Strain-stress Behavior And Microstructure Of Cu-Ag Filamentary Microcomposites

The Cu-Ag filamentary microstructures were prepared by heavy cold drawing and intermediate heat treatment. The microstructure and stress-strain curves of Cu-6%Ag, Cu-12%Ag, Cu-12%Ag-0.1%RE alloys were investigated and the effect of Ag content, strain, microstructure, and rare-earth element on the stress-strain behavior of the Cu-Ag alloy was discussed.With increasing drawing strain, the ultimate tensile strength and Young's modulus of both alloys Cu-6%Ag and Cu-12%Ag show an evident increase in a certain range of drawing strain and a slow increase as drawing strain higher than a certain value. The Cu-12%Ag has higher strain hardening rate and ultimate tensile strength than the Cu-6%Ag. The Young's modulus of the Cu-6%Ag is higher than that of the Cu-12%Ag in the range of lower strain degree while the Yang's modulus of the Cu-6%Ag is lower than that of the Cu-12%Ag in the range of higher strain degree. High density of crystal defects in the filamentary structure of both alloys results in lower Yang's modulus than theoretical predicted value.Adding 0.1 %RE into the Cu-12%Ag can change the morphology of the Cu dendrites and the solubility of Ag in Cu phase. The grain size decreases slightly after microalloying of rare earth elements. At the low or middle draw ratios, adding rare earth elements can improve the ultimate tensile strength, elongation percentage and plastic deformation capacity to a certain degree but decreases the Young's modulus. In the range of heavy drawing strain, the mechanical properties of the Cu-12%Ag are similar to the Cu-12%Ag-0.1%RE. The effect of suitable microalloying of rare earth elements in the Cu-Ag alloy on mechanical properties is remarkable in the range of lower drawing strain but unremarkable in the range of higher drawing strain.The heat treatments were carried out at different temperatures for the Cu-12%Ag alloy subjected to a heavy drawing. The effect of final heat treatments on the relationship between stress and strain behaviors and the microstructure wereinvestigated. For the alloy annealed at 200℃, the ultimate tensile strength and Young's modulus decrease slightly while the elongation percentage and elastic proportional limit increase. For the alloy annealed at 300℃, the ultimate tensile strength decreases significantly while the Young's modulus decreases mildly. For the alloy annealed at 400℃, the ultimate tensile strength and Young's modulus decrease significantly. The elongation percentage and elastic proportional limit show an insignificant change when the annealing temperature is lower than 400℃. For the alloy annealed at 500℃, the ultimate tensile strength and Young's modulus show a slower decrease and the elongation percentage and elastic proportional limit increase significantly.