Metastable phase separation kinetics controlled by superheating and undercooling of liquid Fe-Cu peritectic alloys

The effects of superheating and undercooling on the metastable phase separation (MPS) kinetics for glass-fluxed Fe65Cu35 peritectic alloy were investigated by experiments and simulations. MPS occurred in the experimental undercooling range of 175–297 K, and induced the eccentric core-shell macrosegregation (ECSM) structure. It was first demonstrated that the relationship of the phase separation undercooling ΔTPS and the phase separation time tPS with the superheating ΔTH and the undercooling ΔT could be described by curved-surface functions. The increasing ΔTPS was observed under the smaller ΔTH or greater ΔT condition. Both the rising ΔTH and the ΔT contributed to the extension of the tPS, and then resulted in the expansion of Cu-rich zone as well as the microhardness improvement of Fe-rich zone, indicating the more thorough MPS. Numerical simulations showed that the surface segregation, Marangoni convection and Stokes sedimentation mainly pushed the evolution of the ECSM.