Neodymium-iron-boron magnet with double main phases and light rare earth diffusion based on asymmetric cerium distribution and preparation method of neodymium-iron-boron magnet

Abstract

The invention discloses a neodymium-iron-boron magnet with double main phases and light rare earth diffusion based on asymmetric cerium distribution and a preparation method, and relates to the technical field of neodymium-iron-boron magnets. The method comprises the steps that a diffusion matrix is prepared through a double-main-phase technology, in the double-main-phase technology, the components of a main-phase alloy and an auxiliary-phase alloy are RaCebFe100-a-b-c-dMcBd, R is PrNd alloy or Nd metal, M is at least one of Cu, Al, Zr, Co and Ga, the content of Ce in the main-phase alloy is larger than that of Ce in the auxiliary-phase alloy, then the upper surface and the lower surface of the diffusion matrix are coated with a diffusion source solution, and the diffusion matrix is obtained through heat treatment. Carrying out heat treatment and aging treatment to obtain a neodymium-iron-boron magnet; the diffusion source solution is formed by mixing a diffusion source and a solvent, and the diffusion source is (PrmNdn) aAlbCucZrdCoeMgf. The neodymium-iron-boron magnet obtained through the method has high residual magnetism and high coercive force at the same time, the diffusion efficiency of the diffusion source is high, and the rare earth utilization rate is increased.

Description

Technical Field

[0001] This invention relates to the field of neodymium iron boron magnet technology, specifically to a neodymium iron boron magnet based on asymmetric cerium distribution with dual main phases and light rare earth diffusion, and its preparation method. Background Technology

[0002] In the field of permanent magnet materials, partially replacing neodymium / praseodymium (Nd / Pr) with cerium (Ce) is a core technological path to reduce the cost of raw materials for NdFeB magnets and an important direction for achieving diversified utilization of rare earth resources. However, the industrialization process of cerium magnets is limited by key performance bottlenecks: the introduction of cerium will severely degrade the microstructure of the magnet, specifically by increasing the proportion of non-magnetic phases at grain boundaries and deteriorating the continuity of their distribution, thereby significantly weakening the coercivity (Hcj) and temperature stability of the magnet, making it difficult to meet the performance requirements of high-end applications.

[0003] Currently, the technical approaches to improving the coercivity of Ce-containing neodymium iron boron magnets in the industry can be mainly divided into three categories:

[0004] 1. The first category is the traditional composition optimization scheme, which improves performance by reducing the Ce substitution ratio or adding heavy rare earth elements such as dysprosium / terbium (Dy / Tb); however, the improvement of coercivity by traditional composition optimization is limited, and the design of increasing the amount of praseodymium and neodymium and heavy rare earth elements contradicts the original intention of reducing costs by Ce substitution and realizing the sustainable use of rare earth resources.

[0005] 2. The second type is the dual-phase / dual-alloy technology, which achieves a reasonable distribution of Ce element by controlling the microstructure; however, the coercivity level of magnets after optimization of the dual-phase process still cannot meet the performance requirements of high-performance applications.

[0006] 3. The third category is the mature heavy rare earth grain boundary diffusion technology, which improves coercivity by constructing a heavy rare earth shell on the outer layer of the grains. However, when traditional heavy rare earth diffusion schemes are directly applied to Ce-containing magnets, they not only significantly increase the consumption of heavy rare earths, but also lead to a significant decrease in the remanence of the substrate. At the same time, due to the poor compatibility between the inherent grain boundary characteristics of Ce-containing magnets and heavy rare earth diffusion elements, the discontinuous CeFe2 phase and the unevenly distributed Nd-rich phase present in large quantities at the substrate grain boundaries are prone to causing diffusion source agglomeration and blocking diffusion channels, resulting in low diffusion efficiency and insufficient rare earth utilization, which restricts the efficient allocation of rare earth resources. In addition, the chemical composition gradient between traditional heavy rare earth or light-heavy mixed rare earth diffusion sources and the main phase is too large, which can easily damage the grain boundary structure. Furthermore, direct contact between the diffusion source and the substrate will form a surface heavy rare earth enrichment layer, which hinders the penetration of diffusion elements into the interior of the magnet. Summary of the Invention

[0007] This invention aims to address the technical problems in existing methods for improving the coercivity of Ce-containing NdFeB magnets, such as increased consumption of heavy rare earth elements, significant decrease in remanence of the substrate, limited improvement in coercivity, and low diffusion efficiency. The invention provides a NdFeB magnet based on asymmetric cerium distribution with dual main phases and light rare earth diffusion, along with its preparation method. This method employs a synergistic approach of "dual main phase matrix structure optimization," "PrNd-based diffusion source composition design," and "grain boundary regulation by alloying elements such as Mg," resulting in NdFeB magnets that simultaneously possess high remanence and high coercivity, high diffusion source efficiency, and improved rare earth utilization.

