Neodymium-iron-boron magnet, method for simultaneously improving magnetic properties and mechanical properties of a magnet

Abstract

The application provides a method for simultaneously improving the magnetic performance and mechanical performance of a neodymium-iron-boron magnet. In the rapid solidification stage, paramagnetic nanorod-shaped refractory particles are uniformly added and mixed into the neodymium-iron-boron alloy liquid by high-pressure injection, thereby obtaining alloy powder doped with the paramagnetic nanorod-shaped refractory particles, so that the paramagnetic nanorod-shaped refractory particles can be randomly distributed between the main phase grains of the sintered neodymium-iron-boron alloy, thereby generating rod-shaped second-phase substances in situ in the grain boundary phase, isolating the demagnetization coupling effect between the main phase grains, and improving the coercivity. In the application, the rod-shaped phase distributed between the main phase grains of the neodymium-iron-boron alloy can hinder the propagation of cracks, delay the transmission rate of cracks by using its dispersed distribution and refractory characteristics, and consume the energy transmission inside the magnet, thereby simultaneously improving the mechanical performance of the magnet along the magnetization axis and the non-magnetization axis direction, and increasing the material strength and toughness.

Description

Technical Field

[0001] This application relates to the field of rare earth permanent magnet materials technology, and more specifically to a neodymium iron boron magnet and a method for simultaneously improving the magnetic and mechanical properties of the magnet. Background Technology

[0002] Sintered NdFeB magnets, known as the "King of Magnets" due to their excellent magnetic properties, are widely used in aerospace, wind power generation, energy-saving home appliances, electronics, and new energy vehicles. However, existing NdFeB magnets suffer from poor strength and toughness, exhibiting brittleness and susceptibility to fracture and surface peeling during manufacturing and processing. This brittleness primarily stems from the intrinsic characteristics of their multiphase material composition. The grain boundary phase within sintered NdFeB magnets acts as a grain boundary weakening phase, significantly reducing the magnet's strength. Cracks in existing sintered NdFeB magnets typically accumulate and propagate within the grain boundary phase during processing and use, making the material highly susceptible to brittle fracture. This negatively impacts the material's stability and safety during service, severely limiting the application of sintered NdFeB magnets in high-intensity working environments. Summary of the Invention

[0003] This application addresses the shortcomings of existing technologies by providing a neodymium iron boron magnet and a method for simultaneously improving the magnet's magnetic and mechanical properties. During the magnet melting stage, this application involves spraying specially shaped, insoluble particles to generate rod-shaped second-phase material in situ within the grain boundary phase. This effectively isolates the demagnetizing coupling between the main phase grains, enhancing the coercivity of the neodymium iron boron magnet. The rod-shaped second-phase material, with its dispersed distribution and refractory properties, can also slow crack propagation, hindering crack growth and decomposing longitudinal crack propagation into oblique or horizontal propagation. This consumes energy transfer within the magnet, thereby improving the magnet's mechanical properties along the magnetization and non-magnetization axes, significantly increasing the material's strength and toughness. The specific technical solution adopted in this application is as follows.

[0004] First, to achieve the above objectives, a neodymium iron boron magnet is proposed, in which paramagnetic nanorod-shaped refractory particles are mixed in during the rapid solidification stage of the preparation process by high-pressure injection; the paramagnetic nanorod-shaped refractory particles are randomly distributed between the main phase grains of the sintered neodymium iron boron alloy.

[0005] Optionally, in any of the neodymium iron boron magnets described above, the mass percentage of paramagnetic nanorod-shaped refractory particles in the neodymium iron boron magnet is set between 0.1% and 1.0%.

[0006] Optionally, the neodymium iron boron magnet as described above, wherein the paramagnetic nanorod-shaped refractory particles comprise any one of the following powders or a mixture of any of the following powders with a particle size range of 100 nm to 2 μm: metallic Ti, oxides of metallic Ti, metallic Si, oxides of metallic Si, metallic Ta, alloys containing metallic Ta, elemental carbon, ceramic polymers, silicate compounds, and boride alloys.

[0007] Optionally, in any of the above-described neodymium iron boron magnets, the particle size of the neodymium iron boron alloy powder that constitutes the main phase grains of the neodymium iron boron alloy is between 1 and 6 μm.

