CN108346508B - Preparation method for enhancing texturing of nanocrystalline complex-phase neodymium-iron-boron permanent magnet - Google Patents

Preparation method for enhancing texturing of nanocrystalline complex-phase neodymium-iron-boron permanent magnet Download PDF

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CN108346508B
CN108346508B CN201710050591.7A CN201710050591A CN108346508B CN 108346508 B CN108346508 B CN 108346508B CN 201710050591 A CN201710050591 A CN 201710050591A CN 108346508 B CN108346508 B CN 108346508B
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permanent magnet
phase
thermal deformation
neodymium
iron
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CN108346508A (en
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杜娟
张中佳
王凤青
刘平
郑强
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Ningbo Institute of Material Technology and Engineering of CAS
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    • 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
    • H01F41/0273—Imparting anisotropy
    • 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
    • H01F1/0576—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 pressed, e.g. hot working
    • 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
    • H01F41/0266—Moulding; Pressing

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  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Hard Magnetic Materials (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)

Abstract

The invention provides a preparation method for enhancing the texturing of a nanocrystalline complex phase neodymium iron boron permanent magnet. The method carries out thermal deformation treatment on the NdFeB composite blank obtained by hot pressing treatment at a low temperature at a low speed, and obtains the fully-dense anisotropic NdFeB complex-phase permanent magnet block. Compared with the traditional process, the crystal grain growth can be effectively inhibited by deformation orientation at low temperature, and meanwhile, the uniform distribution of grain boundary phases at low temperature is facilitated by low-speed thermal deformation, the hard magnetic phase texture is enhanced, the formation and the expansion of cracks in the deformation process can be inhibited, and the densification and the magnetic performance of the block body are improved.

