Microstructure evolution and properties of Cu-Ag microcomposites with different Ag content

The Cu-Ag microcomposites containing 6, 12 and 24 wt.% Ag were prepared by cold drawing combined with intermediate heat treatments. The microstructure was observed and the tensile strength and electrical conductivity were determined at various draw ratios. The original Ot dendrites, eutectic colonies and secondary precipitates evolve into filamentary bundles with tight arrangement of double phases during heavy cold drawing. The strength increases and the electrical conductivity decreases with draw ratio increasing. High Ag content produces high hardening rate, high tensile strength and low electrical conductivity. A continuous eutectic net can result in distinct strengthening and strong scattering. The strengthening in the Cu-6 wt.% Ag depends mainly on the strengthening of Cu matrix. The increased density of the interface between Cu matrix and eutectic colonies in the Cu-12 wt.% Ag with strong drawing strain creates an additional strengthening profit from the filamentary mixture. More Ag precipitates and higher interface density in the Cu-24 wt.% Ag result in earlier presence of the additional strengthening profit. The eutectic morphology has more important effect on the strength and conductivity in the Cu-Ag microcomposites than the eutectic volume fraction. (c) 2006 Elsevier B.V. All rights reserved.