[0008] To achieve the above objectives, this application also provides a method for simultaneously improving the magnetic and mechanical properties of a magnet, used to prepare a neodymium iron boron magnet. The steps include: grinding paramagnetic material particles to below 2 μm and then further dispersing them by vibration to obtain paramagnetic nanorod-shaped refractory particles; melting a neodymium iron boron alloy liquid, and uniformly adding the paramagnetic nanorod-shaped refractory particles to the neodymium iron boron alloy liquid by high-pressure injection during the rapid solidification stage; subjecting the mixed alloy liquid to vacuum rapid solidification treatment to obtain alloy rapid solidification sheets, and crushing the alloy rapid solidification sheets to obtain mixed powder; subjecting the mixed powder to magnetic field orientation pressing and cold isostatic pressing to obtain a green blank; and subjecting the green blank to sintering and tempering treatment to obtain a neodymium iron boron magnet.

[0009] Optionally, as described in any of the above methods, the paramagnetic nanorod-shaped refractory particles are obtained by grinding and oscillation treatment according to the following steps: mechanically grinding the particles of the paramagnetic material to obtain precursor particles with a particle size of less than 50 μm; further grinding the precursor particles to less than 2 μm using high-energy ball milling; then placing the small-diameter precursor particles obtained by grinding in a vacuum container and performing periodic ultrasonic oscillation dispersion treatment for 20-120 min to obtain paramagnetic nanorod-shaped refractory particles.

[0010] Optionally, as described in any of the above methods, during the rapid solidification stage, when the paramagnetic nanorod-shaped refractory particles are uniformly added and mixed into the NdFeB alloy liquid by high-pressure injection: the angle between the injection direction and the flow direction of the NdFeB alloy liquid is less than 45 degrees, and the injection rate is lower than the rotation speed of the cooling copper rod.

[0011] Optionally, as described in any of the above methods, during the rapid solidification stage, when the paramagnetic nanorod-shaped refractory particles are uniformly added and mixed into the NdFeB alloy liquid by high-pressure injection: the injection rate of the paramagnetic nanorods is 5-15 m / s, and the mass percentage of the injected material is set between 0.1% and 1.0%.

[0012] Optionally, in any of the neodymium iron boron magnets described above, the paramagnetic nanorod-shaped refractory particles include one or a combination of metallic Ti and its oxides, metallic Si and its oxides, metallic Ta and its alloys, carbon, ceramic polymers, silicate compounds, and boride alloys, wherein the particle size of the paramagnetic nanorod-shaped refractory particles ranges from 100 nm to 2 μm.

[0013] Optionally, for any of the neodymium iron boron magnets described above, the step of crushing the alloy quick-setting sheet to obtain mixed powder includes: first, subjecting the alloy quick-setting sheet to hydrogen crushing to obtain coarse powder with a particle size of ~8μm; then subjecting the coarse powder to hydrogen crushing and high-energy air jet milling to obtain fine mixed powder with a particle size distribution range of 1-6μm.

[0014] Beneficial effects

[0015] The method for simultaneously improving the magnetic and mechanical properties of magnets provided in this application, and the neodymium iron boron magnets prepared therefrom, allow for the uniform addition and mixing of paramagnetic nanorod-shaped refractory particles into the neodymium iron boron alloy liquid via high-pressure injection during the rapid solidification stage of the preparation process. This results in alloy powder uniformly doped with paramagnetic nanorod-shaped refractory particles, which are then randomly distributed between the main phase grains of the sintered neodymium iron boron alloy during the sintering process. This allows for the in-situ generation of rod-shaped second-phase material at the grain boundaries, effectively isolating the demagnetizing coupling between the main phase grains and improving coercivity. Furthermore, the paramagnetic nanorod-shaped refractory particles distributed between the main phase grains of the neodymium iron boron alloy in this application can hinder crack propagation. By utilizing the dispersed distribution and refractory properties of the rod-shaped phase, the crack propagation rate is slowed down, causing the longitudinal crack propagation to decompose into oblique or horizontal propagation, consuming energy transfer within the magnet, thereby simultaneously improving the mechanical properties of the magnet along the magnetization and non-magnetization axes, increasing the strength and toughness of the material.

[0016] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing this application. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the present application and form part of the specification. Together with the embodiments of the present application, they serve to explain the present application but do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 This is a schematic diagram of the periodic ultrasonic frequency of the dispersion treatment of precursor particles in this application.

