Misoriented Lamellar Microstructures in Mo-Si-Ti Alloy Due to Asymmetrical Nucleation Distance and Interfacial Energies: A Phase-Field Analysis

The material properties are crucially affected by the microstructure formed during solidification, which is typically divided into three stages: (I) Early stage of nucleation in molecule scale, which is beyond the scope of the mean-field model; (II) Middle stage of nucleation, where the dispersed nuclei have formed; (III) Late stage of nucleation, where the nuclei contact with each other. In previous studies, the formation of the stable eutectic lamellae is mostly based on the assumption that a stable solid-solid interface has already been established, corresponding to the stage (III), and the growth stage (II) is often overlooked. In the current work, by varying the nucleation density and distance, an alternative mechanism for the misoriented microstructure formation in Mo-Si-Ti alloy is proposed, which considers nucleation stage (II). Furthermore, the misoriention angle as a function of the nucleation density, distance, and the interfacial energies is quantified by systematic phase-field simulations. The simulated composition distribution reveals the mechanism for the misorientation of eutectic lamellar pairs, which becomes more pronounced when the solids-fluid interfacial energies are unequal. It is expected that the present work provides a potential perspective for the fundamental understanding of misoriented microstructures in solidification. In the current work, by varying the nucleation density and distance, an alternative mechanism for the misoriented microstructure formation in Mo-Si-Ti alloy is proposed, which considers middle stage of nucleation. Furthermore, the misorientation angle as a function of the nucleation density, distance, and the interfacial energies is quantified by systematic phase-field simulations.image (c) 2024 WILEY-VCH GmbH