Phase-field simulation on the heteroepitaxial nucleation of (Fe,Co) solid solution on facet phase in undercooled liquid

•Heterogeneous growth phase field model is modified to apply to Fe-Co-Si system.•Crystal orientation of (Si) affects the growth velocity and grain morphology of (Fe,Co) neclei.•Undercooling promotes the formation of nucleation defects. The nucleation process of (Fe,Co) solid solution epitaxially grown on the primary phase (Si) has been investigated by the phase-field method in Fe-41 wt%Co alloy. The effects on nucleation by such factors as the crystal orientation of the primary phase, the undercooling, the interface thickness, the anisotropy factor, the effective deposition rate, and the phase-field variable of primary phase were analyzed in great details. The results show that the nucleus morphology on Si {111} crystal surface is more complete than those on Si {110} and Si {100}. At high undercooling, more defects form in the nucleus. When the ratio of the interface thickness to the capillary length is W0/d0=5, the nucleus contain the least defects. As the anisotropy coefficient increases, the interface disturbance of the nucleus is more complex. But when the anisotropy coefficient is ε=0.03, the interface disturbance is the minimal, and the nucleus morphology is the most integrated. The nucleation radius increases as the effective deposition rate rises from 2 to 7ML/s. When the phase-field variable of primary phase takes ϕS=0, the nucleus morphology is the most complete.