Microstructural evolution and its effect on the mechanical properties of Cu–Ag microcomposites

Abstract

Abstract The microstructure and the mechanical properties of Cu– Ag alloys with 7 and 24 wt.% Ag are investigated. The microstructure of the alloys is mostly determined by the silver content. That of Cu-24 wt.% Ag alloys consists of a Cu-rich solid solution and the eutectic. Otherwise, the microstructure of Cu-7 wt.% Ag alloys consists of primarily solidified dendrites of a Cu-rich solid solution and small Ag-rich particles. The composition strongly influences the work-hardening rate. In order to achieve an ultimate tensile strength of 1 GPa, a logarithmic cold-deformation strain, η, of about 3.7 is required (η = ln A 0/A) for the 7 wt.% Ag alloy, whereas for Cu-24 wt.% Ag alloys η = 3.1 is sufficient. In as-cast alloys with 7 wt.% Ag a strong segregation is observed, which, consequently, leads to a strong decrease of the age-hardening effect. Therefore, the Cu-7 wt.% Ag alloy has to be homogenised before aging. The application of Cu–Ag alloys with a Ag-content below 8 wt.%, i. e. an the maximum solubility at the eutectic temperature, bears mainly two advantages: (i) less addiction to shear-band formation, and (ii) a higher electrical conductivity in comparison to equivalently treated Ag-rich alloys due to the small Ag content.