WO2021136366A1 - 一种适用于大块稀土永磁材料的晶界扩散方法 - Google Patents

一种适用于大块稀土永磁材料的晶界扩散方法 Download PDF

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WO2021136366A1
WO2021136366A1 PCT/CN2020/141348 CN2020141348W WO2021136366A1 WO 2021136366 A1 WO2021136366 A1 WO 2021136366A1 CN 2020141348 W CN2020141348 W CN 2020141348W WO 2021136366 A1 WO2021136366 A1 WO 2021136366A1
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grain boundary
magnet
rare earth
boundary diffusion
diffusion
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French (fr)
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金佳莹
严密
陶永明
李美勋
魏中华
赵栋梁
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Zhejiang University
Zhejiang Innuovo Magnetics Industry Co Ltd
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Zhejiang University
Zhejiang Innuovo Magnetics Industry Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C28/00—Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/0555—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 pressed, sintered or bonded together
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H01F41/0293—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
    • B22F2003/1051—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding by electric discharge
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C2202/00—Physical properties
    • C22C2202/02—Magnetic

Definitions

  • the invention relates to the field of permanent magnets, in particular to a grain boundary diffusion method suitable for bulk rare earth permanent magnet materials.
  • NdFeB has excellent comprehensive magnetic properties and is widely used in the fields of energy, information, transportation and national defense. It is one of the most important rare earth functional materials and key basic materials for the national economy. However, the temperature stability of sintered NdFeB is poor, and the working temperature is usually lower than 100°C. Applications such as electric vehicles, wind power, and aerospace are greatly restricted. At present, the use of cheap, high-abundance rare earth La/Ce/Y to replace the expensive Nd/Pr/Dy/Tb greatly reduces the raw material cost of rare earth permanent magnets, which has attracted widespread attention at home and abroad.
  • the intrinsic magnetism of the 2:14:1 phase formed by lanthanum, cerium and yttrium is weaker than that of neodymium iron boron, and the magnetic dilution of the rich and abundant rare earth permanent magnet is significant, especially the low coercivity, which cannot meet the commercial requirements. This problem is difficult to solve and has long restricted the development and application of high-abundance rare earth permanent magnets.
  • the methods to improve the coercivity of NdFeB mainly include: 1) Smelting and adding heavy rare earths, but introducing a large amount of uniformly distributed Dy/Tb into the main phase not only consumes scarce heavy rare earth resources, greatly increases the cost of raw materials, but also greatly increases the cost of raw materials. Reduce remanence and magnetic energy product; 2) Refine the grains, but the magnetic powder is easy to oxidize after the particle size is reduced. When the grains drop below 3 ⁇ m, the coercive force will decrease; 3) Grain boundary diffusion can greatly increase the coercive force of the magnet And the operation is simple, which can greatly improve the utilization efficiency of rare earths. Therefore, grain boundary diffusion is the current research hotspot. However, due to the limitation of the diffusion depth of the elements, the ordinary grain boundary diffusion process is only suitable for magnets with a thickness of less than 5mm, so large-scale applications are limited.
  • CN107275028A discloses an interface control method for grain boundary diffusion NdFeB magnets.
  • the interface control treatment is carried out at a temperature lower than the diffusion temperature of 20-100 °C, so that the heavy rare earth elements Dy and Tb are distributed on the outer surface layer of the main phase crystal grains. Control the content of Dy and Tb entering the crystal grains, thereby alleviating the reduction of remanence caused by grain boundary diffusion to a certain extent.
  • the depth of grain boundary diffusion is an important factor affecting magnetic properties, especially coercivity.
  • the grain boundary diffusion technology of bulk rich and abundant rare earth permanent magnet is more difficult.
  • the grain boundary diffusion technology of high-abundance rare-earth permanent magnets puts forward higher requirements.
  • the present invention prepares an initial magnet rich in rare earths through sintering or hot pressing or thermal deformation processes.
  • the alloy diffusion source is mainly Nd/Pr, and the spark plasma sintering technology is applied to the bulk rich, high, and rich
  • the grain boundary diffusion of rare-earth permanent magnets makes full use of the characteristics of SPS pressurized discharge plasma heating.
  • the diffusion coefficient and diffusion depth of the elements in the diffusion alloy source are significantly improved, and the diffusion depth is greatly improved.
