Influence of intermetallic compounds on the electrical resistivity of architectured copper clad aluminum composites elaborated by a restacking drawing method

Highlights: • Drawing of architectured Al/Cu composites containing micro-filaments • After annealing, intermetallic compounds (IMC) volume fraction is inversely proportional to the wire diameter. • Equivalent resistivity of the composites can be predicted by a simple model. • Until 12% of IMC in the composite, the resistivity remains stable. • Estimation of the average electrical resistivity of Al-Cu IMC around 4.5 μΩ·cm Architectured wires containing 61 restacked Copper Clad Aluminum (CCA) wires were cold-drawn down to a diameter of 1 mm without intermediate annealing. Samples were taken at intermediate diameters of 3 mm and 1.7 mm to observe the wire structure at different steps. Independently of the wire diameter, the structure did not exhibit any porosity and initial CCA wires were uniformly distributed inside the structure with constant equivalent diameters. Post-elaboration annealing treatments performed on CCA and architectured wires led to the formation of Al₂Cu, AlCu and Al₄Cu₉ intermetallic compounds (IMC). It was shown that IMC growth kinetics do not depend on the wire diameter, indicating no marked influence of the plastic deformation. The volume fraction of IMC strongly increased with the reduction of the diameter and impacted the electrical resistivity of the architectured wire. The equivalent resistivity has been easily computed by a linear rule of mixture model, with three electrical resistances in parallel (Al, Cu and IMC), weighted by their respective volume fraction. This model allowed extracting a mean resistivity of IMCs of 4.5 μΩ·cm. It also demonstrated that this restacking drawing process, without any intermediate annealing treatment is an interesting method for the elaboration of architectured wires with optimized functional properties.