Effect of External Heat Extraction on Dendritic Growth into Undercooled Melts

摘要

Solidification characteristics in most rapid solidification processes are controlled by heat extraction by the chill substrate and by melt undercooling, especially near the substrate. A dendrite growth model for this situation is derived in the present study. The model involves combined effects of the undercooled melt and the substrate as effective heat sinks. A dendrite is assumed to grow into an undercooled melt, with heat evolution at the dendrite tip occurring both into the undercooled melt and into the chill substrate through the growing solid. The significance of the proposed dendrite model and the stability of dendrite growth under the thermal conditions considered are discussed, using the Fe-Cr-Ni alloy system as an example.