Microstructures and properties of the Fe-based amorphous foil/aluminum dissimilar joint by ultrasonic-assisted soldering

Bulk metallic glasses (BMGs) have no periodicity in a long range. To adopt BMGs in broader fields of engineering applications, joining between BMGs/BMGs or BMGs/crystalline alloys is crucial. Fe-based amorphous foils are one of the most excellent soft magnetic materials and have been applied in amorphous motors. One big challenge during assembling amorphous stators with aluminum shells is how to obtain a robust joining between them. In this study, ultrasonic-assisted soldering of 100 μm thick Fe-based amorphous foils with aluminum alloys was investigated by using Sn-based fillers in air. To enhance the wetting abilities, ultrasounds with a resonant frequency of about 27 kHz and vibration amplitude of 15 μm were introduced during the soldering process. It was found that both interfaces of the filler/Fe-based amorphous and the filler/aluminum plate were metallurgically joined by the Sn-Zn filler. Both the ultrasonic power and soldering time resulted in the homogeneously distributed and refined Zn-rich phases. Fretting of the filler on the aluminum surface was observed and it was severe when the ultrasonic power and the soldering time were large enough. Ultrasounds may have positive effects on the interfacial wetting and microstructure refinement.