定向凝固过程中柱状晶的生长机制

为了控制定向凝固过程中柱状晶的连续稳定生长,将真空感应熔炼与连续定向凝固技术相结合,开发出真空连续定向凝固技术。在一定的工艺参数下,在自制的定向凝固设备上成功制备出具有单向凝固组织的直径8mm的Al-1%Si合金棒材。通过对棒材不同位置的微观组织进行研究,分析了连续定向凝固过程中柱状晶形成和长大过程。结果表明:凝固过程开始阶段,新晶粒的出现阻碍原晶粒生长,使晶体呈现一种新的有序结构;柱状晶长大过程中受到晶粒淘汰机制和柱状晶合并机制的综合作用。

Growth mechanism of column crystals in directional solidification

Continuous directional solidification with argon as a cover gas was used to continuously grow a column crystal. The system combined vacuum induction melting and continuous directional solidification. An 8 mm diameter Al-1%Si bar was grown as a unidirectional crystal using the vacuum vertical continuous directional casting system. The structure of samples from different positions in the bar were studied to analyze the shape and development of the columne crystal. The observations show that new grains prevent the original grains from growing, thus the crystals grow with a new ordered structure. The column crystal growth is affected by the elimination rule and the column crystal merge mechanism.