Three-dimensional phase-field simulations of microstructure evolution in Cu–Co immiscible alloys

Immiscible alloys hold great promise for industrial and electronic applications. The complexity of liquid-phase separation and the difficulty of in situ observation often necessitate numerical simulation. However, two-dimensional models cannot capture genuine three-dimensional morphology or coupled multiphysics effects. To overcome these limitations, a three-dimensional phase-field model was developed for the Cu–Co binary system, coupled with systematic undercooling experiments to investigate the dynamic evolution mechanisms of phase separation. The results show that, under the combined effects of Marangoni motion and Ostwald ripening, Cu–Co alloys with different compositions undergo distinct microstructural evolutions, eventually forming core-shell structures with a Co-rich core and a Cu-rich shell. The phase with a lower volume fraction preferentially migrates and nucleates toward the interior of the melt, while differences in surface tension determine the final morphology of the core-shell structure. The simulation results show a high degree of consistency with the experimentally processed alloys morphologies, thereby validating the model and providing a reference for three-dimensional modeling of alloy microstructural evolution under coupled multiphysics conditions.