Soldering of Zr-based bulk metallic glass and copper by Au–12Ge eutectic alloy

Zr-based bulk metallic glass and copper with different surface roughness were soldered using low temperature eutectic Au–12Ge (wt%) solder on a thermomechanical simulator. The cross-sectional microstructures of the brazed joints were analyzed by scanning electron microscopy (SEM) and transmission electron microscope (TEM) in detail, and the compositional distribution along the interface was analyzed by energy-dispersive spectrometer (EDS). Results show that the surface roughness of base metals plays an important role in the quality of the brazed joint because the surface roughness can enlarge the effective contact area, which can improve the brazing surface quality between two materials. A moderate roughness of treated Zr-based metallic glass of 18 μm is shown to be the best for the soldering, while the surface roughness has a weak effect on the soldering behavior of Au–12Ge solder on copper. After soldering, long-range diffusion of atoms occurs between the base metal and solder, and five distinct regions are formed at the joint region.