Description

Preparation method for enhancing texturing of nanocrystalline complex-phase neodymium-iron-boron permanent magnet
Technical Field
The invention relates to the technical field of magnetic materials, in particular to a preparation method for enhancing the texturing of a nanocrystalline complex phase neodymium iron boron permanent magnet.
Background
In 1993, Skomski and Coey theoretically predict that the anisotropic nanocomposite permanent magnet has the magnetic energy product of 120MGOe, which is far higher than the theoretical value of 64MGOe of the existing powder sintered NdFeB magnet, and the rare earth content is low, so that the anisotropic nanocomposite permanent magnet is expected to become a next-generation high-performance low-cost permanent magnet material. However, experimentally preparing such ideal nanostructures is a huge challenge.
The hot-pressing thermal deformation technology is an effective means for preparing a fully-dense anisotropic single-phase NdFeB permanent magnet, and is generally considered to be a rare earth-rich phase serving as a grain boundary liquid phase to promote grain rotation, so that the magnet forms a flaky crystal structure, and strong magnetocrystalline anisotropy is obtained. In order to prepare the soft and hard magnetic phase composite thermal deformation magnet, researchers adopt the ways of mixing rare earth-rich quick quenching powder and rare earth-poor quick quenching powder, mixing rare earth-poor quick quenching powder and low-melting-point alloy and the like for trial.
The microstructure shows that only the rare earth-rich liquid phase area of the thermal deformation magnet mixed by rare earth-rich quick quenching powder and rare earth-poor quick quenching powder forms a hard magnetic phase texture, and the rare earth-poor area basically has no deformation orientation; for the thermal deformation magnet mixed by rare earth-poor quick quenching powder and low-melting-point alloy, the low-melting-point alloy is introduced as a grain boundary phase to improve the deformation orientation capability of the composite magnet, so that the fully-compact nanocrystalline complex-phase permanent magnet material with obvious anisotropy can be prepared. However, the conventional high heat distortion temperature, typically above 700 ℃, causes overgrowth of lamellar crystals with lateral dimensions of several microns, well in excess of the exchange coupling dimensions required for the soft and hard magnetic phases. In addition, the conventional thermal deformation process has short deformation time and uneven distribution of low-melting-point grain boundary phases, which deteriorates the anisotropy of the composite magnet.
Disclosure of Invention
In view of the above technical situation, the present invention aims to provide a method for preparing a nano-crystalline complex phase neodymium iron boron permanent magnet with enhanced texturing, which not only can realize deformation of the complex magnet at a lower temperature, but also can further enhance the texturing capability of the deformed magnet.
In order to achieve the purpose, the inventor adopts a hot-pressing thermal deformation method, and discovers that low-temperature and low-speed deformation is adopted in the thermal deformation process after a large amount of experimental research, namely, the temperature is controlled to be 550-700 ℃, so that the growth of crystal grains can be effectively inhibited, and the exchange coupling effect between soft and hard magnetic phases is ensured; the low-speed deformation is adopted, namely the deformation speed v along the pressure direction is controlled to be less than or equal to 4um/s, the uniform distribution of crystal boundary phases at low temperature can be promoted, the enhancement of the hard magnetic phase texture is facilitated, the formation and the expansion of cracks in the low-temperature deformation process can be inhibited, and the densification and the magnetic performance of the block body are improved.
Namely, the technical scheme of the invention is as follows: a method for preparing a nano-crystalline complex phase neodymium iron boron permanent magnet with enhanced texturing adopts a hot pressing thermal deformation method, namely, the method comprises a hot pressing process of preforming powder of a neodymium iron boron complex phase permanent magnet material into a blank body and a thermal deformation process of microtexturing the blank body into an anisotropic block body, and is characterized in that: in the thermal deformation process, the deformation rate v along the pressure direction is controlled to be less than or equal to 4um/s, and the deformation temperature is controlled to be 550-700 ℃.
The neodymium iron boron biphase composite permanent magnetic material is an intermetallic compound Re2Fe14The main components of the permanent magnetic material based on B are rare earth elements of neodymium (Nd), iron (Fe) and boron (B), and in order to obtain different performances, part of the neodymium can be replaced by other rare earth metals of dysprosium (Dy), praseodymium (Pr) and the like. The anisotropic block prepared from the powder of the Nd-Fe-B permanent magnetic material contains a hard magnetic phase Re2Fe14B and soft magnetic phase alpha-Fe.
Preferably, the temperature is controlled to 550 to 650 ℃, more preferably 600 to 650 ℃ during the thermal deformation.
