Investigation of the Softening Resistance Behavior and Its Mechanism in Cu-Ni-Si Alloys with Discontinuous Precipitates

In this study, isothermal annealing experiments were conducted on copper-nickel-silicon alloys containing continuous precipitates (CP) and discontinuous precipitates (DP) to investigate the effects of different types of precipitate phases on the microstructural evolution and softening temperature during annealing, as well as to analyze the differences in softening mechanisms. The experimental results revealed that the softening temperature of the CP alloy, subjected to 75% cold deformation, was 505 °C. In contrast, the DP alloy achieved softening temperatures of 575 °C and 515 °C after 75% and 97.5% cold deformation, respectively. This indicates that the DP alloy exhibits significantly superior softening resistance compared to the CP alloy, attributed to the distinct softening mechanisms of the two alloys. In the CP alloy, softening is primarily influenced by factors such as the coarsening of the precipitate phase, the occurrence of recrystallization, and the reduction in dislocation density. In the DP alloy, the balling phenomenon of the DP phase is more pronounced, and its unique microstructure exerts a stronger hindrance to dislocation and grain boundary motion. This hindrance effect reduces the extent of recrystallization and results in a smaller decrease in dislocation density. In summary, the DP alloy, due to its unique microstructure and softening mechanisms, demonstrates better softening resistance, providing higher durability and stability for high-temperature applications.