A low cost magnet and method of making the same

Abstract

This application discloses a neodymium iron boron magnet, which comprises the following components: R: 28-33 wt%, B: 0.85-0.94 wt%, Co: 0.05-0.6 wt%, Cu: 0.05-0.5 wt%, Ga: 0.3-0.6 wt%, M1: 0.05-1.1 wt%, M2: 0.1-0.5 wt%, Fe: 63.2-69 wt%; wherein R is a rare earth element, R includes at least PrNd, and R The NdFeB magnet comprises R1, selected from one or both of Gd and Ce; M1 selected from at least one element of Al and Sn; M2 selected from at least one element of Zr, Ti, and Nb; the NdFeB magnet comprises a main phase grain, a thin-layer grain boundary phase, and a triangular grain boundary phase, wherein the distribution of the triangular grain boundary phase satisfies the following condition: the area of ​​all triangular grain boundary phases within the cross-section of the NdFeB magnet accounts for 6% to 8.5% of the total area of ​​the cross-section; the triangular grain boundary phase includes R6T. 13 Phase M1, where M is selected from one or more of Al, Cu, Ga, Ti, Sn, Zr, and Nb, T is selected from one or two of Fe and Co, and R6T 13 The ratio of the atomic percentage of R1 to the atomic percentage of R in the M1 phase, R1 / R, is 6.0% to 9.0%.

Description

Technical Field

[0001] This application relates to the field of magnetic materials. More specifically, this application relates to a low-cost magnet and a method for preparing the same. Background Technology

[0002] Since their invention, rare earth magnetic materials have been widely used in industries such as energy, transportation, machinery, medical devices, and home appliances due to their excellent magnetic properties, and their products are involved in many sectors of the national economy. Currently, the rapid development of electric vehicles, wind power generation, and other fields is leading to a growing demand for improved permanent magnet performance.

[0003] As a rare-earth magnetic material, neodymium iron boron (NdFeB) sintered magnets are among the most important permanent magnets. Since many applications of NdFeB sintered magnets operate in high-temperature environments, they require not only high remanence but also high coercivity. Coercivity is a key parameter of permanent magnet materials; higher coercivity indicates stronger resistance to demagnetization. In applications, not only is high coercivity desirable for NdFeB sintered magnets, but good temperature stability is also essential for operation at high temperatures. Common methods to improve the coercivity of NdFeB sintered magnets include replacing Nd with heavy rare-earth elements Dy and Tb. However, Dy and Tb are scarce and expensive, and their addition can reduce the remanence of the magnet. Furthermore, Dy and Tb are susceptible to fluctuations in rare-earth policies, potentially leading to price instability or significant volatility.

[0004] Therefore, obtaining rare-earth permanent magnets with good remanence, coercivity, and squareness consistency while reducing the amount of heavy rare-earth elements added is an urgent problem to be solved in this field. Furthermore, with increasing market competition, it is also pressing to further reduce the amount of light rare-earth elements (PrNd) used without adding heavy rare-earth elements. Summary of the Invention

[0005] In order to at least solve one or more of the technical problems mentioned above, this application proposes solutions to improve the prior art in several aspects.

[0006] According to one aspect of this application, a neodymium iron boron magnet is provided, wherein the neodymium iron boron magnet comprises the following components:

[0007] R: 28-33 wt%,

[0008] B: 0.85~0.94wt%,

[0009] Co: 0.05~0.6wt%,

[0010] Cu: 0.05–0.5 wt%,

[0011] Ga: 0.3–0.6 wt%,

[0012] M1: 0.05~1.1wt%,

[0013] M2: 0.1~0.5wt%,

[0014] Fe: 63.2–69 wt%;

[0015] Wherein, R is a rare earth element, R includes at least PrNd, and R includes R1;

[0016] R1 is selected from one or both of Gd and Ce;

[0017] M1 is selected from at least one element of Al and Sn;

[0018] M2 is selected from at least one element among Zr, Ti and Nb;

[0019] The neodymium iron boron magnet comprises a main phase grain, a thin-layer grain boundary phase, and a triangular grain boundary phase. The distribution of the triangular grain boundary phase satisfies the following condition: the area of ​​all triangular grain boundary phases within the cross-section of the neodymium iron boron magnet accounts for 6% to 8.5% of the total cross-sectional area; the triangular grain boundary phase includes R6T... 13 Phase M1, where M is selected from one or more of Al, Cu, Ga, Ti, Sn, Zr, and Nb, T is selected from one or two of Fe and Co, and R6T 13 The ratio of the atomic percentage of R1 to the atomic percentage of R in the M1 phase, R1 / R, is 6.0% to 9.0%.