  • the magnetic properties of the magnet is suitable for large initial magnets prepared by different processes.
  • the thickness of the magnet can reach 60mm, which breaks through the limit of element diffusion depth and magnet thickness, and the magnetic performance increases significantly, which meets the needs of industrial production and market .
  • a grain boundary diffusion method suitable for bulk rare earth permanent magnetic materials the thickness of the bulk rare earth permanent magnetic material is 10-60 mm, and the grain boundary diffusion method includes the following steps:
  • the initial magnet is prepared by sintering or hot pressing or thermal deformation process.
  • the initial magnet is rich in rare earths with high abundance.
  • its composition is: (R a A 1-a ) b Q bal M c B d ,
  • R is one or more of the high abundance rare earth elements La, Ce, Y
  • A is one or more of other lanthanide light rare earth elements except La, Ce, Y
  • Q is Fe
  • M is Al, Cr, Cu, Zn, Ga, Ge, Mn, Mo, Nb, P, Pb, Si, Ta, Ti, V, Zr, O, F
  • N, C, S, and H elements, B is boron element;
  • a, b, c, d satisfy the following relationship: 0.3 ⁇ a ⁇ 0.8, 26 ⁇ b ⁇ 36, 0 ⁇ c ⁇ 3 , 0.8 ⁇ d ⁇ 1.3; more preferably, 0.5 ⁇ a ⁇ 0.8;
  • the diffusion alloy source is rich in Nd/Pr, and its composition is: (R u A'1 -u ) v M'1 -v , in terms of mass percentage, R is one or more of the high-abundance rare earth elements La, Ce, and Y, A'is one or two of Nd and Pr elements, and M'is Fe, Co, Ni, Al, Cr, Cu, One or more of Zn, Ga, Ge, Mn, Mo, Si, Ti, O, F, and H; u and v satisfy the following relationship: 0 ⁇ u ⁇ 0.2, 0.5 ⁇ v ⁇ 1;
  • the heating rate is 20 ⁇ 400°C/min
  • the diffusion temperature is 400 ⁇ 900°C
  • the applied pressure is 2 ⁇ 50MPa
  • the temperature is kept warm.
  • the time is 20-180min
  • the vacuum degree is less than 10 -3 Pa, and the final magnet is obtained.
  • the method of supporting the grain boundary diffusion alloy source in step (2) includes: magnetron sputtering, electroplating, chemical vapor deposition, physical vapor deposition, direct physical contact, and adhesive bonding.
  • the thickness of the bulk rare earth permanent magnet material is 15-30 mm.
  • the final magnet prepared in step (3) has the following composition: (R x A” 1-x ) y Q bal M” z B w ,
  • R is selected from high abundance rare earth elements La, Ce, and Y ;
  • A" is selected from other lanthanide light rare earth elements except La, Ce, Y;
  • Q is selected from Fe, Co, Ni elements;
  • M is selected from Al, Cr, Cu, Zn, Ga, Ge, Mn, Mo, Nb, P, Pb, Si, Ta, Ti, V, Zr, O, F, N, C, S, H elements;
  • B is boron element;
  • x, y, z, w satisfy the following relationship: 0.2 ⁇ x ⁇ 0.8 , 26 ⁇ y ⁇ 40, 0.5 ⁇ z ⁇ 6, 0.75 ⁇ w ⁇ 1.3. More preferably, 0.5 ⁇ x ⁇ 0.8.
  • the present invention has the following beneficial effects:
  • the present invention is suitable for sintering or hot pressing or thermal deformation method to prepare rich and high abundance rare earth permanent magnets, with light rare earth neodymium as the main body to form a grain boundary diffusion alloy source.
  • the rich and abundant rare earth permanent magnet due to its more complex and diverse grain boundary phase composition and distribution (the difference between different La, Ce, Y and their composite magnets), the Nd/Pr-rich diffusion source and its alloying elements During the SPS diffusion process, phase change and element interdiffusion will occur with the original grain boundary phase, resulting in a substantial increase in the diffusion coefficient; the diffusion of high-abundance rare earth elements will form a continuous thin-layer grain boundary phase, and the iron-rich new grain boundary phase will decrease In order to reduce the iron content in the thin continuous grain boundary phase, Nd/Pr diffuses in the main phase grain epitaxial layer to form a Nd-Pr-rich hard magnetic shell layer, which significantly improves the coercivity and remanence of the magnet.
