熔盐电解法制备铝钪合金及其微观结构分析

发布时间：2018-09-17 12:36

【摘要】：本文主要介绍了实验室条件下小型电解槽的设计与制作,使用电解槽测试并电解出纯铝、铝钛合金和铝钪合金,分析探讨了铝钪合金的细化效果和细化机制。电解体系采用冰晶石-氧化铝作为电解实验的主要体系,氟化镁和氟化钙作为添加剂。在电解的过程中不断发现问题,做了大量的改进并付诸实践,以保证电解过程有序的进行。比如：把原来阴极的棒状结构改为盘状,原来阳极的筒状改为圆柱状,提高了电流效率；所选用的石墨由原来的高纯石墨换为粗石墨克服了阴阳极的断裂问题。经过多次改进,最终设计和制作出一套易操作、高效率的电解设备,并使用它在单次实验中制备出约1公斤的铝钪合金。对熔盐电解法制备的铝钪合金成分及微观结构等进行了分析。结果表明电解制备的铝钪合金细化效果明显优于熔配制备的合金。随着含钪量的增加,细化效果也越来越显著。和电解法相比较,熔配法制备的铝钪合金不但晶粒细化效果不明显,而且钪的分布也不均匀,容易出现偏聚现象。钪对铝合金晶粒的细化作用主要因为Al3Sc与Al有高匹配性,两者晶格的错配度小于1%。Al3Sc符合作为非均质形核的结构条件,能很好的润湿基体的晶粒,减小两者之间的接触角,使Al3Sc相和基体晶粒接触的结晶面具有比较小的表面张力,有利于非均质形核的形成,能够达到细化晶粒的目的。对熔盐电解法制得的铝钪合金晶粒的面积、平均直径、长半径、短半径和长短径之比进行定量测量和计算,绘制出晶粒的特征尺寸随着铝钪合金中钪含量增加的变化曲线图；并采用概率密度分布具体分析了上述特征尺寸的分布图。结果表明,随着钪含量的增加,概率密度分布曲线图逐渐向左移动,峰值越来越大,晶粒的尺寸越来越小,分布范围也逐渐缩小,并且集中度明显增高。
[Abstract]:This paper mainly introduces the design and manufacture of a small electrolytic cell under laboratory conditions, tests and electrolyzes pure aluminum, aluminum titanium alloy and aluminum scandium alloy by electrolytic cell, and analyzes and discusses the refining effect and mechanism of aluminum scandium alloy. Cryolite-alumina was used as the main electrolysis system, and magnesium fluoride and calcium fluoride were used as additives. In the process of electrolysis, problems are found, and a large number of improvements have been made and put into practice to ensure that the electrolysis process is carried out in an orderly manner. For example, the rod structure of the original cathode is changed to the disk shape, the cylinder shape of the anode is changed to the cylindrical shape, and the current efficiency is improved, and the graphite selected is changed from the original high purity graphite to the coarse graphite to overcome the problem of the rupture of the cathode and the anode. After many improvements, a set of electrolysis equipment with easy operation and high efficiency was designed and manufactured, and the aluminum-scandium alloy of about 1 kg was prepared by using it in a single experiment. The composition and microstructure of aluminum-scandium alloy prepared by molten salt electrolysis were analyzed. The results show that the refining effect of electrolytic aluminum-scandium alloy is better than that of melting alloy. With the increase of scandium content, the refining effect is more and more remarkable. Compared with the electrolysis method, the Al-SC alloy prepared by the melting method has not obvious grain refinement effect, and the distribution of scandium is not even, so it is easy to appear the phenomenon of segregation. The effect of scandium on grain refinement of aluminum alloy is mainly due to the high matching between Al3Sc and Al. The mismatch degree of lattice between Scandium and Al is smaller than that of 1%.Al3Sc, which is suitable for the structure condition of heterogeneous nucleation, and can wetting the grains of the matrix well and reducing the contact angle between them. The crystal mask which makes the Al3Sc phase contact with the matrix grain has a relatively small surface tension, which is favorable to the formation of heterogeneous nucleation and can achieve the purpose of grain refinement. The grain area, average diameter, long radius, short radius and ratio of short radius to long diameter of Al-SC alloy prepared by molten salt electrolysis were measured and calculated quantitatively, and the curves of characteristic grain size with the increase of scandium content in Al-Scandium alloy were plotted. The distribution map of the above characteristic dimensions is analyzed by probability density distribution. The results show that with the increase of scandium content, the distribution curve of probability density gradually moves to the left, the peak value becomes larger and larger, the grain size is smaller, the distribution range is gradually reduced, and the concentration is obviously increased.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TF821

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