电场对定向凝固类包晶合金凝固组织的影响

为研究直流电流对亚包晶合金凝固过程的影响,选用与亚包晶合金都存在相似凝固过程的AMPD-4.1%SCN透明亚包晶模拟物为研究对象。使用显微镜感光器件(CCD)和智能通讯测温仪表对实验过程进行实时拍照和温度记录,研究了亚包晶透明模拟物在电场作用下的结晶过程和晶体生长规律。结果表明：在电场的作用下,由电迁移效应使定向结晶的亚包晶模拟物的初生β相颗粒逐渐向正极方向迁移,使凝固界面前沿的液相成分与包晶点的成分(0.05%SCN,原子分数)接近,从而促进包晶反应的进行；电场的作用使电流偏聚产生的焦耳热效应和溶质富集引起的成分过冷,使定向凝固的枝晶尖端产生特殊分裂的生长形貌,使枝晶尖端分裂,枝晶间距减小。

Effect of Electric Field on Solidification Structure of Directionally Solidified Peritectic Alloys

It is known that the AMPD-4.1% SCN (Aminomethyl Propanediol-4.1% Succinonitrile) transparent hypoperitectic polymer alloy and the Ni₃Al hypoperitectic alloy present the similarity in directional solidification behavior, therefore, the former was selected as the reference material to simulate the effect of DC current on the directional solidification process of the later one. During the experiment, the real-time photo shooting and real-time temperature recording were carried out by the microscope photosensitive device (CCD) and an intelligent communication temperature measuring instrument. The results show that under the action of electric field, the primary β phase particles of the directionally crystallized subperitectic alloy migrate to the positive pole, which facilitates the peritectic reaction by making the composition of liquid phase near peritectic point at the frontier of solidification interface. The special growth morphology of dendrite tip splitting and the dendrite spacing decreasing of directionally solidified dendrite tip under the action of electric field may be mainly caused by Joule heating effect caused by electric field and supercooling caused by solute enrichment. Last but not least, results of the similar experiment for Ni₃Al-based alloy Ni-20Al-10Fe-0.2B proved fairly well the above observed growth morphology of the AMPD-4.1% SCN transparent hypoperitectic polymer alloy.