  • the present invention constructs an "ideal magnet” element distribution: the crystal grain core is rich in La, Ce, Y, the crystal grain shell is rich in Nd, Pr, and the non-ferromagnetic continuous thin layer of the grain boundary phase isolates the adjacent crystal grains. Ferromagnetic coupling.
  • the substitution amount of La, Ce, Y of this ideal magnet is up to 80wt%. It has both high coercivity and high remanence. It makes full and reasonable use of the interaction effects of various rare earth elements, including La, Ce, Y and their composite magnets.
  • Element segregation/grain boundary phase formation/valence state control interactions including elemental mass transfer/phase transition/magnetic coupling interactions between Nd and Pr-based diffusion sources and high-abundance rare earth permanent magnets, as well as diffusion surface layers To the magnetic coupling/magnetic isolation effect between internal tissue structures at different depths.
  • the present invention is based on spark plasma sintering technology for grain boundary diffusion.
  • SPS grain boundary diffusion is an effective means to construct the above-mentioned "ideal magnet” element distribution.
  • the phase change of the magnet itself is superimposed during the heating process, and the influence of electric current, plasma and pressure is additionally applied, which can increase the diffusion coefficient of the elements and form high-speed diffusion inside the magnet.
  • the channel accelerates rare earth and alloy elements to enter the depths of the magnet.
  • Nd and Pr which have more excellent intrinsic magnetism, enter the grain shell, and tend to focus on the grain boundary diffusion, accelerating the phase transition, thereby increasing the diffusion depth of the elements and the magnetic properties Its temperature stability is significantly improved, so it has become a grain boundary diffusion method suitable for bulk rare earth permanent magnetic materials.
  • the present invention utilizes the characteristics of rapid heating speed and short heating time of the spark plasma sintering technology, which greatly suppresses the growth of crystal grains in the diffusion process.
  • SPS sintering of general metal materials the realization of uniform fine-grained structure through SPS diffusion is of special significance for rich rare earth permanent magnets.
  • the introduction of complex new grain boundary phases in rich and high-abundance rare earth permanent magnets intensifies liquid phase sintering, and the problem of abnormal grain growth is particularly prominent.
  • the invention matches the initial magnet composition, grain boundary phase structure, main phase grain composition distribution, etc.
  • the grain boundary diffusion is carried out, and the gas impurities generated by the alloy diffusion source (especially fluoride, nitride, hydride) due to high-temperature discharge are discharged in time, which promotes the diffusion and migration of elements, and is more suitable for the easy-to-oxidize rich and high Abundant rare earth permanent magnets improve the coercivity of the magnets.
  • the alloy diffusion source especially fluoride, nitride, hydride
  • the diffusion method proposed in the present invention consumes less light rare earth elements and does not use expensive heavy rare earth elements.
  • the magnetic properties of the prepared magnets reach or exceed the traditional NdFeB, but the cost is reduced to one-third of the NdFeB One or even lower, so as to give full play to the advantages of high-abundance rare earth permanent magnets with high magnetic performance, low price, and not relying on scarce rare earth elements, and promote the development and utilization of green and clean energy (wind power generation) and utilization (electric vehicles) Wait.
  • the initial magnet with a thickness of 25mm (Pr 0.12 Nd 0.48 Ce 0.4 ) 30.8 Fe bal Cu 0.3 Al 0.2 Ga 0.2 Zr 0.3 B 1.05 is prepared by a sintering process; the grain boundary diffusion alloy powder Nd 80 Al 20 is loaded on the initial magnet through direct contact After the surface of the magnet is placed in a discharge plasma device, the heating rate is 400°C/min, the diffusion temperature is 700°C, the applied pressure is 20MPa, and the holding time is 40min. The final magnet is obtained.
  • the initial magnet (Nd 0.4 La 0.2 Ce 0.4 ) 32 Fe bal Nb 0.3 Ti 0.2 Ga 0.5 Co 0.3 B 0.9 is prepared by a sintering process; the grain boundary diffusion alloy powder Nd 98 H 2 is bonded by PVP adhesive After loading on the surface of the initial magnet, put it into a discharge plasma device, the heating rate is 20°C/min, the diffusion temperature is 900°C, the applied pressure is 50MPa, and the holding time is 100min. The final magnet is obtained.
