Regulation of dislocation density and precipitates to maximize the mechanical strength and electrical conductivity in continuously extruded Cu–Ni–Si alloys

Without homogenization or special micro-alloying treatment, the tensile strength and electrical conductivity of a commercial Cu–Ni–Si alloy can achieve 813 MPa and 51.2% IACS, respectively. The excellent combination properties were achieved by regulating the thermomechanical treatment to obtain a critical status of precipitates and dislocation densities. Although a short time pre-aging process can increase the mechanical strength, the electrical conductivity was not dramatically enhanced due to the limited precipitation process. A long-time pre-aging process or a too-high density of dislocations is not favorable to the nucleation of new precipitates, which, instead, causes the coarsening of pre-precipitates, resulting in a limited increase in strength. A critical dislocation density can be determined to boost the nucleation sites of precipitates to simultaneously maximize the mechanical and electrical properties of Cu–Ni–Si alloys. The obtained mechanical and electrical properties can meet the requirements for very large-scale lead frames. Thus, our investigation not only provides a new route for manufacturing high-performance Cu–Ni–Si alloys but also new insights into the role of dislocations in enhancing the mechanical properties of age-hardening alloys.