Journal of Welding Science

Eutectic tin-zinc solder can be a suitable replacement for tin-lead solder due to its low cost, suitable melting temperature, and desirable mechanical properties. However, due to the high vapor pressure of zinc, manufacturing this alloy using the melt method is very difficult and expensive. In this study, Sn-8.9%Zn lead-free solder was fabricated using the angular accumulative extrusion method of tin sheets and zinc powder in 10, 12, and 15 passes, and characterized. Microstructural investigations were performed using optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction spectroscopy. The shear strength and hardness of the solders were also measured. The results showed that after 12 passes, the dispersion of zinc powder in the tin matrix was improved, and the dissolution of zinc was confirmed by a decrease in the XRD peak intensities. However, after 15 passes, cracks appeared in the structure. The shear strength of the tin-zinc solder joint was about 60% higher than that of commercial tin-lead solder. The wetting angle of this solder on copper was measured to be 21 degrees, and its electrical resistance was measured to be 4.1 nanoohms, which is within the acceptable range for electronic applications, although it has a weaker performance compared to tin-lead solder.

Copper coils are essential components of induction hardening machines. The traditional manufacturing process of these coils utilizes extruded copper profiles. In this study, the production of copper profiles using metal 3D printing was experimentally investigated. Two copper samples with hollow square cross-sections, produced by extrusion and metal 3D printing, were evalated for the purpose of manufacturing induction hardening coils. Density, electrical conductivity, hardness, and surface roughness tests were performed in accordance with the relevant standards. The quantitative results for the extruded and 3D-printed samples were, respectively: density of 99% and 93% of the theoretical density of copper; electrical conductivity of 100.8% and 99.1% relative to the annealed copper standard; Brinell hardness of 50 and 59 HB; and surface roughness (Ra) of 0.324-0.533 and 11.949-13.194. The results indicated that the extruded sample possessed higher density, superior electrical conductivity, and a smoother surface, whereas the 3D-printed sample exhibited higher hardness, lower density, and greater surface roughness. These findings demonstrate that metal 3D printing can be utilized for the manufacturing of induction hardening coils.