CN114783751A - Grain boundary diffusion process of high-performance sintered neodymium-iron-boron magnet - Google Patents
Grain boundary diffusion process of high-performance sintered neodymium-iron-boron magnet Download PDFInfo
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- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0293—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
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- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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Abstract
The invention belongs to the field of rare earth permanent magnet materials, and particularly relates to a grain boundary diffusion process of a high-performance sintered neodymium-iron-boron magnet. According to the invention, the sintered neodymium iron boron initial magnet without the heavy rare earth element is pretreated, then the double-layer film of the heavy rare earth element Dy and the double-layer film of the heavy rare earth element Tb are sequentially deposited on the surface by adopting a magnetron sputtering method, and the high-coercivity sintered neodymium iron boron magnet is prepared by a vacuum heat treatment grain boundary diffusion process.
Description
Technical Field
The invention belongs to the field of rare earth permanent magnet materials, and particularly relates to a grain boundary diffusion process of a high-performance sintered neodymium-iron-boron magnet.
Background
The sintered Nd-Fe-B permanent magnet material has the advantages of high magnetic energy product and high coercive force, and is an indispensable energy exchange material in the fields of electroacoustic devices, electronic appliances, rail transit, wind power generation, new energy automobiles and the like. But the application of the magnet in the high-temperature field is limited due to the thermal demagnetization phenomenon caused by low Curie temperature and poor thermal stability, the room-temperature coercive force of a common commercial N50 sintered neodymium-iron-boron magnet can reach 12.10kOe, and the corresponding coercive force is 9.41kOe when the magnet is heated to 50 ℃, and the amplitude is reduced by 22.2%; heating to 80 ℃ until the coercive force is only 7.01kOe, and the reduction amplitude reaches 42.1 percent; when the temperature is 120 ℃, the coercivity is less than half of the coercivity at room temperature. When the magnet is heated to 200 ℃ and then cooled to room temperature, the coercive force of the magnet is recovered to 6.71kOe, and the irreversible magnetic loss is 44.5%. The above results show that: the coercive force of the sintered neodymium-iron-boron magnet is rapidly reduced along with the temperature rise, and the coercive force is still reduced to a certain degree after the sintered neodymium-iron-boron magnet is restored to the room temperature. The method for greatly improving the room-temperature coercive force of the sintered neodymium-iron-boron magnet is an effective means for compensating the irreversible magnetic loss of the sintered neodymium-iron-boron magnet in a high-temperature state.
The grain boundary diffusion technology is that heavy rare earth and its compound are coated on the surface of magnet by means of vacuum evaporation, coating and electrophoretic deposition, and then high-temp. heat treatment is carried out to diffuse along the grain boundary liquid phase and finally form (Nd, HRE) on the surface layer of crystal grain2Fe14B hard magnetic shell layer structure, thereby effectively improving the coercive force of the sintered neodymium iron boron magnet and reducing the residual magnetic loss to the maximum extent. Loewe et al in germany explored the grain boundary diffusion process of different rare earth elements (Dy, Tb) in Dy-free and Dy-containing magnets, and the research results showed that: the diffusion rate of the rare earth elements in a magnet without Dy is slower than that of a magnet containing Dy, and the diffusion rate of Tb in two initial magnets is much higher than that of Dy (K.Loewe.et al. acta materialia.2017,124, 421-429.). By comparing the grain boundary diffusion behaviors of Dy in magnets without Dy and magnets containing Dy, Japan K.Hono et al find that when the magnet containing Dy diffuses in the grain boundary, a large amount of Dy flows into an initial Dy-rich shell layer of the magnet from the grain boundary phase, and a second Dy-rich shell layer is formed around the initial Dy-rich shell layer, so that the coercive force of the magnet reaches more than 3.0T (K.Hono.et al. The professor of Shenzhen Shenzhou and the professor of Shenzhen morning of Jiangxi Rich university agree that the formation of a Dy core-shell structure by the initial magnet is a necessary condition for realizing the diffusion of Tb from the surface of the magnet to the deeper part of the magnet. Aiming at the problems of disordered Dy distribution, large heavy rare earth consumption and the like existing in the preparation of the initial magnet by the single alloy method, the double alloy method is adopted to prepare the initial magnet containing Dy and carry out grain boundary expansionPowder TbH2The coercive force of the magnet is increased from 17.37kOe to 24.97kOe after 890 ℃ thermal diffusion for 10h and 500 ℃ tempering for 3h (G.Q.Xie.et al. journal of Alloys and Compounds.2021,856, 158-191.). However, the initial magnet prepared by the double-alloy method cannot ensure the distribution of Dy in the magnet, and a Nd-rich shell layer is coated around part of the independent Dy nucleation.
