Neodymium-iron-boron magnet and preparation method thereof

Abstract

The invention relates to a neodymium iron boron magnet, which comprises a triangular region crystal boundary, and the triangular region crystal boundary comprises a delta phase; the delta phase comprises (R, Ce, T) 30 + u (Fe, Co) 70-u-v [(AlmGanCu1-m-n)] v in atomic percent, u is more than or equal to-5 and less than or equal to 5, v is more than or equal to 5 and less than or equal to 10, m is more than 0 and less than 1, and n is more than or equal to 0 and less than 1; delta phase distribution in the crystal boundary of the triangular region meets the condition that N1 / N is greater than or equal to 0.6; n1 / N represents the ratio of the number N1 of delta phases with m greater than or equal to 0.5 in the crystal boundary of the triangular region to the total number N of the delta phases in the crystal boundary of the triangular region; the composition of the neodymium-iron-boron magnet is (R < 1-x > Cex) CobB < c > AdTeFebal, and a + b + c + d + e + bal is equal to 100; r contains Nd, and optionally contains one or more of non-Ce rare earth elements; t is selected from one or more of Ti, Zr, V, Nb, Cr, Mo, Ru and Hf; a comprises Al and Ga, or A comprises Al and Cu, or A comprises Al, Ga and Cu. According to the neodymium-iron-boron magnet prepared through the method, more delta phases with the high Al proportion are distributed in the crystal boundary of the triangular area, the number of (Ce, R) Fe2 phases is small, the coercive force of the neodymium-iron-boron magnet is effectively improved, and the magnet has excellent comprehensive performance.

Description

Technical Field

[0001] This disclosure pertains to the field of neodymium iron boron magnets, specifically relating to a neodymium iron boron magnet and its preparation method. Background Technology

[0002] The need for balanced utilization of rare earth resources and improved cost-effectiveness of NdFeB permanent magnets has driven the addition of high-abundance rare earth elements such as cerium (Ce) to become a research hotspot in the NdFeB permanent magnet industry. However, due to the strong interaction between the 4f electrons in Ce atoms and the 3d electrons in Fe atoms, the main phase of NdFeB magnets (Nd,R)2Fe... 14 In the boron crystal structure, the Ce atom at the 4f site has a +4 valence and its magnetic moment is quenched. Therefore, the addition of Ce significantly affects the spatial structure of the main phase and reduces the magnetocrystalline anisotropy field of the main phase, leading to remanence of the magnet. r and coercivity H Cj The concentration of Ce is significantly reduced. On the other hand, with the addition of Ce, a high-Ce-content (Ce,R)Fe2 phase gradually precipitates at the grain boundaries of the magnet. This phase itself is weakly ferromagnetic and has a Laves phase structure, which is severely mismatched with the spatial structure of the main phase. It is prone to forming defects at the contact interface, which is detrimental to the H2 content of Ce magnets. cJ Enhanced resilience.

[0003] To control the valence state of Ce atoms, one approach is to add light rare earth elements with larger ionic radii, such as La. When the amount added is large enough, the Ce atoms can be induced to change from +4 to +3 valence by altering the main phase spatial structure. Another approach is to add other high-abundance rare earth elements, such as Gd, to significantly change the mixed valence state of Ce. By utilizing the ordered occupancy of atoms, the presence of Ce at the 4f lattice position is reduced, thereby changing the different mixing ratios of +3 and +4 Ce. However, the interaction between Ce at the 4f position and the surrounding Fe sublattice remains unchanged. Furthermore, neither of these approaches can effectively control the valence state of Ce atoms in magnets with low Ce content. The magnet still contains a (Ce,R)Fe2 phase with high Ce content, resulting in a low increase in coercivity. Summary of the Invention

[0004] The purpose of this invention is to provide a neodymium iron boron magnet and its preparation method. The neodymium iron boron magnet prepared by the method of this invention has a large number of δ phases with high Al content distributed in the triangular grain boundaries and a small number of (Ce,R)Fe2 phases in the triangular grain boundaries, which effectively improves the coercivity of the neodymium iron boron magnet and gives the magnet excellent comprehensive performance.

[0005] To achieve the above objectives, the present invention provides a neodymium iron boron magnet, wherein the neodymium iron boron magnet includes triangular grain boundaries, and the triangular grain boundaries contain a δ phase;

[0006] The composition of the neodymium iron boron magnet is (R 1-xCe x ) a Co b B c A d T e Fe bal In this context, by atomic percentage, a+b+c+d+e+bal=100, 0≤x≤0.25, 13.5≤a≤15, 0≤b≤3; 5.50≤c≤5.85, 0.5≤d≤3, 0≤e≤0.3; R includes Nd, and optionally includes one or more of the non-Ce rare earth elements; T is selected from one or more of Ti, Zr, V, Nb, Cr, Mo, Ru and Hf; A includes Al and Ga, or A includes Al and Cu, or A includes Al, Ga and Cu;

[0007] The composition of the δ phase is (R, Ce, T). 30+u (Fe,Co) 70-u-v [(Al m Ga n Cu 1-m-n )] v In terms of atomic percentage, -5≤u≤5, 5≤v≤10, 0<m<1, 0≤n<1; the δ phase distribution within the grain boundaries of the triangular region satisfies the following equation (1).

[0008] N1 / N≥0.6 Equation (1);

[0009] Wherein, N1 / N represents the ratio of the number of δ phases N1 with m≥0.5 within the grain boundary of the triangular region to the total number of δ phases N within the grain boundary of the triangular region.

[0010] Optionally, A further includes M, wherein the neodymium iron boron magnet is composed of (R 1-x Ce x ) a Co b B c [M d’ (Ga y Cu z Al 1-y-z ) f ] d T e Fe bal The δ phase has a composition of (R, Ce, T). 30+u (Fe,Co) 70-u-v [(Al m Ga n Cu 1-m-n )M] v M is selected from one or more of Si, Ge and Sn;

[0011] Among them, in terms of atomic percentage, d=d'+f, 0.3f(1-yz)≤b≤3, d'≤0.25f; 0.1≤y+z≤0.5; 0.09≤y×f≤0.4.

[0012] Optionally, the triangular grain boundary further includes a (Ce,R)Fe2 phase;

[0013] When 0 ≤ x < 0.2, the (Ce,R)Fe2 phase distribution within the grain boundaries of the triangular region satisfies the following equation (2).

[0014] S1 / S≤0.5% Equation (2);

[0015] When 0.2≤x≤0.25 and 0.1≤e≤0.3, the (Ce,R)Fe2 phase distribution within the grain boundaries of the triangular region satisfies the following equation (3).

