Magnetic and Crystalline Microstructures of Fe-Pt-B Nanocomposite Ribbons

We investigate magnetic and crystalline microstructures of melt-spun (Fe0.675Pt0.325)100-xBx (x=12, 14, 16, 18,20) nanocomposite ribbons after optimal thermal treatment using a magnetic force microscope. The magnetic microstructures are characterized by darker spots adjacent to brighter ones in a sub-micro scale and in random distribution. It is found that the strength of the exchange coupling interaction between the crystals in the 10-100 nm scale, implied by the maximum value (δM)max of the Henkel plot, could be roughly described by the ratio of the average width of the magnetic spots w^- to the average crystal size D^- for the ribbons. Moreover, we find that the intrinsic coercivity jHc of the ribbons is sensitive to their crystal sizes, and the smaller D^-, the higher jHc. Finally, by using roughness analysis, the curve of the root mean square values (δФ)rms of the phase shift of the magnetic force images versus the boron content x is obtained, which is qualitatively consistent with that of the magnetization σ12 kOe of the ribbons versus x.     

Magnetic domain structures of precipitation-hardened SmCo 2：17-type sintered magnets： Heat treatment effect

The typical magnetic domains of Sm（CObalFe0.25Cuo.07Zr0.02）7.4 magnets quenched through various heattreatment steps have been revealed by using magnetic force microscopy （MFM）. For the specimens in which the nominal c-axis is perpendicular to the imaging plane, the domain configurations change from plate-like for the as-sintered magnet to corrugation and spike-like for the homogenized one, and then to a coarse and finally to a finer domain structure when isothermally aged at 830℃ and then annealed at 400℃. However, only plate-like domains can be detected on the surfaces with the nominal c-axis parallel to the imaging plane. The finer domain （so-called interaction domain） is a characteristic magnetic domain pattern of the SmCo 2：IT-type magnets with high coercivities. Domain walls in a zigzag shape are revealed by means of MFM in final bulk SraCo 2：17-type sintered magnets.     

Magnetic Microstructures of PryFe90－yB10 （y = 8－11.76） Nanocrystalline Ribbons Using Magnetic Force Microscopy ＊

Magnetic microstructure of melt-spun PryFe90-yB10 (y = 8, 8.5, 9, 9.5, 10 and 11.76) nanocrystalline ribbons in an as-grown state has been studied using a magnetic force microscope. The magnetic domains are characterized by dark areas adjacent to bright areas in a sub-micron scale and in random distribution. By comparing with the size of the micro-crystals measured from the TEM image, the exchange coupling effect was confirmed to exist inall the ribbons. Using the roughness analysis, the variation of the root mean-square values of the phase shifts obtained from the magnetic force images versus the content y of Pr were measured, which is very consistent with the curve of the residual induction Bγ versus the content y.     

钐钴永磁合金吸放氢特性及应用研究进展

钐钴永磁合金因卓越的磁性能、优异的高温性能和耐蚀性得到了广泛应用。随着在航空航天,风力发电等行业对高性能钐钴永磁合金需求加强,开发高性能钐钴永磁合金一直是本领域的研究热点。采用吸氢破碎制备单晶磁粉为制备高性能钐钴永磁合金的发展提供了新思路,同时,为了满足氢气服役环境对钐钴永磁合金高温耐氢能力的要求,开发强耐氢钐钴永磁合金的需求日趋迫切,因此需加强钐钴永磁材料吸放氢动力学与热力学机制的认识与了解,以指导研究钐钴合金吸氢破碎和强耐氢合金。本文首先介绍了合金吸放氢动力学与热力学研究中常用的检测与分析方法,然后综述了SmCo₅, Sm₂Co₇和Sm₂Co₁₇合金吸放氢过程中的结构变化和动力学与热力学研究进展,接着对近年来钐钴永磁材料吸氢破碎应用的研究成果进行了总结与讨论,最后对开发易氢破和强耐氢钐钴永磁合金作了展望。     

Magnetic and Crystalline Microstructures of the Sr-La-Co M-type Ferrites by Magnetic Force Microscopy

With proper erosion of sample surface and making a grid of crystal boundaries, the magnetic and crystal1ine microstruct ures of Sr-La-Co M-type ferrites of nominal composition of La0.2 Sr08Fe11.8Co0.2 O19 (at. %) have been investigated by using magnetic force microscopy. By calculating average diameter and thickness, and average alignment degree of the grains of the ferrites, recognizing their domain patterns and calculating the proportion of grains with single domain or multi-domains, the Sr-La-Co M-type ferrites with high magnetic performance have been characterized at microcrystalline and micromagnetic level. In addition, we has interpreted why the grains always present plate-like domains.     

Sm2Co17型永磁材料弹塑变形阶段的微纳压痕尺寸效应

采用准静态法分别对固溶态和最终态Sm₂Co₁₇型永磁的两种取向面样品进行了纳米压痕分析。结果表明,两类磁体不同取向面上的硬度和弹性模量均出现了随着压入深度的增加而减小的现象,表现出典型的压痕尺寸效应。基于Nix-Gao模型的硬度与压入深度拟合结果表明,两种磁体的硬度H₀和特征长度h~*均呈现出明显各向异性。较大的h~*值揭示出最终态磁体在较大的压入深度范围内可观察到明显的尺寸效应现象。进一步地,通过计算反映压痕尺寸效应强弱的效应因子i可知,最终态磁体的i值均比固溶态磁体的大,其中在取向平行加载方向时,i值高出58%。最终态Sm₂Co₁₇磁体中存在的胞状组织结构增强了尺寸效应因子,进而改善了Sm₂Co₁₇型磁体在弹塑变形阶段的塑性。     

Magnetic Microstructure of Sintered Nd-Fe-B Magnets Made from Casting Strips

The magnetic microstructures of two Dy-AI substituted sintered Nd-Fe-13 magnets with the different nominal compositions of Nd12.2Vy0.6Fe80.4Al0.7B6 (at.%) (composition-A,C-A) and Nd13.7Dy0.6Fe78.8Al0.7B6.2(at.%)(composition-B,C-13) prepared by strip casting technique have been revealed by using a magnetic force microscope. The magnetic properties of sintered C-B magnets are worse than that of C-A sintered magnets. In particular, the value of density products (BH)max for sintered C-A magnets is about 32% higher than that of C-B magnets, which is reflected by their quite different magnetic microstructures. We believe that for the C-B samples, the inappropriate composition and thus the redundant Nd2Fe17(B) phase of the casting strips make its final magnetic microstructures worse than the C-A, and then deteriorates the performance of the C-B magnets.     

烧结Nd25.5Dy6.5Co13FebalM1.05B0.98磁体温度稳定性和力学性能研究

本文采用速凝甩带-氢破-气流磨-取向成型-烧结回火等工序,同时添加Dy和Co元素,制备了烧结Nd_25.5Dy_6.5Co₁₃Fe_balM_1.05B_0.98磁体(Co13磁体),室温下磁能积(BH)_max=30.88 MGOe,矫顽力H_cj=19.01 kOe.与Nd₃₀Dy_1.5Co_0.5Fe_balM_1.05B_0.98(35SH)磁体相比, Co13磁体的室温磁性能略低,但温度稳定性显著提升,剩磁温度系数α从–0.136%/℃提升至–0.065%/℃(室温—180℃);居里温度T_C从310℃升高至约454℃;最高使用温度T_W从165℃提升到约200℃.力学性能测试和断口分析表明, Co13磁体中由于Co含量较高,主相晶粒发生解理断裂的比例提高...