Structural and magnetic properties of Sm（Co0.7Fe0.1Ni0.12Zr0.04B0.047.5） melt spun isotropic and anisotropic ribbons

We investigated the structural and magnetic properties of Sm(Co0.7Fe0.1Ni0.12Zr0.04B0.04)7.5 melt spun ribbons. Samples were arc melted then melt spun at 37 m/s up to 55 m/s to obtain ribbon for powdering. Annealing was performed in argon atmosphere for 30- 75 min at 600-870 oC. In as-spun ribbons the hexagonal SmCo7 (TbCu7-type of structure) of crystal structure was determined from x-ray diffraction patterns, while fcc-Co has been identified as a secondary phase. After annealing, the 1:7 phase of the as-spun ribbons transformed into 2:17 and 1:5 phases. X-ray patterns for as-milled powders exhibited very broad peaks making it difficult to identify a precise structure but repre-sented the 1:7 structure after annealing at low temperature (650 oC). TEM analysis showed a homogeneous nanocrystalline microstructure with average grain size of 30-80 nm. Coercivity values of 15-27 kOe were obtained from hysteresis loops traced up to a field of 5 T. The co-ercivity decreased as temperature increases, but it maintained values higher than 5 kOe at 380 oC. The maximum energy product at room temperature increased, as high as 7.2 MGOe, for melt-spun isotropic ribbons produced at higher wheel speeds. Anisotropic ribbons had a maximum energy product close to 12 MGOe.     

Effect of cobalt substitution on magnetic properties and microstructure of nanocrystalline （NdDyTb）12.3（FeZrNbCu）81.7B6.0 ribbons

Effect of Co substitution and annealing treatment on the formation, magnetic properties and microstructure of (NdOyTb)12.3(FeZrNbCu)81.7CoxB6(x=0-15) ribbons prepared by rapid quenching and subsequent annealing was systematically investi-gated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM) and vibrating sample magnetometer (VSM). Phase analysis revealed single-phase material. The remanence polarization Jr and maximum en-ergy product (BH)max increased with increasing x from 0 to 12 and then decreased for x=lS. The intrinsic coercivity Hci of (NdDyTb)12.3 (FeZrNbCU)81.7-xCoxB6 ribbons optimally processed decreased from 1308.7 kA/m for x=0 to 817.4 kA/m for x=15. Optimum magnetic properties with Jr=1.041 T, Hci=944.9 kA/m and (BH)max=155.1 kJ/m3 were achieved by annealing melt-spun ribbon (x=-12) at 675℃ for 10 min. There was no significant influence of Co substitution on microstructure.     

Study on preparation technique and properties of magnetostrictive epoxy bonded Tb1-xPrx（Fe0.4Co0.6）1.93 composites

The magnetic and magnetostrictive properties of epoxy bonded Tb1-xPrx（Fe0.4Co0.6）1.93 （0.85≤x≤1.00） composites, prepared with different epoxy proportions using cold compression-molding technique, were investigated. It is found that the optimal conditions were with a compaction pressure of 100 MPa and a mass ratio of resin to powder of 5：100. The Tb0.1Pr0.9（Fe0.4Co0.6）1.93 composite rod had a high magnetostriction of 770 ppm at an applied magnetic field of 960 kA/m, whereas the Pr（Fe0.4Co0.6）1.93 composite reached 500 ppm at 400 kA/m. The good magnetostrictive properties of Pr（Fe0.4Co0.6）1.93 composite at low-field （≤400 kA/m） could be explained by its low anisotropy. These results indicated that the epoxy bonded Tb1-xPrx（Fe0.4Co0.6）1.93 rod samples for high Pr content of x=0.9-1.0 were of practical value.     

Rare earth permanent magnets Sm2(Co,Fe,Cu,Zr)17 for high temperature applications

Sintered Sm(CobalFexCu0.1Zr0.03)7.5 (x=0.09-0.21) permanent magnets with higher Fe content were found to have higher remanence Br and maximum energy product (BH)max at room temperature. Br and (BH)max reached maximum of 0.96 T and 176.7 kJ/m3, respectively at room temperature when the Fe content x reached 0.21. However, the intrinsic coercivity Hci at room temperature increased gradually when the Fe content x increased from 0.09 to 0.15, but when x further increased to 0.21, Hci decreased. Hci attained its peak value of 2276.6 kA/m with Fe content x=0.15 at room temperature. For magnets with x=0.15, Br, (BH)max and Hci reached 0.67 T, 81.2 kJ/m3 and 509.4 kA/m at 500℃, respectively, showing good high temperature stability, which could be used in high temperature applications.     

