Фазовая диаграмма системы Ag-Si

К оглавлению: Другие диаграммы (Others phase diargams)


Ag-Si (Silver-Silicon) R.W. Olesinski and G.J. Abbaschian The assessed Si-Ag phase diagram, which is a simple eutectic, is based primarily on the work of [63Hag], supplemented by the data of [61Bol], [69Mou], and [75Pre]. Independently, [88Che] assessed the Si-Ag phase diagram thermodynamically. The liquidus was calculated by the common-tangent method and was based on the assumption that the enthalpy and entropy of mixing functions are temperature independent and that the mutual solid solubilities of Si and Ag are nil. It was not possible to obtain good agreement between the calculated (Ag) liquidus and experimental data if the optimization included the measured enthalpy of mixing or (Si) liquidus data. The system has a eutectic around 835 C and 89.0 at.% Ag. The mutual solubilities of Si and Ag in the solid state are negligible. The (Si) solidus in the high-temperature range has the retrograde character, with a maximum solubility of about 4 x 10-4 at.% Ag around 1350 C. The Si-Ag liquid solution is athermal around 85 at.% Ag, endothermic below that composition, and negligibly exothermic on the Ag-rich side of the composition range, clearly indicating a tendency to form Ag-rich intermediate phases, possibly those observed during rapid solidification experiments. No evidence of extended solid solubility of Si in (Ag) has been discovered [65Luo] , although a decrease of Ag lattice parameter in rapidly quenched alloys was interpreted as implying that a small amount of Si did dissolve in (Ag). The occurrence of two metastable phases was reported on the Ag-rich side of the diagram: a cph structure at 75 to 95 at.% Ag and an orthorhombic phase containing about 70 at.% Ag. Both phases were obtained in rapidly solidified alloys at cooling rates above 105 C/s by melt spinning on Cu substrates. The cph phase started decomposing above 100 C, and the orthorhombic phase decomposed to the equilibrium phases on heating to high temperatures. 61Bol: B.I. Boltaks and H. Shih-yin, Sov. Phys. Solid State, 2, 2383-2388 ( 1961); also Fiz. Tverd. Tela, 2, 2677-2684 (1960). 63Hag: J.P. Hager, Trans. AIME, 227, 1000-1002 (1963). 65Luo: H.L. Luo, W. Klement, Jr., and T.R. Anantharaman, Trans. Indian Inst. Met., 214-218 (1965). 69Mou: P. Mouron and G. Vuillard, C.R. Acad. Sci. (Paris), Ser. C, 269, 595- 598 (1969) in French. 75Pre: B. Predel and H. Bankstahl, J. Less-Common Met., 43, 191-203 (1975) in German. 88Che: P.Y. Chevalier, Thermochim. Acta, 130, 33-41 (1988). Published in Bull. Alloy Phase Diagrams, 10(6) Dec 1989. Complete evaluation contains 3 figures, 5 tables, and 28 references. 1