Effect of Flow on Dimensions of Dendrite in Undercooled Melt

流动对过冷熔体中枝晶尺寸的影响

• 批准号: 08650867
• 负责人: MIYATA Yasunori
• 金额: $ 1.34万
• 依托单位: Nagaoka University of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08650867/
• 关键词: undercooled solidification; loop cell; interfacial stability; alloy; dendrite; convection; 凝固; 局所平衡; 成長速度; 温度勾配; 対流; 界面形態; 融液; 流動

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.

熔体流动影响过冷熔体凝固中枝晶的尺寸。研究熔体流动对尺寸的影响非常重要，因为尺寸与溶质的微观偏析密切相关。这项工作研究了熔体流动对尺寸的影响。枝晶的尺寸通常是通过热量和溶质的传输来确定的。过冷熔体中的凝固仅由热传输控制。通过实验和理论研究了纯材料凝固过程中熔体流动对枝晶尺寸的影响。然后研究了熔体流动对合金枝晶尺寸的影响。为了引入熔体中的流动，设计并制造了具有圆形横截面的环形单元。通过加热单元的一部分，由浮力驱动熔体流动。流的速度由施加到加热器的电力控制。熔体流动使得在给定的过冷度下凝固时枝晶的生长速率增加。熔体流动对尺寸的影响对于低过冷度下的凝固非常重要。这些在纯材料和合金的凝固过程中都可以观察到。理论上解释说，到达枝晶尖端的较冷熔体在尖端产生温度梯度，并且生长速率必须增加以维持热/溶质守恒。熔体流动与枝晶体之间较长的相互作用时间使得熔体流动对过冷熔体凝固的影响显着。