[0016] S1 / S≤1.55% Equation (3);

[0017] Wherein, S1 / S represents the ratio of the area S1 of all (Ce,R)Fe2 phases within the grain boundary of the triangular region inside the cross section of the magnet to the total area S of the cross section.

[0018] A second aspect of the present invention provides a method for preparing neodymium iron boron magnets, wherein the method comprises: mixing a main alloy powder and an R'-Al auxiliary alloy powder to obtain (R... 1-x Ce x ) a Co b B c A d T e Fe bal alloy powder;

[0019] For (R) 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder is sequentially formed to obtain a compact, and the compact is then subjected to sintering and tempering heat treatment to obtain a magnet;

[0020] Wherein, the (R) 1-x Ce x ) a Co b B c A d T e Fe balIn the alloy powder, R contains Nd and optionally contains one or more of the non-Ce rare earth elements; T is selected from one or more of Ti, Zr, V, Nb, Cr, Mo, Ru and Hf; A includes Al and Ga, or A includes Al and Cu, or A includes Al, Ga and Cu.

[0021] The atomic percentage ratio of R' to Al is 3 / 11 to 3.

[0022] Optionally, the mass ratio of the main alloy powder to the R'-Al auxiliary alloy powder is (22-160):1.

[0023] Optionally, the R'-Al auxiliary alloy powder further includes X; X is selected from one or more of Si, Ga and Cu; the R'-Al auxiliary alloy powder does not contain Ce;

[0024] Wherein, the (R) 1-x Ce x ) a Co b B c A d T e Fe bal In the alloy powder, A also includes M, and the composition of A is M. d’ (Ga y Cu z Al 1-y-z ) f M is selected from one or more of Si, Ge and Sn;

[0025] Among them, 0.3f(1-yz)≤b≤3, d≤0.25f; 0.1≤y+z≤0.5; 0.09≤y×f≤0.4.

[0026] Optionally, the method further includes: preparing a main alloy sheet and an R'-Al auxiliary alloy sheet using a rapid solidification process; mixing the main alloy sheet and the R'-Al auxiliary alloy sheet; and then subjecting the mixture to hydrogen crushing and air jet milling to obtain the (R) alloy sheet. 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder; the (R) 1-x Ce x ) a Co b B c A d T e Fe balThe D50 particle size of the alloy powder is 4–4.6 μm; the grinding pressure of the air jet mill is 0.55–0.75 MPa.

[0027] Optionally, the forming process is an orientation forming process, which is carried out under the condition that the orientation magnetic induction intensity is 1.2 to 1.5T;

[0028] The density of the pressed blank is 3.8–4.2 g / cm³. 3 .

[0029] Optionally, the sintering temperature is 1020–1080°C, and the holding time is 2–5 hours.

[0030] The tempering heat treatment temperature is 420–650℃, and the holding time is 1–6 hours.

[0031] A third aspect of the present invention provides a neodymium iron boron magnet prepared using the method described in the second aspect of the present invention.

[0032] Through the above technical solutions, this invention employs a dual-alloy method using R'-Al alloy as an auxiliary alloy to prepare NdFeB magnets. This ensures sufficient enrichment of R and Al elements at grain boundaries during liquid-phase sintering, enabling Al to participate more effectively in intergranular reactions and achieving a more rational distribution of Al in the main phase and grain boundary phases. Specifically, on the one hand, some Al elements inevitably diffuse from the grain boundaries into the main phase to replace Fe atoms, reducing the intensity of the interaction between rare earth atoms at the 4f crystal position and the (Fe,Al) sublattice, which may change the valence state of the 4f crystal position atoms and improve coercivity by increasing the intrinsic magnetocrystalline anisotropy of the main phase. On the other hand, Al that does not enter the main phase is enriched at the grain boundaries, which is conducive to the transformation of the (Ce,R)Fe2 phase into (R,Ce)6Fe. 12 The formation of the A2 phase (δ phase) reduces the precipitation of the (Ce,R)Fe2 phase and simultaneously generates a higher Al content (m≥0.5) δ phase. This reduces the solidification of Ga and Cu elements in the δ phase of the grain boundary triangular region, allowing more Ga and Cu elements to participate in the reaction in the thin-layer region of the grain boundary, effectively repairing the main phase grain defects and improving the intrinsic coercivity of the magnet. Furthermore, compared with traditional preparation processes, the method provided by this invention does not require high-temperature tempering, has a simple process flow, and the prepared NdFeB magnet has a higher Al content δ phase distributed in the triangular grain boundary, while the (Ce,R)Fe2 phase in the triangular grain boundary is less abundant. This effectively improves the coercivity of the NdFeB magnet with only a slight decrease in remanence, resulting in excellent overall performance.

[0033] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0034] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0035] Figure 1 The images show SEM images of neodymium iron boron magnets prepared in Example 1 and Comparative Example 1 of the present invention. The middle and right images show the SEM images of the samples after first-stage tempering and second-stage tempering of the comparative examples, respectively.

[0036] Figure 2 The diagram shows the distribution of the δ phase and (Ce,R)Fe2 phase in the triangular region of the cross-section of the neodymium iron boron magnet prepared in Comparative Example 3 of the present invention.

[0037] Figure 3 This is a schematic diagram of the S1 / S values ​​of the grain boundaries in the triangular region within the cross-section of the neodymium iron boron magnets prepared in Example 3 and Comparative Example 3 of the present invention. Detailed Implementation

[0038] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0039] The first aspect of this disclosure provides a neodymium iron boron magnet, wherein the neodymium iron boron magnet includes triangular grain boundaries, and the triangular grain boundaries contain a δ phase;

[0040] The composition of the neodymium iron boron magnet is (R 1-x Ce x ) a Co b B c A d T e Fe bal In this composition, by atomic percentage, a+b+c+d+e+bal=100, 0≤x≤0.25; 13.5≤a≤15; 0≤b≤3; 5.50≤c≤5.85; 0.5≤d≤3; 0≤e≤0.3; preferably, 0.1≤x≤0.2; 14≤a≤15; 0.3≤b≤1; 5.6≤c≤5.8; 0.6≤d≤1.2; 0.15≤e≤0.25; R includes Nd, and optionally includes one or more of the non-Ce rare earth elements; T is selected from one or more of Ti, Zr, V, Nb, Cr, Mo, Ru and Hf; A includes Al and Ga, or A includes Al and Cu, or A includes Al, Ga and Cu;

[0041] The composition of the δ phase is (R, Ce, T). 30+u (Fe,Co) 70-u-v [(Al mGa n Cu 1-m-n ),M] v In terms of atomic percentage, -5≤u≤5, 5≤v≤10, 0<m<1, 0≤n<1; the δ phase distribution within the grain boundaries of the triangular region satisfies the following equation (1).