[0008] This invention is achieved through the following technical solution:

[0009] The first objective of this invention is to provide a method for preparing a neodymium iron boron magnet based on asymmetric cerium distribution with dual main phases and light rare earth diffusion, comprising the following steps: The diffusion matrix was prepared using a dual-phase process, wherein both the main phase alloy and the auxiliary phase alloy in the dual-phase process have an R composition. a Ce b Fe 100-a-b-c-d M c B d R is a PrNd alloy or Nd metal, M is selected from at least one of Cu, Al, Zr, Co, and Ga, and satisfies 0≤b≤20, 30≤a+b≤32, 0.1≤c≤1.8, and 0.9≤d≤1; the Ce content in the main phase alloy is greater than that in the auxiliary phase alloy. The diffusion source solution was coated on the upper and lower surfaces of the diffusion substrate, and neodymium iron boron magnets were obtained after heat treatment and aging treatment. The diffusion source solution is prepared by mixing a diffusion source with a solvent, wherein the diffusion source component is (Pr m Nd n ) a Al b Cu c Zr d Co e Mg f And satisfy 80≤a≤95, 5≤b+c+d+e+f≤20, m+n=100.

[0010] This invention employs a precise hierarchical synergy and interconnected approach involving "dual-phase matrix structure optimization," "PrNd-based diffusion source composition design," and "grain boundary control using alloying elements such as Mg," forming a complete technology chain of "basic optimization - core enhancement - interface fine-tuning." This ultimately achieves the simultaneous maximization of coercivity and remanence, successfully solving the core challenge of high-performance cerium-containing magnets without relying on any heavy rare earth elements. Specifically:

[0011] First, an asymmetric dual-main-phase design with high cerium content in the main phase and low cerium content in the auxiliary phase was adopted. High-quality dual-main-phase diffusion matrix was prepared through asymmetric main-auxiliary phase composition control. This optimized the diffusion efficiency limitation of current Ce-containing magnets caused by grain boundary phase discontinuity, fundamentally improving the microstructure, suppressing harmful phases, and constructing a clean and continuous grain boundary network, thus paving an "ideal channel" for the efficient transport of diffusion elements. Then, Pr and Nd, which are highly compatible with the cerium-containing matrix, were used as the main diffusion source, improving the rare earth utilization rate of the diffusion source, fundamentally addressing the issue. This method avoids the severe magnetic dilution effect caused by heavy rare earth elements Dy / Tb, achieving "precise modification" of the magnetic shell on the grain surface to improve coercivity while maintaining high remanence. Finally, an appropriate amount of low-melting-point Mg is added to the diffusion source. Its key role is to adjust the melting point and fluidity of the grain boundary phase. The composite low-melting-point alloy optimizes the grain boundary phase, increases the fluidity of the diffusion source at the grain boundary, improves the problem of low diffusion efficiency of Ce-containing magnets, and promotes the uniform distribution of Pr, Nd and other elements along the optimized grain boundary and the reconstruction of the grain boundary phase.

[0012] Therefore, the neodymium iron boron magnets prepared by the method of the present invention have both high remanence and high coercivity, high diffusion efficiency of the diffusion source, and improved rare earth utilization.

[0013] Furthermore, the weight ratio of Ce content in the main phase alloy to the auxiliary phase alloy is (12.5-17.5):(2.5-7.5).

[0014] Furthermore, the weight ratio of Ce content in the main phase alloy to the auxiliary phase alloy is 15:5.

[0015] Furthermore, the Mg content in the diffusion source component is 5-15 wt%.

[0016] Furthermore, the Mg content in the diffusion source component is 5 wt%.

[0017] Furthermore, the diffusion matrix composition is R. a Ce b Fe 100-a-b-c-d M c B d R is a PrNd alloy or Nd metal, and M is selected from at least one of Cu, Al, Zr, Co, and Ga, and satisfies 5≤b≤15, 30≤a+b≤32, 0.1≤c≤1.8, and 0.8≤d≤1.