Rare earth permanent magnets Sm2（Co,Fe, Cu,Zr）17 for high temperature applications

Sintered Sm（Coba1FexCu0.1Zr0.03）7.5 （x=0.09-0.21） permanent magnets with higher Fe content were found to have higher remanence Br and maximum energy product （BH）max at room temperature. Br and （BH）max reached maximum of 0.96 T and 176.7 kJ/m^3, respectively at room temperature when the Fe content x reached 0.21. However, the intrinsic coercivity Hci at room temperature increased gradually when the Fe content x increased from 0.09 to 0.15, but when x further increased to 0.21, Hcidecreased. Hci attained its peak value of 2276.6 kA/m with Fe content x=0.15 at room temperature. For magnets with x=0.15, Br, （BH）max and Hc1 reached 0.67 T, 81.2 kJ/m^3 and 509.4 kA/m at 500 ℃, respectively, showing good high temperature stability, which could be used in high temperature applications.     

烧结工艺对高温Sm(Co,Fe,Cu,Zr)z永磁体磁性能与显微组织的影响

用粉末冶金法制备了Sm(Co0.7Fe0.1Cu0.16Zr0.04)6.7烧结磁体,设计了8种不同烧结工艺;并对磁体的磁性能在烧结过程中的变化以及烧结工艺条件与显微组织的关系进行了系统研究.结果表明适当提高预烧结温度与烧结温度有利于磁性能的改善,但预烧结温度与烧结温度过高或过低都会使磁性能大大降低.矫顽力对烧结工艺非常敏感;样品在1 185℃预烧结后再在1 200℃烧结有最好的综合磁性能,其内禀矫顽力高达1 931 kA/m.还用扫描电子显微镜、电子探针光谱仪对显微组织及元素分布进行了分析,结果表明磁性能的改变可以认为是显微组织变化与元素在各相中分布变化的结果.     

高温稀土永磁Sm2(Co,Cu,Fe,Zr)17的烧结工艺

通过改变烧结工艺制度,制备了高温稀土永磁Sm(Cobal Fe0.26Cu0.05Zr0.026)70,其磁性能和温度系数(β)分别为:Br为1.08T,Hci为2 286 kA/m,Hcb为932 kA/m,(BH)max为220.8kJ/m3;β为-0.19%/℃.研究表明:提高烧结温度或真空预烧温度都可使材料的性能明显提高,特别是用后者制得的材料拥有较高的矫顽力和低的温度系数,具有较好的高温性能.然而,烧结温度或真空预烧温度过高时,Sm会从基体相中析出,使材料的磁性能降低,而且烧结温度过高还会使晶粒长大,导致材料矫顽力降低.     

高温稀土永磁Sm2(Co,Cu,Fe,Zr)17的研制

利用粉末冶金方法研制了Sm(CobalFe0.24Cu0.08Zr0.027)7.0,Sm(CpbalFe0.27Cu0.05Zr0.027)7.0,Sm(CobalFe0.26Cu0.05Zr0.026)7.0 3种高温永磁,并对其磁性能、温度稳定性和显微结构进行了分析.结果表明:样品Sm(CobalFe0.27Cu0.05Zr0.027)7.0具有最高的内禀矫顽力(2 165.6 kA·m-1)和最大磁能积(212.0kA·m-3);3种磁体的温度系数都较低,最高使用温度均在400℃以上,大大高于一般商用磁体;增加Sm,Co,Cu的含量和减少Fe的含量可以提高材料的温度稳定性.X射线分析表明,合金中含有Sm2(Co,Fe)17主相,Sm(Co,Cu)5相,含Zr化合物等.Sm(Co,Cu)5相、单质Zr、晶粒边界等钉扎畴壁,使合金具有较高的矫顽力.     