[0019] Figure 2 This is a schematic diagram of the high-pressure injection method used in the rapid solidification stage of the neodymium iron boron magnet preparation process in this application;

[0020] Figure 3 This is a schematic diagram of the microstructure of the sintered NdFeB magnet prepared in this application;

[0021] In the diagram, 1 represents molten alloy; 2 represents a crucible; 3 represents rod-shaped refractory particles; 4 represents a high-pressure jet head; 5 represents a tundish; 6 represents a cooling copper roll; 7 represents a casting sheet; and 8 represents a water-cooling pan. Detailed Implementation

[0022] To make the objectives and technical solutions of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the described embodiments of this application without creative effort are within the scope of protection of this application.

[0023] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0024] The meaning of "and / or" as used in this application includes situations where each exists alone or both exist simultaneously.

[0025] In this application, "inner" and "outer" refer to directions relative to the container, with the direction from the outer shell of the container toward the interior of the neodymium iron boron magnet being "inner" and the opposite being "outer"; rather than a specific limitation on the device mechanism of this application.

[0026] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0027] The terms "upper" and "lower" as used in this application refer to the direction of the vertical pressure exerted on the mold during the pressing and molding of neodymium iron boron magnets, where the direction of the pressure is "upper" and vice versa, and do not constitute a specific limitation on the device mechanism of this application.

[0028] This application provides a method for utilizing Figure 1 The apparatus shown is a method for simultaneously improving the magnetic and mechanical properties of the prepared NdFeB magnets. This application allows for the formulation of materials according to the nominal composition of commonly used commercial NdFeB permanent magnet alloys, or the alloy composition ratio can be adjusted according to the requirements of magnet preparation.

[0029] In the preparation process of this application, precursor particles are incorporated into the aforementioned alloy material to effectively isolate the demagnetizing coupling between the main phase grains through the particle material distributed between the main phase grains. The precursor particles can be selected as paramagnetic nanorod-shaped refractory particles, which can be mixed into the NdFeB alloy material through high-pressure injection during the rapid solidification stage of the preparation process. During sintering, the paramagnetic nanorod-shaped refractory particles are randomly distributed between the sintered NdFeB alloy main phase grains, generating rod-shaped second phase material in situ in the grain boundary phase, effectively isolating the demagnetizing coupling between the main phase grains and improving coercivity.

[0030] In practice, considering that sintered Nd-Fe-B magnets are ferromagnetic materials, the proportion of impurity phases (paramagnetic or antiferromagnetic) should not be too high, otherwise it will destroy the structure of the ferromagnetic phase and deteriorate the magnetic properties. Therefore, the mass ratio of paramagnetic nanorod-shaped refractory particles mixed in NdFeB alloy materials is generally set between 0.1% and 1.0%.

[0031] The mechanical and magnetic properties of NdFeB magnets with different doping ratios can be found in the table below: When the mixing ratio is too low, the filling effect on the grain boundary phase is not obvious and it is difficult to play a role; when the ratio is appropriate, it can fill the grain boundary phase, maintain perfect isolation between the main phase and the grain boundary phase, and optimize the mechanical and magnetic properties at the same time; when the ratio is too high, it will destroy the structure of the main phase and deteriorate the magnetic properties of the magnet.

[0032] Table 1 Mechanical properties at different addition amounts

[0033] Add X Flexural strength / MPa Tensile strength / MPa Compressive strength / MPa Hardness / HV X＝0 390 140 1050 580 X＜0.1％ 410 160 1080 630 X＝0.1％ 550 210 1200 710 0.1％＜X＜1％ 480 185 1120 650 1％＜X 350 90 980 530

[0034] Table 2 Magnetic properties at different addition amounts

[0035] Add X Coercivity / kOe Remanence / kGs Magnetic energy product / MGOe <![CDATA[Density / g / cm 3 > X＝0 17.36 13.64 45.10 7.6803 X＜0.1％ 18.53 13.64 45.08 7.7328 X＝0.1％ 21.40 13.62 45.21 7.8131 0.1％＜X＜1％ 19.85 13.59 44.97 7.7563 1％＜X 1.35 10.34 3.85 7.3549

