Carbon Restrains the Precipitation of Cu-Rich Nanoparticles in CuFeMnNi HEAs.

In this study, we report a strategy to suppress the formation of large Cu-rich particles by adding excessive interstitial carbon into CuFeMnNi high-entropy alloys. With the increase in C contents in the CuFeMnNi HEAs annealed at 1000 °C, the size and area fraction of the submicron Cu-rich particles markedly decreased. Of note, the CuFeMnNi 1.5 at. %C alloy containing nanosized Cu-rich particles (13 nm) displayed excellent strength-ductility synergy, with yield strength of 695 ± 10 MPa, ultimate tensile strength of 925 ± 20 MPa, and ductility of 21.5%. This is because the addition of carbon significantly increases the diffusion speed of Cu atoms, thereby restraining the growth of Cu-rich nanoparticles. As a result, the comprehensive mechanical properties of the prepared HEAs were significantly enhanced. Additionally, the active diffusion channels induced by high-temperature short-time annealing significantly inhibited the grain growth, which improved the ductility. This work creates a new strategy for solving the dilemma caused by the large Cu-rich particles in the Cu-containing HEAs.