Investigation of resistance heat assisted ultrasonic welding of 6061 aluminum alloys to pure copper

• New concept of resistance heat assisted ultrasonic welding (RUSW).
• 6061 Al and pure Cu were successfully welded by RUSW.
• The output power of transducer and the temperature of the interface are increased significantly in RUSW.
• The microstructure and the mechanical properties of the RUSW joints were improved.

This paper proposes a new welding method for joining non-ferrous metals: resistance heat assisted ultrasonic welding. Resistance heat generated by the electric Joule effect is used as an additional electrical energy source to assist ultrasonic welding process. A comparison is conducted between two dissimilar Al–Cu joints, one produced by ultrasonic welding and the other by resistance heat assisted ultrasonic welding. In the resistance heat assisted ultrasonic process, the peak power of ultrasonic vibration increases significantly. The interfacial reaction between aluminum and copper is studied as a function of the current. The thickness of the intermetallic compound layer, which is predominantly composed of CuAl2, increases with the current. At a relatively high current (1500 A), resistance heat assisted ultrasonic welding produced a dendritic solidification microstructure at the interface, due to the occurrence of a eutectic reaction, α-Al + θ → L, during the welding process. The influence of current on the mechanical properties of the joints is also discussed.

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