[0036] Considering that in common NdFeB magnets, the particle size of NdFeB alloy powder, which makes up the main phase grains of NdFeB alloy, is usually between 1 and 6 μm, the particle size of the doped paramagnetic nanorod-shaped refractory particles is too small to fill the grain boundary phase, while the particle size of the doped particles is too large, which will destroy the main phase structure. Therefore, this application compares the changes in mechanical and magnetic properties caused by different particle sizes in Tables 3 and 4. Generally, the particle size range of paramagnetic nanorod-shaped refractory particles can be controlled between 100 nm and 2 μm: when the particle size is too small, the filling effect on the grain boundary phase is not obvious and it is difficult to play a role; when the particle size is appropriate, it can fill the grain boundary phase, maintain perfect isolation between the main phase and the grain boundary phase, and optimize the mechanical and magnetic properties; when the particle size is too large, it will destroy the structure of the main phase, reduce the magnet density, and deteriorate the magnetic properties of the magnet.

[0037] Table 3 Mechanical properties under different doping particle sizes

[0038] Particle size Y Flexural strength / MPa Tensile strength / MPa Compressive strength / MPa Hardness / HV Y < 100nm 390 140 1050 580 Y = 100nm 425 155 1070 640 100nm < Y < 2μm 550 210 1200 710 Y = 2μm 490 188 1130 660 Y > 2μm 320 75 850 630

[0039] Table 4 Magnetic properties under different doping particle sizes

[0040] Particle size Y Coercivity / kOe Remanence / kGs Magnetic energy product / MGOe <![CDATA[Density / g / cm 3 > Y < 100nm 17.36 13.64 45.10 7.6803 Y = 100nm 17.96 13.63 45.05 7.7369 100nm < Y < 2μm 21.40 13.62 45.21 7.8131 Y = 2μm 20.03 13.58 45.01 7.7612 Y > 2μm 1.56 9.86 2.29 7.4749

[0041] Powders with a thermal conductivity >150 W / (m·℃), such as metallic Ti, oxides of metallic Ti, metallic Si, oxides of metallic Si, metallic Ta, alloys containing metallic Ta, carbon, ceramic polymers, silicate compounds, and boride alloys, or mixtures of any of the above powders, can be added as paramagnetic nanorod-shaped refractory particles to NdFeB alloy materials after grinding and dispersing to meet the relevant particle size requirements. This isolates the demagnetizing coupling effect between the main phase grains and improves coercivity.

[0042] The specific preparation process can be carried out using the following steps:

[0043] (1) Batching: The alloy is batched according to the nominal composition of commercial neodymium iron boron permanent magnet alloys;

[0044] (2) Pretreatment of precursor particles: After grinding the paramagnetic material particles to below 2μm, further vibration dispersion treatment is performed to obtain paramagnetic nanorod-shaped refractory particles.

[0045] (3) Melting: Melting NdFeB alloy liquid. The specific melting method can adopt the conventional commercial sintering NdFeB magnet melting method, only in the rapid solidification stage, the paramagnetic nanorod refractory particles are uniformly added and mixed into the NdFeB alloy liquid by high pressure injection;

[0046] (4) Airflow mill: Vacuum rapid solidification treatment is performed on the mixed alloy liquid to obtain alloy rapid solidification flakes, and the alloy rapid solidification flakes are crushed to obtain mixed powder.

[0047] (5) Press molding: The mixed powder is subjected to magnetic field orientation pressing molding and cold isostatic pressing to obtain a green embryo;

[0048] (6) Sintering and Tempering: The green blank is sintered and tempered to obtain NdFeB magnets. The sintering and tempering process here can directly adopt existing traditional sintering and tempering processes to obtain magnets with... Figure 2 The microstructure shown indicates a high-performance sintered NdFeB magnet with excellent overall properties.

[0049] In a preferred embodiment, to grind and disperse the precursor particles to a suitable size, in the precursor particle pretreatment step (2), any one of the following, or a mixture of the particles: metallic Ti and its oxides, metallic Si and its oxides, metallic Ta and its alloys, carbon, ceramic polymers, silicate compounds, and boride alloys, can be ground and vibrated in the following manner to obtain paramagnetic nanorod-shaped refractory particles with a particle size range of 100 nm to 2 μm:

[0050] Step 2-1: Mechanically grind the paramagnetic material particles to obtain precursor particles with a particle size of less than 50 μm.

