Indexed on: 01 Mar '96Published on: 01 Mar '96Published in: Metallurgical and Materials Transactions A
The effect of a parallel shear flow and anisotropic interface kinetics on the onset of instability during the directional solidification of a binary alloy at constant velocity is calculated. The model for anisotropy is based on the motion of steps. A shear flow (linear Couette flow or asymptotic suction profile), parallel to the crystal-melt interface in the same direction as the step motion, decreases interface stability in that the critical solute concentration decreases. A shear flow counter to the step motion enhances stability for small shear rates; for larger shear rates, the neutral curve develops a bimodal structure, and the critical solute concentration slowly decreases with shear rate.