High-stability high-magnetic-energy-product rare earth permanent magnet material and preparation method thereof

Abstract

This invention relates to the field of magnetic materials, specifically to a high-stability, high-energy-product rare-earth permanent magnet material and its preparation method. The main alloy of the high-stability, high-energy-product rare-earth permanent magnet material, by atomic percentage, has a composition of (Nd... a La 1‑a ) x Fe 100‑w‑x‑y‑ z Co w M y B z M is selected from Cr, Al, and Cu; a, w, x, y, and z satisfy the following relationships: 0.8 ≤ a ≤ 1, 0.5 ≤ w ≤ 1.5, 11 ≤ x ≤ 16, 0 ≤ y ≤ 1.5, 4.5 ≤ z ≤ 6.5; the composition of the grain boundary phase alloy, expressed as an atomic percentage, is Ho. 100‑u Ta u 10≤u≤20; The neodymium iron boron magnet material of this invention has excellent magnetic properties, possessing both ultra-high remanence and high coercivity. Its maximum operating temperature can be greater than or equal to 240℃.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials, specifically to a high-stability, high-energy-product rare-earth permanent magnet material, its preparation method, and its application. Background Technology

[0002] Neodymium iron boron (NdFeB) permanent magnets are the highest-performing magnetic materials to date. Due to their extremely high energy product, coercivity, and energy density, they are hailed as the "King of Magnets" and have been widely used in emerging technology fields such as wind power generation, maglev trains, and new energy vehicles. These new fields also place higher demands on the stability and other properties of NdFeB permanent magnets. Research has shown that the stability of NdFeB permanent magnets can be improved and their magnetic properties further enhanced through methods such as partial substitution (or doping) of alloying elements. For example, adding Cu and Al can increase the Curie temperature and coercivity of sintered rare-earth permanent magnets, thereby improving the thermal stability of the magnet. However, adding these elements leads to a decrease in remanence and energy product. The grain boundary diffusion technology that emerged in the early 21st century, by infiltrating heavy rare-earth elements or rare-earth alloys into the magnet through grain boundary diffusion, effectively improves the magnet's coercivity and energy product while significantly reducing the amount of heavy rare-earth elements used to lower costs.

[0003] The aforementioned technologies have attracted widespread attention in the industry and have been industrialized. However, the field still needs to continue researching magnetic materials with higher stability and coercivity to meet the future technological development's continuous pursuit of high-performance magnetic materials and promote the continuous progress of related industries. Summary of the Invention

[0004] The purpose of this invention is to provide a neodymium iron boron (NdFeB) magnet material that combines stability and high coercivity, as well as its preparation method and applications. The NdFeB magnet material described in this invention possesses excellent magnetic properties, exhibiting both ultra-high remanence and high coercivity.

[0005] The inventors of this invention have discovered that using zinc oxide nanoparticles as an additive to prepare rare earth permanent magnet materials can effectively pin grain boundaries, inhibit irregular grain growth, improve the wettability between the grain boundary phase and the main phase grains, and suppress the nucleation of antimagnetic domains. This significantly improves the boundary structure and magnetic properties of the rare earth permanent magnet materials, thereby enhancing their remanence and energy product while also providing good high-temperature demagnetization resistance.

[0006] The inventors of this invention further discovered that, under the premise that zinc oxide nanoparticles pin the grain boundaries, the introduction of tantalum (Ta) can further suppress grain coarsening, promote grain isolation, form finer and more uniform grains, and by optimizing the overall grain morphology and grain boundary continuity, can more effectively hinder the propagation of nucleated antimagnetic domains, thereby significantly improving the coercivity of rare earth permanent magnet materials and improving their temperature stability and anti-demagnetization properties.

