Phase-field simulation of phase separation coupled with thermodynamic databases in FeNiCrCoCu high-entropy alloys

The simulation of microstructural evolution in multi-principal element alloys is still challenging although for alloy development it is of high importance. In the work, a phase-field model linked with CALPHAD thermodynamic databases is utilized to explore the microstructural evolution during diffusion-controlled phase separation in the Fe-Ni-Cr-Co-Cu high-entropy alloy system with elastic lattice misfit. The compositional fluctuation and temperature effect on the elemental distribution and the kinetics of Cu-enriched phase formation are systematically investigated. The simulated results show that the Cu-enriched phase has a complicated core-shell structure consisting of a Cu-enriched core and a Ni/Fe shell. The latter as a buffer layer possesses retardant effect on the formation of Cu-enriched precipitates. Furthermore, the high Ni/Fe concentration delays the phase separation, growth and coarsening of the Cu-enriched phase, leading to particle refinement and the increasing width of the Ni/Fe shell. Besides, high temperature accelerates the phase separation and simultaneously promotes the growth and coarsening of nanoscale Cu-enriched precipitates. The present work expands the knowledge of phase separation in multicomponent alloy systems and provides insights to optimize material microstructure and properties.