晶界纳米改性烧结钕铁硼永磁合金的强韧化机理研究

To solve the technical problems on the poor mechanical properties of sintered NdFeB permanent magnet, the fund applicant who combined oneself investigation experiences reviewed the long history of mechanical properties research of sintered NdFeB permanent magnet, finding out that the key to improve the properties of sintered NdFeB permanent magnet is strengthening its low strength intergranular phase. By analyzing relevant research on doping, the comprehensive consideration the influence of Al doping on the magnetic and mechanical properties of sintered NdFeB permanent magnet were made，and the rationality of Al doping for sintered NdFeB permanent magnet were described. Based on the mechanism of the regulating grain boundary,the strengthening theory of materials,the essential of strengthening and toughening by NdAl-rich phase,and the characteristics of microstructure and fracture of sintered NdFeB permanent magnet, we presented and then demonstrated strictly the technical model of regulating the precipitation of NdAl-rich phase and its strengthening and toughening, which may be described as guiding the even precipitation of NdAl-rich phase to realize the strengthening and toughening of grain boundary efficaciously, using of cladding the matrix phase with Al nano-particles and forming the great many centers of nucleation of NdAl-rich phase at the grain boundary in the sintering process by adjusting the process. Aimed at the key technical problems, we analyzed and demonstrated the technical feasibility of the method with the relevant investigation. In this application project, we expect to explore the NdAl-rich phase mechanism on precipitation, regulation, strengthening and toughening for grain boundary by investigating process and analyzing microstructure, providing the technical and theory supports for the development of the new kind product of sintered NdFeB permanent magnet with good magnetic and mechanical properties.

为解决烧结NdFeB永磁合金的力性差的技术难题，申请者结合自身研究体会，对烧结NdFeB长期的力性研究作了系统梳理和归纳，发现力性改善的关键是强化低强度晶界相；通过分析相关研究结果，综合考量对磁性和力性的影响，阐述了Al掺杂的合理性。依据晶界改性原理、富NdAl相强韧化晶界的本质、材料强度理论、烧结NdFeB的组织断裂特性，及Al传统掺杂研究结果，提出并严格论证了调控晶界富NdAl相析出机制及其强韧化晶界的技术构想：将Al纳米颗粒包覆主相晶界，通过烧结使界面附近微区形成多个形核中心，诱导富NdAl相均匀析出，调控工艺，调节富NdAl相微组织的形成，有效实现晶界强韧化。针对技术关键，根据预研基础分析了技术手段的可行性。本项目期望通过工艺和微组织调控，探索晶界富NdAl相的析出、生长机理，探明富NdAl相对晶界的强韧化的调制机制，为开发有优良力性磁性烧结NdFeB永磁新产品提供理论与技术支持。

烧结NdFeB永磁材料以其优良磁性能，广泛应用于计算机、电子、机电等领域；烧结NdFeB永磁因其脆性，其器件在制备、应用等过程容易开裂；本项目研究旨在改善NdFeB永磁材料的力学性能，同时优化磁性能研究，以综合提高材料使用性能，对促进我国NdFeB产业发展做出一些努力。.本研究以晶界为研究对象，研究改性晶界的方式，包括晶界掺杂，晶界扩散，放电等离子烧结技术（SPS）对烧结钕铁硼的晶界的成分、结构的影响变化，对材料的力性和磁性的影响规律。从晶界掺杂方面，主要通过晶界掺杂Al，Cu，改性晶界，研究材料力性的影响机理。从晶界扩散角度，研究了Al，Cu，Tb或PrCu合金对晶界的成分结构改变，探索晶界改性对磁性、微观的力学性质（晶面滑移）以及耐腐蚀性的影响规律。从制备技术方面，探索了SPS不同温度对晶界成分影响机制，从而研究材料的力学性能的影响规律。研究结果概括如下：.1.通过晶界Al纳米包覆钕铁硼磁粉，改性晶界。实验表明，在一定的成分范围（0-0.9wt%）矫顽力随掺杂浓度增大而增大，提升幅度最大为30.3%，剩磁损失最大为2.86%，大小可以忽略。.2.通过晶界扩散，以TbH3纳米粉为扩散源。结果表明，TbH3纳米粒子的扩散使材料的矫顽力提高了6.9 kOe，组织观察发现有较深、较厚和连续的(Nd,Tb)2Fe14B层。.3.采用磁控溅射在烧结钕铁硼磁体表面形成Al膜，通过晶界扩散，使Al扩散至晶界，结果表明，矫顽力和耐腐蚀性得以提高。磁体最高矫顽力为1184 kA/m，与初始磁铁相比提高了21.8%；.4.采用SPS技术，研究SPS温度对晶界成分和磁体抗弯强度的影响，阐述了力性提高的机理，首次研究出两者之间关系公式。.5.采用晶界扩散和SPS过程相结合，制备各向异性热变形CeFeB磁体，结果表明，磁体性能Jr=0.66 T,Hci=514 kA / m, (BH)m=55 kJ / m3。PrCu有益于提高磁性和提高塑性变形能力，增强c轴取向。.总之，通过Al等元素改性晶界，提高了应力条件下晶界相晶面原子的滑移能力，从而提高了力性，而这些元素磁隔绝作用，能提升矫顽力。