[0018] Furthermore, the diffusion matrix surface gains 0.5-1 wt% weight after being coated with the diffusion source solution.

[0019] Further, the diffusion matrix is ​​prepared by: hydrogenating and gas milling the main phase alloy slabs and the auxiliary phase alloy slabs respectively, then mixing them, and then oriented and sintering to obtain the diffusion matrix; the diffusion source solution is prepared by: melting and preparing the diffusion source alloy slabs, hydrogenating and gas milling to obtain diffusion matrix diffusion source fine powder, and mixing it with anhydrous ethanol at a mass ratio of 1:(3-5) to obtain the diffusion source solution.

[0020] Furthermore, the heat treatment and aging treatment include the following steps: The diffusion substrate coated with the diffusion source solution was kept at 800-1000℃ for 600-1000 min, followed by first-stage aging at 600-800℃ for 120-300 min, and second-stage aging at 500-700℃ for 120-300 min.

[0021] The second objective of this invention is to provide a neodymium iron boron magnet based on asymmetric cerium distribution with dual main phases and light rare earth diffusion, which is prepared by the method described above.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention employs a precise hierarchical synergy and interlocking approach among "dual-phase matrix structure optimization," "PrNd-based diffusion source composition design," and "grain boundary regulation by alloying elements such as Mg," forming a complete technical chain of "basic optimization - core enhancement - interface fine-tuning." Ultimately, it achieves the simultaneous maximization of coercivity and remanence, successfully solving the core challenge of high-performance cerium-containing magnets without relying on any heavy rare earth elements. Therefore, the NdFeB magnets prepared using the method of this invention simultaneously possess high remanence and high coercivity, high diffusion source efficiency, and improved rare earth utilization. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0024] The embodiments of the present invention will be described in detail below. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0025] The "scope" disclosed in this invention is defined in the form of a lower limit and an upper limit. A given scope is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific scope. The scope defined in this way can include or exclude end values, and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a scope.

[0026] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0027] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0028] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other substances not listed may also be included, or that only the listed substances may be included.

[0029] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0030] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0031] It should be noted that, unless otherwise specified, the experimental methods used in the embodiments are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0032] Comparative Example 1

[0033] The matrix is ​​a single alloy with the alloy composition: (PrNd) 21.5 Ce 10 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94

[0034] Neodymium iron boron magnet manufacturing process: After spinning, the wafers are crushed by hydrogen and ground by air jet mill to obtain fine powder with a particle size of 3.5-4.0 micrometers; then, they are oriented and shaped under a 2T magnetic field, isostatically pressed at 200 MPa, sintered at a temperature of 1060℃ for 5 hours, followed by first-stage aging at 680℃ for 2 hours and second-stage aging at 620℃ for 2 hours.

[0035] Comparative Example 2

[0036] The matrix uses a dual-phase process, and the final alloy composition is: (PrNd) 21.5 Ce 10 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0. 1B 0.94

[0037] Neodymium iron boron magnet manufacturing process: The main phase alloy and auxiliary phase alloy are respectively treated by hydrogen crushing and air jet milling to obtain fine powder with a particle size of 3.5-4.0 micrometers. The main phase alloy (PrNd) is then... 26.5 Ce5Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0. 1B 0.94 And auxiliary phase alloy (PrNd) 16.5 Ce 15 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 Mix the powders at a 1:1 ratio, then shape them under a 2T magnetic field, press them at 200 MPa isostatically, sinter them at 1060℃ for 5 hours, followed by first-stage aging at 680℃ for 2 hours and second-stage aging at 620℃ for 2 hours.

[0038] Comparative Example 3

[0039] The alloy matrix is ​​a single alloy with the composition: (PrNd) 21.5 Ce 10 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94

[0040] Neodymium iron boron magnet manufacturing process: (1) The alloy slabs were crushed by hydrogen and ground by air jet mill to obtain fine powder with a particle size of 3.5-4.0 micrometers. Then, they were oriented and shaped under a 2T magnetic field, isostatically pressed at 200 MPa, sintered at 1060℃ for 5 hours, and then aged at 680℃ for 2 hours for the first stage and 620℃ for 2 hours for the second stage. (2) The diffusion source component is DyH X A diffusion source solution is obtained by mixing diffusion source powder with anhydrous ethanol at a mass ratio of 1:4. (3) The diffusion source solution was applied to the upper and lower surfaces of the magnet, increasing its weight by 0.85 wt%. The coated magnet was then kept at 950 °C for 12 h with a vacuum degree < 1 × 10⁻⁶. -3 Pa, followed by first-stage aging at 680℃ for 2 hours, and second-stage aging at 620℃ for 2 hours.

