Modeling remelting induced destabilization of lamellar eutectic structure in an undercooled Ni-18.7 at.% Sn eutectic alloy

Abstract

Achieving a high melt undercooling (ΔT) is expected as an effective strategy to significantly reduce lamellar spacing of bulk eutectic alloys. However, the undercooled eutectic alloys usually exhibit coarse anomalous eutectic structure (AES) when ΔT exceeds a certain value. In our recent work (Scripta Materialia, 177 (2020) 123–127), we showed that in an undercooled Ni-18.7 at.% Sn eutectic alloy the remelting induced destabilization of primary lamellar eutectic structure (PLES) during the post-recalescence period can lead to the formation of the AES using high-temperature laser scanning confocal microscopy technique. In this work, an analytical model within the framework of interface stability analyses is established to quantitatively describe the destabilization of PLES during the post-recalescence period. The model calculations show good agreement with the experimental results. The analyses based on the derived model indicate that the destabilization of PLES is driven by solute supersaturation and capillary force. The former amplifies the interface perturbation of the eutectic lamellae and initiates the destabilization, while the latter dominates the subsequent morphological transition process. We further showed that our model is consistent with the reported experimental results of other undercooled eutectic alloys.