  • the initial magnet with a thickness of 60mm (Pr 0.14 Nd 0.56 La 0.1 Ce 0.2 ) 36 Fe bal Ga 0.35 Al 0.25 Cu 0.2 Zr 0.15 B 0.93 is prepared by a sintering process; the grain boundary diffusion alloy source Pr 80 Al 20 is produced by magnetron sputtering After loading on the surface of the initial magnet, put it into a discharge plasma device, the heating rate is 400°C/min, the diffusion temperature is 700°C, the applied pressure is 25MPa, and the holding time is 180min. The final magnet is obtained.

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Abstract

本发明公开了一种适用于大块稀土永磁材料的晶界扩散方法。本发明使用放电等离子烧结技术对大块磁体进行晶界扩散处理，改善磁体的综合磁性能。包括以下步骤：(1)通过烧结或热压或热变形工艺制备得到初始磁体；(2)在磁体表面负载晶界扩散合金源；(3)将负载后的初始磁体放入放电等离子装置中，使用放电等离子加热升温进行晶界扩散，得到最终磁体。通过控制放电等离子烧结过程中电流及压力等参数，显著提高元素的扩散系数和扩散深度。本发明制备的晶界扩散的大块稀土永磁材料，高丰度稀土La、Ce、Y取代量可达80wt％，磁性能增幅显著，且不受磁体厚度的限制，磁体厚度可达60mm，满足了工业生产及市场需求。

Description

一种适用于大块稀土永磁材料的晶界扩散方法 技术领域
本发明涉及永磁领域，具体来说，涉及一种适用于大块稀土永磁材料的晶界扩散方法。
背景技术
钕铁硼具有优异的综合磁性能，广泛应用于能源、信息、交通和国防等领域，是最重要的稀土功能材料和国民经济的关键基础材料之一。然而烧结钕铁硼的温度稳定性差，工作温度通常低于100℃，电动汽车、风电及航空航天等应用大幅受限。目前，使用廉价的高丰度稀土La/Ce/Y，取代价格昂贵的Nd/Pr/Dy/Tb，大幅降低稀土永磁的原材料成本，获得了国内外广泛关注。然而，镧铈钇形成的2:14:1相的内禀磁性弱于钕铁硼，富高丰度稀土永磁的磁稀释显著，尤其是矫顽力低，无法满足商用要求。该问题难以解决，长期制约了高丰度稀土永磁的发展和应用。
目前，提高钕铁硼矫顽力的方法主要包括：1)熔炼添加重稀土，但在主相中大量引入均匀分布的Dy/Tb，不仅消耗稀缺重稀土资源，极大提高原材料成本，而且大幅降低剩磁和磁能积；2)晶粒细化，但磁粉粒径下降后易氧化，晶粒降至3μm以下时，矫顽力反而降低；3)晶界扩散，可大幅提高磁体矫顽力，且操作简单，可大幅提高稀土的利用效率。因此，晶界扩散是目前的研究热点。然而由于元素扩散深度的限制，普通晶界扩散工艺仅适用于厚度小于5mm的磁体，因此规模化应用受限。
CN107275028A公开了一种晶界扩散钕铁硼磁体的界面调控方法，在低于扩散温度20～100℃的温度下进行界面调控处理，使重稀土元素Dy、Tb分布于主相晶粒外表层，控制进入晶粒内部的Dy、Tb含量，从而在一定程度上缓解了晶界扩散导致的剩磁降低。但是，晶界扩散深度是影响磁性能尤其是矫顽力的重要因素。实现磁体内部均匀的高矫顽力，要求沿晶扩散深度越深越好，尤其是对于厚度大于10mm的大块磁体，更需要实现一定的扩散深度才能满足高矫顽力要求；然而，重稀土扩散源的扩散深度越深，晶内扩散现象就越明显，Dy、Tb进入主 相晶粒内部导致磁体剩磁急剧下降，与高矫顽力相矛盾。