[0007] In view of this, a first aspect of the present invention provides a method for preparing a high-stability, high-energy-product rare-earth permanent magnet material, comprising the following steps:

[0008] S1: The main alloy powder is prepared using three processes: rapid solidification casting, hydrogen explosion, and air jet milling. The composition of the main alloy, expressed as an atomic percentage, is (Nd... a La 1-a ) x Fe 100-w-x-y-z Co w M y B z ;

[0009] M is selected from Cr, Al, and Cu;

[0010] a, w, x, y, z satisfy the following relationship:

[0011] 0.8≤a≤1, 0.5≤w≤1.5, 11≤x≤16, 0≤y≤1.5, 4.5≤z≤6.5;

[0012] S2: The grain boundary phase alloy is cast into an ingot using a casting process, and then prepared into grain boundary phase alloy powder using a mechanical ball milling process. The composition of the grain boundary phase alloy, expressed as an atomic percentage, is Ho. 100-u Ta u , 10≤u≤20;

[0013] S3: Mix the grain boundary phase alloy powder and nano zinc oxide powder evenly in a mixer under a protective medium to obtain a grain boundary phase alloy modified with nano zinc oxide, wherein the weight of the added nano zinc oxide powder accounts for 0.2 to 0.8% of the total powder weight.

[0014] S4: The main alloy powder and the grain boundary phase alloy powder modified with nano zinc oxide are mixed evenly in a mixer under a protective medium to obtain a mixed powder;

[0015] S5: The mixed powder is oriented and pressed in a magnetic field environment, and then pressed into a green body by cold isostatic pressing;

[0016] S6: Sinter the green blank, perform a first-stage tempering, and then a second-stage tempering to obtain the high-stability, high-energy-product rare-earth permanent magnet material, neodymium iron boron magnet.

[0017] In some embodiments, the average particle diameter of the nano zinc oxide powder is 50-100 nm, for example, it can be 50-90 nm, 50-80 nm, 60-100 nm, 60-90 nm, 60-80 nm, 60-75 nm, 70-90 nm or 70-80 nm.

[0018] In some embodiments, the average particle diameter of the nano zinc oxide powder is 65 nm or 75 nm.

[0019] In some embodiments, the average particle diameter of the nano zinc oxide powder is 70–80 nm.

[0020] In some embodiments, the average particle diameter of the nano zinc oxide powder is 75 nm.

[0021] In some embodiments, the main alloy comprises, by weight percentage:

[0022] 10%–13% Nd, 1%–2% La, 0.4%–1% Co, 4%–7% B, and 0.2%–0.4% of one or more selected from Cr, Al or Cu, with the balance being Fe and unavoidable impurities.

[0023] In some embodiments, the main alloy comprises, by weight percentage:

[0024] Nd 10.3%–12.5%, La 1.2%–1.5%, Co 0.5%–0.7%, B 4.62%–6.2%, and one or more selected from Cr, Al or Cu 0.25%–0.3%, with the balance being Fe and unavoidable impurities.

[0025] In some embodiments, the main alloy comprises, by weight percentage:

[0026] Nd 10.3%, La 1.2%, Co 0.5% and B 6.1%,

[0027] Nd 11.6%, La 1.5%, Co 0.53%, B 4.62% and Cr 0.25%,

[0028] Nd 12.5%, La 1.2%, Co 0.7%, B 6.2% and Al 0.3%,

[0029] Nd 12.5%, La 1.2%, Co 0.7%, B 6.2% and Al 0.3%, or

[0030] Nd 12.5%, La 1.2%, Co 0.7%, B 6.2% and Al 0.3%,

[0031] And the remainder of Fe and unavoidable impurities.

[0032] In some embodiments, the main alloy comprises, by weight percentage, 10.3% Nd, 1.2% La, 0.5% Co and 6.1% B, with the balance being Fe and unavoidable impurities.

[0033] In some embodiments, the main alloy comprises, by weight percentage, 11.6% Nd, 1.5% La, 0.53% Co, 4.62% B and 0.25% Cr, with the balance being Fe and unavoidable impurities.

[0034] In some embodiments, the main alloy comprises, by weight percentage, 12.5% ​​Nd, 1.2% La, 0.7% Co, 6.2% B, and 0.3% Al, with the balance being Fe and unavoidable impurities.

[0035] In some embodiments, the main alloy comprises, by weight percentage, 12.5% ​​Nd, 1.2% La, 0.7% Co, 6.2% B, and 0.3% Al, with the balance being Fe and unavoidable impurities.

[0036] In some embodiments, the main alloy comprises, by weight percentage, 12.5% ​​Nd, 1.2% La, 0.7% Co, 6.2% B, and 0.3% Al, with the balance being Fe and unavoidable impurities.

