亚快速定向凝固中枝胞转变的原位观测  

IN-SITU OBSERVATION OF DENDRITE-MICROCELL TRANSITION IN NEAR-RAPID DIRECTIONAL SOLIDIFICATION

作　　者：王祖锦[1] 黄韬[1] 李建国[1] 毛协民[1] 傅恒志[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室

出　　处：《材料研究学报》1995年第2期167-170,共4页Chinese Journal of Materials Research

基　　金：国家自然科学基金

摘　　要：通过对高纯ＣＢｒ４－Ｘ模拟合金亚快速定向凝固的原位观测，展示了枝晶向细胞晶转变的形态演化过程，发现枝晶通过尖端开裂使测枝消失并伴随一次间距大幅度减小，转变过程中还出现尖端生长速度对抽拉速度的明显偏离和尖端半径的变化，文中对尖端开裂的演化机制进行了理论分析．Theoretical models and extensive experimental studies at low growth rates now have well described the morphological transitions from planar to cellular then dendritic with the increase of growth rate during conventinal directional solidifcation. However, so far there is only a little understanding on the dendrite to cell transition during rapid solidifiication.In this paper, a morphological transition from dendrites to cells at high growth rates were observed with a transparent simulant alloy CBr4-X. The investigation shows that at high growth rates the tip splitting instability plays a leading role in the morphological transition and a sharp decrease of primary spacings occurs during the dendrite-to-cell transiton in such a way that the dendritic tips split rapidly. Theoretical analysis shows that tip splitting is a kind of critical mutation caused by tip instability, and affectd by diffusion kinetics and capilary forces.

关 键 词：合金 凝固 亚快速定向凝固 尖端开裂 枝胞转变 

分 类 号：TG111.4[金属学及工艺—物理冶金] TG115.21[金属学及工艺—金属学]