热变形纳米晶钐钴基高温永磁的织构化和矫顽力机制研究

SmCo-based permanent magnets are the irreplaceable key materials in national defense and civil high technology fields. The nanocrystalline SmCo-based permanent magnets with advantages of high coercivtiy, high corrosion resistance and good mechanical properties are hopeful to be a new generation high temperature permanent magnet. While the magnets are difficult to get crystallographic texture, so the magnetic energy product is only 1/4 of the theoretic value. Therefore, anisotropic nanocrystalline SmCo-based magnets with high performances will be prepared by SPS, and the effect of hot press/deformation on the microstructure as well as magnetic properties of the SmCo-based bulks will be studied. The stress-strain relationship and the constitutive modle during hot deformation will be specified by the the combination of GLEEBLE hot deformation expirement and DEFORM simulated calculation. The texture and microstructure will be observed by EBSD, XRD, HRTEM, and the microstructural deformation as well as texture-evolution mechanisms of the magnet will be in-turn revealed. Moreover, by observing the .magnetic domain movement via the magneto-optical Kerr Microscope, MFM and Lorentz-Transmission Electron Microscope, and by calculating of the magnetization and anti-magnetization behaviors via VSM and micromagnetics simulation, the coercivity mechnism will be revealed. The project would develop a new comprehensive preparation technique for hot deformed nanocrystalline SmCo-based magnets, and would reveal the modulation law among microstructure, texture, magnetic domain and magnetic properties, which would provide significant theoretical and scientific supports about the novel high temperature permanent magnets with high performances.

钐钴基永磁是国防及民用高技术领域不可替代的关键材料。纳米晶钐钴基永磁具有矫顽力高、耐蚀性强和力学性能好等优点，有望成为新一代高温永磁。但这类材料难以获得晶体织构，其磁能积仅为理论值的1/4。对此，本项目拟采用放电等离子热压/热变形新技术制备高性能各向异性纳米晶钐钴基永磁，研究热压/热变形工艺对结构和磁性能的影响；然后将GLEEBLE热模拟实验和DEFORM软件模拟相结合，分析变形中的应力-应变关系，建立变形本构方程；利用EBSD、织构XRD、高分辨TEM等对织构和微结构进行分析，揭示其变形和织构形成机制。另外，采用磁光克尔显微镜、磁力显微镜、洛伦兹透射电镜观察磁畴的静态/动态行为，利用VSM和微磁学计算分析磁化和反磁化行为，揭示其矫顽力机制。研究预期提出一套完备的各向异性纳米晶钐钴基永磁的制备新技术，阐明显微组织-织构-磁畴-磁性能间的调制规律，为开发新一代高温永磁提供理论依据和科学指导。

近几年，随着我国高新技术的快速发展，对Sm-Co磁体提出了更高的要求，磁体既需要具备高性能、小型化，又需要满足耐高温、稳定可靠等特点。因此，对Sm-Co磁体展开系统地研究显得尤为重要。目前，热变形Sm-Co纳米晶磁体由于其制备工艺简单，综合性能更优，在高温领域具有良好的应用前景，但仍存在一些问题需要深入研究。热变形SmCo5磁体的变形及织构形成机理尚不清楚，热变形SmCo7系磁体的相稳定性也缺乏系统的探讨。此外，传统的热压-热变形(HP-HD)技术制备Sm-Co磁体的效率有限，产品难以实现规模化量产，而无法形成市场竞争力。针对上述三种情况，本文对热变形SmCo5磁体的变形及织构形成机制和热变形SmCo7系磁体的相稳定性进行了深入的研究，并对Sm-Co磁体的热变形方式进行了改善。.利用放电等离子烧结(SPS)结合HP-HD技术（镦粗式变形）制备出具有不同变形量的各向异性SmCo5纳米晶磁体，系统研究了不同变形量下磁体的磁性能、织构及微观结构，讨论了其变形及织构形成机理。结果表明，随变形量的增加，在微观结构方面：晶粒尺寸增加，部分等轴晶过渡为板条状晶粒且逐渐有序排列，促使磁体织构形成；.利用HP-HD技术制备了具有各向异性的SmCo6.8Hf0.2纳米晶磁体，系统的分析了其在热变形过程中微观结构、织构和磁性能的演化。结果表明，随着热变形温度的升高，1:7H相的稳定性降低，导致2:17R及1:5H相生成，其中1:5H相以球形析出相的形式随机分布，2:17R相以孪晶的形式存在。.利用前挤出变形技术（挤压式变形）制备了不同挤压宽度的各向异性SmCo5纳米晶磁体。系统地研究了挤压宽度对热挤压磁体微观结构以及磁性能的影响，并对其均匀性及织构形成机理展开讨论。