[0042] N1 / N≥0.6 Equation (1);

[0043] Wherein, N1 / N represents the ratio of the number of δ phases N1 with m≥0.5 within the grain boundary of the triangular region to the total number of δ phases N within the grain boundary of the triangular region.

[0044] In the neodymium iron boron magnet provided by this invention, some Al atoms diffuse from the grain boundaries into the main phase to replace Fe atoms. This reduces the intensity of the interaction between Ce at the 4f site and the (Fe,Al) sublattice, thereby changing the valence state of the 4f site atoms, enhancing the magnetocrystalline anisotropy of the main phase, and improving coercivity. Simultaneously, some Al atoms remain at the grain boundaries, suppressing the precipitation of the (Ce,R)Fe2 phase, further optimizing the magnet's microstructure, effectively improving the magnet's coercivity, and enhancing its overall performance.

[0045] In this disclosure, elements such as Zr, Nb, and Ti can form a number of high-melting-point compounds with Fe or Al elements, including 1:2 phases such as TFe2 and TAl2. Therefore, the addition of T elements is beneficial for the local solidification of some Al and Fe elements at the grain boundaries, avoiding the participation of a large number of Al atoms in the solidification process of the main phase. This effectively promotes the participation of Al atoms in the evolution of the grain boundary phase and can increase the enrichment of Al elements at the grain boundaries to a certain extent, making it easier for the magnet grain boundaries to form the δ phase, thereby further improving the magnetic properties such as coercivity of the magnet.

[0046] In one specific embodiment, A further includes M, wherein the neodymium iron boron magnet is composed of (R 1-x Ce x ) a Co b B c [M d’ (Ga y Cu z Al 1-y-z ) f ] d T e Fe bal The δ phase has a composition of (R, Ce, T). 30+u (Fe,Co) 70-u-v [(Al m Ga n Cu 1-m-n )M]v M is selected from one or more of Si, Ge and Sn; wherein, in atomic percentage, 0.3f(1-yz)≤b≤3; d'≤0.25f; 0.1≤y+z≤0.5; 0.09≤y×f≤0.4; preferably, 0.4f(1-yz)≤b≤0.8f(1-yz), d'≤0.25f; 0.15≤y+z≤0.3; 0.1≤y×f≤0.3. In the above embodiments, the introduction of Ga element is beneficial to the formation of more δ phase in the triangular crystal region of the magnet, while the introduction of Cu element can form a thin grain boundary phase in the magnet. By controlling the preferred contents of Ga, Cu and Al, Al element can be effectively enriched in the grain boundary, making it easier for the magnet grain boundary to form a δ phase with high Al content. At the same time, Cu and / or Ga elements can enter the thin grain boundary region more often to enhance the demagnetizing coupling effect, repair the surface defects of the main phase grains, and make the magnet have high coercivity and excellent magnetic properties.

[0047] The NdFeB magnet disclosed herein has a higher Al content in the delta phase within the grain boundaries of the triangular region, which further enhances the coercivity of the magnet.

[0048] In this disclosure, the N1 / N value of a neodymium iron boron magnet can be represented by the average result of the N1 / N values ​​of multiple cross sections of the magnet. That is, multiple different cross sections of the magnet can be randomly selected to measure the N1 / N value, for example, 5 to 10 cross sections can be selected; the average value of the N1 / N values ​​of these multiple different cross sections represents the N1 / N value of the magnet.

[0049] In one specific embodiment, the triangular grain boundary further includes a (Ce,R)Fe2 phase;

[0050] When 0 ≤ x < 0.2, the (Ce,R)Fe2 phase distribution within the grain boundaries of the triangular region satisfies the following equation (2).

[0051] S1 / S≤0.5% Equation (2);

[0052] When 0.2≤x≤0.25 and 0.1≤e≤0.3, the (Ce,R)Fe2 phase distribution within the grain boundaries of the triangular region satisfies the following equation (3).

[0053] S1 / S≤1.55% Equation (3);

[0054] Wherein, S1 / S represents the ratio of the area S1 of all (Ce,R)Fe2 phases within the grain boundary of the triangular region inside the cross section of the magnet to the total area S of the cross section.

[0055] In this disclosure, the (Ce,R)Fe2 phase includes CeFe2, RFe2 and (Ce,R)Fe2 phase.

[0056] In this disclosure, the S1 / S value of a neodymium iron boron magnet can be represented by the average result of the S1 / S values ​​of multiple cross sections of the magnet. That is, multiple different cross sections of the magnet can be randomly selected to measure the S1 / S value, and the average value of the S1 / S values ​​of these multiple different cross sections represents the S1 / S value of the magnet.

[0057] For example, the S1 / S value of a neodymium iron boron magnet can be determined by the following method: performing scanning electron microscopy tests on any five or more cross sections of the magnet, statistically analyzing the area of ​​all (Ce,R)Fe2 phases within the triangular grain boundaries of each cross section, calculating the S1 / S value of each cross section, and then calculating the average value of the S1 / S values ​​of all cross sections as the S1 / S value of the neodymium iron boron magnet; the size of the observation area is, for example, 104μm×104μm and 70μm×70μm; the magnification is 2000 to 3000 times.

[0058] In a preferred embodiment, 0 ≤ S1 / S ≤ 0.5%. The NdFeB magnet provided in this disclosure can have a lower area ratio of (Ce,R)Fe2 phase within the triangular grain boundaries, thereby avoiding spatial structure mismatch between the (Ce,R)Fe2 phase and the main phase, and preventing the formation of defects at the contact interface.

[0059] The NdFeB magnet disclosed herein exhibits significantly improved coercivity, minimal decrease in remanence, and superior overall performance.

[0060] A second aspect of this disclosure provides a method for preparing neodymium iron boron magnets, wherein the method includes: mixing a main alloy powder and an R'-Al auxiliary alloy powder to obtain (R... 1-x Ce x ) a Co b B c A d T e Fe bal alloy powder;

[0061] For (R) 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder is formed to obtain a compact, and the compact is sintered and tempered to obtain a magnet;

[0062] Wherein, R' includes one or more of the non-Ce rare earth elements; the (R) 1-x Ce x ) a Co b B c Ad T e Fe bal In the alloy powder, R includes Nd, and optionally includes one or more of the non-Ce rare earth elements; T is selected from one or more of Ti, Zr, V, Nb, Cr, Mo, Ru and Hf; A includes Al and Ga, or A includes Al and Cu, or A includes Al, Ga and Cu; a+b+c+d+e+bal=100, 0≤x≤0.25, 13.5≤a≤15, 0≤b≤3, 5.50≤c≤5.85, 0.5≤d≤3, 0≤e≤0.3; preferably, 0.1≤x≤0.2; 14≤a≤15; 0.3≤b≤1; 5.6≤c≤5.8; 0.6≤d≤1.2; 0.15≤e≤0.25;

[0063] The atomic percentage ratio of R' to Al is 3 / 11 to 3.