[0041] Comparative Example 4

[0042] The alloy matrix is ​​produced using a dual-phase process, and its composition is (PrNd). 21.5 Ce 10 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 .

[0043] Neodymium iron boron magnet manufacturing process: (1) The main phase alloy and auxiliary phase alloy were subjected to hydrogen crushing and air jet milling respectively to obtain fine powder with a particle size of 3.5-4.0 micrometers. The main phase alloy (PrNd) was then used. 26.5 Ce5Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 And auxiliary phase alloy (PrNd) 16. 5Ce 15 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 Mix the powders at a 1:1 ratio, then shape them under a 2T magnetic field, press them at 200 MPa isostatically, sinter them at 1060℃ for 5 hours, then perform a first-stage aging at 680℃ for 2 hours and a second-stage aging at 620℃ for 2 hours. (2) The diffusion source component is DyH X A diffusion source solution is obtained by mixing diffusion source powder with anhydrous ethanol at a mass ratio of 1:4. (3) The diffusion source solution was applied to the upper and lower surfaces of the magnet, increasing its weight by 0.88 wt%. The coated magnet was then kept at 950°C for 12 hours with a vacuum degree <1×10⁻⁶. -3 Pa, followed by first-stage aging at 680℃ for 2 hours, and second-stage aging at 620℃ for 2 hours.

[0044] Example 1

[0045] The alloy matrix was prepared using a dual-phase process and its composition is (PrNd). 21.5 Ce 10 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0. 1B 0.94 .

[0046] Neodymium iron boron magnet manufacturing process: (1) The main phase and auxiliary phase alloy flakes were subjected to hydrogen crushing and air jet milling to obtain fine powder with a particle size of 3.5-4.0 micrometers. (PrNd) 31.5 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 And auxiliary phase alloy (PrNd) 11.5 Ce 20 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 Mix the powders at a 1:1 ratio, shape them under a 2T magnetic field, press them at 200 MPa isostatically, sinter at 1060℃ for 5 hours, then perform a first-stage aging at 680℃ for 2 hours and a second-stage aging at 620℃ for 2 hours. (2) The diffusion source component is (Pr 25 Nd 75 ) 80 (Al 25 Co 25 Cu 50 ) 15 Mg5 is a fine powder with a particle size of 3-3.5 μm obtained by smelting, hydrogen crushing, and air jet milling. It is mixed with anhydrous ethanol at a mass ratio of 1:4 to obtain a diffusion source solution. (3) The diffusion source solution was applied to the upper and lower surfaces of the magnet, increasing its weight by 0.86 wt%. The coated magnet was then kept at 950 °C for 12 h with a vacuum degree < 1 × 10⁻⁶. -3Pa, followed by first-stage aging at 680℃ for 2 hours, and second-stage aging at 620℃ for 2 hours.

[0047] Example 2

[0048] The difference between this embodiment and Embodiment 1 is that the main phase alloy is (PrNd). 14 Ce 17.5 Fe 67.01 Al l0.15 Ga 0.1 Cu 0. 2Co 0.1 B 0.94 The alloy with the auxiliary phase is (PrNd). 29 Ce 2.5 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 The weight gain of the diffusion source solution coating was 0.88 wt%.

[0049] Example 3

[0050] The difference between this embodiment and Embodiment 1 is that the main phase alloy (PrNd) 16.5 Ce 15 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 And auxiliary phase alloy (PrNd) 26.5 Ce5Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 The diffusion source solution coating resulted in a weight gain of 0.85 wt%.

[0051] Example 4

[0052] The difference between this embodiment and Embodiment 1 is that the main phase alloy (PrNd) 19 Ce 12.5 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 And auxiliary phase alloy (PrNd) 24 Ce 7.5 Fe 67.01 Al l0.15 Ga 0.1 Cu0.2 Co 0.1 B 0.94 The weight gain of the diffusion source solution coating was 0.89 wt%.

[0053] Example 5

[0054] The difference between this embodiment and Embodiment 1 is that the alloy matrix is ​​a single alloy with the composition: (PrNd). 21.5 Ce 10 Fe 67.0 1Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 The weight gain of the diffusion source solution coating was 0.88 wt%.

