El rincón rico en Estaño del sistema Cobre-Estaño-Zinc

Abstract

Tesis para optar al título de Magister en Ciencia y Tecnología de Materiales

The Sn-rich corner on the Cu-Sn-Zn phase diagram is investigated. This system has application in the searching the new Pb-free solders for electronic assembly. The study is focused on the types and the temperatures of the invariant reactionsm, the probable topology of the liquidus surfaces and phase equilibrium in this region. Twenty-two alloys were prepared and analyzed by optical microscopy, scanning electron microscopy, electron-probe microanalysis and differential thermal analysis. Some selected alloys were isothermally annealed at 180 degree C for 45 days. The isothermal section al 180 degree C proposed in this investigation, exhibit tie-lines joining Betha and SnBetha phases. These tie-lines invalidate tie-lines between gamma_Cu-Zn and n phases proposed by Lee et al [97Lee, 98Lee]. The solubility of Zn in the n phase was found to be approximately of 15 at =520 \\ at 180 degree C, which is in disagreement with the zero-solubility calculated by Lee et al at 250 degree C [97Lee] and at 160 degree C. The Betha, gamma_Cu-Zn and Epsilon_Cu-Zn phases have a maximum solubility of approximately 15, 0.6 and 0.4 =520 \\ at of Sn, respectively. In addition, a thermodynamic calculation of Sn-Zn system, using Thermo-Calc software, is performed. In this calculation the description of the liquid phase of Fries and Lukas [91Fri] is improved in order to obtain the optimum set of coefficients.