In industrial production and daily life, copper and aluminum are two highly representative metallic materials, each occupying an important position due to their unique advantages. Copper boasts excellent electrical and thermal conductivity and strong chemical stability, while aluminum stands out for its lightweight, low cost, and abundant resources. Effectively joining copper and aluminum can combine the advantages of both materials, optimize product performance, and reduce production costs, thus having wide application demand in many fields such as power transmission, rail transportation, and new energy. However, the significant differences in the physicochemical properties of copper and aluminum present numerous challenges to their joining process, leading to the development of various targeted joining technologies.
The core difficulty in joining copper and aluminum stems from their fundamental differences. Physically, copper has a melting point of approximately 1083℃, while aluminum's melting point is only 660℃. This significant difference in melting points means that in traditional welding processes, aluminum tends to melt first and excessively leak out, making it difficult to form a uniform weld. Simultaneously, their coefficients of thermal expansion differ, resulting in significant internal stress during temperature changes after joining, which can easily lead to joint cracking. Chemically, aluminum readily forms a dense oxide film in air. This oxide film has a high melting point and poor conductivity; if not effectively removed, it severely impacts the conductivity and connection strength of the joint. Furthermore, copper and aluminum can form intermetallic compounds under certain conditions. These compounds are brittle and significantly reduce the mechanical properties of the joint, affecting connection reliability.
Several mature copper-aluminum joining technologies have been developed to suit different application scenarios. Brazing is a commonly used method. By selecting a suitable filler metal and melting it at a temperature below the melting points of the copper and aluminum base materials, capillary action fills the joint gap, achieving a connection. This technology effectively controls the melting degree of the base materials, reduces internal stress, and is suitable for small components requiring high connection precision. Crimping technology, with its advantages of ease of operation and high efficiency, is widely used in fields such as power cable connections. External force causes plastic deformation of the copper-aluminum joint, breaking the oxide film on the aluminum surface and allowing the two metals to come into close contact, forming a connection. Subsequent methods such as tin plating and coating with anti-corrosion layers can improve the joint's corrosion resistance.
With the development of industrial technology, advanced technologies such as fusion welding and friction welding have been gradually applied to the field of copper-aluminum joining. Fusion welding technology solves the welding problems caused by differences in melting points by precisely controlling heat source parameters, making it suitable for joining large components. Friction welding utilizes the heat generated by mechanical friction to bring the metal at the joint to a plastic state, and then completes the connection by applying pressure. It has advantages such as stable joint quality, high welding efficiency, and no pollutant emissions, which aligns with the development trend of green manufacturing.
Copper-aluminum joining technology is a significant breakthrough in the field of materials application. It achieves the complementarity of the advantages of different materials and promotes technological upgrades in related industries. In the future, with the continuous improvement of requirements for connection reliability, efficiency, and environmental protection, copper-aluminum joining technology will develop towards greater precision and intelligence, providing stronger technical support for industrial production and social development.