[0037] In some implementations, 15 ≤ u ≤ 20.

[0038] In some implementations, 15.7 ≤ u ≤ 18.5.

[0039] In some implementations, 17 ≤ u ≤ 18.5.

[0040] In some implementations, u is 15.7 or 18.5.

[0041] In some embodiments, in step S3, the weight of the added nano zinc oxide powder accounts for 0.4% to 0.8% of the total powder weight, for example, 0.4% to 0.7% or 0.4% to 0.6%.

[0042] In some implementations, in step S3, the added nano zinc oxide powder accounts for 0.4% to 0.6% of the total powder weight.

[0043] In some implementations, in step S3, the added nano zinc oxide powder accounts for 0.4%, 0.5%, or 0.6% of the total powder weight.

[0044] In some implementations, in step S4, the protective medium is petroleum ether.

[0045] In some embodiments, in step S5, the mixed powder is oriented and pressed under a magnetic field of 1.5 to 3 T. In some embodiments, in step S5, the mixed powder is oriented and pressed under a magnetic field of 1.5 to 2.5 T.

[0046] In some embodiments, the pressing pressure in step S5 is 140–250 MPa. In some embodiments, the pressing pressure in step S5 is 150–210 MPa.

[0047] In some embodiments, the pressing time in step S5 is 50–200 s. In some embodiments, the pressing time in step S5 is 60–150 s.

[0048] In some embodiments, the sintering temperature in step S6 is 825–1050°C. In some embodiments, the sintering temperature in step S6 is 850–1000°C.

[0049] In some embodiments, the sintering time in step S6 is 1.5 to 7.5 hours. In some embodiments, the sintering time in step S6 is 2 to 6 hours.

[0050] In some implementations, the maximum operating temperature of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 240°C, and further greater than or equal to 250°C.

[0051] In some embodiments, the maximum operating temperature of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 240°C and less than 275°C; further, it is greater than or equal to 250°C and less than 275°C.

[0052] In some embodiments, the remanent magnetic properties of the high-stability, high-energy-product rare-earth permanent magnet material are greater than or equal to 14.5 kGs; further greater than or equal to 14.9 kGs.

[0053] In some embodiments, the remanent magnetic properties of the high-stability, high-energy-product rare-earth permanent magnet material are greater than or equal to 14.5 kGs and less than 15.2 kGs; further greater than or equal to 14.9 kGs and less than 15.2 kGs.

[0054] In some embodiments, the intrinsic coercivity of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 29 kOe; further greater than or equal to 34 kOe.

[0055] In some embodiments, the intrinsic coercivity of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 29 kOe and less than 36 kOe; further greater than or equal to 34 kOe and less than 36 kOe.

[0056] In some embodiments, the maximum magnetic energy product of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 45 MGsOe; further greater than or equal to 55 MGsOe.

[0057] In some embodiments, the maximum magnetic energy product of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 45 MGsOe and less than 58 MGsOe; further greater than or equal to 55 MGsOe and less than 58 MGsOe.

[0058] In a second aspect, the present invention provides a high-stability, high-energy-product rare-earth permanent magnet material, which is prepared by the preparation method of the high-stability, high-energy-product rare-earth permanent magnet material described in any of the foregoing embodiments.

[0059] In a third aspect, the present invention provides the application of the above-described high-stability, high-energy-product rare-earth permanent magnet material as a magnetic device.

[0060] In some implementation schemes, the neodymium iron boron magnet material is used as a magnetic device in many fields such as rail transportation, military equipment, wind power generation, low-altitude flight, artificial intelligence, aerospace, medical devices and precision manufacturing.

[0061] Based on common knowledge in the field, the above-described embodiments can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0062] The reagents and raw materials used in this invention are all commercially available.

[0063] In this invention, the symbols for each element have conventional meanings in the art, specifically: "Nd" for neodymium, "La" for lanthanum, "Cr" for chromium, "Ho" for holmium, "Al" for aluminum, "Cu" for copper, "Ta" for tantalum, "Co" for cobalt, "Ti" for titanium, "Fe" for iron, and "B" for boron. Detailed Implementation

[0064] Unless otherwise stated, the following terms and phrases as used herein are intended to have the following meanings. A particular term or phrase should not be considered uncertain or unclear unless specifically defined, but should be understood in its ordinary sense. When a trade name appears herein, it is intended to refer to the corresponding product or its active ingredient.

