The influence of anisotropy on the evolution of interfacial morphologies in directional solidification: A phase-field study

Abstract

By adjusting the interface energy, curvature, and velocity, the anisotropy plays an important role in the interaction between interfacial processes and transport processes, determining the solidification structures. In this paper, through the quantitative phase-field model, the influence of anisotropy on the evolution of interfacial morphologies in directional solidification is investigated. To represent different interfacial anisotropies, the solidification processes with different preferred crystallographic orientations are performed. Then the effect of anisotropy on morphological evolution is discussed systematically. At the planar growth stage, the interfacial anisotropy makes no difference in the transport processes and morphological evolution. At the onset time of planar instability, the anisotropy determines the detailed evolution by adjusting the interface stiffness. At the planar-cellular-transition stage, with the influence of anisotropy, the interfacial curvature decreases from {\theta}0=0{\deg} to {\theta}0=40{\deg}. Hence, the solute concentration ahead of the interface increases from {\theta}0=0{\deg} to {\theta}0=40{\deg}, while the instantaneous velocity of the interface decreases from {\theta}0=0{\deg} to {\theta}0=40{\deg}. At the quasi-steady-state stage, the anisotropy determines the growth direction and tip velocity of the primary dendrite, as well as the onset of sidebranches.