[0020] According to one embodiment of this application, the content of R is 29.5 to 33 wt%, and R does not include Dy and Tb.

[0021] According to one embodiment of this application, the neodymium iron boron magnet comprises at least one of the following characteristics:

[0022] a.Cu: 0.25–0.5 wt%;

[0023] b.Al: 0.5–1.1 wt%;

[0024] c.Ga: 0.3–0.45 wt%;

[0025] d.Ti: 0.15–0.3 wt%.

[0026] According to one embodiment of this application, the content of R1 is 3 to 7 wt%.

[0027] According to one embodiment of this application, the distribution of the triangular grain boundary phase satisfies the following condition: the area of ​​all triangular grain boundary phases within the cross-section of the NdFeB magnet accounts for 7% to 8.5% of the total area of ​​the cross-section; preferably, the triangular grain boundary phase includes R6T. 13 M1 phase, the R6T 13 The distribution of the M1 phase satisfies the following condition: all R6T phases within the cross-section of the neodymium iron boron magnet... 13 The area of ​​the M1 phase accounts for 5.5% to 7% of the total cross-sectional area, preferably 6% to 7%.

[0028] According to one embodiment of this application, the triangular region grain boundary phase of the neodymium iron boron magnet includes at least one of the following characteristics:

[0029] a. The triangular grain boundary phase includes an Fe-rich high-M phase, and the ratio of the atomic percentage of R1 to the atomic percentage of R in the Fe-rich high-M phase, R1 / R, is 4.0% to 11.0%, preferably 4.0% to 9.0%.

[0030] b. The triangular grain boundary phase includes R6T 13 M1 phase, and R6T 13 The ratio of the atomic percentage of R1 to the atomic percentage of R in the M1 phase, R1 / R, is 6.0% to 8.5%.

[0031] c. The triangular grain boundary phase includes a Cu-rich phase, and the ratio of the atomic percentage of R1 to the atomic percentage of R in the Cu-rich phase, R1 / R, is 4.0% to 6.5%, preferably 4.0% to 6.0%.

[0032] According to another aspect of this application, this application provides a method for preparing a neodymium iron boron magnet, comprising:

[0033] 1) The pre-configured raw material alloy is processed into rapidly solidified alloy sheets using a rapid solidification process;

[0034] 2) The rapidly solidified alloy sheet obtained in step 1) is hydrogen-milled, and after adding additives, it is subjected to air jet milling to obtain alloy powder. The average particle size D50 of the alloy powder is 3 to 5 μm.

[0035] 3) Press the alloy powder obtained in step 2) into a compact under magnetic field orientation with a magnetic field strength of 1.4-2.5T to obtain a compact, or obtain a compact through a second isostatic pressing treatment;

[0036] 4) Place the pressed blank obtained in step 3) into a sintering furnace and sinter and age it in a vacuum or inert atmosphere to finally obtain a neodymium iron boron magnet;

[0037] The aging process is a three-stage aging process: the first stage aging temperature is 800-950℃, and the holding time is 0.5-4h; the second stage aging temperature is 450-550℃, and the holding time is 2-10h; the third stage aging temperature is 600-700℃, and the holding time is 2-10h.

[0038] According to one embodiment of this application, in step 4), the aging process further includes: cooling to 150-250°C after the second aging stage, with a cooling rate of 3-8°C / min; and cooling to room temperature after the third aging stage, with a cooling rate of 3-8°C / min.

[0039] According to one embodiment of this application, in step 1), the rapid solidification process includes melting the alloy raw material in a vacuum induction melting furnace at a melting temperature of 1400-1500℃, and casting the molten liquid onto a copper roller to obtain a rapid solidification alloy sheet of 0.15-0.4mm.

