Low-temperature joining of Fe-based amorphous foil with aluminum by ultrasonic-assisted soldering with Sn-based fillers

•Fe-based amorphous/aluminum was robustly soldered by ultrasonic-assisted way.•Scallop α-Al solid solutions and FeZn13 were formed at two interfaces.•Ultrasonic corrosion was severe on the aluminum up to 50 μm depth.•Activation energy for FeZn13 was 30.9 kJ/mol on the Fe-based amorphous.

Low temperature joining of amorphous alloys has big challenges to prevent them from crystallization. An ultrasonic-assisted soldering method was proposed to join the Fe-based amorphous alloys with the aluminum plates in air by using Sn-based solders. No obvious defects were observed and the joining ratio was more than 90%. At the interface of solder/aluminum, scallop α-Al solid solutions were formed and large fretting (pits) with a size of 50 μm on the aluminum plates was found due to ultrasonic vibrations. At the interface of solder/amorphous, Fe–Zn intermetallic compound (FeZn13) was probably formed. Its formation activation energy was approximately 30.9 kJ/mol between the amorphous iron and the Sn–9Zn during the solid state diffusion, which was much lower compared with crystallized couples. The enhanced diffusion/reaction and the much low activation energy in this work are probably attributed to the amorphous state of the Fe-based foils. Adding nickel in the Sn–Zn solder can improve the hardness of the joints by formation of NiAl3 intermetallic particles and depress the corrosion on the aluminum. Both the initially interfacial wetting and the microstructure refinement during solidification of the filler solder were improved by ultrasonic vibrations.

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