We have recently developed a thermodynamic database for micro-soldering alloys which consists of the elements Pb, Bi, Sn, Sb, Cu, Ag, Zn, and In. In this paper, the phase equilibria and the related thermodynamic properties of the SnAg-Cu base alloys are presented using this database, alloy systems being one of the promising candidates for Pb-free solders. The isothermal section diagrams of the Sn-Ag-Cu ternary system were experimentally determined by SEM-EDS, x-ray diffraction and metallographic techniques. Based on the present results as well as the previous data on phase boundaries and thermochemical properties, thermodynamic assessment of this system was carried out. The isothermal and vertical section diagrams, liquidus surface, mass fractions of the phase constitution, etc., were calculated. The predictions of surface energy and viscosity were also investigated. Moreover, a non-equilibrium solidification process using the Scheil model was simulated and compared with the equilibrium solidification behavior in some Sn-Ag-Cu base alloys. Calculated results based on the Scheil model were incorporated into a three-dimensional solidification simulation and the prediction of practical solidification procedures was performed.
A thermodynamic assessment of the Bi-Mn binary system was conducted using the CALPHAD approach. Consistent thermodynamic descriptions, which agreed well with the selected experimental data, were obtained using a sub-regular solution model for solution phases and a line-compound model for intermetallic compounds. There are several discrepancies between the phase diagram drawn in a previous study and that calculated in this study. The two-phase separation that appeared in the previous phase diagram was not calculated and the calculated liquidus boundaries at around 1000 K changed smoothly compared with that in the previous diagrams. From the viewpoint of thermodynamic consideration, the calculated phase diagram presented in this study is reasonable.
The strength of four binary systems NaCl-Na 2 CO 3 , KCl-K 2 CO 3 , KCl-NaCl and K 2 CO 3 -Na 2 CO 3 was investigated in order to develop expendable salt core for high pressure die casting processes. Four point bending test was conducted to determine the strength of specimens made from molten salts by using the permanent mold casting technique. The strength of the system NaCl-Na 2 CO 3 was over 20 MPa at the Na 2 CO 3 composition between 20 mol% and 30 mol%, and between 50 mol% and 70 mol%. The highest strength was about 30 MPa at the composition of NaCl-70 mol%Na 2 CO 3 . This strength was 5 times as high as that of commonly used sand cores. The system KCl-K 2 CO 3 also showed 20 MPa in strength. It was observed that there were the primary particles surrounded by the eutectic structure in the solidification structure of the systems NaCl-Na 2 CO 3 and KCl-K 2 CO 3 at the composition where the peak strength was obtained. The presence of the primary particles played an important role to strengthen the structure because the primary particles can prevent or deflect the crack propagation. In contrast to these binary systems, the systems KCl-NaCl and K 2 CO 3 -Na 2 CO 3 were very brittle due to the phase decomposition or other solid-solid phase transformation of the solid solution phase. The strength of these systems was under 6 MPa.
Low-frequency elastic modulus, internal friction, tensile stress-strain loops, and thermally-induced strain recovery of single-crystal fibers obtained by pulling-down method from the melts of NiFeGaCo alloys were studied. A minimum of the elastic modulus and the maximum peak of the internal friction were obtained at the martensitic transition temperature. A large super-elastic strain of about 10% was obtained in the fiber of the Ni 49 Fe 18 Ga 27 Co 6 alloy. Thermodynamic estimation by the Clausius-Clapeyron equation was consistent with the experimental results.
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