[0040] According to one embodiment of this application, in step 4), the sintering process parameters include: a sintering temperature of 1030–1120°C and a sintering time of 4–12 h, preferably 6–12 h. Attached Figure Description

[0041] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein:

[0042] Figure 1 A scanning electron microscope image of a cross-section of the magnet of Embodiment 1 of this application is shown;

[0043] Figure 2 A scanning electron microscope image of a cross-section of the magnet in Comparative Example 1 of this application is shown. Detailed Implementation

[0044] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0045] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0046] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0047] The specific embodiments of this application are described in detail below with reference to the accompanying drawings. Unless otherwise specified, the materials, reagents and equipment used in the embodiments of this application are obtained through conventional commercial channels.

[0048] In a first aspect, this application provides a neodymium iron boron magnet, wherein the neodymium iron boron magnet comprises the following components:

[0049] R: 28-33 wt%,

[0050] B: 0.85~0.94wt%,

[0051] Co: 0.05~0.6wt%,

[0052] Cu: 0.05–0.5 wt%,

[0053] Ga: 0.3–0.6 wt%,

[0054] M1: 0.05~1.1wt%,

[0055] M2: 0.1~0.5wt%,

[0056] Fe: 63.2–69 wt%;

[0057] Wherein, R is a rare earth element, R includes at least PrNd, and R includes R1;

[0058] R1 is selected from one or both of Gd and Ce;

[0059] M1 is selected from at least one element of Al and Sn;

[0060] M2 is selected from at least one element among Zr, Ti and Nb;

[0061] The neodymium iron boron magnet comprises a main phase grain, a thin-layer grain boundary phase, and a triangular grain boundary phase. The distribution of the triangular grain boundary phase satisfies the following condition: the area of ​​all triangular grain boundary phases within the cross-section of the neodymium iron boron magnet accounts for 6% to 8.5% of the total cross-sectional area; the triangular grain boundary phase includes R6T... 13 Phase M1, where M is selected from one or more of Al, Cu, Ga, Ti, Sn, Zr, and Nb, T is selected from one or two of Fe and Co, and R6T 13 The ratio of the atomic percentage of R1 to the atomic percentage of R in the M1 phase, R1 / R, is 6.0% to 9.0%.

[0062] The technical solution of this application embodiment, by adding Gd or Ce to replace part of the light rare earth elements Pr and Nd, while controlling the content of elements such as B, Cu, and Ga, and combining this with a three-stage aging process in the alloy preparation process, significantly increases the area ratio of the triangular region grain boundary phase in the magnet, and further enhances the R6T... 13 The area ratio of the M1 phase is also increased to a certain extent, thereby enabling precise control of the intergranular structure of the NdFeB magnet. The prepared NdFeB magnet has the advantage of low cost on the one hand, and high remanence, coercivity and squareness on the other hand.

[0063] In some embodiments, the content of R is 29.5–33 wt%, and R does not include Dy and Tb. Exemplarily, the content of R can be 29.5 wt%, 30.0 wt%, 30.5 wt%, 31.0 wt%, 31.5 wt%, 32.0 wt%, 32.5 wt%, 33.0 wt%, or any value within the range of any of the above values. As described above, this application effectively and precisely adjusts the intergranular structure of NdFeB magnets by adding Gd or Ce and controlling the content of other elements, so that the composition of NdFeB magnets does not require the addition of high-cost heavy rare earth elements Dy and Tb.

[0064] In some embodiments, the content of R1 is 3 to 7 wt%. Exemplarily, the content of R1 can be 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, 5.5 wt%, 6.0 wt%, 6.5 wt%, 7.0 wt%, or any value within the range of any of the above values.

[0065] In some embodiments, the neodymium iron boron magnet comprises Cu: 0.25–0.5 wt%. Exemplarily, the Cu content can be 0.25 wt%, 0.28 wt%, 0.30 wt%, 0.32 wt%, 0.35 wt%, 0.38 wt%, 0.40 wt%, 0.42 wt%, 0.45 wt%, 0.48 wt%, 0.50 wt%, or any value within the range of any of the above values.

