Strengthening mechanism of ultra-high strength Cu–20Ag alloy wire induced by cumulative strain

This study deals with the evolution of strength and microstructure in Cu–20Ag alloy during wire drawing from an initial diameter of 7.84 mm–0.02 mm. The final wire had a strength of 1670 MPa and 53.8% of the conductivity of international annealed copper standard (IACS). Electron backscattering diffraction (EBSD) and transmission electron microscope (TEM) were used for microstructural characterization in the later stages of deformation, we found that many boundaries resulting from the lamellar structures and the occurrence of nano-twins formed in the lamellar improved the strength of the wire. When the wire diameter is less than 2.95 mm，with an essentially constant dislocation density, the strength can be related solely to strengthening boundaries by a grain size refinement. The strengthening mechanism of the wire during cumulative strain is discussed.