[0051] Step 2-2 involves using high-energy ball milling to further grind the precursor particles to below 2 μm. The resulting small-diameter precursor particles are then placed in a vacuum container and subjected to periodic ultrasonic oscillation. Figure 1 The periodic ultrasonic frequencies shown were used for 20-120 minutes of oscillation dispersion treatment. Ultrasonic waves of different amplitudes were used to disperse particles with inconsistent agglomeration levels, resulting in paramagnetic nanorod-shaped refractory particles. In this step,

[0052] In a preferred implementation, (3) in the smelting step, the paramagnetic nanorod-shaped refractory particles can be uniformly added and mixed into the NdFeB alloy liquid by high-pressure injection during the rapid solidification stage:

[0053] In the rapid solidification stage of commercial sintered NdFeB magnet melting, a high-pressure injection method is used. At an injection angle not exceeding 45 degrees relative to the flow direction of the NdFeB alloy liquid, and at a injection rate lower than the rotation speed of the cooling copper rod, 0.1%-1.0% (by mass) of paramagnetic nanorod-shaped refractory material is added to the NdFeB alloy solution. After injection, vacuum rapid solidification treatment yields rapidly solidified alloy flakes. Because the powder particles become too energetic after ball milling and tend to agglomerate, resulting in powder particles ranging from 100nm to 2μm, periodic ultrasonic vibration is required to ensure uniform powder dispersion.

[0054] In this step, the particle size range of the paramagnetic nanorod-shaped refractory particles is generally between 100 nm and 2 μm. The spraying rate is typically set to 5-15 m / s to ensure uniform distribution of the nanophase within the rapidly solidifying sheet and to prevent the kinetic energy of the particles from disrupting the nucleation of columnar crystals. The spraying angle should ideally be parallel to the flow direction of the molten alloy, ensuring it is parallel to the orientation direction within the rapidly solidifying sheet. Excessive angle can disrupt the orientation of the rapidly solidifying sheet and the growth behavior of the columnar crystals, deteriorating the magnetic properties.

[0055] In step (4) of the air jet milling process, the rapidly solidified alloy sheets can first be subjected to hydrogen crushing to obtain coarse powder with a particle size of ~8μm. Then, the coarse powder is further subjected to hydrogen crushing and high-energy air jet milling to further process it into fine powder with a particle size distribution range of 1-6μm, which can be used for pressing, molding, sintering and tempering to obtain NdFeB magnet finished products. Considering that the existing production equipment can only prepare magnetic powder with a particle size between 1-6μm, the particle size of the paramagnetic nanorod refractory particles is generally preferably set to be lower than the magnetic powder particle size in order to fill the grain boundary phase and avoid destroying the main phase structure.

[0056] The pressing, sintering, and tempering steps can be performed using conventional processes: fine NdFeB alloy powder is magnetically oriented and pressed into shape, followed by cold isostatic pressing to obtain a green compact; then, the green compact is processed using traditional sintering and tempering processes to obtain a finished product. Figure 3 The microstructure shown indicates a high-performance sintered NdFeB magnet with excellent overall properties.

[0057] The improvement in mechanical properties of the neodymium iron boron magnets obtained through the above steps, compared to traditional magnets without the addition of paramagnetic nanorod-shaped refractory particles, is shown in the table below:

[0058] Table 1 Mechanical Properties

[0059] sample Flexural strength / MPa Tensile strength / MPa Compressive strength / MPa Hardness / HV Comparative Example 1 390 140 1050 580 Example 1 550 210 1200 710

[0060] The improvement in magnetic properties of the neodymium iron boron magnets obtained through the above steps, compared to traditional magnets without the addition of paramagnetic nanorod-shaped refractory particles, is shown in the table below:

[0061] Table 2 Magnetic Properties

[0062] sample Coercivity / kOe Remanence / kGs Magnetic energy product / MGOe <![CDATA[Density / g / cm 3 > Comparative Example 1 17.36 13.64 45.10 7.6803 Example 2 21.40 13.62 45.21 7.8131

[0063] In summary, this application utilizes the high-pressure injection of precursor particles during rapid solidification to generate paramagnetic nanoparticles in situ during magnet preparation by applying a local field. The nanoparticles are preferentially distributed between the main phase grains, effectively isolating the demagnetizing coupling between the main phase grains.

