Фазовая диаграмма системы Pd-Si

К оглавлению: Другие диаграммы (Others phase diargams)

Pd-Si (Palladium-Silicon) M.S. Chandrasekharaiah The assessed phase diagram for the Pd-Si system is based primarily on [81Lan], [81Wys], and [83Lan]. The assessed diagram can be regarded as reliable except for the composition region around 18 at.% Si. The solubility of Si in (Pd) up to its melting temperature is so insignificant (<0.01 at.% Si [83Lan]) that (Pd) can be considered to be pure Pd. The (Si) terminal solid solution can also be considered as pure, solid Si because the solubility of Pd in (Si) up to the melting point of Si is insignificant [81Lan] . [65Duw] reported the formation of an amorphous alloy phase by rapid cooling. A number of investigators have subsequently investigated different aspects of this metastable amorphous alloy. Most of these observations confirm that when Pd-Si melts in the composition region of 15 to 23 at.% Si are rapidly cooled (> 104 K/s), the metastable amorphous phase results. This so-called metallic glass phase has some attractive properties and is an important metastable phase of the Pd-Si system. Three other crystalline metastable phases have been reported. [56Rao] proposed Pd9Si4 based on their single datum of a thermal halt at 875 C for an alloy of 33 at.% Si. However, this phase has not been observed by subsequent workers [ 71Roe, 81Lan, 81Wys]. It is not certain whether a phase, even a metastable phase, of this formula exists. [71Roe] and [83Lan] reported the phase Pd4Si as being of cubic form. According to [83Lan], this phase is formed peritectically and belongs to the equilibrium diagram. However, at heating and cooling rates of 1 K/min, [81Wys] failed to observe the presence of this phase in the equilibrium system. [85Shu] also were unable to identify this phase. It may be concluded that Pd4Si is a metastable intermetallic in this system. No structural details are available. [83Lan] described three different metastable systems in the Pd-Si system depending on the rates of cooling of the alloy melts of 13 to 23 at.% Si. At rates faster than 104 K/s, the resultant phase is always the metastable, glassy alloy; this is called metastable state I. At rates between 102 and 104 K/s, the samples were observed to contain the phases Pd525Si, Pd9Si2, Pd3Si, and Pd2Si [83Lan], called the metastable state II. Samples obtained at rates slower than 102 K/s are classified as belonging to metastable state III. Thus, there is a small uncertainty in the Pd-Si system near the composition region of ~18 at.% Si. 56Rao: N.K. Rao and H. Winterhager, Trans. Indian Inst. Met., 10, 139 (1956-57) . 60Aro: B. Aronsson and A. Nylund, Acta Chem. Scand., 14, 1011-1018 (1960). 65Duw: P. Duwez, R.H. Willens, and R.C. Crewdson, J. Appl. Phys., 36, 2267- 2269 (1965). 66Nyl: A. Nylund, Acta Chem. Scand., 20, 2381-2386 (1966). 71Roe: E. Roeschel and C.J. Raub, Z. Metallkd., 62, 840-842 (1971). 81Lan: H. Langer and E. Wachtel, Z. Metallkd., 72, 769-775 (1981) in German. 81Wys: J.A. Wysocki and P.E. Duwez, Metall. Trans. A, 12, 1455-1460 (1981). 83Lan: H. Langer and E. Wachtel, Z. Metallkd., 74, 535-544 (1983) in German. 85Shu: R.D. Shull, A.J. McAlister, and M.J. Kaufman, J. Met., 37 (1985). Published in J. Alloy Phase Diagrams, 5(2), 1989. Complete evaluation contains 2 figures, 4 tables, and 36 references. Special Points of the Pd-Si System