Pre-aging induced concurrent enhancement of mechanical properties and softening resistance performance of Cu–Ni–Co–Si alloys

The effect of pre-aging on the microstructure and properties of the Cu-3.0Ni-1.0Co-0.9Si alloy subjected to two-stage aging treatment was investigated. The microstructure evolution, strengthening mechanism, and softening resistance performance of the alloy during thermomechanical treatment were discussed. The results demonstrated that the pre-aged two-stage aging treatment simultaneously enhanced the mechanical properties and softening resistance performance. The alloy achieved an excellent tensile strength of 1003 MPa, a high softening temperature of 510 °C, and a considerable electrical conductivity of 40 %IACS. Notably, compared to conventional two-stage aging, this strategy resulted in significant improvements of 104 MPa in tensile strength and 35 °C in softening temperature. Microstructural analysis revealed that the enhancement was attributed to the formation of fine, dispersed precipitates during pre-aging, which were inherited into the subsequent thermomechanical process, resulting in a favorable dual-scale precipitate distribution. Furthermore, first-principles calculations and experimental evidence indicated that the low interfacial energy between these precipitates and the Cu matrix was the underlying mechanism for the low coarsening rate and high recrystallization braking force, leading to superior softening resistance. This work provided a feasible strategy for developing high-performance Cu–Ni–Co–Si alloys with an optimal combination of strength, conductivity, and thermal stability.