相较于传统钕铁硼，大块富高丰度稀土永磁的晶界扩散技术难度更大。传统富稀土晶界相、新晶界相(CeFe 2相、La 2O 3相等)、稀土元素差异分布等均显著影响晶内/晶界扩散过程，合金源体系设计也更复杂，这对富高丰度稀土永磁的晶界扩散技术提出了更高的要求。因此，如何提高富高丰度稀土永磁的晶界扩散深度，实现一种适用于大块稀土永磁材料的晶界扩散方法，制备兼具高矫顽力和高剩磁的富高丰度稀土永磁，是一个国际性难题。
发明内容
为解决上述技术难题，本发明通过烧结或热压或热变形工艺制备得到富高丰度稀土的初始磁体，合金扩散源以Nd/Pr为主，将放电等离子烧结技术应用于大块富高丰度稀土永磁的晶界扩散，充分利用SPS加压放电等离子加热的特点，通过控制放电等离子烧结过程中电流及压力等参数，显著提高扩散合金源中各元素的扩散系数和扩散深度，大幅改善磁体的磁性能；该方法适用于不同工艺制备得到的大块初始磁体，磁体的厚度可达60mm，突破了元素扩散深度和磁体厚度的限制，磁性能增幅更显著，满足了工业生产及市场需求。
为实现上述目的，本发明采用如下技术方案：
一种适用于大块稀土永磁材料的晶界扩散方法，所述的大块稀土永磁材料的厚度为10～60mm，所述的晶界扩散方法包括以下步骤：
(1)通过烧结或热压或热变形工艺制备得到初始磁体，所述的初始磁体富高丰度稀土，以质量百分数计，其成分为：(R aA 1-a) bQ balM cB d，R为高丰度稀土La、Ce、Y元素中的一种或几种，A为除La、Ce、Y外的其他镧系轻稀土元素中的一种或几种，Q为Fe、Co、Ni元素中的一种或几种，M为Al、Cr、Cu、Zn、Ga、Ge、Mn、Mo、Nb、P、Pb、Si、Ta、Ti、V、Zr、O、F、N、C、S、H元素中的一种或几种，B为硼元素；a、b、c、d满足以下关系：0.3≤a≤0.8，26≤b≤36，0≤c≤3，0.8≤d≤1.3；进一步优选的，0.5≤a≤0.8；
(2)在初始磁体表面负载晶界扩散合金源，所述的扩散合金源富Nd/Pr，以质量百分数计，其成分为：(R uA’ 1-u) vM’ 1-v，R为高丰度稀土La、Ce、Y元素中的一种或几种，A’为Nd、Pr元素中的一种或两种，M’为Fe、Co、Ni、Al、Cr、Cu、Zn、Ga、Ge、Mn、Mo、Si、Ti、O、F、H元素中的一种或几种；u、 v满足以下关系：0≤u≤0.2，0.5≤v≤1；
(3)将负载后的初始磁体放入放电等离子装置中，使用放电等离子加热升温进行晶界扩散，升温速度为20～400℃/min，扩散温度400～900℃，施加压力2～50MPa，保温时间20～180min，真空度小于10 -3Pa，得到最终磁体。
优选的，步骤(2)中负载晶界扩散合金源的方式包括：磁控溅射、电镀、化学气相沉积、物理气相沉积、直接物理接触、粘接剂粘结。
优选的，所述大块稀土永磁材料的厚度为15～30mm。
步骤(3)中制备的最终磁体，以质量百分数计，其成分为：(R xA” 1-x) yQ balM” zB w，R选自高丰度稀土La、Ce、Y元素；A”选自除La、Ce、Y外的其他镧系轻稀土元素；Q选自Fe、Co、Ni元素；M”选自Al、Cr、Cu、Zn、Ga、Ge、Mn、Mo、Nb、P、Pb、Si、Ta、Ti、V、Zr、O、F、N、C、S、H元素；B为硼元素；x、y、z、w满足以下关系：0.2≤x≤0.8，26≤y≤40，0.5≤z≤6，0.75≤w≤1.3。进一步优选的，0.5≤x≤0.8。
本发明与现有技术相比具有的有益效果：
