Phase-field study on the effects of process and material parameters on the tilt angle during directional solidification of ternary eutectics

Abstract

In the directional solidification of molten alloys, the configuration of growing phases plays a vital role in the properties of the resulting materials. During directional eutectic solidification, the growth direction and the velocity can be controlled by an imprinted temperature gradient. For this kind of process, different instabilities can occur. One observed instability is tilted growth of the solid phases against the direction of the imprinted temperature gradient. In ternary eutectics this phenomenon can occur in systems with isotropic phases. To investigate the effects of the different process and material parameters, simulation studies with a thermodynamically consistent phase-field model based on the grand potential approach, are conducted. An idealized system with different isotropic interfacial energies, diffusion coefficients, lamellar spacings, solidification velocities and slopes of the imposed temperature gradient is systematically studied. The effects on tilting are analyzed and discussed. To quantitatively determine the tilt angle automatized, an unsupervised measurement method is developed. Based on the results of the measurements, a fitting function is derived to predict the tilt angles.