Large-scale phase-field simulations of ternary eutectic microstructure evolution

Abstract

The microstructure evolution of ternary eutectic alloys is subject of current research for multicomponent alloys, due to the large variety of patterns and their widely adjustable properties. In experiments, contact zones between the different aligned patterns are commonly observed. However, their formation and influence on the microstructure evolution was not yet investigated. To study 3D patterns and the integrated contact zones, large-scale phase-field simulations of an idealized system are conducted, enabling the quantification of the rod shapes. First, the lamellar spacing with the minimum undercooling lambda_JH from the Jackson–Hunt approach is numerically determined. Then, the domain size and initial filling are systematically varied, to analyze the influence of these two quantities on the pattern formation and to determine the required computational domain size for statistical volume elements (SVE). The statistical measures indicate a minimum size of 400 x 400 voxel cells, equivalent to 4.3lambda_JH x 4.3lambda_JH , parallel to the solidification front and the necessity of large scale simulations to resolve SVEs. Different stable patterns, beside the hexagonal structures, are found, depending on the domain size, the initial filling and the undercooling of these patterns. In large-scale simulations, the formation and evolution of contact zones is observed, which are reported from experiments.