[0055] Example 6

[0056] The difference between this embodiment and Embodiment 1 is that the main phase alloy (PrNd) 16.5 Ce 15 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 And auxiliary phase alloy (PrNd) 26.5 Ce5Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 The diffusion source component is (Pr 25 Nd 75 ) 80 (Al 25 Co 25 Cu 50 ) 10 Mg 10 The diffusion source solution coating resulted in a weight gain of 0.86 wt%.

[0057] Example 7

[0058] The difference between this embodiment and Embodiment 1 is that the main phase alloy (PrNd) 16.5 Ce 15 Fe 67.01 Al l0.15 Ga 0.1 Cu 0.2 Co 0.1 B 0.94 And auxiliary phase alloy (PrNd) 26.5 Ce5Fe 67.01 Al l0.15 Ga0.1 Cu 0.2 Co 0.1 B 0.94 The diffusion source component is (Pr 25 Nd 75 ) 80 (Al 25 Co 25 Cu 50 5Mg 15 The diffusion source solution coating resulted in a weight gain of 0.87 wt%.

[0059] The performance test results of the neodymium iron boron magnets prepared in the above embodiments and comparative examples are shown in Table 1.

[0060] Table 1. Performance test results of NdFeB magnets prepared in the examples and comparative examples.

[0061] As can be seen from the data in Table 1:

[0062] (1) As can be seen from the data of Comparative Example 1, Comparative Example 3 and Example 5, on the same single alloy matrix, using conventional DyH X While the diffusion source (Comparative Example 3) increased the coercivity to 16.18 kOe, it caused a significant drop in remanence from 12.70 kGs to 12.42 kGs. However, using the PrNd-based diffusion source of this invention (Example 5), the coercivity was also increased to 16.05 kOe, while the remanence remained at a high level of 12.82 kGs. This is because the diffusion source of this invention, based on Pr and Nd, has natural chemical compatibility with the cerium-containing magnet matrix, avoiding the strong lattice distortion and magnetic dilution that may be caused by heavy rare earth elements. It can effectively reconstruct the grain boundary phase and form a (Pr,Nd)-Fe-B enriched shell with a high magnetocrystalline anisotropy field on the grain surface, thereby directly and efficiently increasing the coercivity without reducing the remanence.

[0063] (2) A comparison of the data from Examples 1 and 2-4 shows that when the cerium content of the main phase and the auxiliary phase is a "high-low" asymmetric distribution, the magnet obtains higher coercivity after diffusion. This design allows the main phase to maintain a high cerium content to control costs, while the auxiliary phase effectively suppresses the formation of coarse and harmful CeFe2 phase by regulating the microscopic distribution of cerium, thereby purifying and connecting the grain boundary network and ensuring the formation of clean, continuous, and high-quality grain boundaries. Among them, when the weight ratio of cerium content of the asymmetric main phase to the auxiliary phase is 15:5, the optimal balance between cost and performance is found, the remanence reaches a high level of 12.83 KGs, and the coercivity is as high as 16.61 kOe. That is, the matrix prepared with the weight ratio of cerium content of the asymmetric main phase to the auxiliary phase of 15:5 has the best performance and can lay the best microstructural foundation for subsequent diffusion. Therefore, the preferred weight ratio of Ce content in the main phase alloy to the auxiliary phase alloy is (12.5-17.5):(2.5:7.5), and the most preferred ratio is 15:5.

[0064] (3) A comparison of the data from Examples 3, 6, and 7 shows that a Mg content of 5-15% in the diffusion source can maintain high remanence and coercivity. However, as the Mg content in the diffusion source increases from 5% (Example 3) to 15% (Example 7), both the remanence and coercivity of the magnet show a decreasing trend. Among them, the performance is optimal when the Mg content is 5%. When the Mg content exceeds 10%, the decrease in remanence and coercivity increases. This is because an appropriate amount of Mg can lower the melting point of the diffusion source and improve the fluidity of the grain boundaries. However, excessive Mg will form too many low-magnetic phases at the grain boundaries, destroying the interfacial bonding between the grain boundaries and the main phase. At the same time, it will invade part of the main phase region, leading to the deterioration of magnetic properties. The composite addition of Mg element in the diffusion source plays a role in optimizing the properties of the grain boundary phase, which helps to form a more uniform, thinner, and non-magnetic grain boundary isolation layer, increases the wettability of the grain boundary phase and the main phase grains, improves the continuity of grain boundary distribution, further improves the problem of low diffusion efficiency of conventional diffusion sources, and improves the utilization rate of rare earth resources. Therefore, the preferred Mg content is 5-10%, and the most preferred content is 5%.