Disclosure of Invention
In order to solve the technical problems, the invention is realized by the following technical scheme: a grain boundary diffusion process of a high-performance sintered neodymium-iron-boron magnet sequentially comprises the following steps:
after preprocessing the sintered neodymium iron boron initial magnet without the heavy rare earth element, sequentially depositing double-layer films of the heavy rare earth element Dy and the heavy rare earth element Tb on the surface by adopting a magnetron sputtering method, and performing a vacuum heat treatment grain boundary diffusion process to obtain the sintered neodymium iron boron magnet with high coercivity.
The method for pretreating the sintered neodymium-iron-boron initial magnet without heavy rare earth elements specifically comprises the following steps:
(1) cutting a large sintered neodymium-iron-boron magnet into square samples of 10mm multiplied by 3-6 mm, wherein the sample size along the c-axis direction is 3-6 mm;
(2) polishing the sintered neodymium iron boron sample by using 800, 1500, 2000, 3000 and 5000-mesh sand paper in sequence until the surface is in a mirror surface shape;
(3) sequentially carrying out ultrasonic treatment on a polished sample for 3-5 min by using distilled water and 3-5 wt.% of HNO3Carrying out ultrasonic treatment on the solution for 30-60 s and absolute ethyl alcohol for 3-5 min to obtain a clean surface;
(4) and drying the magnet to obtain the pretreated magnet.
Further preferably, in the pretreatment method, in the step (3), the polished sample is sequentially subjected to ultrasonic treatment with distilled water for 5min and 3 wt.% of HNO3The ultrasonic treatment of the solution for 60s and the ultrasonic treatment of absolute ethyl alcohol for 5min obtain the best effect of cleaning the surface.
The magnetron sputtering method adopts two sputtering sources to deposit Dy and Tb in a layered manner, and comprises the following specific steps: placing the preprocessed magnet into a magnetron sputtering sample stage, placing 99.9 wt.% of high-purity Dy and 99.9 wt.% of high-purity Tb target materials into corresponding strong magnetic target positions, and vacuumizing to 1.0 multiplied by 10-4～8.0×10-5Pa, filling 99.999 vol.% of high-purity argon, adjusting the flow of the argon to 40-60 sccm, the working pressure to 0.5-2 Pa, the sputtering power to 70-100W, and controlling the sputtering time to obtain Dy/Tb heavy rare earth double-layer films with different thicknesses. Further preferably, the magnetron sputtering coating process parameters are as follows: the gas flow is 40sccm, the working pressure is 1Pa, and the sputtering power is 100W, so that the time can be saved, and the film forming quality is optimal.
The thickness of the heavy rare earth Dy film layer is 1-6 mu m, the thickness of the heavy rare earth Tb film layer is 1-6 mu m, and the total thickness of the double-layer film is 2-12 mu m. Further preferably, the thickness of the heavy rare earth Dy film layer is 3 μm, and the effect is best when the thickness of the heavy rare earth Tb film layer is 3 μm.
Wrapping the heavy rare earth double-layer film intermediate body with a molybdenum foil, and performing vacuum heat treatment on the molybdenum foil to perform grain boundary diffusion; the technological parameters of the vacuum heat treatment grain boundary diffusion are as follows: vacuum degree of the single-temperature-zone tube furnace: 6X 10-4Pa, diffusion temperature: 800 ℃ and 950 ℃, diffusion time: 5-8 h, annealing temperature: 450-650 ℃, annealing time: 2-6 h. Further preferably, the diffusion temperature is 900 ℃, the diffusion time is 5 hours, the annealing temperature is 500 ℃, and the annealing time is 3 hours, so that the effect is optimal.
The invention provides a method for preparing high-performance sintered neodymium iron boron by depositing a heavy rare earth double-layer film, aiming at the problem that the coercivity improvement of a grain boundary diffusion simple substance heavy rare earth element in the prior art is limited. The method can effectively improve the coercive force of the sintered neodymium-iron-boron magnet.
Compared with the traditional grain boundary diffusion neodymium iron boron magnet, the sintered neodymium iron boron magnet obtained by the process can obviously improve the coercive force and has a uniform microstructure. The basic principle is that Dy/Tb atoms sequentially replace the edges of main phase grains to finally form Nd with gradually increased anisotropy constant when a heavy rare earth double-layer film is subjected to grain boundary diffusion2Fe14B/Dy2Fe14B/Tb2Fe14The gradient structure layer B and the diffusion magnet are influenced by a high anisotropy constant, so that the system can be turned over under the action of a high magnetic field, and the coercive force of the sintered neodymium iron boron magnet can be effectively improved.