[0064] This invention employs a dual-alloy method to prepare NdFeB magnets. By using an R'-Al auxiliary alloy with an appropriate Al content, sufficient R' and Al elements are present at the grain boundaries in the initial state of liquid-phase sintering. The effective enrichment of R (e.g., Nd) and Al elements at the grain boundaries allows Al to participate more effectively in grain boundary reactions, making it easier for the magnet grain boundaries to form the δ phase, and enabling the formation of more δ phases with m≥0.5. This reduces the precipitation of the (Ce,R)Fe2 phase, further optimizing the magnet's microstructure and effectively improving its coercivity. Simultaneously, some Al atoms diffuse into the main phase, replacing Fe atoms, which reduces the intensity of the interaction between Ce and the (Fe,Al) sublattice at the 4f site, thereby altering the valence state of the 4f site atoms and enhancing the magnetocrystalline anisotropy of the main phase. This effectively improves the magnet's coercivity and overall performance.

[0065] In a preferred embodiment, the atomic percentage ratio of R' to Al is 1 to 3. By controlling the preferred atomic percentage ratio of R' to Al in the above embodiments, the NdAl2 phase in the alloy can be smaller in size, have a lower melting point, and be easier to break and melt; it also allows for a more rational distribution of Al elements in the main phase and grain boundary phase, enabling Al to participate more effectively in grain boundary reactions. This makes it easier for the magnet grain boundaries to form the δ phase, and allows for the formation of a larger proportion of the δ phase with a high Al content, effectively improving the magnet's coercivity.

[0066] In one specific embodiment, the mass ratio of the main alloy powder to the R'-Al auxiliary alloy powder is (22-160):1. In the above embodiment, controlling the preferred mass ratio of the main alloy powder to the auxiliary alloy powder allows for a reasonable distribution of Al elements in the main phase and grain boundary phase, enabling Al to participate more effectively in grain boundary reactions. This makes it easier for the magnet grain boundaries to form and for a larger proportion of the δ phase with high Al content to form, thus giving the magnet excellent magnetic properties.

[0067] In one specific embodiment, the R'-Al auxiliary alloy powder further includes X; X is selected from one or more of Si, Ga and Cu, and the atomic percentage of X is 0 to 10 at%; the R'-Al auxiliary alloy powder does not contain Ce;

[0068] In one specific embodiment, the (R) 1-x Ce x ) a Co b B c A d T e Fe bal In the alloy powder, A also includes M, and the composition of A is M. d’ (Ga y Cu z Al 1-y-z ) f M is selected from one or more of Si, Ge, and Sn; wherein, 0.3f(1-yz)≤b≤3, d≤0.25f; 0.1≤y+z≤0.5; 0.09≤y×f≤0.4; preferably, 0.4f(1-yz)≤b≤0.8f(1-yz), d'≤0.25f; 0.15≤y+z≤0.3; 0.1≤y×f≤0.3. In the above embodiments, the introduction of Ga element is beneficial to the formation of more δ phase in the triangular crystal region of the grain boundary of the magnet, while the introduction of Cu element can form a thin layer phase at the grain boundary in the magnet. By controlling the preferred contents of Ga, Cu, and Al, Al element can be effectively enriched in the grain boundary, making it easier for the δ phase to form at the magnet grain boundary. At the same time, Cu element can enter the thin layer region of the grain boundary more to enhance the demagnetizing coupling effect and repair the surface defects of the main phase grains, so that the magnet has high coercivity and excellent magnetic properties.

[0069] In one specific embodiment, the method further includes: preparing a main alloy sheet and an R'-Al auxiliary alloy sheet using a rapid solidification process; mixing the main alloy sheet and the R'-Al auxiliary alloy sheet; and then subjecting the mixture to hydrogen crushing and air jet milling to obtain the (R) alloy sheet. 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder; the (R) 1-x Ce x ) a Co b B c A d T e Fe balThe D50 particle size of the alloy powder is 4–4.6 μm; the grinding pressure of the air jet mill is 0.5–0.8 MPa. In another embodiment, the auxiliary alloy can be prepared as an ingot, then pre-crushed into coarse auxiliary alloy particles, and the coarse auxiliary alloy particles are mixed with the main alloy sheet.

[0070] In one specific embodiment, after hydrogen crushing, the resulting coarse powder particles are fed into a three-dimensional mixer for uniform mixing; after air jet milling, the resulting powder is fed into a three-dimensional mixer for thorough mixing.

[0071] In one specific embodiment, the forming process is an orientation forming process, which is carried out under an orientation magnetic induction intensity of 1.2–1.5T; the density of the pressed preform is 3.8–4.2 g / cm³. 3 .

[0072] In one specific embodiment, the sintering temperature is 1020–1080°C and the holding time is 2–8 h; preferably, the temperature is 1035–1080°C and the holding time is 3–5 h.

[0073] In one specific embodiment, the tempering heat treatment temperature is 420–650°C, and the holding time is 1–6 hours; preferably, the temperature is 420–560°C, and the holding time is 2–4 hours.

[0074] This disclosure employs a single-stage low-temperature tempering process, which can obtain magnets with high coercivity, shortening the process flow and reducing production costs and carbon emissions.

[0075] The third aspect of this disclosure provides neodymium iron boron magnets prepared using the method described in the second aspect of this disclosure.

[0076] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0077] Example 1

[0078] S1. The following steps are used to prepare the main alloy powder, R'-Al auxiliary alloy powder, and (R) powder respectively. 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder:

[0079] (1) The main alloying raw material is prepared with an atomic percentage of at%, and the composition of the main alloying raw material is Nd 8.79 Pr 2.46 Ce 2.68 Co 0.34B 5.83 Cu 0.16 Ga 0.1 Fe bal After the prepared main alloy raw materials are induction melted, the main alloy quick-solidation sheet is cast using a quick-solidation process; the thickness of the main alloy quick-solidation sheet is 0.23mm, the surface linear velocity of the roller in the quick-solidation process is 1m / s, and the casting temperature in the quick-solidation process is 1450℃.

[0080] (2) R'-Al auxiliary alloy raw material is prepared with atomic percentage at%, where R' is Nd and the atomic percentage ratio of Nd to Al is 1. The prepared auxiliary alloy raw material is melted and cooled to form an ingot. The ingot is stamped and ground to obtain auxiliary alloy coarse particles. The maximum particle size of the auxiliary alloy coarse particles is 5 mm.

