The phase equilibria of the Sn-Ag-In system were investigated by means of differential scanning calorimetry (DSC) and metallography. The isothermal sections at 180-600°C, as well as some vertical sections, were determined. Thermodynamic assessment of this system was also carried out based on the experimental data of thermodynamic properties and phase equilibria using the calculation of phase diagram (CALPHAD) method, in which the Gibbs energies of the liquid, fcc, and hcp phases are described by the subregular solution model, and those of compounds are represented by the sublattice model. The thermodynamic parameters for describing the phase equilibria were optimized, and reasonable agreement between the calculated and experimental results was obtained. The maximum bubble-pressure method and dilatometric method have been used in measurements of the surface tension and density of the binary In-Sn and ternary (Sn-3.8Ag) eut ϩ In (5 at.% and 10 at.% ) liquid alloys, respectively. The experiments were performed in the temperature range from 160-930°C. The experimental data of the surface tension were compared with those obtained by the thermodynamic calculation of Butler's model.

Chemical reactions between Cu substrates and Zn-Al high-temperature solder alloys, , at temperatures ranging from 420°C to 530°C were experimentally investigated by a scanning electron microscope using backscattered electrons (SEM-BSE) and an electron probe microanalyzer (EPMA). Intermediate phases (IMPs), b(A2) or b¢(B2), c(D8 2 ), and e(A3) phases formed and grew during the soldering and aging treatments. The consumption rate of the IMP for Cu substrates is described by the square root of t in both the alloys, while the additional Cu in the molten Zn-Al alloy slightly suppresses the consumption of Cu substrates. The growth of IMPs during soldering treatment is controlled by the volume diffusion of constituent elements, and its activation energy increases in the order of Q e < Q c < Q b . In view of the aging process, the growth of IMPs is considered to be controlled by the volume diffusion. In particular, the layer thickness of c rapidly grows over 200°C, although the thickness of the b layer grows very slowly.

The effects of alloying elements on the macroscopic morphologies in Cu-Fe base alloys were experimentally investigated. It was found that macroscopic homogeneity can be achieved by the addition of Mn, Ni, Al, or Co in the Cu-Fe base alloys, while the core-type macroscopic morphologies with Cu-rich or Fe-rich cores, which are radially separated as two layers in the inner and outer parts of the ingot solidified in the cast-iron mold, were formed by the addition of C, Cr, Mo, Nb, Si, or V. It is shown that the formation of the core-type macroscopic morphology is strongly connected with the existence of a stable miscibility gap of the liquid phase in the Cu-Fe base alloy due to the addition of alloying elements. The liquid phase with less volume fraction always forms the center part. This result can be explained by a mechanism that the minor droplets as the second phase are forced to move into the thermal center due to Marangoni motion, which is caused by the temperature dependence of interfacial energy between two liquid phases.

No abstract