Growth Mechanism of Dendritic Secondary-Arms and Microsegregation

枝晶次生臂的生长机制与微观偏析

• 批准号: 04650627
• 负责人: MIYATA Yasunori
• 金额: $ 0.77万
• 依托单位: Nagaoka University of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04650627/
• 关键词: Dendrite; Micrisegregation; Melt flow; Primary-arm; Secondary-arm; Growth theory; Stability of interface; 成長機構; 先端曲率半径; 成長速度; ビスカス・フィンガー

The growth mechanism is investigated experimentally and theoretically for dendritic arms.(1) Experimental apparatus for the dendritic growth under melt flow is built up, and the growth rate and tip radius of curvature of dendrite are measured in the undercooled solidification of succinonitrile melt. The growth rate increases with the increase of melt flow for a given undercooling. THe natural convection in the melt is estimated to affect the growth as strong as the forced flow velocity 1 mm.(2) Migration of bubbles in melt, which will be accidentally included in the melt and will affect the growth of dendrite. is studied. Migration is observed in the microgravity condition. A bubble moves under temperature gradient from the cold place to the hot place by Marangoni convection. Therefore, the migration will contribute to destabilize the interface of dendrite in the solidification of undercooled melt.(3)A dendritic growth theory, which includes self-consistently the marginal stability of the interface, is proposed. It takes into account the growth along the interface, which is induced by the conservation of the flux of heat through the interface. The predictions and experiments are successfully compared for the growth rate and the tip radius of curvature for the dendrite in undercooled solidification of succinonitrile.

对枝晶臂的生长机理进行了实验和理论研究。(1)搭建了熔体流动条件下枝晶生长的实验装置，测量了丁二腈熔体过冷凝固过程中枝晶的生长速率和尖端曲率半径。对于给定的过冷度，增长率随着熔体流动的增加而增加。据估计，熔体中的自然对流对生长的影响与强制流速1 mm一样强。(2)熔体中气泡的迁移，气泡会意外地包含在熔体中，从而影响枝晶的生长。被研究。在微重力条件下观察到迁移。气泡通过马兰戈尼对流在温度梯度下从冷处移动到热处。因此，过冷熔体凝固过程中，迁移会导致枝晶界面不稳定。(3)提出了自洽地包含界面边际稳定性的枝晶生长理论。它考虑了沿界面的生长，这是由通过界面的热通量守恒引起的。成功地比较了丁二腈过冷凝固中枝晶的生长速率和尖端曲率半径的预测和实验。