Microstructure And Electrical Conductivity Of Cu-Ag Filamentary Microcomposites

The Cu-Ag filamentary microstructures were prepared by heavy cold drawing and intermediate heat treatment. The characteristics of Cu-6%Ag filamentary microstructure and electrical resistivity under different strain condition were investigated and the effect of strain degree on the electrical conductivity of this alloy was discussed. The values of the electrical resistivity of Cu-6%Ag, Cu-6%Ag-0.2%Zr and Cu-24%Ag alloys at various temperatures and draw ratios were investigated. The effects of solute concentration, measured temperature and strain level on the electrical conductivity of the alloys were investigated.With increasing the draw ratio, the Cu-rich dendrites, eutectic colonies and Ag precipitates in the as-cast and homogenized Cu-6%Ag structure develop into the fine filamentary structure and the electrical resistivity increases. The mechanism responsible for the change of electrical resistivity with strain degree is that there is a change of the electronic scattering effect of the dislocation, the phase interface between Ag precipitates and Cu grains and the interface between eutectic filamentary bundles and Cu matrix in the alloy under different strain degree. The change of the electrical resistivity with strain when the filamentary structure evolves into nanoscale at heavy draw ratios is generally in accord with the interfacial scattering model proposed in the presented investigation on the composites with higher Ag contents.The filamentary composite structures of Cu-6%Ag, Cu-6%Ag-0.2%Zr and Cu-24%Ag composites all evolve from the primary a grains, eutectic colonies and secondary precipitates in the original as-cast structure during heavy drawing strain. At low temperatures the Zr or Ag solute obviously impairs the conductivity. With the increase of measured temperature, the conductivity decreases for all tested composites, especially for the Cu-6%Ag. With the increase of drawing strain level, the electrical resistivity slightly increases at measured temperatures lower than 293K and slightly decreases at measured temperatures higher than 393K. The electrical resistance is mainly produced by dislocation and interface scattering at lower measured temperatures and by phonon scattering at higher measured temperatures.