Annealing effects on the microstructure, strength, and electrical resistivity in a dual-phase Cu-15 wt%Ag alloy

The precipitation behavior and the microstructural evolution of a dual-phase Cu-15 wt%Ag alloy during annealing were investigated. We discussed the effects of dislocation density, grain size, solute atom concentration, and precipitation morphology on strength and electrical conductivity. The results showed that continuous precipitation and discontinuous precipitation simultaneously occurred during the annealing of the Cu-15 wt%Ag alloy. It was accompanied by pronounced recovery and recrystallization, significantly decreasing the strength and electrical resistivity of the cold-rolled Cu-15 wt%Ag alloy. After 48 h of annealing at 350 °C, the fully recrystallized Cu-15 wt%Ag alloy exhibited a higher strength (299 MPa) and a lower electrical resistivity (1.92 μΩ cm) compared to the samples annealed at higher temperatures. The higher strength was attributed to smaller grain size and higher volume fraction of the continuous precipitation zone. Nanoscale Ag precipitates formed by continuous precipitation provided more extensive precipitation strengthening than sub-micrometer Ag precipitates formed by discontinuous precipitation. In addition, reducing the dislocation density and the concentration of solid atoms by controlling the annealing conditions was an effective strategy to weaken the dislocation scattering and impurity scattering effect in the Cu-15 wt%Ag alloy. The electrical resistivity of the fully crystallized Cu-15 wt%Ag alloy was linearly correlated to the concentration of Ag solute atoms. The electrical resistivity of the annealed Cu-15 wt%Ag alloy increased by 0.117 μΩ cm when 1 at.% Ag was dissolved in the Cu solid solution.