重稀土元素对铁基块体非晶合金过冷液相热稳定性及其磁学性能影响机理研究

Fe-based bulk amorphous alloys doped with heavy rare earth elements would exhibit a series of interesting phenomena concerning about thermal stability of supercooled liquid and their magnetic properties. The present project is going to study thoroughly the evolution of short-range ordered (SRO) structure that is responsible for all these phenomena. Previous studies have shown that heavy rare earth elements can significantly change the SRO structure in Fe-based bulk amorphous alloys, which results in the exothermic phenomenon in the supercooled liquid region, the changing of initial crystal phase, and subsequently the improved magnetostriction. In our project, we are intended to explore the changes of SRO structure, the isomer shift, the hyperfine magnetic field, the magnetic moment and bonding properties by firstly adjusting the alloy compositions, and then combining methods of M?ssbauer spectroscopy and extended X-ray absorption fine structure spectroscopy. Moreover, variation of the microstructure and their corresponding distribution after annealing at different time and temperature will be analyzed using differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, et. al. Finally, the essential relationship between SRO structure and the glass forming ability, thermal stability, crystallization behavior, and magnetic properties will be revealed by analyzing the formation and evolution of this special SRO structure. In conclusion, our project is expected to provide a theoretical basis for the improvement of glass forming ability and magnetic properties of novel materials, and finally design and produce sensor core materials with excellent magnetostrictive and nanocomposite permanent magnetic materials.

铁基块体非晶合金掺杂重稀土元素后，其过冷液相热稳定性和磁学性能都会出现一系列有趣的现象，本项目针对产生这些现象的主要原因- - 短程有序结构的演变展开研究。前期研究表明，重稀土元素能够明显改变铁基块体非晶合金的短程有序结构，致使过冷液相区出现放热现象、初始晶化相发生显著变化以及磁致伸缩明显提高。本项目拟通过调节合金成分，采用穆斯堡尔谱与扩展X射线吸收精细结构谱相结合的方法，研究其短程有序结构、同质异能移、超精细磁场、磁矩和键合性质的变化；利用差示扫描量热仪、X射线衍射、透射电子显微镜等方法，研究不同时间和温度热处理后，合金微观结构的变化及分布情况。通过分析合金短程有序结构的形成和演变过程，从机理上揭示其与非晶形成能力、热稳定性、晶化行为和磁性能的本质联系，为提高材料非晶形成能力，优化磁学性能提供理论依据，最终获得性能更为优异的磁致伸缩传感器芯体材料和纳米双相复合永磁材料。

铁基块体金属玻璃掺杂重稀土元素后，其过冷液相热稳定性明显增强，力学和磁学性能均受影响。本项目针对产生这些现象的主要原因以及背后的物理机制展开了深入研究。我们的研究表明，重稀土元素的添加能够明显改变铁基块体非晶合金的短程有序结构，致使过冷液相区出现反常放热现象、初始晶化相发生显著变化，以致过冷液相区明显增宽，非晶形成能力大幅度提高，并在保证饱和磁感应强度没有显著恶化，矫顽力略微增大的情况下使体系的磁致伸缩明显提高。本项目通过调节合金成分，采用X射线光电子能谱的方法，研究了其短程有序结构和键合性质随成分的变化及其与块体金属玻璃非晶形成能力、宏观力学行为等宏观物理性能的内在关系。利用差示扫描量热仪、X射线衍射、透射电子显微镜等方法，研究了不同时间和温度热处理后，合金微观结构的变化及分布情况。通过进一步分析和研究我们获得了该合金体系短程有序结构的形成和演变过程，从机理上揭示了其与非晶形成能力、热稳定性、晶化行为和铁基金属玻璃本征塑性及磁性能的本质联系。以上研究工作为提高非晶合金的形成能力，优化宏观性能提供了理论依据。同时，通过本项目我们研究探索了一系列具有优异软磁性能和力学性能的磁致伸缩传感器芯体材料如Fe-RE-B-Si-Nb体系、Fe-RE-Nb-B体系、热塑性成型材料如(Co0.5Fe0.5)62Nb6M2B30体系， 以及软磁性能优异的非晶合金基体/α-Fe纳米晶双相复合纳米晶合金材料如Fe-B-C-Cu体系、Fe-Nb-B-Cu体系、Fe-Si-B-P-Cu体系等。