Preferably, the deformation rate v in the pressure direction during the thermal deformation is controlled to be 0.02 um/s.ltoreq.v.ltoreq.4 um/s, and more preferably 0.5 um/s.ltoreq.v.ltoreq.1 um/s.
The thermal deformation device used in the thermal deformation process is not limited, and is preferably a vacuum induction thermal deformation device.
Preferably, the blank is placed in a 304 stainless steel protective sleeve with equal diameter and the like and then subjected to thermal deformation treatment.
Preferably, the pre-heat preservation is carried out for 10min to 30min before the thermal deformation.
Preferably, during the thermal deformation, a vacuum is first drawn to 10 deg.C-4Pa, and filling a small amount of Ar gas as protective gas.
Preferably, the neodymium iron boron two-phase composite permanent magnetic material is doped with a low-melting-point alloy phase containing rare earth elements, and in the thermal deformation process of the invention, the doped rare earth liquid phase fills a grain boundary phase to promote the orientation texture of hard magnetic grains. Preferably, the mass of the doped alloy accounts for 1-10% of the mass of the neodymium iron boron two-phase composite permanent magnet material, and more preferably 2-8%.
Compared with the prior art, the invention carries out thermal deformation treatment on the neodymium iron boron complex phase blank obtained by the hot pressing treatment at low temperature at low speed to obtain the texture-enhanced fully-compact Re2Fe14B, compounding permanent magnet blocks. Compared with the traditional process, the method can effectively inhibit the deformation orientation at low temperatureThe crystal grains grow up, and the low-speed thermal deformation is beneficial to the uniform distribution of grain boundary phases at low temperature, the texture of the hard magnetic phase is enhanced, the formation and the expansion of cracks in the deformation process can be inhibited, and the densification and the magnetic performance of the block body are improved.
Drawings
FIG. 1 is an SEM picture of fracture morphology of a bulk permanent magnet prepared in example 1 along a pressure direction;
FIG. 2 is an SEM image of fracture morphology of a bulk permanent magnet produced in comparative example in the pressure direction;
fig. 3 is a demagnetization curve at room temperature of the bulk permanent magnets prepared in example 1, example 2, and comparative example.
Detailed Description
The present invention is further described with reference to the following drawings and examples, which are intended to facilitate the understanding of the present invention and are not intended to be limiting.
Example 1:
in this example, the raw material was commercial rare earth-poor two-phase magnetic powder NdFeB (15-7) available from migu magnet (tianjin) ltd, and this raw material was mixed with a low melting point alloy powder Nd70Cu30Mixing, wherein the doping amount of the Nd-Cu alloy powder accounts for 8% of the mass of the raw material, and obtaining a doping raw material.
The preparation method of the Nd-Cu alloy powder comprises the following steps:
(1) preparing Nd according to the components of the NdCu alloy and carrying out vacuum induction melting70Cu30Alloy ingot casting;
(2) breaking the Nd under argon protection70Cu30Grinding and sieving the alloy cast ingot to obtain NdCu alloy powder with the particle size of below 90 um;
the doped raw material is adopted to prepare the anisotropic Nd by a hot-pressing thermal deformation method2Fe14B, the complex phase permanent magnet block material is as follows:
(1) and (3) hot pressing: loading a certain amount of the doped raw material into a hard alloy mold, and performing vacuum induction hot pressing thermal deformation in a vacuum of 4 × 10-2Hot-pressing preforming under the conditions of Pa, pressure 215MPa and 700 DEG CObtaining a blank body;
(2) thermal deformation process: putting the blank obtained in the step (1) into a 304 stainless steel sheath with equal diameter and equal height, and then putting into a hard alloy die with preset size; using a high vacuum induction hot-pressing thermal deformation device, and vacuumizing to 10 DEG-4Pa, recharging a small amount of Ar as protective gas; and then, controlling the deformation rate v along the pressure direction to be 1um/s at 600 ℃ to carry out hot-pressing deformation to a preset size, thereby obtaining the dual-phase composite permanent magnet block material.
Example 2:
in this example, the same doping raw material as in example 1 was used.
The doped raw material is adopted to prepare the anisotropic Nd by a hot-pressing thermal deformation method2Fe14B, the complex phase permanent magnet block material is as follows:
(1) exactly the same as the step (1) of example 2;
(2) substantially the same as the step (2) of the example 2, except that the hot press forming is performed to the predetermined size under the condition of 600 ℃ under the control of the deformation rate v of 2um/s along the pressure direction, and the dual-phase composite permanent magnet block material is obtained.
Comparative example:
in this example, the same doping raw material as in example 1 was used.
The doped raw material is adopted to prepare the anisotropic Nd by a hot-pressing thermal deformation method2Fe14B, the complex phase permanent magnet block material is as follows:
(1) exactly the same as the step (1) of example 2;
(2) substantially the same as the step (2) of example 2, except that the hot press deformation was performed to a predetermined size under the condition of 600 ℃ under the control of the deformation rate v ═ 8um/s in the pressure direction, to obtain the dual-phase composite permanent magnet block material.
Fig. 1 and 2 are SEM pictures of fracture morphology of the bulk permanent magnet in the pressure direction, which were obtained in example 1 and comparative example, respectively. Comparing fig. 1 and fig. 2 with the comparative example, it is shown that the texturing of the nanocrystals is enhanced under the slow deformation condition, resulting in good orientation texture.
Fig. 3 is a demagnetization curve of the bulk permanent magnets prepared in the above examples 1 and 2 and comparative example at room temperature, showing that controlling the slow deformation along the pressure direction enhances the anisotropy of the permanent magnets.
Table 1 below shows the magnetic properties of the bulk permanent magnets obtained in examples 1 and 2 and comparative examples, and shows that the magnetic properties of the bulk permanent magnets obtained by slow deformation are improved as compared with the comparative examples.
Table 1:
Hci(kOe) Br(kG) (BH)max(MGOe)
example 1 8.14 12.15 31.18
Example 2 7.23 11.91 28.21
Comparative examples 7.03 11.18 24.63
The embodiments described above are intended to illustrate the technical solution of the present invention in detail, and it should be understood that the embodiments described above are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modification, supplement or similar substitution made within the scope of the principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. A method for preparing a nano-crystalline complex phase neodymium iron boron permanent magnet with enhanced texturing adopts a hot pressing thermal deformation method, namely, the method comprises a hot pressing process of preforming powder of a neodymium iron boron complex phase permanent magnet material into a blank body and a thermal deformation process of microtexturing the blank body into an anisotropic block body, and is characterized in that: in the thermal deformation process, the deformation rate along the pressure direction is controlled to be not less than 0.02um/s and not more than 4um/s, and the temperature is controlled to be 550-600 ℃;
the neodymium iron boron biphase composite permanent magnetic material is an intermetallic compound Re2Fe14B is a basic permanent magnetic material, wherein a low melting point alloy phase containing rare earth elements is doped;
the anisotropic bulk has a structure containing a hard magnetic phase Re2Fe14B and soft magnetic phase alpha-Fe.
2. The method for preparing the textured and enhanced nano-crystalline complex phase neodymium-iron-boron permanent magnet according to claim 1, which is characterized in that: and in the thermal deformation process, controlling the deformation rate v along the pressure direction to be 0.5 um/s-1 um/s.
3. The method for preparing the textured and enhanced nano-crystalline complex phase neodymium-iron-boron permanent magnet according to claim 1, which is characterized in that: pre-insulating for 10-30 min before thermal deformation.
4. The method for preparing the textured and enhanced nano-crystalline complex phase neodymium-iron-boron permanent magnet according to claim 1, which is characterized in that: and putting the blank into a 304 stainless steel protective sleeve with the same diameter and height, and then carrying out thermal deformation treatment.
5. The method for preparing the textured and enhanced nano-crystalline complex phase neodymium-iron-boron permanent magnet according to claim 1, which is characterized in that: in the thermal deformation process, a high vacuum induction thermal deformation device is used and is vacuumized to 10 DEG-4Pa, and filling a small amount of Ar gas as protective gas.
6. The method for preparing the textured and enhanced nano-crystalline complex phase neodymium-iron-boron permanent magnet according to claim 1, which is characterized in that: the mass of the doped alloy accounts for 1-10% of that of the neodymium iron boron two-phase composite permanent magnetic material.
7. The method for preparing the textured and enhanced nano-crystalline complex phase neodymium-iron-boron permanent magnet according to claim 6, which is characterized in that: the mass of the doped alloy accounts for 2-8% of that of the neodymium iron boron two-phase composite permanent magnetic material.
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CN109473248A (en) * 2018-11-21 2019-03-15 重庆科技学院 A kind of NdCeFeB anisotropic permanent magnet and preparation method thereof
CN111554504B (en) * 2020-05-26 2021-01-12 北京大学 Nano-scale textured rare earth permanent magnet material and preparation method thereof
CN113996791B (en) * 2021-09-27 2023-05-02 宁波金鸡强磁股份有限公司 Manufacturing method of high-performance hot-pressing neodymium-iron-boron magnetic ring

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CN102982995A (en) * 2012-12-17 2013-03-20 湖南航天工业总公司 Microwave curing process of bonded NdFeB magnet
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