Effect of Co content on precipitation behavior of γ′ phase strengthened CoNi-based alloys

The CoNi-based alloys with nano-precipitates exhibit significant advantages in high-temperature applications due to their excellent thermal stability. This study investigates the influence of Co content (0 at%, 22.5 at%, 45.0 at%) on the morphological evolution, coarsening kinetics of γ' phases, and γ/γ' lattice misfit. The results reveal that the γ/γ' lattice misfit increases with increasing Co content. The addition of Co not only increases the number density of γ' phases but also effectively suppresses the coarsening of precipitates. Moreover, the coarsening rate constant of the γ' phase decreases with increasing Co content, with the alloy containing 45.0 at% Co exhibiting the lowest coarsening rate at 1.04 × 10−28 m3/s. Additionally, the increase in Co content enhances the hardness of the alloy, primarily due to the increased volume fraction of the γ' phase. This study contributes to understanding the mechanism of Co content variation on the characteristics and thermal stability of precipitates, providing support for the design of CoNi-based alloys. [Display omitted]