1)本发明适用于烧结或热压或热变形法制备得到的富高丰度稀土永磁，以轻稀土钕镨为主体组成晶界扩散合金源。在富高丰度稀土永磁中，因其更复杂多样化的晶界相成分及分布(不同La、Ce、Y及其复合磁体间的差异)，富Nd/Pr的扩散源及其合金元素会在SPS扩散过程中，与原有晶界相间发生相变及元素互扩散，导致扩散系数大幅提高；高丰度稀土元素扩散形成连续的薄层晶界相，富铁的新晶界相降低了薄层连续晶界相中的铁含量，Nd/Pr扩散在主相晶粒外延层形成富钕镨的硬磁壳层，显著提高磁体的矫顽力和剩磁。本发明构筑了一种“理想磁体”的元素分布：晶粒核心富La、Ce、Y，晶粒壳层富Nd、Pr，非铁磁性的连续薄层晶界相隔绝相邻晶粒间的铁磁耦合。这种理想磁体La、Ce、Y取代量最高达80wt％，兼具高矫顽力和高剩磁，充分合理地利用各类稀土元素的交互效应，包括La、Ce、Y及其复合磁体的元素偏析/晶界相成相/价态调控等交互作用，包括Nd、Pr基扩散源与富高丰度稀土永磁间的元素传质/相变/磁耦合等交互作用，还包括扩散表层到内部不同深度组织结构间的磁耦合/磁隔离效应。
2)本发明基于放电等离子烧结技术进行晶界扩散。SPS晶界扩散是构建上述“理想磁体”元素分布的有效手段，加热过程中叠加磁体本身的相变，额外施加了电流、等离子及压力的影响，能够提高元素的扩散系数，磁体内部形成高速 扩散通道，加速稀土及合金元素进入磁体深处，内禀磁性更优异的Nd、Pr进入晶粒壳层，且趋于以晶界扩散为主，加速相变，从而提高元素的扩散深度，磁性能及其温度稳定性均显著提高，因而成为一种适用于大块稀土永磁材料的晶界扩散方法。
3)本发明利用放电等离子烧结技术升温速度快，加热时间短的特点，大幅抑制扩散过程中的晶粒长大。不同于一般金属材料的SPS烧结，通过SPS扩散实现均匀细晶组织对于富高丰度稀土永磁具有特殊意义。富高丰度稀土永磁中复杂新晶界相的引入，加剧液相烧结，晶粒异常长大问题尤其突出。本发明通过SPS扩散参数与初始磁体成分、晶界相组织结构、主相晶粒成分分布等相匹配，与晶界扩散源成分、元素迁移传质、合金化元素参与复杂相变等相匹配，可避免扩散后磁体表层-内部区域间形成粗晶-细晶过渡区，实现均匀细晶组织。并且在SPS真空环境下进行晶界扩散，及时排出合金扩散源(尤其是氟化物、氮化物、氢化物)由于高温放电产生的气体杂质，促进元素扩散迁移，也更适用于易氧化的富高丰度稀土永磁，提高磁体的矫顽力。
4)本发明提出的扩散方法，消耗较少的轻稀土元素，不用昂贵的重稀土元素，制备得到的磁体磁性能达到或超过传统钕铁硼，其成本却降至钕铁硼的三分之一甚至更低，从而充分发挥富高丰度稀土永磁集高磁性能、低价格、不依赖于紧缺稀土元素于一体的优势，促进绿色清洁能源的开发(风力发电)和利用(电动汽车)等。
具体实施方式
下面结合具体实施例对本发明做进一步说明，但本发明并不仅仅局限于以下实施例：
实施例1：
通过烧结工艺制备得到厚度为25mm的初始磁体(Pr 0.12Nd 0.48Ce 0.4) 30.8Fe balCu 0.3Al 0.2Ga 0.2Zr 0.3B 1.05；晶界扩散合金粉末Nd 80Al 20通过直接接触的方式负载在初始磁体表面后，放入放电等离子装置中，升温速度为400℃/min，扩散温度700℃，施加压力20MPa，保温时间40min，得到最终磁体，磁性能为B r＝12.4kG，H cj＝15.5kOe，(BH) max＝36.6MGOe。
实施例2：
通过烧结工艺制备得到厚度为20mm的初始磁体(Nd 0.4La 0.2Ce 0.4) 32Fe balNb 0.3Ti 0.2Ga 0.5Co 0.3B 0.9；晶界扩散合金粉末Nd 98H 2通过PVP粘接剂粘结的方式负载在初始磁体表面后，放入放电等离子装置中，升温速度为20℃/min，扩散温度900℃，施加压力50MPa，保温时间100min，得到最终磁体，磁性能为B r＝12.2kG，H cj＝12.5kOe，(BH) max＝33.4MGOe。
实施例3：
