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 preaging 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.