Фазовая диаграмма системы Al-Pt

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Al-Pt (Aluminum-Platinum) A.J. McAlister and D.J. Kahan The equilibrium phases of the Al-Pt system are (1) the liquid, L; (2) the fcc terminal solid solutions (Al) and (Pt); (3) Al21Pt5, a complex cubic phase with nil solubility; (4) Al21Pt8, a tetragonal phase with nil solubility; (5) Al2Pt, a cubic phase of CaF2 type, with a solubility of about 1.0 at.% at 850 C; (6) Al3Pt2, a hexagonal phase with a structure related to, but not isotypic with, Al3Ni2 and with nil solubility; (7) AlPt, a cubic phase with FeSi structure and nil solubility; (8) b, a cubic phase of the CsCl type, occurring above 1260 C, with an approximate solubility range of 51 to 56 at.%; (9) Al3Pt5, a rhombohedral phase of the Ge3Rh5-type, with a solubility range of 1 to 2 at.%; (10) AlPt2, the high-temperature modification of AlPt2 with the Ni2Si structure and a solubility range of 1 to 2 at.%; (11) AlPt2(LT), the low-temperature modification of AlPt2, with the GaPt2(LT) structure and a solubility range of 1 to 2 at.%; (12) AlPt3, a cubic phase with the AuCu3 structure and a solubility of about 10 at.%; and (13) AlPt3(LT), a tetragonal variant of the AuCu3 structure, occurring below 1290 C, with solubility extending from about 74 to 78 at.% at 859 C. The Al-Pt phase diagram is complex, and only some of its features have been determined reliably. Al21Pt8, Al2Pt, Al3Pt2, Al3Pt5, and AlPt3 have been observed in two or more independent studies and have been established as equilibrium phases. Other aspects of the diagram are problematic. Some question has been raised as to the phase in equilibrium with (Al) and the liquid near 20 at.% Pt at 657 C (although the weight of evidence favors the cubic Al21Pt5 phase). Debate also has occurred over the existence of the high- and low-temperature modifications of AlPt2. The high-temperature b phase has been observed directly only once. The existence of the low-temperature modifications of AlPt3 remains uncertain. Finally, measurements of liquidus, solidus, and invariant temperatures have not been confirmed. The assessed phase diagram is based on review of the work of [64Huc], [70Dar], [75Cha], [76Cha], [78Bha], and [80Pia]. An fcc phase has been observed upon heating a thin film diffusion couple at 410 C. A hexagonal phase of nominal composition Al21Pt6 has also been observed. [80Pia] observed this phase transform to the cubic l phase upon heat treatment at 200 C for several hours. An extremely fine precipitate of a cubic phase has been reported as a metastable extension of the equilibrium e phase. In aged samples, another phase of nominal composition Al6Pt has been observed. It was classified as orthorhombic. 64Huc: R. Huch and W. Klemm, Z. Anorg. Allg. Chem., 329, 123-135 (1964) in German. 70Dar: A.S. Darling, G.L. Selman, and R. Rushforth, Platinum Met. Rev., 14, 124-130 (1970). 75Cha: T. Chattopadhyay and K. Schubert, J. Less-Common Met., 41, 19-32 (1975). 76Cha: T. Chattopadhyay and K. Schubert, J. Less-Common Met., 45, 79-83 (1976). 78Bha: S. Bhan and H. Kudielka, Z. Metallkd., 69, 333-334 (1978) in German. 80Pia: G. Piatti and G. Pellegrini, J. Mater. Sci., 15, 2403-2408 (1980). Published in Bull. Alloy Phase Diagrams, 7(1), Feb 1986. Complete evaluation contains 1 figure, 5 tables, and 27 references. Special Points of the Al-Pt System