Effects of pre-annealing process on microstructure and properties of the Cu-12%Ag composite wire

The as-cast Cu-12%Ag (mass fraction)alloy was pre-annealing treated either at the high temperature 700 degrees C for 2 h followed by 720 degrees C for 2 h or at the low temperature 450 degrees C for 10 h. The composite wires were prepared by drawing the annealed alloy at ambient temperature. The effect of the pre-annealing treatment on the properties of a Cu-Ag microcomposite with middle Ag content was investigated by observing the microstructure and measuring the tensile strength and electrical conductivity. The pre-annealing treatment at the high temperature will eliminate the dendritic segregation more completely in Cu matrix, reduces the volume fraction of eutectic colonies and induces the precipitation of coarse secondary particles, which can result in a low level of electron scattering at solute atoms and phase interfaces. The pre-annealing treatment at the low temperature will,eliminate the dendritic segregation partially, reserves some of non-equilibrium eutectic colonies and induces the precipitation of fine secondary particles, which can result in a high level of dispersion strengthening. There is higher tensile strength for the alloy pre-annealed at the low temperature and higher electrical conductivity for the alloy pre-annealed at the high temperature under the condition of certain draw deformation. In general, the pre-annealing treatment at the high temperature can obtain better matched relationship between strength and conductivity in the microcomposite compared with that at the low temperature.