[0081] (3) After mixing the main alloy quick-setting flakes with the auxiliary alloy coarse particles, hydrogen crushing treatment is performed to obtain alloy coarse powder particles. The alloy coarse powder particles are then fed into a three-dimensional mixer for homogenization and then subjected to air jet milling for micro-pulverization to obtain (R 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder, (R 1-x Ce x ) a Co b B c A d T e Fe bal The composition of the alloy powder is (Nd) 0.64 Pr 0.18 Ce 0.18 ) 13.96 Co 0.31 B 5.75 (Al 0.74 Cu 0.16 Ga 0.10 ) 0.92 Fe bal The mass ratio of the main alloy rapid-solidifying flakes to the auxiliary alloy coarse particles is 62:1; the hydrogen absorption pressure for hydrogen crushing is 200 MPa, the dehydrogenation temperature is 550℃, and the grinding pressure of the air jet mill is 0.6 MPa. 1-x Ce x ) a Co b B c A d T e Fe bal The average particle size D50 of the alloy powder is 4.43 μm;

[0082] S2. Neodymium iron boron magnets are prepared using the obtained main alloy powder and auxiliary alloy powder:

[0083] For (Nd) 0.64 Pr 0.18 Ce 0.18 ) 13.96 Co 0.31 B 5.75 (Al 0.74 Cu 0.16 Ga 0.10 ) 0.92 Fe bal Alloy powder was shaped to obtain a compact. The compact underwent sintering and tempering heat treatment, and was then machined into a φ10mm×8mm neodymium iron boron magnet, designated CT-1. The shaping process was an orientation shaping process, performed under N2 gas protection and with an orientation magnetic induction intensity of 1.5T. The compact's density was 4.1 g / cm³. 3 The sintering process was carried out in a vacuum sintering furnace at a vacuum degree of 9.8 × 10⁻⁶. -3 Pa, the sintering temperature is 1025℃ and the holding time is 3h; the tempering heat treatment temperature is 440℃ and the holding time is 1h.

[0084] The microstructure of the prepared NdFeB magnet 1 was tested. The observation plane was perpendicular to the easy magnetization direction of the magnet. The test results showed that the triangular region grain boundary phase of the magnet included the δ phase and the (Ce,R)Fe2 phase, wherein the composition of the δ phase was (R,Ce,T). 30+u (Fe,Co) 70-u-v [Al m Ga n (Cu,M) 1-m-n ] v Where -5≤u≤5, 5≤v≤10, 0.5≤m<0.65, and 0.3≤n≤0.45.

[0085] The distribution of the δ phase and (Ce,R)Fe2 phase in the NdFeB magnet prepared in Example 1 was detected, and the results are as follows: Figure 1 As shown, a large number of δ phases (indicated by white arrows) can be observed in the magnet. Through measurement, N1 / N is 1 and S1 / S is 0, indicating that the proportion of δ phase in the triangular region grain boundary phase of the magnet is relatively high. No (Ce,R)Fe2 phase was found in the triangular region grain boundary phase, which gives the magnet high coercivity and excellent comprehensive magnetic properties.

[0086] Comparative Example 1

[0087] According to Example 1 (R) 1-x Ce x ) a Cob B c A d T e Fe bal The alloy powder was prepared according to the specified composition ratio to obtain a single alloy raw material, wherein the composition of the single alloy raw material is (Nd... 0.64 Pr 0.17 Ce 0.18 ) 13.96 Co 0.31 B 5.75 (Al 0.75 Cu 0.16 Ga 0.10 ) 0.92 Fe bal .

[0088] Referring to the preparation method in Example 1, the difference from Example 1 is that the tempering heat treatment includes a first-stage tempering heat treatment and a second-stage tempering heat treatment. The first-stage tempering heat treatment is performed at a temperature of 440°C for 1 hour, yielding a neodymium iron boron magnet, denoted as DCT-1. The second-stage tempering heat treatment involves first holding the magnet at 900°C for 2 hours, then cooling it, and then heating it to 440°C and holding it for 1 hour, yielding a neodymium iron boron magnet, denoted as DCT-1-1.

[0089] Example 2

[0090] S1. The following steps are used to prepare the main alloy powder, R'-Al auxiliary alloy powder, and (R) powder respectively. 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder:

[0091] (1) The main alloying material is prepared with an atomic percentage at%, and the composition of the main alloying material is (Nd, Pr). 12.98 Co 1.0 7B 5.63 Cu 0.10 Ga 0.40 Al 0.28 Fe bal After the prepared main alloy raw materials are induction melted, the main alloy quick-solidation sheet is cast using a quick-solidation process; wherein, the thickness of the main alloy quick-solidation sheet is 0.3 mm; the quick-solidation process adopts the method of Example 1;

[0092] (2) R'-Al auxiliary alloy raw material is prepared with atomic percentage at%, where R' is PrNd and the atomic percentage ratio of PrNd to Al is 3. After the prepared auxiliary alloy raw material is induction melted, the auxiliary alloy quick-solidified sheet is cast using a quick-solidification process. The quick-solidification process is the same as the method for preparing the main alloy quick-solidified sheet.

[0093] (3) After mixing the main alloy rapid-setting sheet and the auxiliary alloy rapid-setting sheet, hydrogen crushing treatment is performed to obtain coarse alloy powder particles. The coarse alloy powder particles are then fed into a three-dimensional mixer for homogenization and then subjected to air jet milling to obtain (R 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder, (R 1-x Ce x ) a Co b B c A d T e Fe bal The composition of the alloy powder is (Nd) 0.81 Pr 0.19 ) 14.53 Co 1.03 B 5.49 (Ga 0.26 Cu 0.07 Al 0.67 ) 1.49 Fe bal The mass ratio of the main alloy rapid-solidification flakes to the auxiliary alloy coarse particles was 22.9:1; the hydrogen crushing treatment and air jet mill micronization were carried out using the method of Example 1. 1-x Ce x ) a Co b B c A d T e Fe bal The average particle size D50 of the alloy powder is 4.36 μm;

[0094] S2. Neodymium iron boron magnets are prepared using the obtained main alloy powder and auxiliary alloy powder:

[0095] For (Nd) 0.81 Pr 0.19 ) 14.53 Co 1.03 B 5.49 (Ga 0.26 Cu 0.07 Al 0.67 ) 1.49 Febal Alloy powder was shaped to obtain a compact, which was then sintered and tempered before being machined into a cylindrical NdFeB magnet 2 with a thickness (orientation direction) of φ10mm × 8mm, denoted as CT-2. The shaping process followed the method described in Example 1, and the sintering was performed in a vacuum sintering furnace at a vacuum degree of 9.8 × 10⁻⁶ mm. -3 Pa, the sintering temperature is 1050℃ and the holding time is 2h; the tempering heat treatment temperature is 480℃ and the holding time is 1h.

