Bimetallic Terminal Pressure Welding Metallurgical Bonding: A Process For Joining Dissimilar Metals Such As Copper And Aluminum.

In the field of electrical connections, the transition between dissimilar metals, copper and aluminum, has always been a challenging problem requiring precise handling in engineering design. bimetallic lugs solves this problem at the material level by using pressure welding metallurgical bonding method—no solder is needed, pure solid pressure causes the two metals to form an interatomic bond at the contact interface, and the connection strength tends to be consistent with the base material.

Three-tiered characteristics of the interface structure

The bi metal cable lug pressure weld joint exhibits clear layered characteristics at the microscopic level:

• Bonding zone: Significant grain refinement, influenced by intense plastic deformation, forming a high-density dislocation structure, with tensile strength approaching or exceeding that of the aluminum-side base material.

• Heat-Affected Zone: Pressure welding is a cold-state process, resulting in an extremely narrow heat-affected zone. The microstructural changes are far less pronounced than in friction welding or explosive welding, which helps maintain the conductivity of both copper and aluminum.

• Base material area: The copper end and aluminum end retain their original physical properties, and their conductivity and coefficient of thermal expansion are not affected by the process. The thermal cycle stress of bi metal lugs connectors during operation is thus effectively dispersed.

The Formation Mechanism of Metallurgical Bonding in Pressure Welding

The core of pressure welding lies in interface purification and atomic contact driven by plastic deformation. During the pressure application process, the oxide film on the copper-aluminum interface breaks down with the material flow, extruding fresh metal from the cracks. The two clean metal surfaces come together at extremely close range, ultimately achieving the contact conditions required for interatomic bonding. This process requires no external heat source and can achieve metallurgical bonding at room temperature.

Taking the production of bi metallic cable lugs terminals as an example, the copper and aluminum ends undergo multiple upsetting processes in the pressure welding equipment. Oxides and air gaps are gradually removed from the interface with each deformation, resulting in a processed structure rather than a cast structure in the bonding area. This avoids the problem of embrittlement of intermetallic compounds in copper-aluminum welding processes.

The stability of the pressure welding quality of bimetallic terminals depends on the coordinated operation of three parameters: the number of upsetting processes, the amount of deformation, and the precision of the die. Insufficient deformation leads to residual oxides at the interface, while excessive deformation may cause cracks. A standardized upsetting procedure is a prerequisite for obtaining reliable metallurgical bonding. This is why professional manufacturers consider mold tolerance control and process parameter management as core aspects of the bimetallic terminal block production quality system.