通过热变形工艺制备得到厚度为15mm的初始磁体(Nd 0.5Y 0.1Ce 0.4) 30Fe balZr 0.1Cu 0.25Co 0.5Mo 0.15Al 0.3Ga 0.1B 1.01；晶界扩散合金粉末Nd 40Pr 30Ce 10Al 5Cu 15通过PVP粘接剂粘结的方式负载在初始磁体表面后，放入放电等离子装置中，升温速度为350℃/min，扩散温度600℃，施加压力2MPa，保温时间60min，得到最终磁体，磁性能为B r＝11.5kG，H cj＝16.3kOe，(BH) max＝28.5MGOe。
实施例4：
通过烧结工艺制备得到厚度为60mm的初始磁体(Pr 0.14Nd 0.56La 0.1Ce 0.2) 36Fe balGa 0.35Al 0.25Cu 0.2Zr 0.15B 0.93；晶界扩散合金源Pr 80Al 20通过磁控溅射的方式负载在初始磁体表面后，放入放电等离子装置中，升温速度为400℃/min，扩散温度700℃，施加压力25MPa，保温时间180min，得到最终磁体，磁性能为B r＝12.6kG，H cj＝18.2kOe，(BH) max＝38.2MGOe。
实施例5：
通过热变形工艺制备得到厚度为15mm的初始磁体(Nd 0.2La 0.1Ce 0.7) 26Fe balZr 0.1Cu 0.2Co 0.5Al 0.3Si 0.1B 1.0；晶界扩散合金源Pr 55Ce 15Cu 30通过磁控溅射的方式负载在初始磁体表面后，放入放电等离子装置中，升温速度为100℃/min，扩散温度600℃，施加压力5MPa，保温时间40min，得到最终磁体，磁性能为B r＝10.3kG，H cj＝11.0kOe，(BH) max＝20.1MGOe。

Claims (4)

  1. 一种适用于大块稀土永磁材料的晶界扩散方法，所述的大块稀土永磁材料的厚度为10～60mm，其特征在于，所述的晶界扩散方法包括以下步骤：
    (1)通过烧结或热压或热变形工艺制备得到初始磁体，所述的初始磁体富高丰度稀土La/Ce/Y，以质量百分数计，其成分为：(R aA 1-a) bQ balM cB d，R为高丰度稀土La、Ce、Y元素中的一种或几种，A为除La、Ce、Y外的其他镧系轻稀土元素中的一种或几种，Q为Fe、Co、Ni元素中的一种或几种，M为Al、Cr、Cu、Zn、Ga、Ge、Mn、Mo、Nb、P、Pb、Si、Ta、Ti、V、Zr、O、F、N、C、S、H元素中的一种或几种，B为硼元素；a、b、c、d满足以下关系：0.3≤a≤0.8，26≤b≤36，0≤c≤3，0.8≤d≤1.3；
    (2)在初始磁体表面负载晶界扩散合金源，所述的扩散合金源富Nd/Pr，以质量百分数计，其成分为：(R uA’ 1-u) vM’ 1-v，R为高丰度稀土La、Ce、Y元素中的一种或几种，A’为Nd、Pr元素中的一种或两种，M’为Fe、Co、Ni、Al、Cr、Cu、Zn、Ga、Ge、Mn、Mo、Si、Ti、O、F、H元素中的一种或几种；u、v满足以下关系：0≤u≤0.2，0.5≤v≤1；
    (3)将负载后的初始磁体放入放电等离子装置中，使用放电等离子加热升温进行晶界扩散，升温速度为20～400℃/min，扩散温度400～900℃，施加压力2～50MPa，保温时间20～180min，真空度小于10 -3Pa，得到最终磁体。
  2. 根据权利要求1所述的晶界扩散方法，其特征在于，所述初始磁体中高丰度稀土La、Ce、Y的质量百分比为50％-80％。
  3. 根据权利要求1所述的晶界扩散方法，其特征在于，步骤(2)中负载晶界扩散合金源的方式包括：磁控溅射、电镀、化学气相沉积、物理气相沉积、直接物理接触、粘接剂粘结。
  4. 根据权利要求1所述的晶界扩散方法，其特征在于，所述大块稀土永磁材料的厚度为15～30mm。
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