Optimisation of heat-treatment parameters for Cu–Ni–Co–Si alloy using in situ high-temperature measurements

Cu–Ni–Co–Si alloys are widely used in electrical and electronic applications owing to their superior mechanical properties, high electrical conductivity and favourable formability. To address the trade-off between strength and conductivity in conventional processes, this study optimised the solution and ageing regimes using in situ high-temperature hardness, conductivity and X-ray diffraction measurements. When held at 1000 °C for 5 h, the in situ hardness stabilised at 12 HV. Treatment at 450 °C for 2 h yielded optimal properties, including an in situ hardness of 95 HV, conductivity of 24.7% IACS and a dislocation density of 13.15 × 10 14 m −2 . The optimised alloy exhibited uniformly dispersed nano-sized (Ni, Co) 2 Si precipitates, forming a coherent interface with the Cu matrix, achieving favourable strength–conductivity synergy. In situ conductivity analysis was used to establish kinetic equations at 450 °C: σ 450 °C = 0.2006 + 0.0099 ln t (conductivity vs. ageing time) and f 450 °C = 56.5794 + 5.1476 ln t (precipitation vs. time), consistent with experiments. Precipitation strengthening played a crucial role, accounting for 60.7% of the total strength. This optimised single-stage heat treatment streamlines production and enhances performance, providing a viable material solution for high-end electrical applications.