In this study, we investigated the microstructure, mechanical properties, and thermal performance of Sn-xBi-1Ag (x = 35, 37, 45, and 47 wt.%) solders, with a particular focus on the effect of adding trace Si atoms. The impact of different Ag concentrations on the properties of Sn-xBi-Ag-0.5Si solders was also studied. The results indicated that as the amount of Bi added to Sn-xBi-1Ag solder alloys increased, the tensile strength, microhardness, melting temperature, and melting range decreased somewhat, but the wettability improved. The Cu₆Sn₅ layer between the soldering alloy and the Cu substrate became thinner upon increasing the Bi content. Adding microcrystalline Si atoms to the Sn-Bi-1Ag alloy improved the tensile strength and microhardness, but the melting point and melting range were not significantly changed. The wettability was optimized, and the diffusion layer formed with the Cu matrix was significantly thinner. By increasing the Ag content in the Sn-Bi-(1,3)Ag-0.5Si alloy, the tensile strength of the alloy was continuously strengthened, while the hardness decreased slightly and the melting point and melting range increased slightly. The wettability was greatly improved, and the Cu₆Sn₅ layer became thinner.

As a kind of high-performance tool material, the phase relationship and microstructure evolution of Fe-Mo-Co alloy during manufacturing processes deserve attention and study. In the present work, isothermal sections of the Fe-Mo-Co system at 800 and 1350 °C were investigated using the equilibrium alloy method and diffusion couple technology. No ternary compounds were found in either isothermal section. Four three-phase regions and two three-phase regions were determined at 1350 and 800 °C, respectively. The μ-Fe₇Mo₆ phase presents a continuous solid solution in the two isothermal sections. A set of self-consistent thermodynamic parameters of the Fe-Mo-Co ternary system were obtained. The calculated results using the obtained thermodynamic parameters are in good agreement with the experimental results.