With the rapid development of aerospace, automobile manufacturing, and electronics industries, composite components of copper and aluminum dissimilar metals have become more and more widely used. Relevant research on copper-aluminum dissimilar metal welding focuses on brazing, laser welding, friction stir welding, ultrasonic welding, etc.
Ultrasonic welding (Ultrasonic welding) is a solid-state welding technology. It uses high-frequency vibration of ultrasonic waves and under the action of static pressure, converts the mechanical vibration energy of ultrasonic frequency into deformation work and friction heat between the workpieces to be welded, thereby A welding method that enables reliable connection of workpieces.
Compared with other welding processes, its advantages such as short welding time and low energy input make this welding process more efficient, thereby saving costs and improving production efficiency. These characteristics make this technology suitable for the welding of copper foil-aluminum foil dissimilar metals.
Ultrasonic welding can be divided into the following processes: initial contact process, friction heat generation process, welding softening process, solid phase bonding process, and over-welding process.
- Initial contact process: In the initial stage of the ultrasonic welding process, under the action of welding pressure, the two workpieces to be welded form close contact, generating frictional heat and causing a short connection, thereby fully transmitting ultrasonic vibration to the contact of the workpieces to be welded. noodle.
- Friction heat generation process: During the ultrasonic welding process, the relative friction between the workpieces to be welded caused by ultrasonic vibration gradually expands from the initial friction between bumps to surface friction. During this period, impurities such as the oxide film on the metal surface are broken up and dispersed into the material.
- Welding softening process: During the reciprocating friction process of the ultrasonic vibration of the copper-aluminum ultrasonic welding interface, the temperature of the contact interface of the workpiece to be welded increases rapidly, resulting in a large amount of plastic deformation, and the thermal effect continues to intensify.
- The relative displacement between the workpieces to be welded increases sharply, and the outer area of the upper weldment is lifted upward. Material softening and large amounts of plastic deformation caused by frictional heat generate connections in some areas of the welding interface.
- Solid phase bonding process: As friction continues, after the oxide film on the surface of the workpiece to be welded is removed, the contact area of the welding interface continues to increase. The relative displacement of the welded workpiece in this process is small, and the welding interface connection area shows strong fluctuations.
- Under the combined action of welding static pressure and ultrasonic vibration, the joint points and joint area of the welding interface gradually increase. When the copper-aluminum bonding force exceeds the vibration tangential force, a strong joint is formed. In the later stage of the solid-phase connection process, the fluctuations in the connection area of the welding interface basically disappear, and the bonding area is relatively calm.