[0065] As used herein and unless otherwise stated, the terms “comprising,” “including,” and “having” include their grammatical equivalents and should generally be understood as open-ended and non-restrictive, e.g., not excluding other unlisted elements or steps.

[0066] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0067] The present invention will be further illustrated below with specific examples, but the present invention is not limited to the following embodiments.

[0068] Example 1

[0069] S1: Raw materials are prepared according to the following weight percentages: Nd 10.3%, La 1.2%, Co 0.5%, B 6.1%, with the balance being Fe. The raw materials are placed in a vacuum induction melting furnace and cast into ingots to obtain rare earth permanent magnet ingots. The rare earth permanent magnet ingots are heat-treated and subjected to hydrogen absorption and dehydrogenation treatment in a rotary hydrogen crushing furnace for 3 hours. The rare earth permanent magnet ingots are crushed to obtain coarse powder. The coarse powder is ground into powder by an air jet mill under inert gas protection to produce neodymium iron boron rare earth powder.

[0070] S2: Raw materials are prepared by casting process according to the weight percentage ratio of Ho 84.3% and Ta 15.7%, and grain boundary phase alloy powder is prepared by mechanical ball milling process.

[0071] S3: Mix grain boundary phase alloy powder and nano zinc oxide powder (average particle diameter is about 75nm) in a mixer under the protection of petroleum ether, according to the weight percentage ratio of 99.6% grain boundary phase alloy powder and 0.4% nano zinc oxide powder, to obtain grain boundary phase alloy powder modified with nano zinc oxide powder.

[0072] S4: Take 3% of the total mass of NdFeB rare earth powder and nano-modified grain boundary phase alloy powder. Mix the nano-modified grain boundary phase alloy powder with NdFeB rare earth powder in two batches. First, take 25% of the total mass of nano-modified grain boundary phase alloy powder, mix it with NdFeB rare earth powder and stir for 5 minutes. Then add the remaining 75% of nano-modified grain boundary phase alloy powder, mix and stir for 20 minutes, and then let it stand for 30 minutes to obtain a mixed powder of NdFeB rare earth powder and nano-modified grain boundary phase alloy powder.

[0073] S5: The mixed powder is placed in the mold of the molding machine for pre-pressing; the pre-pressed mixed powder is placed in an orientation magnetic field with a magnetic induction intensity of 1.5T for orientation, and pressed into shape under cold isostatic pressing at 150MPa to obtain a rough blank, wherein the direction of the orientation magnetic field is perpendicular to the pressing direction.

[0074] S6: The blank is placed in a vacuum sintering furnace and sintered at 850℃ for 1.8h. Then, it undergoes a secondary aging heat treatment. Under vacuum or inert gas protection, it undergoes a primary heat treatment at 860℃ for 1.5h, followed by a secondary heat treatment at 520℃ for 2h. It is then cooled to room temperature by natural cooling to obtain neodymium iron boron rare earth permanent magnet material.

[0075] Example 2

[0076] S1: Raw materials are prepared according to the following weight percentages: Nd 11.6%, La 1.5%, Cr 0.25%, Co 0.53%, B 4.62%, with the balance being Fe. The raw materials are placed in a vacuum induction melting furnace and cast into ingots to obtain rare earth permanent magnet ingots. The rare earth permanent magnet ingots are heat-treated and subjected to hydrogen absorption and dehydrogenation treatment in a rotary hydrogen crushing furnace for 3 hours. The rare earth permanent magnet ingots are crushed to obtain coarse powder. The coarse powder is ground into powder by an air jet mill under inert gas protection to produce neodymium iron boron rare earth powder.

[0077] S2: Raw materials are prepared by casting process according to the weight percentage ratio of Ho 81.5% and Ta 18.5%, and grain boundary phase alloy powder is prepared by mechanical ball milling process;

[0078] S3: Mix grain boundary phase alloy powder and nano zinc oxide powder (average particle diameter is about 75nm) in a mixer under the protection of petroleum ether, according to the weight percentage ratio of 99.4% grain boundary phase alloy powder and 0.6% nano zinc oxide powder, to obtain grain boundary phase alloy powder modified with nano powder.