[0065] Finally, it should be noted that the above specific embodiments are only used to describe the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation of the present invention and is not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions or improvements can be made to some or all of the technical features. These modifications, equivalent substitutions, and improvements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a neodymium iron boron magnet based on asymmetric cerium distribution with dual principal phases and light rare earth diffusion, characterized in that, Includes the following steps: The diffusion matrix was prepared using a dual-phase process, wherein both the main phase alloy and the auxiliary phase alloy in the dual-phase process have an R composition. a Ce b Fe 100-a-b-c-d M c B d R is a PrNd alloy or Nd metal, M is selected from at least one of Cu, Al, Zr, Co, and Ga, and satisfies 0≤b≤20, 30≤a+b≤32, 0.1≤c≤1.8, and 0.9≤d≤1; the Ce content in the main phase alloy is greater than that in the auxiliary phase alloy. The diffusion source solution was coated on the upper and lower surfaces of the diffusion substrate, and neodymium iron boron magnets were obtained after heat treatment and aging treatment. The diffusion source solution is prepared by mixing a diffusion source with a solvent, wherein the diffusion source component is (Pr m Nd n ) a Al b Cu c Zr d Co e Mg f And satisfy 80≤a≤95, 5≤b+c+d+e+f≤20, m+n=100.

2. The method for preparing a neodymium iron boron magnet based on asymmetric cerium distribution and light rare earth diffusion according to claim 1, characterized in that, The weight ratio of Ce content in the main phase alloy to the auxiliary phase alloy is (12.5-17.5):(2.5-7.5).

3. The method for preparing a neodymium iron boron magnet based on asymmetric cerium distribution and light rare earth diffusion according to claim 2, characterized in that, The weight ratio of Ce content in the main phase alloy to the auxiliary phase alloy is 15:

5.

4. The method for preparing a neodymium iron boron magnet based on asymmetric cerium distribution and light rare earth diffusion according to claim 1, characterized in that, The Mg content in the diffusion source component is 5-15 wt%.

5. The method for preparing a neodymium iron boron magnet based on asymmetric cerium distribution and light rare earth diffusion according to claim 4, characterized in that, The Mg content in the diffusion source component is 5 wt%.

6. The method for preparing a neodymium iron boron magnet based on asymmetric cerium distribution and light rare earth diffusion according to claim 1, characterized in that, The diffusion matrix component is R. a Ce b Fe 100-a-b-c-d M c B d R is a PrNd alloy or Nd metal, and M is selected from at least one of Cu, Al, Zr, Co, and Ga, and satisfies 5≤b≤15, 30≤a+b≤32, 0.1≤c≤1.8, and 0.8≤d≤1.

7. The method for preparing a neodymium iron boron magnet based on asymmetric cerium distribution and light rare earth diffusion according to claim 1, characterized in that, The diffusion matrix gains 0.5-1 wt% weight after being coated with the diffusion source solution.

8. A method for preparing a neodymium iron boron magnet based on asymmetric cerium distribution and light rare earth diffusion according to any one of claims 1-7, characterized in that, The diffusion matrix is ​​prepared by: hydrogenating and gas milling the main phase alloy slabs and the auxiliary phase alloy slabs respectively, then mixing them, and then oriented and sintering to obtain the diffusion matrix; the diffusion source solution is prepared by: melting and preparing the diffusion source alloy slabs, hydrogenating and gas milling to obtain diffusion matrix diffusion source fine powder, and mixing it with anhydrous ethanol at a mass ratio of 1:(3-5) to obtain the diffusion source solution.

9. A method for preparing a neodymium iron boron magnet based on asymmetric cerium distribution and light rare earth diffusion according to any one of claims 1-7, characterized in that, The heat treatment and aging treatment include the following steps: The diffusion substrate coated with the diffusion source solution was kept at 800-1000℃ for 600-1000 min, followed by first-stage aging at 600-800℃ for 120-300 min, and second-stage aging at 500-700℃ for 120-300 min.

10. A neodymium iron boron magnet based on asymmetric cerium distribution with dual main phases and light rare earth diffusion, prepared by the method described in any one of claims 1-9.

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