Precipitation thermodynamics, kinetics and mechanism of Cu–Ni–Si alloy modified by trace 0.1 wt% P doping

This study investigates the effects of 0.1 wt.% phosphorus (P) doping on the performance and microstructure of Cu-Ni-Si alloys. Cu-Ni-Si and Cu-Ni-Si-P alloys were prepared via vacuum induction melting. Through performance testing, microstructural characterization, and thermodynamic and kinetic analysis, the transformation mechanism of the precipitates formed during the aging process was explored. Results indicate that adding 0.1 wt.% P markedly improves the hardness and electrical conductivity of the base Cu-Ni-Si alloy. After aging at 500 °C for 12 h, the Cu-Ni-Si-0.1P alloy exhibits a hardness of 247 HV and an electrical conductivity of 49.22 %IACS. Notably, only the δ-Ni 2 Si phase precipitates in Cu-Ni-Si, whereas both the δ-Ni 2 Si and Ni 12 P 5 phases precipitate in Cu-Ni-Si-0.1P at the early aging stage; at the late aging stage, the Ni 12 P 5 phase transforms into the Ni 3 P phase, which features lower elastic strain energy. Thermodynamic and kinetic analyses reveal that P effectively reduces the activation energy required for phase precipitation in Cu-Ni-Si-P alloys. This reduction not only facilitates precipitate formation but also decreases the concentration of solute atoms in the alloy matrix, thereby synergistically enhancing the alloy’s hardness and electrical conductivity.