[0064] Meanwhile, the random distribution of the above-mentioned paramagnetic nanorod-shaped refractory particles can further effectively block the propagation of cracks, decompose the longitudinal transmission of internal cracks into oblique or horizontal transmission when the magnet is subjected to force, consume the energy transfer inside the magnet, and significantly improve the overall mechanical properties of the magnet during the stress process.

[0065] The process employed in this application is simple, requiring only a high-pressure nozzle to be installed at the front end of traditional NdFeB magnet sintering equipment to achieve uniform doping of paramagnetic nanorod-shaped refractory particles. This process has relatively low equipment requirements and can be directly modified from existing NdFeB sintering production equipment, facilitating large-scale deployment and use.

[0066] The above are merely embodiments of this application, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application.

Claims

1. A neodymium iron boron magnet, characterized in that, During the rapid solidification stage of the preparation process, the neodymium iron boron magnet is mixed with paramagnetic nanorod-shaped refractory particles through high-pressure injection. The paramagnetic nanorod-shaped refractory particles are randomly distributed between the main phase grains of the sintered NdFeB alloy; In the neodymium iron boron magnet, the mass percentage of paramagnetic nanorod-shaped refractory particles is set between 0.1% and 1.0%. The paramagnetic nanorod-shaped refractory particles comprise any one of the following powders or a mixture of any of the following powders with a particle size range of 100 nm to 2 μm: Metallic Ti, oxides of metallic Ti, metallic Si, oxides of metallic Si, metallic Ta, alloys containing metallic Ta, elemental carbon, ceramic polymers, silicate compounds, boride alloys; In the neodymium iron boron magnet, the particle size of the neodymium iron boron alloy powder that makes up the main phase grains of the neodymium iron boron alloy is between 1 and 6 μm.

2. A method for preparing a neodymium iron boron magnet as described in claim 1, characterized in that the step... include: After grinding the paramagnetic material particles to below 2 μm, further vibration dispersion treatment was performed to obtain paramagnetic nanorod-shaped refractory particles. In the process of melting NdFeB alloy liquid, the paramagnetic nanorod-shaped refractory particles are uniformly added and mixed into the NdFeB alloy liquid by high-pressure injection during the rapid solidification stage. The mixed alloy liquid is subjected to vacuum rapid solidification treatment to obtain alloy rapid solidification flakes, and the alloy rapid solidification flakes are crushed to obtain mixed powder. The mixed powder was subjected to magnetic field orientation pressing and cold isostatic pressing to obtain a green embryo; The green embryo is sintered and tempered to obtain neodymium iron boron magnets.

3. The method as described in claim 2, characterized in that, The paramagnetic nanorod-shaped refractory particles were obtained by grinding and vibration treatment according to the following steps: Precursor particles with a particle size of less than 50 μm are obtained by mechanically grinding the particles of paramagnetic material. The precursor particles were further ground to below 2 μm using high-energy ball milling. The small-diameter precursor particles obtained by milling were then placed in a vacuum container and subjected to periodic ultrasonic vibration dispersion treatment for 20-120 min to obtain paramagnetic nanorod-shaped refractory particles.

4. The method as described in claim 2, characterized in that, During the rapid solidification stage, the paramagnetic nanorod-shaped refractory particles are uniformly added and mixed into the NdFeB alloy liquid by high-pressure injection: The angle between the spray direction and the flow direction of the NdFeB alloy liquid is less than 45 degrees, and the spray rate is lower than the rotation speed of the cooling copper rod.

5. The method as described in claim 4, characterized in that, During the rapid solidification stage, the paramagnetic nanorod-shaped refractory particles are uniformly added and mixed into the NdFeB alloy liquid by high-pressure injection: the injection rate of the paramagnetic nanorods is 5-15 m / s, and the mass ratio of the injected material is set between 0.1% and 1.0%.

6. The method as described in claim 2, characterized in that, The steps of crushing alloy quick-setting flakes to obtain mixed powder include: first, hydrogen crushing the alloy quick-setting flakes to obtain coarse powder with a particle size of 8 μm; then, hydrogen crushing and high-energy air jet milling of the coarse powder to obtain fine mixed powder with a particle size distribution range of 1-6 μm.

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