【作者】 韩瑞平；

【导师】 崔春翔；

【作者基本信息】 河北工业大学 ， 材料学， 2010， 博士

【摘要】 纳米复合永磁材料是将饱和磁化强度高的软磁相与各向异性场高的硬磁相复合起来做成的多相磁体，利用软硬磁性相间的耦合作用可以获得优异的磁性能，并具有潜在的广阔应用前景。本论文用熔体快淬法制备薄带磁体，用X射线衍射仪、电子显微镜、热分析仪、振动样品磁强计等对Nd₂Fe₁₄B型磁体进行了元素替代研究，重点探讨了M=Co, Cr, Al, Zr元素及快淬速度等因素对Nd-Fe-M-B薄带磁体的结构与磁性能的影响。研究发现，在Nd-Fe-B系合金中加入一定量的Co所制得的Nd₁₀Fe₈₁B₆Co₃合金以35m/s速度快淬，并经800℃退火20分钟后与未加Co的合金相比，剩磁Mr由52.9 emu/g提高到84.3emu/g，但矫顽力略有降低。在Nd_11.3Fe₈₀B_5.2Co_3.5合金中加入Cr、Al、Zr元素得到Nd_11.3Fe_80-xB_5.2Co_3.5Mx合金，并发现这些元素会不同程度地促进合金中非晶相的形成；而当Mx=Cr0.4，并经30 m/s速度快淬，在800℃退火20min后，薄带合金矫顽力Hc为5375.7 Oe，最大磁化强度Ms=149.2emu/g，剩磁Mr=96.5 emu/g，剩磁比Mr/Ms=0.65；当Mx=Al1.5时，以35m/s速度快淬，经800℃退火8min后，材料Hc达到7227.8 Oe，Ms=99.4emu/g，Mr=96.5 emu/g，Mr/Ms=0.51；当Mx=Zr2时，以35m/s速度快淬，经800℃退火15min后，薄带磁体Hc达到9311.4 Oe，Ms=190.1emu/g，Mr=116.4 emu/g，Mr/Ms=0.61。将Nd₁₀Fe₈₁Co₃B₆合金分别以15 m/s、35 m/s、50 m/s的速度快淬成薄带，发现淬速越高淬态薄带中非晶相含量越多，35m/s淬速的薄带经800℃退火10min后晶化完好，两相交换耦合作用最好，矫顽力达到3139.8 Oe，剩磁达到84.3 emu/g；此外，快淬速度对主相Nd2（Fe,Co）14B的居里温度影响不大，三种不同淬速薄带的Nd2（Fe,Co）14B相的居里温度约为630 K。更多还原

【Abstract】 The nanocomposite permanent magnetic materials are multi-phase magnets which are composed of soft magnetic phases with high saturated magnetization and hard magnetic phases with high anisotropy field. Due to the outstanding magnetic properties obtained by means of exchange-coupling interaction between soft magnetic phases and hard magnetic phases, these magnetic materials can be potentially used in broad areas. In this paper, the ribbon magnets were prepared by melt-spinning method, the X-ray diffractometer, electron microscope, thermal analyzer and vibrating specimen magnetometer etc were used to study the element substitution of Nd₂Fe₁₄B-type magnets. The effects of M=Co, Cr, Al, Zr and melt-spinning speeds on the structure and magnetic properties of Nd-Fe-M-B ribbon magnets were mainly discussed.It was found that when a given amount of Co was added into the Nd-Fe-B alloy, the remanence of Nd₁₀Fe₈₁B₆Co₃ ribbons melt spun at 35 m/s and followed by annealing at 800 oC for 20 min was increased from 52.9 emu/g of the Nd10Fe84B6 ribbons to 84.3 emu/g, while the coercivity of annealed Nd₁₀Fe₈₁B₆Co₃ ribbons was decreased slightly.The Nd_11.3Fe_80-xB_5.2Co_3.5Mx alloys were prepared by substituting Cr, Al or Zr for Fe in the Nd_11.3Fe₈₀B_5.2Co_3.5 alloy. It was found that all alternative elements can facilitate the formation of amorphous phase differently. When the Nd_11.3Fe_80-xB_5.2Co_3.5Mx ribbons were melt spun at 35 m/s and followed by annealing at 800 oC for 20 min, the magnetic properties of the annealed ribbons with M=Cr and x=0.4 have the coercivity （Hc） of 5375.7 Oe, maximum magnetization （Ms） of 149.2 emu/g, remanence （Mr） of 96.5 emu/g and remanence ratio （Mr/Ms） of 0.65; While the magnetic properties of the annealed ribbons with M=Al and x=1.5 are Hc=7227.8 Oe, Ms=99.4 emu/g, Mr=96.5 emu/g and Mr/Ms=0.51; Furthermore, the magnetic properties of the annealed ribbons with M=Zr and x=2 amount to much better values: Hc= 9311.4 Oe, Ms=190.1emu/g, Mr=116.4 emu/g and Mr/Ms=0.61.When the Nd₁₀Fe₈₁Co₃B₆ alloy were melt-spun at the speeds of 15 m/s, 35 m/s and 50 m/s respectively, it was found that the content of amorphous phase was increased with increasing the melt-spinning speed. After the Nd₁₀Fe₈₁Co₃B₆ ribbons were annealed at 800oC for 10min, the annealed ribbons melt-spun at 35m/s were fully crystallized and the best exchange coupling action was built up, then the coercivity of annealed ribbons amounted to 3139.8 Oe, the remanence reached 84.3 emu/g. In addition, the Curie temperature of main phase Nd2（Fe,Co）14B was little affected by melt-spinning speed, it’s about 630K in the ribbons melt-spun at three different speeds.更多还原