc continuous solid solution, (Cu,Pt); (3) ordered Cu3Pt, with a range of composition; and (4) ordered CuPt, also with a range of composition. The assessed diagram is an update of the diagram of [Hansen], which was based on the data of [07Doe], who provided the only available liquidus and solidus data for the Cu-Pt system. Because there have been no other studies, the assessed liquidus and solidus curves of the assessed diagram are based on the experimentally determined thermodynamic functions for the solid solution and on a thermodynamic model for the liquid phase. As seen in the assessed diagram, the experimental data for the liquidus and solidus are rather limited, covering only the Cu-rich region from ~3 to 43 at.% Pt. Moreover, these were measured at the beginning of this century. Further experimental research, especially in the Pt-rich alloys, is needed to delineate properly the liquidus and solidus boundaries. Additionally, it would be desirable to have comprehensive experimental thermodynamic data for the liquid phase to provide a sounder basis for thermodynamic modeling. [55Sch] proposed the L12 structure for Cu3Pt in the range 18 to 23 at.% Pt and a periodic antiphase structure or long-period superlattice (LPS) in 24 to 26 at.% Pt alloys. [73Oga] revealed the existence of one-dimensional antiphase domain structures (L12-s or 1D-LPS) in 19.7 to 26.5 at.% Pt alloys. The 1D-LPS consists of tetragonal cells built up in terms of the original disordered fcc lattice. The eutectoid decomposition of the disordered (Cu,Pt) solid solution into ordered Cu3Pt and CuPt was suggested first by [55Hir], who proposed that under perfect thermal equilibrium conditions, Cu3Pt and CuPt coexist from 25 to 40 at.% Pt at 0 K. Subsequently, [68Dzh] investigated Cu-28.2 and 28.8 at.% Pt alloys and proposed the eutectoid decomposition of the solid solution into ordered Cu3Pt and CuPt. A similar reaction was found to occur in the Cu-Pd system. The peritectoid reaction for the formation of the 1D-LPS and the eutectoid reaction (Cu,Pt) = 1D-LPS + CuPt, both shown in the assessed diagram, are tentative and await experimental confirmation. The (Cu,Pt)/(Cu,Pt) + CuPt boundary between the temperature range 725 to 815 C, as shown in the assessed diagram, is proposed tentatively on the basis of data from [54Ass] and [70Ira]. It is evident from the extensive literature that the phase relationships are very complex in the region ~30 to 90 at.% Pt. Although the various investigations agree with regard to the phase boundary for the order-disorder transition in this composition range, there is no consensus with regard to the actual phase equilibria below the order-disorder boundary. The existence of rhombohedral Cu3Pt5, orthorhombic CuPt3, and cubic CuPt3 are accepted tentatively based on various reports. However, there are no reports of the existence of two-phase regions between any of these ordered phases. The phase diagram proposed by [74Mii] shows order transitions between Cu3Pt5 and the orthorhombic and cubic forms of CuPt3. These transitions, shown in the assessed diagram, are tentative and await further experimental studies. [75Kan] and [77Kan] made theoretical calculations of the effect of pressure on the stability of CuPt. For an equiatomic alloy, [75Kan] derived a critical pressure of 90 kbar for the transition of the rhombohedral CuPt lattice to a tetragonal AuCu-type lattice. On the other hand, the pressure-temperature phase diagram of [77Kan] showed a CuPt = CrNi = AuCu type transition with increasing pressure. [81Ich] determined the effect of pressure on the order- disorder transformation temperature (Tc) of a 50.4 at.