Self-consistent modeling of morphology evolution during unidirectional solidification

A self-consistent model is developed to describe the morphology evolution during unidirectional solidification, which shows that, for a given temperature gradient, the interface morphology will go planar → shallow cell → deep cell → dendrite → cell → planar with increasing growth velocity. By examining the interaction of adjacent cells/dendrites, a wide allowable range of primary spacing for given growth conditions is determined, which shows a good agreement with experimental results. Numerical results show that cellular/dendritic and dendritic/cellular transitions appear not at a unique velocity but over a range of velocities, the critical velocity for the transition being dependent on the primary spacing before the transition.