【作者】 孙继兵；

【导师】 崔春翔；

【作者基本信息】 河北工业大学 ， 材料物理与化学， 2004， 博士

【摘要】 Sm-Fe-N基化合物由于具有高的各向异性场及高居里温度而引起了稀土永磁材料领域的极大关注。本论文通过采用粉末冶金法及在粉末制备过程中加入高温HDDR、机械研磨、高能球磨、盘磨的新工艺，对Sm-Fe与Sm-Fe-M（M=Ti，Nb）合金及其氮化物粉末与粘结磁体进行了研究发现，Sm-Fe合金与Sm₂Fe_17-xNb_x（x≤4）合金退火态主相均为菱方Zh₂Zn₁₇型结构。Sm₂Fe_17-xTi_x合金退火后快冷，x＜1.0时，主相为Sm₂（Fe，Ti）₁₇相；在x=1时主相为Sm₃（Fe，Ti）₂₉相，x≥2.0时为Fe_9.5SmTi_1.5相，而x≤2合金退火后慢冷主相均为Sm₂（Fe，Nb）₁₇。Nb与Ti可减少Sm-Fe基合金铸态与退火态中α-Fe含量。不同温度下氢气与Sm-Fe合金的作用包括氢化、歧化、解吸与再复合过程，其中解吸与再复合过程应以与歧化反应平衡的逆反应SmH_y+α-Fe→Sm₂Fe₁₇+H₂方式进行。在连续的不同循环HDDR处理过程中，吸氢一歧化在升温（400℃／h的升温速度）的过程中即可完成，而DR过程在保温过程中达到平衡，即SmH_y+α-Fe（?）Sm₂Fe₁₇+H₂，抽真空是使该反应向右进行完成解吸与再复合过程的主要驱动力。HDDR使粉末颗粒产生裂纹，颗粒表面不光滑，有蜂窝状孔洞、密堆积小颗粒及细小颗粒分布。在封闭氮气氛中氮化后，2：17型氮化相能稳定存在，而Sm₃（Fe，Ti）₂₉型相在晶格应力较大时变得不稳定；SmFe₁₁Ti、Fe_9.5SmTi_1.5相消失，富Fe相（α-Fe与Fe₂Ti或Fe₂Nb）含量增加。经HDDR处理后的Sm-Fe与Sm-Fe-M粉末的氮化机制本质上与未HDDR处理粉末在封闭气氛与流动气氛中的氮化机制相同，均由N与Sm-Fe的“反应”阶段与氮的均匀化过程组成，但经HDDR后合金的“反应”速度慢。在流动氮气氛中氮化可使氮化相Sm₂（Fe，M）₁₇N_y过饱和，单胞体积膨胀超过10％，Ti与Nb提高氮化速度与合金中氮含量。氮化后Ti，Nb及HDDR工艺均可提高Sm-Fe-N基合金的矫顽力但降低磁化强度。与未HDDR处理的Sm-Fe与Sm-Fe-M相同，经HDDR处理后也得到了各向异性粘结磁体，Sm₂Fe_16.5Ti_0.5N_y磁体在15000 Oe外场下的矫顽力最高值为2900 Oe。未经HDDR处理合金中的颗粒及晶粒尺寸基本在100nm以上，不能得到纳米耦合结构。经HDDR处理后，均在Sm-Fe与Sm-Fe-M氮化物部分区域形成了双相耦合机制，其中α-Fe以两种形式存在：一种是颗粒嵌入基体2：17相中，另一种为与2：17相弥散混合。 高能球磨细化Sm-Fe基合金或氮化物粉末的过程由三个阶段组成：大粉末颗粒→压延或断裂成层片状→断裂成小颗粒，高能球磨明显降低粉末的矫顽力，在球磨到一定时间后，Sm₂Fe₁₇型相完全非晶化，α-Fe没有非晶化。更多还原