% Pt alloy by electrical resistivity measurements. Their results showed that Tc decreases linearly with increasing pressure at the rate of -0.9 C/kbar. In addition, X-ray diffraction of alloys annealed at 550 C and 120 kbar did not reveal the presence of any high-pressure phase. This indicated that the ordered L11 type is stable at least up to 120 kbar, which disclaimed the theoretical observations of [75Kan] and [77Kan]. The negative dependence observed for the variation of Tc with pressure is anomalous with respect to other ordering alloys, wherein pressure favors the ordered state. [81Ich] attributed this anomaly to the apparent decrease in the specific volume on disordering, which makes the disordered state more favorable on the application of pressure. Electrical resistivity measurements of the effect of pressure on Tc in a 48.1 at.% Pt alloy by [82But] revealed a triple point of coexistence of CuPt and AuCu types with the disordered phase at 10 kbar and 727 C in disagreement with the observations of [75Kan] and [ 81Ich]. 07Doe: F. Doerinckel, Z. Anorg. Allg. Chem., 54, 333-336 (1907) in German. 37Lin: J.O. Linde, Ann. Phys., 30, 151-164 (1937) in German. 44Kub: O. Kubaschewski and H. Ebert, Z. Electrochem., 50, 138-144 (1944) in German. 44Sch: A. Schneidner and U. Esch, Z. Electrochem., 50, 290-301 (1944) in German. 52Wal: C.B. Walker, J. Appl. Phys., 23(1), 118-123 (1952). 54Ass: P. Assayag and M. Dode, Compt. Rend., 239, 762-764 (1954) in French. 55Hir: T. Hirone and K. Adachi, Sci. Rep. Res. Inst. T“hoku Univ., A7, 282-293 (1955). 55Sch: K. Schubert, B. Kiefer, M. Wilkens, and R. Haufler, Z. Metallkd., 46, 692-715 (1955) in German. 62Bau: W.L. Baun and J.J. Renton, Tech. Rep. No. ASD-TDR-62-926, Air Force Materials Laboratory, Wright-Patterson Air Force Base, OH (1962). 68Dzh: E.A. Dzhanibusinov and A.A. Presnyakov, Akad. Nauk Ukr. SSR, Metallofiz. , 20, 240-244 (1968) in Russian. 70Ira: R.S. Irani and R.W. Cahn, Nature, 226, 1045-1046 (1970). 71Buc: R.A. Buchanan, Ph.D. thesis, Materials Science and Eng., Vanderbilt University, Nashville, TN (1971). 73Oga: S. Ogawa, H. Iwasaki, and A. Terada, J. Phys. Soc. Jpn., 34(2), 384-390 (1973). 73Wu: N.C. Wu, H. Iwasaki, and S. Ogawa, Trans. Jpn. Inst. Met., 14, 309-313 ( 1973). 74Mii: R. Miida and D. Watanabe, J. Appl. Crystallogr., 7, 50-59 (1974). 75Kan: A.K. Kanyuka, V.I. Ryzhkov, and A.A. Smirnov, Fiz. Met. Metalloved., 40( 5), 950-957 (1975) in Russian; TR: Phys. Met. Metallogr. (USSR), 40(5), 40-46 ( 1975). 76Koz: E.V. Kozlov, A.S. Tailashev, Y.A. Sazanov, and A.A. Klopotov, Strukt. Mekhanizm Fazovykh Prevrashchenii Met. i Splavov, 146-149 (1976) in Russian. 77Kan: A.K. Kanyuka, Ukr. Fiz. Zh., 22(9), 1566-1568 (1977) in Russian. 79Has: S. Hashimoto and H. Iwasaki, Proc. AIP Conf., Modulated Struct., 53, American Institute of Physics, 283-285 (1979). 81Ich: M. Ichikawa, H. Iwasaki, and S. Endo, Jpn. J. Appl. Phys., 20(3), 623- 627 (1981). 82But: A.K. Butylenko, I.Y. Dekhtyar, and N.S. Kobzenko, Ukr. Fiz. Zh., 26(12), 2052-2054 (1982) in Russian. 85Tak: T. Takezaka, K. Mitsui, T. Yokoyama; reported in [86Mit]. 86Mit: K. Mitsui, Y. Mishima, and T. Suzuki, Philos. Mag. A, 53(3), 357-376 ( 1986). Submitted to the APD Program. Complete evaluation contains 11 figures, 8 tables, and 88 references. Special Points of the Cu-Pt System