Drawings
FIG. 1 is a demagnetization curve of a double-layer film magnet with grain boundary diffusion of 3 μmDy +3 μmTb in example 1;
FIG. 2 is a back scattering scanning test chart of the near surface of the double-layer magnet with grain boundary diffusion of 3 μmDy +3 μmTb in example 1;
FIG. 3 is a demagnetization curve of the magnet after grain boundary diffusion of the samples of examples 2-4;
FIG. 4 is a demagnetization curve of a magnet of a single-layer film having grain boundary diffusion of 6 μmDy in comparative example 1;
FIG. 5 is a near-surface back-scattering scanning test chart of a magnet of a 6 μmDy single-layer film with grain boundary diffusion in comparative example 1;
FIG. 6 is a demagnetization curve of a magnet of a single layer film of 6 μmTb grain boundary diffusion in comparative example 2;
FIG. 7 is a back scattering scan test chart of the near surface of the magnet after grain boundary diffusion of 6 μmTb single-layer film in comparative example 2;
FIG. 8 is a demagnetization curve of a double-layer film magnet with grain boundary diffusion of 3 μmTb +3 μmDy in comparative example 3;
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it is to be understood that various changes or modifications may be made by those skilled in the art after reading the present disclosure, and such equivalents may fall within the scope of the present disclosure.
Example 1
The embodiment provides a method for preparing high-performance sintered neodymium iron boron by depositing a heavy rare earth double-layer film, which specifically comprises an initial magnet pretreatment step, a heavy rare earth double-layer film deposition step and a vacuum heat treatment step:
1. initial magnet pretreatment:
(1) cutting a large commercial N50 sintered NdFeB magnet into a square sample with the size of 10 multiplied by 3mm along the direction of a c axis;
(2) polishing the sintered neodymium iron boron sample by using 800, 1500, 2000, 3000 and 5000-mesh sand paper in sequence until the surface is in a mirror surface shape;
(3) sequentially subjecting the polished sample to ultrasonic treatment with distilled water for 5min and 3 wt.% of HNO3Ultrasonic treatment of solution for 60sCarrying out ultrasonic treatment on absolute ethyl alcohol for 5min to obtain a clean surface;
(4) and drying the magnet to obtain the pretreated magnet.
2. Heavy rare earth double-layer film deposition: putting the preprocessed magnet into a magnetron sputtering sample stage, putting 99.9% high-purity Dy/Tb target material into a corresponding strong magnetic target position, vacuumizing to 8.0 x 10-5Pa, filling 99.999 percent of high-purity argon, regulating the flow rate of 40sccm, working pressure of 1Pa, sputtering power of 100W, and depositing a 3 mu mDy +3 mu mTb double-layer film by controlling the sputtering time.
3. Vacuum heat treatment: setting the diffusion temperature: diffusion time is 5h at 900 ℃; the annealing temperature is 500 ℃, the annealing time is 3 hours, the heavy rare earth double-layer film intermediate body is wrapped by molybdenum foil, then the quartz boat is placed in a single-temperature-zone tubular furnace, the vacuum pumping is carried out until the pressure is below 6.0 multiplied by 10 < -4 > Pa, the operation procedure is started, after the procedure is finished, the furnace chamber is naturally cooled to the room temperature and is taken out, and then the high-performance sintered neodymium iron boron magnet is obtained.
4. The demagnetization curve of the diffusion magnet is shown in figure 1, and the figure shows that after the Dy-Tb double-layer film is diffused through the grain boundary, the coercive force of the magnet is obviously improved compared with that of the original magnet and reaches 19.96 kOe.
5. The near-surface back scattering scanning test chart of the magnet of the diffusion magnet is shown in the attached figure 2, and the figure shows that the microstructure of the magnet is more uniform after the Dy-Tb double-layer film is diffused through a grain boundary.
Example 2
The preparation process of the present example is substantially the same as that of example 1, except that: when a Dy-Tb double-layer film is deposited, 2 mu mDy +3 mu mTb double-layer films are deposited by controlling the sputtering time, and after vacuum heat treatment, the coercive force of the magnet is obviously improved compared with that of the original magnet, and is specifically 18.19 kOe.
