| Summary: | 碩士 === 元智大學 === 化學工程與材料科學學系 === 100 === The Sn–rich part of the Ni–Pd–Sn ternary system preliminary obtained from the interpolation of the three constituent binary systems using Muggianu method. Based on this proposition, twenty three Ni–Pd–Sn alloys were prepared and annealed at 250 °C. The annealed alloys were analyzed with scanning electron microscopy (SEM), electron–probe microanalysis (EPMA), and electron backscatter diffraction (EBSD) to determine phase equilibria in the Ni–Pd–Sn system. From the experimental data, PdSn4, PdSn3, and PdSn2 binary compounds were found to have remarkable ternary solubility. The backscattered electron image (BEI) reveals the presence of microcracks in the (Pd,Ni)Sn4 phase including the binary and ternary region near the Sn–corner. The crack density was varies on the alloying location, where high cracks density was found in the neighborhood of the Sn–Ni line, rather than the Sn–Pd line. And the microcracks increase significantly with the Ni content in PdSn4 phase, which propagate along the a-axis of the PdSn4 unit cell. A cracking mechanism has been proposed based on these experimental results. In this study, solubility of Ni in PdSn4 was also investigated at various annealing temperatures, specifically in lower temperature case. A good interaction was found between the Ni solubility and the temperature. The Ni solubility in PdSn4 would decrease as a function of annealing temperature suggesting that the NiSn4 should be more thermodynamic stable at lower temperature. Furthermore, a consistent thermodynamic model of the Sn–rich corner of the ternary Ni–Pd–Sn system was developed by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the present experimental results. Applying the results, calculation of the phase diagram was performed with the Thermo–Calc software. The Gibbs free energies of the intermetallic compounds were described by the Sublattice model. A consistent set of thermodynamic parameters has been derived for describing the Gibbs free energies of each solution phase and intermetallic compound in the Ni–Pd–Sn ternary system. The thermodynamic description is in accord well with the experimental results.
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