【Abstract】 Sm-Fe-N matrix compounds have excellent magnetic properties such as high saturationmagnetization, high magnetic anisotropy and relatively high Curie temperature. These propertiesmake the materials highly promising for permanent magnet applications. In this paper, Sm-Feand Sm-Fe-M (M=Ti, Nb) alloys and their nitrides were prepared by means of powdermetallurgy processes appending HDDR (hydrogenation-disproportionation-desorption-recombination ), mechanical grinding, high-enenrgy ball-milling and disc milling, and themicrostructure, phase composition and magnetic properties were investigated in detail. It wasshown that the host phases of annealed Sm-Fe and Sm2Fe17-xNbx (x<4) alloys retained therhombohedral Th2Zn17-type structure. The host phase of Sm2Fe17-xTix alloys with x less than 1quickly cooling from annealing temperature still retain Sm2(Fe,Ti)n, when x is equal to 1.0, thehost phase behaves Sm3(Fe,Ti)29, and when x is equal to or more than 2.0, the host phase finallybecames Fe9.5SmTi1.5. But when slowly cooling from annealing temperature, the host phases ofSm2Fe17-xTix alloys with x no more than 2 retain Th2Zn17-type structure. Nb and Ti addition canreduce the a-Fe content in as-cast and annealed Sm-Fe matrix alloys. The interactions betweenhydrogen and Sm-Fe alloys at different temperature were investigated by means of XRD, it wasfound that the interaction was composed of hydrogenation, disproportionation, desorption andrecombination, and the desorption and recombination processes maybe carried out according tothe reaction SmHy + a-Fe-Sm2Fe17 + H2 above 700C contrary to disproportionation. Thehydrogenation and disproportionation processes had finished when the samples werecontinuously heated up to 800C at the heating rate of 400C/h and the desorption andrecombination processes would reach equilibrium with disproportionation process on the basis ofSmHy+a-Fe-Sm2Fen+H2 and only pumping-vacuum could facilitate the reaction to right.The surface of the powder particles treated by HDDR processes was not smooth and consist ofcracks, honeycomb holes, closed packed small particles and dispersed fine particles with the sizeof dozens to 200 nanometers. When nitrogenated in closed pure N2 atmosphere with constantinitial pressure of 0.13 MPa, all Th2Zn17-type phases can exist stably, Sm3(Fe,Ti)29 becamesunstable when the lattice stress is much larger, SmFe11Ti and Fe9.5SmTi1.5 are disappear, thephases rich in Fe, such as a-Fe, Fe2Ti or Fe2Nb are increased. Nitrogenation mechanism inclosed N2 of Sm-Fe and Sm-Fe-M alloys by HDDR treatment is essentiallyas same as that of those alloys nitrogenated in closed or circulated N2 but not treated by HDDR processes, and nitrogenation is composed of two stages: N reacts with Sm-Fe matrix powders and N diffuses homogeneously in nitrides, but the reaction rate between N and Sm-Fe matrix powders treated by HDDR was slower than that not treated by HDDR. When nitrogenated in circulated pure N2 the 2:17-type nitride phases will be supersaturation and the expansion of unit cell volume could exceed 10%. Ti and Nb addition improve nitrogetion rate and increase nitrogen content of nitrides, moreover, Ti, Nb and HDDR process all improve the coercivity of Sm-Fe-N alloys but decrease the magnetization. Besides the anisotropy bonded magnets of Sm-Fe-N and Sm-Fe-M-N compounds not treated by HDDR were obtained, the anisotropy bonded magnets of Sm-Fe-N and Sm-Fe-M-N treated by HDDR processes were also prepared successfully, and Sm2Fe16.5Ti0.5Ny magnet exhibits the peak coercivity of 2900 Oe under the applied magnetic field of 15000 Oe. The size of particles or grains of the alloys not treated by HDDR are basically more than 100 nm, so the nanocomposite magnets through exchange coupling were not prepared. Howerer, the intergranular exchange-coupling interaction in the nonocrystalline Sm-Fe-N and Sm-Fe-M-N nitrides treated by HDDR was partially formed, and a-Fe can be embedded in 2:17-type matrix phases or dispersed w更多还原