Effect of Flow on Dimensions of Dendrite in Undercooled Melt

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Melt flow affects dimensions of dendrite in the solidiflcation in undercooled melt. It is important to study the effect of melt flow on the dimensions, because the dimensions are very much corelated to the microsegregation of solute. The effect of melt flow on the domensions is studied in this work.Dimensions of dendrite are, in general, determined through the transport of heat and solute. The solidification in undercooled melt is controled by the heat transport alone. The effect of melt flow on the dimensions of dendrite is studied in the solidification for pure material, experimentally and theoretically. Then the effect of melt flow on the dimensions of dendrite is studied for alloy in this work.In order to introduce the flow in the melt, a loop cell with circular cross section is designed and manufectured. The melt flow was drived by the buoyancy force by heating a part of the cell. The velocity of the stream was controled by the electric power applied to the heater.Melt flow makes the growth rate of dendrite increase for the solidification in a given undercooling. The effect of melt flow on the dimensions is significant for the solidification in low undercooling. These are observed in the solidification for the pure material and also for the alloy.It was explained theoretically that the cooler melt coming to the tip of dendrite makes the temperature gradient at the tip, and the growth rate has to increase to maintain the heat/solute conservation. The longer interaction time between the melt flow and dendritic body makes the effect of melt flow significant for the solidification in undercooled melt.