[0096] Comparative Example 2

[0097] According to Example 2 (R) 1-x Ce x ) a Co b B c A d T e Fe bal The alloy powder was prepared according to the specified composition ratio to obtain a single alloy raw material, wherein the composition of the single alloy raw material is (Nd... 0.81 Pr 0.19 ) 14.53 Co 1.03 B 5.49 (Ga 0.26 Cu 0.07 Al 0.67 ) 1.49 Fe bal .

[0098] Following the method for preparing neodymium iron boron magnets in Example 2, a neodymium iron boron magnet, denoted as DCT-2, was obtained.

[0099] Example 3

[0100] S1. The following steps are used to prepare the main alloy powder, R'-Al auxiliary alloy powder, and (R) powder respectively. 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder:

[0101] (1) The main alloying material is prepared with an atomic percentage at%, and the composition of the main alloying material is (Nd, Pr). 10.26 Ce 3.62 Co 0.49 B 5.84 Cu 0.14 Ga 0.25 Nb 0.14 Fe balAfter the prepared main alloy raw materials are induction melted, the main alloy quick-solidation sheet is cast using a quick-solidation process; wherein, the thickness of the main alloy quick-solidation sheet is 0.3 mm; the quick-solidation process adopts the method of Example 1;

[0102] (2) R'-Al auxiliary alloy raw materials are prepared with atomic percentage at%, where R' is PrNd and the atomic percentage ratio of PrNd to Al is 3:11. After the prepared auxiliary alloy raw materials are induction melted, the auxiliary alloy quick-solidified sheets are cast using a quick-solidification process. The quick-solidification process is the same as the method for preparing the main alloy quick-solidified sheets.

[0103] (3) After mixing the main alloy rapid-setting sheet and the auxiliary alloy rapid-setting sheet, hydrogen crushing treatment is performed to obtain coarse alloy powder particles. The coarse alloy powder particles are then fed into a three-dimensional mixer for homogenization and then subjected to air jet milling to obtain (R 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder, (R 1-x Ce x ) a Co b B c A d T e Fe bal The alloy powder has the following composition: [(NdPr)] 0.74 Ce 0.26 ] 13.95 Co 0.49 B 5.79 (Ga 0.23 Cu 0.13 Al 0.64 ) 1.09 Nb 0.13 Fe bal The mass ratio of the main alloy rapid-solidification flakes to the auxiliary alloy coarse particles was 160:1; the hydrogen crushing treatment and air jet mill micronization were carried out using the method of Example 1. 1-x Ce x ) a Co b B c A d T e Fe bal The average particle size D50 of the alloy powder is 4.36 μm;

[0104] S2. Neodymium iron boron magnets are prepared using the obtained main alloy powder and auxiliary alloy powder:

[0105] For [(NdPr)] 0.74 Ce0.26 ] 13.95 Co 0.49 B 5.79 (Ga 0.23 Cu 0.13 Al 0.64 ) 1.09 Nb 0.13 Fe bal Alloy powder was shaped to obtain a compact, which was then sintered and tempered before being machined into a φ10mm×8mm (orientation direction) neodymium iron boron magnet 3, denoted as CT-3. The shaping process followed the method described in Example 1, and the sintering was performed in a vacuum sintering furnace at a vacuum degree of 9.8×10⁻⁶. -3 Pa, the sintering temperature is 1035℃ and the holding time is 2h; the tempering heat treatment temperature is 640℃ and the holding time is 1h.

[0106] Comparative Example 3

[0107] The single alloy raw material was prepared according to the final magnet composition ratio in Example 3, wherein the composition of the single alloy raw material is [(NdPr)]. 0.74 Ce 0.26 ] 13.95 Co 0.49 B 5.79 (Ga 0.23 Cu 0.13 Al 0.64 ) 1.09 Nb 0.13 Fe bal .

[0108] Following the method for preparing neodymium iron boron magnets in Example 3, a neodymium iron boron magnet, designated DCT-3, was obtained.

[0109] Example 4

[0110] The method of Example 3 is used, the only difference being that, (R 1-x Ce x ) a Co b B c A d T e Fe bal The alloy powder has the following composition: [(NdPr)] 0.82 Ce 0.18 ] 13.71 Co 0.37 B 5.50 (Ga 0.21 Cu 0.17 Al 0.62 ) 0.5 Zr 0.14 Fe balA neodymium iron boron magnet was obtained, denoted as CT-4.

[0111] Comparative Example 4

[0112] The method of Comparative Example 3 was used, the only difference being that the composition of the single alloy raw material was [(NdPr)]. 0.82 Ce 0.18 ] 13.71 Co 0.37 B 5.50 (Ga 0.21 Cu 0.17 Al 0.62 ) 0.5 Zr 0.14 Fe bal A neodymium iron boron magnet was obtained, denoted as DCT-4.

[0113] Test Case

[0114] Neodymium iron boron magnets prepared in Examples 1-4 and Comparative Examples 1-4 were selected. The composition of the grain boundary phase in the triangular region within five or more cross sections was analyzed by scanning electron microscopy energy dispersive spectroscopy (EDS) to determine whether it belonged to the δ phase. Ten groups of δ phases were randomly selected. The composition and content of the δ phase were analyzed by scanning electron microscopy energy dispersive spectroscopy (EDS), and the u, v, m and n values ​​were calculated. The results are listed in Tables 1-4.

[0115] (R 1-x Ce x ) a Co b B c A d T e Fe bal The average particle size of the alloy powder was obtained by testing with a particle size analyzer.

[0116] After mirror polishing the magnet of Example 1, a cross-sectional image was taken using a scanning electron microscope. The resulting SEM image is shown below. Figure 1 As shown, the observation plane is perpendicular to the orientation direction of the magnet. In Example 1, the triangular grain boundaries of the magnet contain a large amount of δ phase, and the (Ce,R)Fe2 phase was not observed. In Comparative Example 1, the number of δ phases in the magnets obtained from both heat treatments is significantly less than that in Example 1, and the (Ce,R)Fe2 phase was not observed. The microstructure of the magnet in Comparative Example 3 (as shown in the image) is... Figure 2 Taking the example shown, the δ phase and the (Ce,R)Fe2 phase can be distinguished based on the electron backscattering image. Compared with δ, the expansion morphology of the (Ce,R)Fe2 phase is different. The (Ce,R)Fe2 phase has fewer edges and fewer acute angles. At the same time, due to the higher rare earth content than the δ phase, the contrast of the backscattered electron image of the (Ce,R)Fe2 phase is slightly higher than that of the δ phase.