[0079] S4: Take 3% of the total mass of NdFeB rare earth powder and nano-modified grain boundary phase alloy powder. Mix the nano-modified grain boundary phase alloy powder with NdFeB rare earth powder in two batches. First, take 25% of the total mass of nano-modified grain boundary phase alloy powder, mix it with NdFeB rare earth powder and stir for 5 minutes. Then add the remaining 75% of nano-modified grain boundary phase alloy powder, mix and stir for 25 minutes, and then let it stand for 30 minutes to obtain a mixed powder of NdFeB rare earth powder and nano-modified grain boundary phase alloy powder.

[0080] S5: The mixed powder is placed in the mold of the molding machine for pre-pressing; the pre-pressed mixed powder is placed in an orientation magnetic field with a magnetic induction intensity of 1.8T for orientation, and pressed into shape under cold isostatic pressing at 190MPa to obtain a rough blank, wherein the direction of the orientation magnetic field is perpendicular to the pressing direction.

[0081] S6: The blank is placed in a vacuum sintering furnace and sintered at 850℃ for 2.1h. Then, it undergoes a secondary aging heat treatment. Under vacuum or inert gas protection, it undergoes a primary heat treatment at 870℃ for 2h, followed by a secondary heat treatment at 550℃ for 2.5h. Finally, it is cooled to room temperature by natural cooling to obtain neodymium iron boron rare earth permanent magnet material.

[0082] Example 3

[0083] S1: Raw materials are prepared according to the following weight percentages: Nd 12.5%, La 1.2%, B 6.2%, Al 0.3%, Co 0.7%, with the balance being Fe. The raw materials are placed in a vacuum induction melting furnace and cast into ingots to obtain rare earth permanent magnet ingots. The rare earth permanent magnet ingots are heat-treated and subjected to hydrogen absorption and dehydrogenation treatment in a rotary hydrogen crushing furnace for 3 hours. The rare earth permanent magnet ingots are crushed to obtain coarse powder. The coarse powder is ground into powder by an air jet mill under inert gas protection to produce neodymium iron boron rare earth powder.

[0084] S2: Raw materials are prepared by casting process according to the weight percentage ratio of Ho 81.5% and Ta 18.5%, and grain boundary phase alloy powder is prepared by mechanical ball milling process;

[0085] S3: Take grain boundary phase alloy powder and nano zinc oxide powder (average particle diameter is about 75nm), mix them in a mixer under the protection of petroleum ether according to the weight percentage ratio of 99.5% grain boundary phase alloy powder and 0.5% nano zinc oxide powder, and obtain grain boundary phase alloy powder modified by nano powder.

[0086] S4: Take 3% of the total mass of NdFeB rare earth powder and nano-modified grain boundary phase alloy powder. Mix the nano-modified grain boundary phase alloy powder with NdFeB rare earth powder in two batches. First, take 25% of the total mass of nano-modified grain boundary phase alloy powder and mix it with NdFeB rare earth powder for 10 minutes. Then add the remaining 75% of nano-modified grain boundary phase alloy powder, mix and stir for 25 minutes, and then let it stand for 30 minutes to obtain a mixed powder of NdFeB rare earth powder and nano-modified grain boundary phase alloy powder.

[0087] S5: The mixed powder is placed in the mold of the molding machine for pre-pressing; the pre-pressed mixed powder is placed in an orientation magnetic field with a magnetic induction intensity of 2.2T for orientation, and pressed into shape under cold isostatic pressing of 200MPa to obtain a rough blank, wherein the direction of the orientation magnetic field is perpendicular to the pressing direction.

[0088] S6: The blank is placed in a vacuum sintering furnace and sintered at 850℃ for 2.5h. Then, it undergoes a second-stage aging heat treatment. Under vacuum or inert gas protection, it undergoes a first-stage heat treatment at 900℃ for 2.5h, followed by a second-stage heat treatment at 580℃ for 2h. Finally, it is cooled to room temperature by natural cooling to obtain neodymium iron boron rare earth permanent magnet material.

