2:17型SmCo磁体胞壁相磁晶各向异性参数多样性调控与矫顽力机制研究

Deep insight into the coercivity mechanism of 2:17 type cobalt-based rare earth permanent magnetic material is very important in further enhancing the magnetic properties at high temperature.And it is also a very important way to find new high temperature resistant permanent magnetic materials. In this project, the main purpose is to control the magnetocrystalline anisotropic constant of cell boundary phase in Sm(Co,Fe,Cu,Zr)z magnets. Based on the factor that huge diefferent variation of magnetocrystalline anisotropic constant in RCo5(R=Sm,Nd, Pr, Gd, Dy) alloys, low melting point rare earth and cobalt alloy are introduced into Sm(Co,Fe,Cu,Zr)z matrix magnets with low density and large cell strcuture by grain boundary diffusion. In term of chemical kinetics and thermodynamics, segregation of Nd, Pr, Gd, Dy and Cu elements in cell boundary phase have been tried to realize. The regulatory function of different elements with segregated distribution to the magnetocrystalline anisotropic constant of cell boundary phase in Sm(Co,Fe,Cu,Zr)z magnets are studied. Further, the influence of different variation of magnetocrystalline anisotropic constant of cell boundary phase with temperature increasing to the coercivity of Sm(Co,Fe,Cu,Zr)z magnets at high temperature are clarified. The project is expected to further improve the understanding of coercivity mechanism in Sm(Co,Fe,Cu,Zr)z magnets at high temperature, and also to provid new idears in finding and developing new high temperature resistant permanent magnetic materials.

阐明2:17型SmCo永磁材料的高温矫顽力机制是目前进一步提高磁体高温磁性能的关键，也是寻找新型耐高温永磁性材料的重要途径。本项目以调控Sm(Co,Fe,Cu,Zr)z 磁体胞壁相磁晶各向异性参数为出发点，利用RCo5(R=Sm, Nd, Pr, Gd, Dy)合金间磁晶各向异性常数随温度变化的巨大差异性，尝试通过晶界扩散的方式分别将低熔点稀土钴合金引入疏松和具有大胞状组织的Sm(Co,Fe,Cu,Zr)z基体磁体中，从化学热力学和动力学的角度，实现Nd、Pr、Gd、Dy元素在磁体胞壁相中的偏聚分布，研究不同稀土元素的偏聚分布对磁体胞壁相磁晶各向异性常数随温度变化的多样性调控作用，阐明胞壁相磁晶各向异性常数随温度的不同变化对磁体矫顽力机制的影响。本项目将进一步完善Sm(Co,Fe,Cu,Zr)z磁体高温矫顽力机制的认识，为寻找和开发新型耐高温永磁性材料提供新的思路。

Sm(Co,Fe,Cu,Zr)z磁体矫顽力与温度内在关系的深入认识对发展新型耐高温永磁体具有重要应用价值。磁体胞壁相磁晶各向异性对矫顽力的温度稳定性具有关键影响作用，深化其与矫顽力的关系认识具有重要理论意义。本项目基于类胞壁相RCo5(R=Sm, Nd, Pr, Gd, Dy)合金磁晶各向异性常数随温度变化的巨大差异性，利用稀土元素的偏聚分布调控胞壁相磁晶各向异性常数，研究胞壁相磁晶各向异性常数随温度的不同变化对磁体矫顽力的影响。. 研究通过粉末冶金工艺制备了SmR(Co,Fe,Cu,Zr)z(R=Pr, Gd, Dy)磁体，分析表明Dy元素具有胞壁相偏聚分布的趋势，而Gd、Pr元素则较均匀的分布于胞状组织结构中。微结构分析发现，Dy元素的引入使得2:17R胞内相析出大量无序的微孪晶结构，随着Dy含量的增加密度逐渐增加。相结构分析表明，Dy元素的引入稳定了固溶体中2:17H高温相，在时效处理过程中2:17H相与沉淀硬化形成的2:17R相交错分布，导致了长程无序的2:17R相和微孪晶结构的出现。磁性能结果表明，随着Dy含量的增加，磁体矫顽力温度系数逐渐优化，并出现正矫顽力温度系数的反常现象，其反常温度区间逐渐向高温移动。磁各向异性分析发现，含Dy磁体胞壁相均出现自旋再取向转变，且转变温度(TSR1:5)随Dy含量增加逐渐升高，该转变温度与反常矫顽力对应的起始温度基本一致，表明含Dy磁体的反常矫顽力温度系数与胞壁相的自旋再取向密切相关。反磁化行为分析发现，当磁体胞壁相发生自旋再取向转变时，胞壁与胞内存在很强的交换磁弹性作用，除此之外则逐渐减弱。. 进一步研究了Nd、Tb添加对胞壁相自旋再取向的影响，随着Nd和Tb含量的增加，Sm1-xRx(Co,Fe,Cu,Zr)z (R=Nd, Tb)磁体胞壁相均先后发生两种不同的自旋再取向转变：当x=0.3时，发生由易锥面向易轴取向的转变；当x≥0.5时，产生由易面向易轴的转变。磁性能结果表明，当出现由易锥面向易轴取向转变时，矫顽力温度系数改善，但并未出现正矫顽力温度系数；当出现由易面向易轴的转变时，出现正矫顽力温度系数现象。. 通过本项目的研究，创新性地开发出一种调控Sm(Co,Fe,Cu,Zr)z磁体温度稳定性的新方法，该方法实现了磁体矫顽力的多温区调节。基于自旋再取向的研究对开发新型耐高温永磁材料也具有理论启示意义。