INTERFACE MORPHOLOGIES AND MICROSTRUCTURES DURING DENDRITE-TO-CELL TRANSITION AT HIGH GROWTH RATE

The interface morphologies and microstructures of the directionally solidifiedNi-5wt-%Cu alloy during the dendrite-to-cell transition at high growth rate have been investi-gated by a newly developed equipment for directional solidification. The results show in thevicinity of dendrite-to-cell transition, the well developed sidebranches become shrivelled withthe increase of growth rate and disappear at the dendrite-to-cell transition, and at the sametime the primary spacing decreases. Moreover, the length of mushy zone decreases greatlyduring the dendrite-to-cell transition. Cells obtained at high growth rate have much in commonwith those at low growth rate, but with much smaller cell spacing.