[0089] Example 4

[0090] S1: Raw materials are prepared according to the following weight percentages: Nd 12.5%, La 1.2%, B 6.2%, Al 0.3%, Co 0.7%, with the balance being Fe. The raw materials are placed in a vacuum induction melting furnace and cast into ingots to obtain rare earth permanent magnet ingots. The rare earth permanent magnet ingots are heat-treated and subjected to hydrogen absorption and dehydrogenation treatment in a rotary hydrogen crushing furnace for 3 hours. The rare earth permanent magnet ingots are crushed to obtain coarse powder. The coarse powder is ground into powder by an air jet mill under inert gas protection to produce neodymium iron boron rare earth powder.

[0091] S2: Raw materials are prepared by casting process according to the weight percentage ratio of Ho 81.5% and Ta 18.5%, and grain boundary phase alloy powder is prepared by mechanical ball milling process;

[0092] S3: Take grain boundary phase alloy powder and nano zinc oxide powder (average particle diameter is about 65nm), mix them in a mixer under the protection of petroleum ether according to the weight percentage ratio of 99.5% grain boundary phase alloy powder and 0.5% nano zinc oxide powder, and obtain grain boundary phase alloy powder modified by nano powder.

[0093] S4: Take 3% of the total mass of NdFeB rare earth powder and nano-modified grain boundary phase alloy powder. Mix the nano-modified grain boundary phase alloy powder with NdFeB rare earth powder in two batches. First, take 25% of the total mass of nano-modified grain boundary phase alloy powder and mix it with NdFeB rare earth powder for 10 minutes. Then add the remaining 75% of nano-modified grain boundary phase alloy powder, mix and stir for 25 minutes, and then let it stand for 30 minutes to obtain a mixed powder of NdFeB rare earth powder and nano-modified grain boundary phase alloy powder.

[0094] S5: The mixed powder is placed in the mold of the molding machine for pre-pressing; the pre-pressed mixed powder is placed in an orientation magnetic field with a magnetic induction intensity of 2.2T for orientation, and pressed into shape under cold isostatic pressing of 200MPa to obtain a rough blank, wherein the direction of the orientation magnetic field is perpendicular to the pressing direction.

[0095] S6: The blank is placed in a vacuum sintering furnace and sintered at 850℃ for 2.5h. Then, it undergoes a second-stage aging heat treatment. Under vacuum or inert gas protection, it undergoes a first-stage heat treatment at 900℃ for 2.5h, followed by a second-stage heat treatment at 580℃ for 2h. Finally, it is cooled to room temperature by natural cooling to obtain neodymium iron boron rare earth permanent magnet material.

[0096] Example 5

[0097] S1: Raw materials are prepared according to the following weight percentages: Nd 12.5%, La 1.2%, B 6.2%, Al 0.3%, Co 0.7%, with the balance being Fe. The raw materials are placed in a vacuum induction melting furnace and cast into ingots to obtain rare earth permanent magnet ingots. The rare earth permanent magnet ingots are heat-treated and subjected to hydrogen absorption and dehydrogenation treatment in a rotary hydrogen crushing furnace for 3 hours. The rare earth permanent magnet ingots are crushed to obtain coarse powder. The coarse powder is ground into powder by an air jet mill under inert gas protection to produce neodymium iron boron rare earth powder.

[0098] S2: Raw materials are prepared by casting process according to the weight percentage ratio of Ho 81.5% and Ta 18.5%, and grain boundary phase alloy powder is prepared by mechanical ball milling process;

[0099] S3: Mix grain boundary phase alloy powder and nano zinc oxide powder (average particle diameter is about 75nm) in a mixer under the protection of petroleum ether, according to the weight percentage ratio of 99.2% grain boundary phase alloy powder and 0.8% nano zinc oxide powder, to obtain grain boundary phase alloy powder modified with nano powder.

[0100] S4: Take 3% of the total mass of NdFeB rare earth powder and nano-modified grain boundary phase alloy powder. Mix the nano-modified grain boundary phase alloy powder with NdFeB rare earth powder in two batches. First, take 25% of the total mass of nano-modified grain boundary phase alloy powder and mix it with NdFeB rare earth powder for 10 minutes. Then add the remaining 75% of nano-modified grain boundary phase alloy powder, mix and stir for 25 minutes, and then let it stand for 30 minutes to obtain a mixed powder of NdFeB rare earth powder and nano-modified grain boundary phase alloy powder.

