CELLULAR AND DENDRITIC GROWTH IN RAPIDLY SOLIDIFIED AL-FE AND AL-CU ALLOYS

A recent numerical model of cellular and dendritic growth has been ext ended into the high velocity region where the distribution coefficient , liquidus slope and diffusion coefficient depend on the growth veloci ty. The primary spacing selection mechanism is modelled so that no a p riori assumptions need be made about a spacing selection condition. Th e results are compared with experimental primary spacing measurements obtained using rapid laser resolidification and good agreement is foun d. The numerical results for undercooling and tip radii am compared wi th those predicted for dendrites using marginal stability arguments, s howing the potential and limits of the analytical models. The effect o f high velocity on microsegregation is examined and microsegregation p rofiles are predicted.