Melt Flow and Micro-Segregation in Unidirectional Dendritic Growth

单向枝晶生长中的熔体流动和微观偏析

• 批准号: 02650493
• 负责人: MIYATA Yasunori
• 金额: $ 1.6万
• 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: 1990
• 资助国家: 日本
• 起止时间: 1990 至 1991
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02650493/
• 关键词: Solidification; Dendrite; Melt Flow; Secondary-arm; Micro-segregation; Viscous-Finger; Hele-Shaw cell; Convection; ビスカス・フィンガ-; 過冷却凝固; 一方向凝固; 界面形態; 自然対流; 可視化法; HeleーShawセル

Effects of melt flow on dendritic interface are investigated in the unidirectional solidification. They are studied for (a) the dendritic growth in viscous-fingers in Hele-Shaw cell, experimentally, (b) predictions of tip radius of curvature and the growth rate of the primary dendrite arm, theoretically and for (c) effects of melt flow(convection) on characteristic dimensions of dendrite near the tip.Through the experimental study on the dendritic growth in viscous-fingers in Hele-Shaw cell, the governing equations for viscous-fingers and that of solidifications have shown to be in good correspondence, if one replaces the pressure in viscous-finger to the temperature in solidification in their equations. The shape of interface of viscous-finger is very similar to that of dendrite in solidifications, when a groove is attached on the plate of the Hele-shaw cell. The viscous-finger dendrite is experimentally very useful in studying the growth mechanism of secondary-arms, because their dim … More ensions are larger than that of usual metal dendrite and the pressure near the tip is easily observed.Through the theoretical study of tip radius of curvature and the growth rate of the primary dendrite arm, a new growth mechanism is proposed. It takes into account the contribution of tangential growth on the interface that is driven by the gradient of curvature of the interface. The tip radius of curvature and the growth rate of dendrite are predicted in the solidification of undercooled pure melt. The predictions agreed well with the experiments given in the solidification of succinonitrile dendrite.Through the numerical study of melt flow(convection) near the dendrite tip, it is shown that the characteristic dimensions of dendrite suffers very serious effects by the flow. IF the flow is in same direction of the growth rate of dendrite and faster than the growth rate of dendrite, then the growth rate becomes smaller and it would diminish in some extreme growth condition.The melt flow is studied and shown to contribute to the dimensions of dendrite in the solidifications, especially in the region near the tip of dendrite. This study would contribute to clarify the growth mechanism of secondary-arms. Less

研究了单向凝固中熔体流动对枝晶界面的影响。研究了 (a) Hele-Shaw 池中粘性指状枝晶生长的实验研究，(b) 理论上对尖端曲率半径和初级枝晶臂生长速率的预测，以及 (c) 熔体流动（对流）对尖端附近枝晶特征尺寸的影响。通过对 Hele-Shaw 池中粘性指状枝晶生长的实验研究， 如果将粘性指的压力替换为凝固时的温度，则粘性指的控制方程与凝固的控制方程具有良好的对应性。当 Hele-shaw 池的板上贴有凹槽时，粘性指界面的形状与凝固中枝晶的界面形状非常相似。粘性指状枝晶在研究次级枝晶臂的生长机制方面在实验上非常有用，因为它们的微弱应力比普通金属枝晶的大，并且很容易观察到尖端附近的压力。通过对尖端曲率半径和初级枝晶臂生长速率的理论研究，提出了一种新的生长机制。它考虑了由界面曲率梯度驱动的界面上切向生长的贡献。预测了过冷纯熔体凝固过程中的尖端曲率半径和枝晶生长速率。这一预测与丁二腈枝晶凝固过程中的实验结果吻合良好。通过对枝晶尖端附近熔体流动（对流）的数值研究，表明枝晶的特征尺寸受到流动的严重影响。如果流动与枝晶生长速率相同，并且比枝晶生长速率快，则生长速率会变小，并且在某些极端生长条件下会减小。研究表明，熔体流动对凝固过程中枝晶的尺寸有影响，尤其是在枝晶尖端附近的区域。这项研究将有助于阐明次臂的生长机制。较少的

项目成果

大沼 寛,宮田 保教: "デンドライトまわりの融液流れの数値解析" 日本金属学会誌.

Hiroshi Onuma、Yasunori Miyata：“枝晶周围熔体流动的数值分析”日本金属学会杂志。

Hiroshi Onuma and Yasunori MIYATA: "Numerical Simulation for Melt Flow around Dendrite Tip" NIHON-KINNZOKU-GAKKAISHI.

Hiroshi Onuma 和 Yasunori MIYATA：“枝晶尖端周围熔体流动的数值模拟”NIHON-KINNZOKU-GAKKAISHI。

Yojiro SHIMA and Yasunori MIYATA: "Dendrite Growth by Viscous Finger." Journal of Crystal Growth.

Yojiro SHIMA 和 Yasunori MIYATA：“通过粘性手指生长枝晶。”