Rotary swaging-drawing formation, microstructure, and properties of copper-clad aluminum composite micro-wires

Copper-clad aluminum wires are extensively applied in aerospace, telecommunications, national defense industry, and other fields, because of the combined advantages of the excellent conductivity, thermal conductivity, and low contact resistance of copper and the low density, corrosion resistance, and low costs of aluminum. In this study, a composite wire with high interfacial bonding quality was obtained by hot rotary swaging, which can be utilized in manufacturing to achieve high efficiency and high quality because of its feature of the large single-pass deformation. The processed wire was then prepared by drawing into micro-wires, and given this, a simple, inexpensive, and highly efficient method for preparing micro-wires was developed in this study. Copper-clad aluminum wires with a diameter of φ65 μm, uniformly thick coating, glossy surface, and good interfacial bonding were prepared by the hot rotary swaging-drawing method. The rotary swaging parameters and the microstructure and interfacial bonding of the composite wire were studied, and the effects of drawing and intermediate annealing on its microstructure and properties were discussed. The results show that the reasonable swaging parameters are 350℃ swaging temperature with 40% single-pass deformation. After the rotary swaging, dynamic recrystallization microstructures and interface diffusion layer with thickness of 0.7 μm are formed. The optimum annealing parameter is 350℃/30 min (350℃ annealing temperature with 30 min annealing time), under which the elongation reaches 35.7%, the thickness of interface diffusion layer is 2.1 μm, and the copper layer and the aluminum core are recrystallized with the formation of equiaxed grains. When the annealing temperature exceeds 350℃, copper and aluminum grains and the interface layer thickness increase, which will lead to a lower wire elongation. A wire of φ0.96 mm is fabricated by a 15%-20% single-pass deformation, and then the φ65 μm diameter wire is manufactured by an 8%-15% single-pass deformation without annealing. In the drawing process, 〈111〉 silk texture appears in the copper layer and the aluminum core.