A lattice Boltzmann study of the effect of stirring on the migration rate of a curved interface in binary slurries

Morphological evolution of particles in semisolid slurries has been modeled as the migration of a double-peak shape solid-liquid interface. The valley between the peaks represents the solute-trapping area between the dendrite arms. Various boundary shear conditions were considered to mimic the real processing environments. A lattice Boltzmann model for isothermal miscible binary flows has been utilized to handle the hydrodynamics and chemical diffusion. Fixed solute concentration at the solid-liquid interface was introduced to simulate the steady growth of the solid particle. Numerical simulations reveal that shearing the slurries in a direction perpendicular to the growth direction of the particle tips encourages dendrite growth, which agrees with the theoretical prediction based on interface stability analysis. Shearing the boundary along a direction parallel to the growth direction of the particle tips, however, caused a larger increment in the migration rate of the interface in the valley, and is considered the major reason for dendrite-rosette morphological transformation. (C) 2005 Elsevier Ltd. All rights reserved.