Uncoupling Growth Mechanisms of Binary Eutectics during Rapid Solidification

Eutectic solidification under rapid solidification conditions has enormous applications, as it can produce microstructure-refined and interface-stable combined composite structures with low cost. However, investigations reported that the coupled interfaces will be destroyed under the condition of large undercoolings. For further understanding of the mechanisms of uncoupling growth, we investigated the uncoupling growth process of binary eutectics during rapid solidification using atomistic simulations. We find that both the nucleation rate and the crystallization velocity for the first phase of eutectics are very high; however, nucleation of the second phase is very inactive: its nucleation rate is low and nucleation incubation time is very long. As the nucleation of the eutectic second phase is severely suppressed during rapid solidifications, the crystallization of the second phase lags far behind, therefore we speculate that the uncoupling growth of eutectics during rapid solidification is nucleation-induced.