[0117] The distribution of δ phase within the triangular grain boundaries of a magnet can be determined using the following method: Randomly select five or more arbitrary cross sections of the magnet for analysis. For each cross section, randomly select five or more 70μm×70μm regions. Use EDS to analyze the triangular grain boundaries within each region of each cross section. Determine the total number N of δ phases and the number N1 of δ phases with m≥0.5 in the triangular grain boundaries based on the composition of the triangular grain boundaries. Calculate the N1 / N value for each region and take the average value as the N1 / N value for that cross section. Then calculate the average value of the N1 / N values ​​for all cross sections and take it as the N1 / N value for the magnet. The results are listed in Table 5.

[0118] The distribution of the (Ce,R)Fe2 phase within the triangular grain boundaries of the magnet can be analyzed using Image-Pro Plus image analysis software. Five or more arbitrary cross-sections of the magnet are randomly selected for analysis. For each cross-section, five or more 70μm × 70μm regions are randomly selected. The area S1 of all (Ce,R)Fe2 phases within the triangular grain boundaries of each region in each cross-section and the total area S of each region are measured. The S1 / S value for each region is calculated and averaged as the S1 / S value for that cross-section. The average of the S1 / S values ​​for all cross-sections is then calculated as the S1 / S value for the entire magnet. The results are listed in Table 5. For example, ... Figure 3 As shown, the area marked in green is the area S1 of all (Ce,R)Fe2 phases within the triangular grain boundaries in each region of each cross section.

[0119] The magnetic properties of the neodymium iron boron magnets in Examples 1-4 and Comparative Examples 1-4 were tested using a BH plotter, and the results are listed in Table 5.

[0120] Table 1

[0121]

[0122]

[0123] Table 2

[0124]

[0125] Table 3

[0126]

[0127]

[0128] Table 4

[0129]

[0130] Table 5 Performance data of neodymium iron boron magnets

[0131] Magnet materials <![CDATA[Residual magnetic flux density B r / kGs]]> <![CDATA[Coercive force H cJ / kOe]]> <![CDATA[N1 / N]]> <![CDATA[S1 / S]]> CT-1 13.31 11.64 1 0 DCT-1 13.62 9.48 0.2 0 DCT-1-1 13.5 11.63 0.1 0.1％ CT-2 13.22 18.07 0.6 0 DCT-2 13.30 17.65 0 0 CT-3 13.29 13.42 0.8 1.52％ DCT-3 13.29 13.01 0 2.32％ CT-4 13.05 13.6 1 0.42％ DCT-4 13.06 13.05 0.3 0.53％

[0132] As shown in Tables 1-5, this invention employs a dual-alloy method with R'-Al alloy as the auxiliary alloy to prepare NdFeB magnets. This ensures sufficient enrichment of R and Al elements at the grain boundaries during liquid-phase sintering, allowing Al to participate more effectively in intergranular reactions and achieving a more rational distribution of Al in the main phase and grain boundary phases. Specifically, on the one hand, some Al elements inevitably diffuse from the grain boundaries into the main phase to replace Fe atoms, reducing the intensity of the interaction between rare earth atoms at the 4f crystal position and the (Fe,Al) sublattice, which may change the valence state of the 4f crystal position atoms and improve coercivity by increasing the intrinsic magnetocrystalline anisotropy of the main phase. On the other hand, Al that does not enter the main phase is enriched at the grain boundaries, which is conducive to the transformation of the (Ce,R)Fe2 phase into (R,Ce)6Fe. 12 The presence of the A2 phase (δ phase) reduces the precipitation of the (Ce,R)Fe2 phase and simultaneously generates a larger amount of δ phase with higher Al content (m≥0.5). This reduces the solidification of Ga and Cu elements in the δ phase of the grain boundary triangular region, allowing more Ga and Cu elements to participate in the reaction in the thin-layer region of the grain boundary, effectively repairing the defects in the main phase grains and effectively improving the intrinsic coercivity of the magnet. Compared with Comparative Examples 1-4, the NdFeB magnets prepared in Examples 1-4 have a larger amount of δ phase with higher Al content (m≥0.5) distributed in the grain boundaries of the triangular region, and a smaller amount of (Ce,R)Fe2 phase in the grain boundaries of the triangular region. This results in an effective improvement in coercivity of the NdFeB magnets prepared in Examples 1-4 with only a slight decrease in remanence, and the magnets possess excellent comprehensive performance.

[0133] Comparing Example 1 with Comparative Example 1, it can be seen that, Figure 1 As shown, the magnet prepared in Example 1 contains a large amount of δ phase with high Al content in the triangular grain boundary. The m value of the δ phase in the magnet is between 0.51 and 0.59, which is significantly higher than that in Comparative Example 1. The proportion of Ga in the δ phase is also increased, which can reduce the solidification of Ga and Cu elements in the δ phase of the triangular grain boundary, allowing more Ga and Cu elements to participate in the reaction in the thin grain boundary region, effectively repairing the defects of the main phase grains. Moreover, it does not contain (Ce,R)Fe2 phase, so the magnet prepared in Example 1 only needs to undergo a first-stage tempering heat treatment (440°C) to achieve the coercivity achieved by the magnet in Comparative Example 1 after a first-stage tempering heat treatment (440°C) and a second-stage tempering treatment (including first holding the magnet at 900°C for 2 hours, then cooling and then heating it to 440°C for 1 hour). Therefore, compared with Comparative Example 1, the preparation method provided in this disclosure does not require high-temperature tempering heat treatment to effectively improve the coercivity of NdFeB magnets.

[0134] Comparing Example 2 with Comparative Example 2, it can be seen that in Example 2, the m value of the δ phase in the NdFeB magnet prepared by the dual alloy method is between 0.43 and 0.53, and the δ phase with m ≥ 0.5 accounts for 60% of all δ phases. In contrast, in Comparative Example 2, the m value of the δ phase in the magnet prepared by the single alloy method is all less than 0.5, and the proportion of Al atoms in the δ phase relative to low melting point elements is only between 30% and 36%, which is difficult to increase. This results in a large number of Al atoms participating in the solidification process of the main phase and having difficulty participating in the evolution of the intergranular phase. Therefore, this disclosure uses a dual alloy method with R'-Al alloy as the auxiliary alloy to prepare NdFeB magnets, ensuring that there is sufficient enrichment of R and Al elements at the grain boundaries during liquid phase sintering, so that Al elements can participate more effectively in the intergranular reaction, achieving a more reasonable distribution of Al in the main phase and grain boundary phase, thereby increasing the coercivity by 0.42 kOe with only a slight decrease in remanence.