Example 3
The preparation process of this example is substantially the same as that of example 1, except that: when a Dy-Tb double-layer film is deposited, 3 mu mDy +1 mu mTb double-layer films are deposited by controlling the sputtering time, and after vacuum heat treatment, the coercive force of the magnet is obviously improved compared with that of the original magnet, and is specifically 19.06 kOe.
Example 4
The preparation process of this example is substantially the same as that of example 1, except that: when a Dy-Tb double-layer film is deposited, 3 mu mDy +2 mu mTb double-layer films are deposited by controlling the sputtering time, and after vacuum heat treatment, the coercive force of the magnet is obviously improved compared with that of the original magnet, and is specifically 19.69 kOe.
Examples 2 to 4 the demagnetization curves of the magnet after grain boundary diffusion are shown in FIG. 3. As can be seen from the figure, the coercive force (19.06kOe) of the magnet with the double-layer film of 3 mu mDy +1 mu mTb deposited in the patent is larger than that (17.03kOe) of the magnet obtained by only depositing 6 mu mDy in comparative example 1, and is only 0.07kOe different from that (19.13kOe) of the magnet obtained by depositing 6 mu mTb in comparative example 2, and the use of the method in the patent can save the use amount of the heavy rare earth Tb.
Comparative example 1
In the sintered neodymium iron boron magnet deposited by the embodiment only with the single heavy rare earth Dy film, the deposition thickness, the heat treatment and the annealing process of the heavy rare earth are completely the same as those in the embodiment 1, the demagnetization curve of the diffusion magnet is shown in the attached figure 4, and the figure shows that the improvement of the coercive force of only diffusing the heavy rare earth Dy is not as good as that of a diffusion Dy-Tb double-layer film magnet. FIG. 5 is a near surface back scattering scan test of the magnet after grain boundary diffusion of 6 μmDy monolayer film. As can be seen, the deposition of a single heavy rare earth Dy film forms a core-shell structure (light gray in the figure) in the near-surface region, with the light gray shell thickness decreasing with increasing diffusion depth.
Comparative example 2
In the sintered neodymium iron boron magnet deposited with only a single heavy rare earth Tb film, the deposition thickness, the heat treatment and the annealing process of the heavy rare earth are completely the same as those of the sintered neodymium iron boron magnet deposited in the embodiment 1, the demagnetization curve of the diffusion magnet is shown in an attached figure 6, and the improvement of the coercive force of Tb only diffusing the heavy rare earth is not as good as that of a Dy-Tb double-layer film magnet diffusing the heavy rare earth. FIG. 7 is a near surface back scattering scan test of the magnet after grain boundary diffusion of 6 μmTb monolayer film. As can be seen, the deposition of a single heavy rare earth Tb film forms a core-shell structure (light gray in the figure) in the near-surface region, and the thickness of the light gray shell layer decreases with increasing diffusion depth.
Comparative example 3
In the embodiment, 3 mu mTb +3 mu mDy double-layer film sintered NdFeB magnets are sequentially deposited, the deposition thickness, the heat treatment and the annealing process of heavy rare earth are completely the same as those of the embodiment 1, the demagnetization curve of the diffusion magnet is shown in the attached figure 8, and the improvement of the coercivity of the diffusion Tb-Dy double-layer film is not as good as that of the diffusion Dy-Tb double-layer film magnet.
By comparison, the coercive force of the magnet in example 1 is improved from 12.36kOe to 19.96kOe, the amplification is 61.49%, the coercive force of the magnet after diffusion (17.03kOe) is improved by 17.20% compared with that in comparative example 1, and the coercive force of the magnet after diffusion (19.13kOe) is improved by 4.34% compared with that in comparative example 2, and the production cost can be greatly reduced by using 3 mu mDy instead of Tb because the price of metal Tb is about 5 times that of metal Dy. The coercive force of the magnet of example 4, which only needs to deposit a 5 μm heavy rare earth double-layer film, is larger than that of comparative examples 1 and 2. Therefore, compared with the traditional grain boundary diffusion elemental heavy rare earth element, the coercivity of the Dy-Tb double-layer film formed by sputtering deposition is improved more obviously, the using amount of the heavy rare earth can be saved, and compared with the grain boundary diffusion Tb-Dy double-layer film structure, (Nd, Dy, Tb)2Fe14The B hard magnetic shell layer can effectively improve the coercive force of the sintered neodymium iron boron magnet.
The magnetic performance data of the original sintered nd-fe-b magnet, examples 1-4, and comparative examples 1-3 are given in table 1 below for comparison.
