No solid-solution treatment needed: Peak aging and enhanced properties of cold-drawn Cu-Ag alloy

Abstract TThe aging process has significant effects on the microstructures and properties of copper-based alloys. Furthermore, the effects of aging are increased by conventional solid-solution processing to obtain these materials as supersaturated matrices. In this study, it was observed that the electrical conductivity (85 %IACS) and tensile strength (830 MPa) of a peak-aged, cold-drawn Cu-4.5wt.%Ag alloy prepared without solid-solution treatment were higher than those of the corresponding alloy prepared with solid-solution treatment. The eutectic-, grain-, precipitation-, and dislocation-strengthening effects were investigated via SEM, EBSD, TEM, and XRD analyses. There exist supersaturated Ag atoms in the as-cast Cu-Ag alloy prepared by controlled cooling continuous casting. During the peak-aging process, solute Ag atoms in the as-cast Cu-Ag alloy precipitated from this supersaturated matrix.This precipitation behavior ultimately achieved a strengthening effect equivalent to that of the alloy prepared without solid-solution treatment. The difference in the tensile strengths of the Cu-4.5wt.%Ag alloys fabricated via three different routes was attributed to precipitation and dislocation phenomena. Furthermore, residual solute Ag atoms were found to dramatically decrease electrical conductivity, which explains why the alloy without solid-solution treatment exhibited high conductivity.