[0135] Comparing Example 3 with Comparative Example 3, it can be seen that the m value of the δ phase in the NdFeB magnet prepared by the dual alloy method in Example 3 is between 0.47 and 0.63, and most of them satisfy m≥0.5. In contrast, the m value of the δ phase in the magnet prepared by Comparative Example 3 is in the range of 0.1 to 0.47, and is less than 0.5. At the same time, during the preparation of the magnet by the dual alloy method, Nd and Al elements participate more effectively in the intergranular reaction, promoting the transformation of the (Ce,R)Fe2 phase into the δ phase. As can be seen from Table 5, the area ratio of the (Ce,R)Fe2 phase in the triangular region grain boundary of the magnet prepared by Example 3 (1.52%) is significantly lower than that of Comparative Example 3 (2.32%). Therefore, Example 3 can achieve a coercivity increase of 0.41 kOe with only a slight decrease in remanence compared to Comparative Example 3.

[0136] Comparing Example 4 with Comparative Example 4, it can be seen that the area of ​​the (RCe)Fe2 phase in the triangular region of the magnet prepared by the dual alloy method in Example 4 is slightly lower than that in Comparative Example 4, which enables Example 4 to achieve a 0.55kOe increase in coercivity without a decrease in remanence compared to Comparative Example 4.

[0137] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0138] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0139] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A neodymium iron boron magnet, wherein, The neodymium iron boron magnet includes triangular grain boundaries, and the triangular grain boundaries contain a δ phase; The composition of the neodymium iron boron magnet is (R 1-x Ce x ) a Co b B c A d T e Fe bal In this context, by atomic percentage, a+b+c+d+e+bal=100, 0≤x≤0.25, 13.5≤a≤15, 0≤b≤3; 5.50≤c≤5.85, 0.5≤d≤3, 0≤e≤0.3; R includes Nd, and optionally includes one or more of the non-Ce rare earth elements; T is selected from one or more of Ti, Zr, V, Nb, Cr, Mo, Ru and Hf; A includes Al and Ga, or A includes Al and Cu, or A includes Al, Ga and Cu; The composition of the δ phase is (R, Ce, T). 30+u (Fe,Co) 70-u-v [(Al m Ga n Cu 1-m-n )] v In terms of atomic percentage, -5≤u≤5, 5≤v≤10, 0<m<1, 0≤n<1; the δ phase distribution within the grain boundaries of the triangular region satisfies the following equation (1). N1 / N≥0.6 Equation (1); Wherein, N1 / N represents the ratio of the number of δ phases N1 with m≥0.5 within the grain boundary of the triangular region to the total number of δ phases N within the grain boundary of the triangular region.

2. The neodymium iron boron magnet according to claim 1, wherein, A also includes M, wherein the neodymium iron boron magnet is composed of (R 1- x Ce x ) a Co b B c [M d’ (Ga y Cu z Al 1-y-z ) f ] d T e Fe bal The δ phase has a composition of (R, Ce, T). 30+u (Fe,Co) 70-u-v [(Al m Ga n Cu 1-m-n )M] v M is selected from one or more of Si, Ge and Sn; Among them, in terms of atomic percentage, d=d'+f, 0.3f(1-yz)≤b≤3, d'≤0.25f; 0.1≤y+z≤0.5; 0.09≤y×f≤0.

4.

3. The neodymium iron boron magnet according to claim 1, wherein, The triangular grain boundary also contains the (Ce,R)Fe2 phase; When 0 ≤ x < 0.2, the (Ce,R)Fe2 phase distribution within the grain boundaries of the triangular region satisfies the following equation (2). S1 / S≤0.5% Equation (2); When 0.2≤x≤0.25 and 0.1≤e≤0.3, the (Ce,R)Fe2 phase distribution within the grain boundaries of the triangular region satisfies the following equation (3). S1 / S≤1.55% Equation (3); Wherein, S1 / S represents the ratio of the area S1 of all (Ce,R)Fe2 phases within the grain boundary of the triangular region inside the cross section of the magnet to the total area S of the cross section.

4. A method for preparing neodymium iron boron magnets, wherein, The method includes: mixing the main alloy powder and the R'-Al auxiliary alloy powder to obtain (R 1-x Ce x ) a Co b B c A d T e Fe bal alloy powder; For (R) 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder is formed to obtain a compact, and the compact is sintered and tempered to obtain a magnet; Wherein, R' includes one or more of the non-Ce rare earth elements; the (R) 1-x Ce x ) a Co b B c A d T e Fe bal In the alloy powder, R includes Nd, and optionally includes one or more of the non-Ce rare earth elements; T is selected from one or more of Ti, Zr, V, Nb, Cr, Mo, Ru and Hf; A includes Al and Ga, or A includes Al and Cu, or A includes Al, Ga and Cu; a+b+c+d+e+bal=100, 0≤x≤0.25, 13.5≤a≤15, 0≤b≤3; 5.50≤c≤5.85, 0.5≤d≤3, 0≤e≤0.3; The atomic percentage ratio of R' to Al is 3 / 11 to 3.

5. The method according to claim 4, wherein, The mass ratio of the main alloy powder to the R'-Al auxiliary alloy powder is (22-160):

1.

6. The method according to claim 4, wherein, The R'-Al auxiliary alloy powder further includes X; X is selected from one or more of Si, Ga and Cu; the R'-Al auxiliary alloy powder does not contain Ce; Wherein, the (R) 1-x Ce x ) a Co b B c A d T e Fe bal In the alloy powder, A also includes M, and the composition of A is M. d’ (Ga y Cu z Al 1-y-z ) f M is selected from one or more of Si, Ge and Sn; Among them, 0.3f(1-yz)≤b≤3, d≤0.25f; 0.1≤y+z≤0.5; 0.09≤y×f≤0.

4.

7. The method according to claim 4, wherein, The method further includes: preparing a main alloy sheet and an R'-Al auxiliary alloy sheet using a rapid solidification process; mixing the main alloy sheet and the R'-Al auxiliary alloy sheet; and then subjecting the mixture to hydrogen crushing and air jet milling to obtain the (R) alloy sheet. 1-x Ce x ) a Co b B c A d T e Fe bal Alloy powder; the (R) 1-x Ce x ) a Co b B c A d T e Fe bal The D50 particle size of the alloy powder is 4–4.6 μm; the grinding pressure of the air jet mill is 0.55–0.75 MPa.

8. The method according to claim 4, wherein, The forming process is an orientation forming process, which is carried out under the condition that the orientation magnetic induction intensity is 1.2 to 1.5T; The density of the pressed blank is 3.8–4.2 g / cm³. 3 .

9. The method according to claim 4, wherein, The sintering temperature is 1020–1080℃, and the holding time is 2–5 hours. The tempering heat treatment temperature is 420–650℃, and the holding time is 1–6 hours.

10. A neodymium iron boron magnet prepared by the method according to any one of claims 4 to 10.

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