Coupling eutectic nucleation mechanism investigated by phase field crystal model

Eutectic solidification has been investigated for decades; however, our understanding of the mechanism of eutectic nucleation remains very limited. In this work, we investigated the regular eutectic solidification process by an atomistic simulation method, and a new eutectic nucleation scenario is proposed. We found that, near the eutectic composition, the nucleation of a metastable triangle phase is more energy favorable for diffusion-controlled binary eutectic systems, and the solidification often passes through a transient state. With the proceeding of solidification, alternated A-rich and B-rich domains will be generated at the interface between the transient phase and liquid phase by pseudospinodal decomposition. When the compositions of alternated domains are close to the respective equilibrium values, eutectic phases will be formed inside the domains simultaneously, which further develops into coupling eutectic colonies. Furthermore, the construction of solute interdiffusion field and the formation of interface curvature are explained self-consistently with our eutectic nucleation mechanism. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.