Abstract
The calculated liquidus projection of the Ag-Bi-Ni ternary system has been experimentally examined. Alloys were prepared by induction melting, and their microstructure studied by scanning electron microscopy coupled with energy dispersive x-ray spectroscopy. Of the primary solidification phases, (Ni) solidifies over the largest concentration range, although it was found to be narrower than calculated. The range in which Bi3Ni is the primary solidification phase was found to be broader than calculated. Also, the liquid miscibility gap is broader than predicted from assessed thermodynamic parameters. Differential thermal analysis was used to study temperatures of phase transitions of as-cast alloys, and recorded temperatures of melting of Bi3Ni and BiNi phases in ternary alloys agree well with those calculated.
Highlights
Among alloys considered as Pb-free replacement for solders used at high temperatures, Bi3Ni + (Ag) + (Bi)-2.5Ag and Bi-11Ag alloys are subjects of interest to investigators.[1,2] a number of Ag-Bi-number and size of (Ni) system: (Ag)-Bi-X systems have been studied as possible candidates[3] to replace solders such as Sn-90Pb
The calculated liquid miscibility gap extends from the Ag-Ni side up to approximately 30 at.% Bi
The liquidus projection in the Ag-Bi-Ni ternary system was experimentally studied and compared to the liquidus projection calculated based on thermodynamic assessment in the literature
Summary
Among alloys considered as Pb-free replacement for solders used at high temperatures, Bi-2.5Ag and Bi-11Ag (wt.%) alloys are subjects of interest to investigators.[1,2] a number of Ag-Bi-X systems have been studied as possible candidates[3] to replace solders such as Sn-90Pb (wt.%) The systems studied, both thermodynamically and with respect to phase equilibria, have included Ag-Bi-Cu, Ag-Bi-Sn, Ag-BiZn,[4,5,6] and Ag-Bi-Ni.[7] The phase diagram of the AgBi-Ni system was thermodynamically assessed by Gao et al.[7] They found that there are no ternary intermetallics in this system, and that the solubility of Ag in the two binary intermetallics, i.e. BiNi and Bi3Ni, is negligible. Because of a lack of experimental data regarding liquidus surface and thermodynamics of liquid phase, they based their assessment only on experimental phase equilibria in four isothermal sections in the Ag-Bi-Ni system and thermodynamic assessed data of limiting binary systems.[8,9,10]
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