[0066] In some embodiments, the neodymium iron boron magnet comprises Al: 0.5 to 1.1 wt%. Exemplarily, the Al content can be 0.50 wt%, 0.55 wt%, 0.60 wt%, 0.65 wt%, 0.70 wt%, 0.75 wt%, 0.80 wt%, 0.85 wt%, 0.90 wt%, 0.95 wt%, 1.00 wt%, 1.05 wt%, 1.10 wt%, or any value within the range of any of the above values.

[0067] In some embodiments, the neodymium iron boron magnet comprises Ga: 0.3 to 0.45 wt%. Exemplarily, the Ga content can be 0.30 wt%, 0.32 wt%, 0.35 wt%, 0.38 wt%, 0.40 wt%, 0.42 wt%, 0.45 wt%, or any value within the range of any of the above values.

[0068] In some embodiments, the neodymium iron boron magnet comprises Ti: 0.15 to 0.3 wt%. Exemplarily, the Ti content can be 0.15 wt%, 0.18 wt%, 0.20 wt%, 0.22 wt%, 0.25 wt%, 0.28 wt%, 0.30 wt%, or any value within the range of any of the above values.

[0069] In some embodiments, the distribution of the triangular grain boundary phases satisfies the following condition: the percentage of the area of ​​all triangular grain boundary phases within the cross-section of the NdFeB magnet to the total area of ​​the cross-section is 7% to 8.5%. Exemplarily, the percentage of the area of ​​all triangular grain boundary phases within the cross-section of the NdFeB magnet to the total area of ​​the cross-section can be 7%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, or any value within the range of any of the above values.

[0070] In some embodiments, the triangular grain boundary phase includes R6T. 13 M1 phase, the R6T 13 The distribution of the M1 phase satisfies the following condition: all R6T phases within the cross-section of the neodymium iron boron magnet...13 The area of ​​the M1 phase accounts for 5.5% to 7% of the total cross-sectional area, preferably 6% to 7%. For example, the percentage of the area of ​​all R6T13M1 phases within the cross-section of the neodymium iron boron magnet to the total cross-sectional area can be 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, or any value within the range of any of the above values.

[0071] In some embodiments, the triangular region grain boundary phase of the NdFeB magnet comprises an Fe-rich high-M phase, and the ratio of the atomic percentage of R1 to the atomic percentage of R in the Fe-rich high-M phase, R1 / R, is 4.0% to 11.0%, preferably 4.0% to 9.0%. Exemplarily, the R1 / R ratio in the Fe-rich high-M phase is 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, or any value within the range of any of the above values.

[0072] The Fe-rich, M-rich phase includes R, M, and Fe, where R refers to all rare earth elements, including R1, which is selected from Gd and / or Ce; wherein the atomic percentage of Fe is greater than 40%, and the atomic percentage of M is greater than 6%.

[0073] The Cu-rich phase includes R and Cu, with an atomic percentage of Cu greater than 15%.

[0074] In some embodiments, the triangular region grain boundary phase of the NdFeB magnet includes R6T. 13 M1 phase, and R6T 13 In the M1 phase, the ratio of the atomic percentage of R1 to the atomic percentage of R, R1 / R, is 6.0% to 8.5%. For example, R6T... 13 The R1 / R ratio in phase M1 is 6.0%, 6.2%, 6.5%, 6.8%, 7.0%, 7.2%, 7.5%, 7.8%, 8.0%, 8.2%, 8.5%, or any value within the range of any of the above values.

[0075] In some embodiments, the triangular region grain boundary phase of the NdFeB magnet comprises a Cu-rich phase, and the ratio of the atomic percentage of R1 to the atomic percentage of R in the Cu-rich phase, R1 / R, is 4.0% to 6.5%, preferably 4.0% to 6.0%. Exemplarily, the R1 / R ratio in the Cu-rich phase is 4.0%, 4.2%, 4.5%, 4.8%, 5.0%, 5.2%, 5.5%, 5.8%, 6.0%, or any value within the range of any of the above values.