[0101] S5: The mixed powder is placed in the mold of the molding machine for pre-pressing; the pre-pressed mixed powder is placed in an orientation magnetic field with a magnetic induction intensity of 2.2T for orientation, and pressed into shape under cold isostatic pressing of 200MPa to obtain a rough blank, wherein the direction of the orientation magnetic field is perpendicular to the pressing direction.

[0102] S6: The blank is placed in a vacuum sintering furnace and sintered at 850℃ for 2.5h. Then, it undergoes a second-stage aging heat treatment. Under vacuum or inert gas protection, it undergoes a first-stage heat treatment at 900℃ for 2.5h, followed by a second-stage heat treatment at 580℃ for 2h. Finally, it is cooled to room temperature by natural cooling to obtain neodymium iron boron rare earth permanent magnet material.

[0103] Comparative Example 1

[0104] Comparative Example 1 was prepared according to Example 3, except that Ta was not added to the raw materials prepared in step S2.

[0105] Comparative Example 2

[0106] Comparative Example 1 was prepared according to Example 3, except that the zinc oxide powder modification in step S3 was not performed.

[0107] Comparative Example 3

[0108] Comparative Example 1 was prepared according to Example 3, except that the raw materials in step S2 were 81.5% Ho and 18.5% Ti.

[0109] Test Example 1

[0110] The remanence (Br, kGs), maximum energy product (BH, MGsOe), and intrinsic coercivity (Hcj, kOe) of the neodymium iron boron rare earth permanent magnet materials obtained in the examples and comparative examples were measured using the NIM10000H and NIM200C permanent magnet material magnetic property measurement systems of the National Institute of Metrology, China. The highest operating temperature (°C) of the above samples was tested according to GB / T13560~2017 "Sintered Neodymium Iron Boron Permanent Magnet Materials". The results are shown in Table 1 below.

[0111] Table 1

[0112]

[0113] In Table 1, Comparative Example 1 without Ta, Comparative Example 2 without zinc oxide, and Comparative Example 3 with Ho and Ti all resulted in limited material diffusion channels and decreased coercivity increase. Examples 1-5, by simultaneously adding Ho, Ta, and zinc oxide, simultaneously improved both the coercivity and the maximum operating temperature of the material. It is evident that by employing the technical solution of this invention, simultaneously adding zinc oxide nanoparticles and Ta to the grain boundary phase, and optimizing the distribution of the grain boundary phase and the grain boundary morphology through nano-modification, the zinc oxide nanoparticles pin the grain boundaries, enhancing the magnetocrystalline anisotropy field at the surface of the main alloy grains, suppressing the irregular growth of the main alloy grains, and thus preventing the formation of reversed magnetic domains on the surface of the main alloy grains during demagnetization. This achieves high energy product in NdFeB magnets while improving their high-temperature stability. Furthermore, in the alloy system of this invention, the addition of Ho and Ta elements in a certain ratio has an unexpected synergistic effect on providing the maximum operating temperature of the permanent magnet material.

[0114] While certain features of the invention have been set forth and described herein, many modifications, substitutions, variations, and equivalents will now occur to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and variations that fall within the true scope of the invention.

