复盐固溶-电解共沉积制备稀土镁合金的基础研究

Compared with the Mg-Al alloys, magnesium-rare earth alloys have better elevated temperature strength and creep resistance, which makes them very promising materials with high strength and heat resistance. To resolve the poor homogeneity and the poor stability of magnesium-rare earth alloys and reduce the production costs of the anhydrous raw materials, we plan to direct synthesize high-purity molten salts by combining the dehydration and the chloration of the complex salts and solid solutions using magnesium chloride hexahydrate and rare earth oxides as raw materials. After that, we plan to prepare Mg-Gd-Y and Mg-Nd-Y alloys with high strength and heat resistance by electrochemical codeposition. By studying the interaction between the dehydration of the complex salts and solid solution of magnesium chloride hexahydrate and the chloration of the complex salts and solid solution of rare earth oxides, we plan to explore the formation mechanism of high-purity electrolyte. By studying the effects of the physicochemical properties of molten salts on the electrolysis process, we plan to regulate its physicochemical properties. By establishing the relationship between electrolytic parameters and chemical composition of the target alloys, we can realize the regulation of the chemical composition of magnesium-rare earth alloys.

与传统的镁铝系合金相比，稀土镁合金具有优异的高温强度和蠕变抗力，是一种非常有发展前景的高强耐热材料。为了解决稀土镁合金制备过程中存在的合金均匀性和稳定性差、无水原料制备成本高的问题，本项目拟采用廉价的六水氯化镁和稀土氧化物为原料，通过复盐固溶脱水和复盐固溶氯化相结合的方法直接合成高纯度电解质熔体，进而通过电解共沉积法制备高强耐热的Mg-Gd-Y系和Mg-Nd-Y系合金。通过研究稀土氧化物复盐氯化过程和六水氯化镁复盐脱水过程的相互影响，探索高纯度电解质熔体的形成机制；通过研究电解质熔体物理化学性质对电解过程的影响，指导电解质熔体物化性能调控，实现电解过程能耗的降低；通过建立电解参数与合金成分的对应关系，实现稀土镁合金成分的控制。

针对目前稀土镁合金产品成分均匀性差、性能稳定性差和生产成本高的问题，本项目利用我国丰富的水氯镁石和稀土氧化物为原料制备了高纯度的电解质熔体（电解质熔体中水解产物和金属氧化物的含量之和控制在0.1wt.%以下，可以满足多极槽对原料的要求）。利用上述高纯度电解质熔体为原料，通过共电沉积法制备得到了稀土镁合金，验证了复盐固熔脱水-共电沉积制备镁合金工艺的可行性。研究了熔盐物理化学性质与电流效率的关系，通过调整和优化，将共电沉积制备镁合金过程的电流效率由50%提高至85%以上。通过共电沉积法制备得到了Mg-Y、Mg-Nd、Mg-Gd二元合金和WE系列多元稀土镁合金，并通过改变电解质成分和电解参数实现了合金成分的控制。在此基础上，解决了镁合金制备生产存在的产品稳定性和均匀性差的问题。综合上述结果，本研究为复盐固溶脱水制备无水氯化物熔体奠定了坚实的工作基础。同时认识了高温熔盐物化性质、电解参数对镁合金成分及组织结构的影响规律。项目资助发表新论文2篇，提交发明专利1篇，并培养硕士研究生1名。