【作者】 李杰民；

【导师】 崔春翔；

【作者基本信息】 河北工业大学 ， 材料学， 2003， 硕士

【摘要】 Sm-Fe合金的制备是一个十分复杂的过程，其磁性能受多种因素的影响，因此本课题的目的在于探讨能够优化Sm₂Fe₁₇N_x合金的制备工序，降低生产成本以及提高磁性能的具体途径，这对其实现商品化有着重要的意义。实验中采用真空电弧炉和传统的粉末冶金工艺制备出了不同成分配比的Sm₂（Fe，Zr）₁₇，N_x磁粉，并通过扫描电子显微镜和能谱仪、X射线衍射仪、热重分析仪以及振动样品磁强计等分析手段对Sm₂Fe₁₇N_x、Sm₂（Fe，Zr）₁₇N_x磁粉的微结构和磁性能进行了测试和分析，并着重实验研究了一种熔炼时加入1.0at％的Zr，使铸态组织中几乎只包含Sm₂Fe₁₇而不含α-Fe的工艺路线。实验中研究了不同熔炼电流和熔炼时间对铸态组织的影响，并对不同含量的Sm-Fe合金退火前后的相组成进行了分析，在此基础上确定了熔炼参数和成分配比。通过对不同退火时间和氮化时间下材料的扫描电子显微分析和X-射线衍射分析，确定了最佳的退火时间和氮化时间。分析了不同Zr含量的Sm-Fe-Zr合金的相组成和微结构，研究了Zr含量对铸态组织的影响，结果表明，添加1.0at％的Zr可以明显改善合金的铸态组织，从而可以避免昂长的高温均匀化退火过程，取得了降低制造成本和优化工艺的效果。并通过模型的建立，对其作用原理进行了详细的分析，在理论研究上有所突破。通过Sm-Fe合金和Sm-Fe-Zr合金薄片试样和粉末粒子氮化过程中扩散实验的对比分析，揭示了N原子在Sm-Fe合金和Sm-Fe-Zr合金中的扩散行为。运用Fick第二定律，从理论上计算了扩散参数，为确定氮化时间提供了依据，并对造成实际结果和理论计算之间差距的原因进行了分析。计算了引起材料磁晶各向异性大大增加的点阵常数的变化和体积膨胀量。通过对不同成分配比、不同氮化时间和研磨时间下Sm-Fe合金和Sm-Fe-Zr合金磁粉磁性能的研究，得出了材料磁性能随成分、工艺参数的变化关系。分析了影响材料磁性能的一些重要因素，指出粉末粒径过大以及分布不均，难以获得单畴颗粒是造成材料磁性能不高的主要原因。更多还原

【Abstract】 The preparation of Sm-F-N alloy is a very complex process and it’s magnetic properties are affected by many factors, so it is the purpose for this paper to investigate concrete method which optimizes the preparation of Sm2Fe17Nx alloys, makes the cost lower and magnetic properties higher. It has important significance to realize the commercialization of Sm2Fe17Nx permanent magnet materials. Sm2Fe17 and Sm2(Fe,Zr)17 with different contents are prepared by a vacuum arc furnace and tranditional power metallurgical method. The analysis and measurement of the microstucture and magnetic properties are carried out using scanning electron microscopy with energy-dispersive X-ray analysis, X-ray diffraction technique, thermo-gravimetric analyzer and vibrating sample magnetometer etc. A processing used to obtain the Sm2Fe17 phase without a-Fe in the as-cast state is described. The method consists of adding 1.0% of zirconium to the melt.The effect of the melting-current and melting-time on the microstructure of the as-cast Sm-Fe alloy is investigated and the phase composition of the as-cast Sm-Fe alloy with different Sm content is analyzed. The parameters of the melting process and the proportion between different chemical elements are decided, which are based on the above-mentioned investigation and analysis. By analyzing the microstructure and phase composition of Sm-Fe alloy annealed and nitrided for different time using scanning electron microscopy and X-ray diffraction technique, the optimum values for the annealing time and the nitriding time is determined.The phase composition and microstructure of Sm-Fe-Zr alloy with different amount of Zr are analyzed and the effect of Zr content on the microstructure of as-cast Sm-Fe-Zr alloy is studied. The results indicate that microstructure of as-cast Sm-Fe-Zr alloy is improved obviously with 1.0at% Zr added, and that the long-time high temperature homogenization is unnecessary for the alloys with this microstructure. By this way, the purpose of the research to decrease the cost of preparation and optimize process is achieved. The principle of the effect of Zr additions on the microstructure and phase composition of as-cast alloys is discussed detailedly by establishing appropriate model, which makes progress in theoretical study.Comparison of the data from diffusion experiments conducted on thin plates and powers ofthe Sm-Fe alloy and Sm-Fe-Zr alloy in nitrogenation reveal the behavior of N atoms in Sm-Fe alloy and Sm-Fe-Zr alloy. To calculate the diffusion parameters in theory, the Fick second law is used. The calculational results provide valid evidence for determining the nitriding time. The reason for which causes the difference between the real results and the theoretical calculation is analyzed. The change of lattice constants and the cell volume expansion are calculated, which make an important contribution to the increase of the magnetocrystalline anisotropy.By investigating the magnetic properties of Sm-Fe and Sm-Fe-Zr magnetic powers with different composition, different nitriding time and different milling time, the relationship between the magnetic properties and different composition and parameters of process is achieved. Some important factors to affect the magnetic properties of Sm-Fe and Sm-Fe-Zr magnetic powers are discussed. The conclusion is that the main reason for making the magnetic properties lower is because the radius of the particles of magnetic powers is too large and the distribution is irregular, which can’t result in obtaining the single-domain particles .更多还原