[0076] Secondly, this application also provides a method for preparing a neodymium iron boron magnet, comprising:

[0077] 1) The pre-configured raw material alloy is processed into rapidly solidified alloy sheets using a rapid solidification process;

[0078] 2) The rapidly solidified alloy sheet obtained in step 1) is hydrogen-milled, and after adding additives, it is subjected to air jet milling to obtain alloy powder. The average particle size D50 of the alloy powder is 3 to 5 μm.

[0079] 3) Press the alloy powder obtained in step 2) into a compact under magnetic field orientation with a magnetic field strength of 1.4-2.5T to obtain a compact, or obtain a compact through a second isostatic pressing treatment;

[0080] 4) Place the pressed blank obtained in step 3) into a sintering furnace and sinter and age it in a vacuum or inert atmosphere to finally obtain a neodymium iron boron magnet;

[0081] The aging process is a three-stage aging process: the first stage aging temperature is 800-950℃, and the holding time is 0.5-4h; the second stage aging temperature is 450-550℃, and the holding time is 2-10h; the third stage aging temperature is 600-700℃, and the holding time is 2-10h.

[0082] After adding R1 element to the technical solution of this application embodiment, if only the content of other elements is adjusted, and the three-stage aging process is not adopted, the proportion of R1 element in the grain boundary phase and rare earth elements may be relatively high, thus failing to reduce the R1 / R ratio in the grain boundary phase. However, after adopting the above-mentioned three-stage aging process, the proportion of Pr and Nd elements in the rare earth elements in the grain boundary phase can be effectively increased, and the proportion of R1 element in the rare earth elements in the grain boundary phase can be reduced. The change in the above proportion is beneficial to the demagnetizing coupling effect, thereby improving the coercivity, remanence and squareness of the magnet.

[0083] In some embodiments, in step 1), the composition ratio of the predetermined raw material alloy is based on the composition of the neodymium iron boron magnet of the first aspect of this application.

[0084] In some embodiments, in the three-stage aging process, the temperature of the first stage of aging is 800–950°C, and the holding time is 0.5–4 hours. Exemplarily, the temperature of the first stage of aging is 800°C, 820°C, 850°C, 880°C, 900°C, 920°C, 950°C, or any value within the range of any of the above values. Exemplarily, the holding time of the first stage of aging is 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or any value within the range of any of the above values.

[0085] In some embodiments, in the three-stage aging process, the temperature of the second-stage aging is 450–550°C, and the holding time is 2–10 hours. Exemplarily, the temperature of the second-stage aging is 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, or any value within the range of any of the above values. Exemplarily, the holding time of the second-stage aging is 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or any value within the range of any of the above values.

[0086] In some embodiments, in the three-stage aging process, the temperature of the third aging stage is 600–700°C, and the holding time is 2–10 hours. Exemplarily, the temperature of the third aging stage is 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, or any value within the range of any of the above values. Exemplarily, the holding time of the third aging stage is 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or any value within the range of any of the above values.

[0087] In some embodiments, step 4) of the aging process further includes: cooling to 150–250°C after the second-stage aging at a cooling rate of 3–8°C / min; and cooling to room temperature after the third-stage aging at a cooling rate of 3–8°C / min. Exemplarily, the cooling rate after the second-stage aging can be 3.0°C / min, 3.5°C / min, 4.0°C / min, 4.5°C / min, 5.0°C / min, 5.5°C / min, 6.0°C / min, 6.5°C / min, 7.0°C / min, 7.5°C / min, 8.0°C / min, or any value within the range of any of the above values. For example, the cooling rate after the third stage of aging can be 3.0℃ / min, 3.5℃ / min, 4.0℃ / min, 4.5℃ / min, 5.0℃ / min, 5.5℃ / min, 6.0℃ / min, 6.5℃ / min, 7.0℃ / min, 7.5℃ / min, 8.0℃ / min, or any value within the range of any of the above values.

[0088] In some embodiments, step 1) of the rapid solidification process includes melting the alloy raw material in a vacuum induction melting furnace at a melting temperature of 1400-1500°C, and casting the molten liquid onto a copper roller to obtain a rapidly solidified alloy sheet of 0.15-0.4 mm. Exemplarily, the melting temperature can be 1400°C, 1410°C, 1420°C, 1430°C, 1440°C, 1450°C, 1460°C, 1470°C, 1480°C, 1490°C, 1500°C, or any value within the range of any of the above values.

