气动悬浮条件下高熵合金的快速凝固组织特征及性能研究

The present proposal has chosen high-entropy NiFeCoCrCuxAly（x,y=0.25,0.5,1,1.5,2）alloys as research objectives, their undercooling and even hypercooled state are to be realized by containerless processing with aerodynamic levitation. Under such an extremely nonequilibrium condition, the kinetic mechanism of dendritic growth for different high-entropy alloys is investigated systematically through rapid solidification experiments. Experimental explorations are also performed to reveal the crystal nucleation characteristics and formation kinetics of dendritic microstructures. Furthermore, the specific heat and surface tension of undercooled liquid alloys are measured and calculated by aerodynamic levitation experiment and molecular dynamics methods. A systematic study is accomplished on the rapid dendritic growth mechanism as the function of undercoolings. The nucleation mechanism and atomic motion process are simulated by molecular dynamics method. Moreover, the themophysical parameters of specific heat and surface tension are also explored under different temperatures at the same time. Based on the above research, the mechanical, electromagnetic and corrosion properties of undercooled high-entropy alloys are investigated under the different experimental conditions, which has important scientific significance and practical application prospect in industries.

本项目选取NiFeCoCrCuxAly（其中x,y=0.25,0.5,1,1.5,2）高熵合金作为研究对象，通过调整其中Cu和Al的成分范围形成新的高熵合金。在气动悬浮无容器条件下实现液态高熵合金的深过冷与快速凝固，系统分析不同成分高熵合金的枝晶生长速度随过冷度的变化规律。实验研究深过冷液态高熵合金的比热、表面张力和粘度等热物理性质变化特征，探索微观组织结构和宏观热物理性质与过冷度之间的内禀关系。采用分子动力学模拟方法研究深过冷条件下高熵合金的原子团簇组态特征，阐明高熵合金微观结构与传热传质等物理过程的关系，揭示晶体形核过程的原子运动规律。系统研究高熵合金快速凝固过程的热力学和动力学机制，实现其相组成和组织形态的优化控制。深入揭示不同过冷条件下高熵合金的力学、电磁学和抗腐蚀性能变化规律。

本项目在CoCrFeNi高熵合金中加入Al，Cu，Zr，B和Mn等元素得到高熵合金，通过改变添加元素的含量形成新的高熵合金进行相关研究工作，主要取得以下几个方面的结果：1、系统研究了不同成分高熵合金在不同凝固条件下的组织结构及枝晶生长动力学特征，发现在急冷快速凝固条件下部分高熵合金形成非晶特征；2、在不同溶液中分析了不同成分和过冷度条件下高熵合金的腐蚀特征，表明在平衡凝固条件下不同合金在不同溶液中的耐腐蚀特征不同，在深过冷条件下部分高熵合金的耐腐蚀性能显著提高；3、不同元素添加形成的高熵合金对磁学性能有着较大的影响，同时在深过冷条件下，过冷度变化使得合金的磁学性能有较大幅度改变；4、在深过冷条件下，Cu含量越高，枝晶生长速度越慢，随着过冷度的增大，合金发生偏析现象。无偏析高熵合金的显微硬度随过冷度的增大而增大，合金发生明显偏析时显微硬度随着地冷度的增大而降低。5、高熵合金中元素和含量的改变均对热物理性质和力学性能有着重要的影响。