合金成分对高温Sm(Co,Fe,Cu,Zr)z磁性能与显微组织的影响

用粉末冶金法制备了6种Sm(CobalFe0.1CuyZr0.04)z烧结磁体,每种成分磁体都进行了热处理工艺优化实验;并对合金成分对磁体的显微组织及磁性能的影响进行了研究。结果表明:z值较小的磁体有较多的1∶5相,室温的Br、Hci与(BH)max都较低些,但方形度(K)较好,因此适当减小z值有利于提高高温磁性能;Cu含量的增加使1∶5相的畴壁能(1γ∶5)减少,2∶17相与1∶5相的畴壁能差(Δγ)增加,从而使矫顽力增加,但Cu含量太高,如果不同时增加Sm含量,将导致Br与(BH)max急剧下降;z值较低,同时Cu含量又较高的Sm(CobalFe0.1-Cu0.16Zr0.04)6.7磁体具有最佳室温磁性能与方形度。     

气流磨工艺对Sm(Co,Cu,Fe,Zr)7.5合金粉末特性及磁性能的影响

采用气流磨工艺制备Sm(Co,Cu,Fe,Zr)7.5合金粉末,研究了转速对合金粉末特性的影响及研磨不同阶段的粉末粒度变化,分析了合金磁性能与转速的关系.结果表明,增加转速将细化粉末粒度,提高粉末粒度的均匀性;研磨前阶段粉末粒度明显大于研磨中、后阶段;在转速为3 500 r/min时,所制备的粉末平均粒度约为5 μm,离散度最小,得到合金磁性能最佳,剩磁Br=1.081 T,最大磁能积(BH)max=226 kJ/m3,内禀矫顽力Hcj=2 240 kA/m.     

Magnetic Microstructures of 2:17 Type Sm(Co,Fe,Cu,Zr)z Magnets Detected by Magnetic Force Microscopy

The magnetic microstructures of 2:17 type Sm(Co,Fe,Cu,Zr)z magnets were detected by magnetic force microscopy.Comparing the microstructures of the specimens coated with and without Ta thin film before and after heat-treatment, it is found that: (a) as a protection layer, Ta coating layer about 20 nm thick can effectively restrain Sm volatilization under high temperature;(b) the stress built in the 2:17 type Sm-Co magnets during specimen preparation only affects some local parts of the domain structures;(c) the magnetic microstructures vary largely for specimens heat-treated at high temperature without Ta film coating due to Sm volatilization.In addition, by comparing with high coercivity Fe-Pt point tips, it is found that the Co-Cr thin-film tips are not suitable for detecting the magnetic microstructures of strong permanent magnets.     

粉末特性对Sm2(Co,Cu,Fe,Zr)17永磁材料及性能的影响

在粉末冶金工艺生产Sm2(Co,Cu,Fe,Zr)17的过程中,粉末特性对材料的性能存在较大影响.本研究对气流磨和滚动球磨两种工艺所制备的粉末进行比较,通过粒度分析及显微镜观察,研究了粉末的粒径与形状对材料性能的影响.分析结果表明,气流磨所制备的粉末平均粒径为4.53μm,尺寸分布范围较窄,粉末颗粒成近似球状,所得材料磁性能参数中Br,(BH)max优于滚动球磨.     

Application of high-temperature permanent magnets Sm(Co, Fe, Cu, Zr)z in PPM focusing system

Rare earth permanent magnets Sm(Co, Fe, Cu, Zr)z with outstanding performance and high-temperture thermal stability were fabricated. Optimized by Fe content and process, Sm(Co0.72Fe0.1Cu0.1Zr0.03.03)7.5 magnet with Br>0.75 T and Hci>1300 kA/m at 300 ℃ can be obtained. According to the performance data of Sm(Co0.72Fe0.15Cu10.1Zr0.03)75, the magnetic field along central axis BZ in periodic permanent magnet (PPM) focusing system was simulated using electromagnetic field analysis software Maxwell 2D/3D. The BZ exhibited typical cosine curve along central axis, and the peak value of BZ was high enough to meet the demand of PPM focusing system at room temperature even at 200±20 ℃. Additionally, a kind of simple cooling structure for PPM focusing system was designed by setting cooling pipe between polepieces.Simulated results showed that smooth cosine curve of BZ was successfully achieved with good control of the thickness of cooling pipe.