穗状晶形成及其结构的研究

Study On The Formation And Structure of Spike-like Crystals

凝固过程中的流体流动效应是现代凝固科学研究的热点,尤其是流动与凝固界面的耦合作用及流动对生长成的晶体质量的影响。作者自行设计了一套带有对流驱动系统的强制性晶体生长装置,可以实现液相层流作用下的晶体生长过程,而且流动的发生及流速的改变极为方便。利用透明模型合金 SCN-2%wt.Ace 作为研究对象,详细考察了液相快速流动作用下的强制性晶体生长的行为,首次发现了一种新的晶体形态——穗状晶;作者对其结构和形成过程进行了详细分析,并预示了这种结构的潜在应用价值。

Fluid flow effects on solidification process has become one key field in modern solidification science.Experiments being performed in the micro- gravity and high-g environment are all designed to carry out such studies in order to improve the internal quality of grown functional crystals,e,g. superconducting materials,non-linearoptical crystals,biological(protein) crystals and so on. The authors have developed an experiment set-up for constrained srystal growth with a special convection generator which is used to investigate the influences of layered liquid flow on constrained crystal growth process. Transparent model alloy,SCN-20%wt Ace is used in the study. It is found for the first time that fast liquid flow makes the constrained columnar crytsal morphology change into spike-like crystal morphology.The spike-like-crystals are much finer than the original constrained dendri- tes,and are developed under fast liquid flow,so the micro-segregation may greatly reduced or eliminated,materials of this Kind of internal microstructure my be of superior mechanical properties in the middle and low temperature range.The formation process and structure of spike-like crystals are studied in the paper.