纳米异质结构SmCo5/α-Fe磁体的织构和界面研究

Nanostructural permanent magnets have good prospects for application which can be widely used in many high-tech industries, such as computer, new energy, aeronautics and Astronautics, medical equipment and so on. In this project, the texture, interface and magnetic hardening mechanism of the multimorphological nanostructure SmCo5/α-Fe magnets will be studied. Firstly, the bulk anisotropic multimorphological nanostructure SmCo5/α-Fe magnets will be prepared by hot deformation with low temperature, high pressure and large height reduction based on spark plasma sintering. Secondly, the crystal structure, microstructure, phase composition and distribution, texture of grains and grain boundary, domain structure as well as the magnetic properties will be examined and analyzed. The simulation models in accordance with the experimental characterization results will be established by using the micromagnetism theory, to study of the influence of the microstructure on the magnetic properties. The deformation mechanism, texture formation mechanism and magnetic hardening mechanism of multimorphological nanostructure SmCo5/α-Fe magnets will be researched, and the mechanism of the influence of multimorphological interface on the magnetic properties will also be investigated. Finally, the anisotropic multimorphological nanostructure SmCo5/α-Fe magnets with the energy product larger than 40 MGOe will be prepared. As a result, deformation mechanism and magnetic hardening mechanism of multimorphological nanocomposite magnets will be enriched.

纳米结构永磁体具有良好的应用前景，可以被应用于计算机、新能源、航空航天、医疗器械等诸多高新技术行业。本项目以纳米异质结构SmCo5/α-Fe磁体的织构、界面和磁硬化机理为研究对象。依托放电等离子烧结技术，协同低温、高压和大变形量等条件进行热变形，制备块体各向异性纳米异质结构SmCo5/α-Fe磁体。在此基础上，分析、测定磁体的晶体结构、微观结构和相分布、晶粒和晶界面织构、磁畴结构和磁性能等。并以微磁学为理论基础，基于实验表征结果建立仿真模型，研究磁体的微观组织结构对磁性能的影响。其中，重点考查纳米异质结构SmCo5/α-Fe磁体的变形机制和织构形成机理，及其磁硬化机理；并考查异质界面对磁体的磁性能的影响机理。最终，制备出磁能积超过40 MGOe的各向异性纳米异质结构SmCo5/α-Fe磁体。本研究的结果有望丰富异质结构纳米复合磁体的变形机理和矫顽力理论。

项目针对纳米异质结构SmCo5基磁体的织构、界面和磁硬化机理等方面开展研究工作。首先，依托放电等离子烧结技术和低温高压变形方法，开发了纳米富稀土相诱导低温变形等新技术，实现钴基稀土永磁材料的低温变形兼获强c轴织构和高矫顽力，制备出了兼具有良好的室温磁性能和温度稳定性的热变形Sm0.6Pr0.4Co5、SmCo5/Sm2Co7纳米异质磁体。其中，热变形Sm0.6Pr0.4Co5磁体室温磁能积达到21.1MGOe，是目前报道的热变形钴基稀土永磁的最高值。其次，结合低温高压变形技术制备了多组分(SmCo7/FeCo)/SmCo5纳米异质结构磁体，SmCo5相的引入成功提高磁体矫顽力。再次，以铁纳米片替代传统微米铁粉，同时实现纳米异质结构SmCo5/α-Fe磁体的微结构优化和高软磁相比例，并阐明铁纳米片的纳米化过程，并通过微磁学模拟分析了微结构对磁体磁性能和反磁化过程的影响。还次，提出Sm2Co7相替代SmCo5相制备了纳米异质结构磁体，相同工艺条件下实现磁性能优化，结果显示Sm2Co7/α-Fe磁体中可以产生更优的交换耦合作用，并通过微磁学模拟分析了Sm2Co7/α-Fe纳米异质结构磁体的回复曲线张开现象及其成因，否定了张开现象与界面交换耦合作用的强关联，提出硬磁相的不可逆过程是张开的根本原因。最后，研究了SmCo5/α-Fe纳米异质结构磁体在热变形过程中的相变、微结构演化和织构形成机理。结果显示伴随晶粒长大发生了两阶段相变：Sm(Fe,Co)5和Fe-Co相形成了Sm2(Fe,Co)17-H再转变为Sm2(Fe,Co)17-R相。变形后的磁体中的仅Sm(Fe,Co)5相中形成了强的c轴织构，并提出了滑移、晶粒择优生长以及分散的富钐纳米相的辅助的形变和织构形成机理。