Claims

1. A method for preparing a high-stability, high-energy-product rare-earth permanent magnet material, characterized in that, Includes the following steps: S1: The main alloy powder is prepared using three processes: rapid solidification casting, hydrogen explosion, and air jet milling. The main alloy comprises, by weight percentage: Nd 10%–13%, La 1%–2%, Co 0.4%–1%, B 4%–7%, and one or more selected from Cr, Al or Cu 0.2%–0.4%, with the balance being Fe and unavoidable impurities; S2: The grain boundary phase alloy is cast into an ingot using a casting process, and then prepared into grain boundary phase alloy powder using a mechanical ball milling process. The composition of the grain boundary phase alloy, expressed as an atomic percentage, is Ho. 100-u Ta u , 15≤u≤20; S3: The grain boundary phase alloy powder and nano zinc oxide powder are mixed evenly in a mixer under a protective medium to obtain a grain boundary phase alloy modified with nano zinc oxide, wherein the weight of the added nano zinc oxide powder accounts for 0.4% to 0.6% of the total powder weight; the average particle diameter of the nano zinc oxide powder is 70 to 80 nm. S4: The main alloy powder and the grain boundary phase alloy powder modified with nano zinc oxide are mixed evenly in a mixer under a protective medium to obtain a mixed powder; S5: The mixed powder is oriented and pressed in a magnetic field environment, and then pressed into a green body by cold isostatic pressing; S6: Sinter the green blank, perform a first-stage tempering, and then a second-stage tempering to obtain the high-stability, high-energy-product rare-earth permanent magnet material, NdFeB magnet. The maximum operating temperature of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 250°C. The intrinsic coercivity of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 34 kOe. The maximum magnetic energy product of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 55 MGSOe.

2. The method for preparing the high-stability, high-energy-product rare-earth permanent magnet material according to claim 1, characterized in that, The average particle diameter of the nano zinc oxide powder is 75 nm.

3. The method for preparing the high-stability, high-energy-product rare-earth permanent magnet material according to claim 1, characterized in that, The main alloy comprises, by weight percentage: Nd 10.3%–12.5%, La 1.2%–1.5%, Co 0.5%–0.7%, B 4.62%–6.2%, and one or more selected from Cr, Al or Cu 0.25%–0.3%, with the balance being Fe and unavoidable impurities.

4. The method for preparing the high-stability, high-energy-product rare-earth permanent magnet material according to any one of claims 1-3, characterized in that, The main alloy comprises, by weight percentage: Nd 10.3%, La 1.2%, Co 0.5% and B 6.1%, Nd 11.6%, La 1.5%, Co 0.53%, B 4.62% and Cr 0.25%, Nd 12.5%, La 1.2%, Co 0.7%, B 6.2% and Al 0.3%, Nd 12.5%, La 1.2%, Co 0.7%, B 6.2% and Al 0.3%, or Nd 12.5%, La 1.2%, Co 0.7%, B 6.2% and Al 0.3%, And the remainder of Fe and unavoidable impurities.

5. The method for preparing the high-stability, high-energy-product rare-earth permanent magnet material according to any one of claims 1-3, characterized in that, In step S3, the weight of the added nano zinc oxide powder accounts for 0.4%, 0.5%, or 0.6% of the total powder weight. 15.7≤u≤18.5 6. The method for preparing the high-stability, high-energy-product rare-earth permanent magnet material according to claim 4, characterized in that, u＝18.5； In step S3, the weight of the added nano zinc oxide powder accounts for 0.5% of the total powder weight.

7. The method for preparing the high-stability, high-energy-product rare-earth permanent magnet material according to claim 4, characterized in that, In step S5, the mixed powder is oriented and pressed under a magnetic field of 1.5 to 3T; In step S5, the pressing pressure is 140-250 MPa; In step S5, the pressing time is 50-200 seconds; In step S6, the sintering temperature is 800–1050°C; In step S6, the sintering time is 1.5 to 7.5 hours; In step S6, the tempering conditions include: performing a first-stage tempering at 850℃~920℃ and holding it for 2.5~5 hours, followed by a second-stage tempering at 510℃~590℃ and holding it for 3~5 hours.

8. The method for preparing the high-stability, high-energy-product rare-earth permanent magnet material according to any one of claims 1-3, characterized in that, The maximum operating temperature of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 250°C and less than 275°C. The remanent magnetic properties of the high-stability, high-energy-product rare-earth permanent magnet material are greater than or equal to 14.5 kGs and less than 15.2 kGs. The intrinsic coercivity of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 34 kOe and less than 36 kOe. The maximum magnetic energy product of the high-stability, high-energy-product rare-earth permanent magnet material is greater than or equal to 55 MGsOe and less than 58 MGsOe.

9. A high-stability, high-energy-product rare-earth permanent magnet material, characterized in that, It is prepared using the preparation method of high-stability, high-energy-product rare-earth permanent magnet material as described in any one of claims 1-8.

10. The application of the high-stability, high-energy-product rare-earth permanent magnet material as described in claim 9 as a magnetic device.

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