Comparing the data in table 1, it is found that the coercive force is improved to a certain extent after the heavy rare earth single-layer film is deposited on the surface of the magnet and the double-layer film is subjected to grain boundary diffusion, and the coercive force is improved more obviously compared with the heavy rare earth double-layer film prepared by the heavy rare earth single-layer film under the condition that the thicknesses of the sputtered and deposited films are the same.
Claims (7)
1. The grain boundary diffusion process of the high-performance sintered neodymium-iron-boron magnet is characterized in that after the sintered neodymium-iron-boron initial magnet without heavy rare earth elements is pretreated, heavy rare earth element Dy and heavy rare earth element Tb are sequentially deposited on the surface of the sintered neodymium-iron-boron initial magnet through a magnetron sputtering method to obtain a Dy/Tb heavy rare earth double-layer film, and the high-coercivity sintered neodymium-iron-boron magnet is prepared through a vacuum heat treatment grain boundary diffusion process.
2. The grain boundary diffusion process of the high-performance sintered neodymium-iron-boron magnet according to claim 1, wherein the method for pretreating the sintered neodymium-iron-boron initial magnet without heavy rare earth elements comprises the following steps:
(1) cutting a large sintered neodymium-iron-boron magnet into square samples with the size of 10mm multiplied by 3-6 mm, wherein the sample size along the c-axis direction is 3-6 mm;
(2) polishing the sintered neodymium iron boron sample by using 800, 1500, 2000, 3000 and 5000-mesh sand paper in sequence until the surface is in a mirror surface shape;
(3) sequentially carrying out ultrasonic treatment on a polished sample for 3-5 min by using distilled water and 3-5 wt.% of HNO3Carrying out ultrasonic treatment on the solution for 30-60 s and absolute ethyl alcohol for 3-5 min to obtain a clean surface;
(4) and drying the magnet to obtain the pretreated magnet.
3. The grain boundary diffusion process of the high-performance sintered neodymium-iron-boron magnet according to claim 2, wherein in the step (3), the polished sample is sequentially subjected to ultrasonic treatment with distilled water for 5min and 3 wt.% of HNO3And carrying out ultrasonic treatment on the solution for 60 seconds and absolute ethyl alcohol for 5min to obtain a clean surface.
4. The grain boundary diffusion process of the high-performance sintered neodymium-iron-boron magnet according to claim 1, wherein the magnetron sputtering method is used for depositing Dy and Tb in a layered manner by adopting two sputtering sources, and the specific steps are as follows: placing the magnet after pretreatment into a magnetron sputtering sample table, placing 99.9 wt.% of high-purity Dy target and 99.9 wt.% of high-purity Tb target on corresponding strong magnetic target positions, and vacuumizing to 1.0 multiplied by 10-4～8.0×10-5Pa, filling 99.999 vol.% of high-purity argon, adjusting the flow of the argon to 40-60 sccm, the working pressure to 0.5-2 Pa, the sputtering power to 70-100W, and controlling the sputtering time to obtain Dy/Tb heavy rare earth double-layer films with different thicknesses; the total thickness of the Dy/Tb heavy rare earth double-layer film is 2-12 mu m, wherein the thickness of the heavy rare earth Dy film layer is 1-6 mu m, and the thickness of the heavy rare earth Tb film layer is 1-6 mu m.
5. The grain boundary diffusion process of the high-performance sintered neodymium-iron-boron magnet according to claim 4, characterized in that the magnetron sputtering coating process parameters are as follows: the gas flow is 40sccm, the working air pressure is 1Pa, and the sputtering power is 100W; in the Dy/Tb heavy rare earth double-layer film, the thickness of the heavy rare earth Dy film layer is 3 mu m, and the thickness of the heavy rare earth Tb film layer is 3 mu m.
6. The grain boundary diffusion process of the high-performance sintered neodymium-iron-boron magnet as claimed in claim 1, wherein the grain boundary diffusion is performed by vacuum heat treatment after wrapping with molybdenum foil, and the parameters of the vacuum heat treatment grain boundary diffusion process are as follows: single temperature zone tube furnace vacuum: 6X 10-4Pa, diffusion temperature: 800 ℃ and 950 ℃, diffusion time: 5-8 h, annealing temperature: 450-650 ℃, annealing time: 2-6 h.
7. The grain boundary diffusion process of the high-performance sintered NdFeB magnet as claimed in claim 6, wherein the diffusion temperature is 900 ℃, the diffusion time is 5 hours, the annealing temperature is 500 ℃, and the annealing time is 3 hours.
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