[0089] In some embodiments, in step 4), the sintering process parameters include: a sintering temperature of 1030–1120°C and a sintering time of 4–12 h, preferably 6–12 h. Exemplarily, the sintering temperature is 1030°C, 1040°C, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C, 1100°C, 1110°C, 1120°C, or any value within the range of any of the above values. Exemplarily, the sintering time is 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, or any value within the range of any of the above values. Specific Implementation

[0091] Example 1

[0092] Magnet formula:

[0093]

[0094] 1) Casting rapidly solidified alloy sheets using the alloy raw materials prepared according to the above formula: Melt the alloy raw materials in a vacuum induction melting furnace at a melting temperature of 1500℃, and pour the molten liquid onto a copper roller to obtain rapidly solidified alloy sheets of 0.25mm.

[0095] 2) The rapidly solidified alloy sheets were subjected to hydrogen crushing and micronization to obtain raw alloy powder. The hydrogen crushing was carried out at a hydrogen absorption pressure of 0.3 MPa and a dehydrogenation temperature of 560℃. Micronization was carried out in an air jet mill at a grinding pressure of 0.68 MPa. The average particle size D50 of the raw alloy powder was 4 μm.

[0096] 3) Molding treatment of raw alloy powder: The alloy powder obtained in step 2) is pressed into shape under magnetic field orientation with a magnetic field strength of 1.5T to obtain a pressed blank.

[0097] 4) Place the pressed blank obtained in step 3) into a sintering furnace and perform sintering and aging treatment in a vacuum or inert atmosphere to finally obtain neodymium iron boron magnets.

[0098] The parameters for the sintering process are: sintering temperature of 1060℃ and sintering time of 8 hours.

[0099] The aging process employs a three-stage aging process: a first-stage aging process is performed by heating to 900°C at 7°C / min for 2 hours, followed by cooling to 200°C, then a second-stage aging process is performed by heating to 500°C at 5°C / min for 6 hours, followed by cooling to 200°C, then a third-stage aging process is performed by heating to 630°C at 5°C / min for 6 hours, and finally cooling to room temperature to obtain the final magnet.

[0100] Example 2

[0101] The same magnet formulation as in Example 1 was used, and the preparation steps were the same as in Example 1 except for the aging treatment.

[0102] The only difference is that the aging process adopts a conventional two-stage aging process: the aging process includes a first-stage aging process and a second-stage aging process. The temperature of the first-stage aging process is 890℃ and the holding time is 4h; the temperature of the second-stage aging process is 500℃ and the holding time is 8h, to obtain neodymium iron boron magnets.

[0103] Example 3

[0104] A different magnet formulation was used than in Example 1, but the preparation steps were the same as in Example 1, except for the magnet formulation.

[0105] Magnet formula:

[0106]

[0107] Example 4

[0108] The same magnet formulation as in Example 3 was used, and the preparation steps were the same as in Example 3 except for the aging treatment.

[0109] The specific aging process is a two-stage aging process: the aging process includes a first-stage aging process and a second-stage aging process. The temperature of the first-stage aging process is 880℃ and the holding time is 4h; the temperature of the second-stage aging process is 550℃ and the holding time is 8h, to obtain neodymium iron boron magnets.

[0110] Example 5

[0111] A different magnet formulation was used than in Example 1, but the preparation steps were the same as in Example 1, except for the magnet formulation.

[0112] Magnet formula:

[0113]

[0114] Comparative Example 1

[0115] A different magnet formulation was used than in Example 1, but the preparation steps were the same as in Example 1, except for the magnet formulation.

[0116] Magnet formula:

[0117]

[0118] The testing methods used in this application are as follows:

[0119] Microstructural testing methods:

[0120] Scanning electron microscopy (SEM) was performed on at least 10 cross-sections of the magnet perpendicular to the orientation direction. The area of ​​all triangular grain boundary phases within each cross-section was statistically analyzed, and the percentage of the area of ​​all triangular grain boundary phases within each cross-section to the total area of ​​that cross-section was calculated. The average value of all cross-sections was then taken as the percentage of the area of ​​all triangular grain boundary phases within the cross-section of the NdFeB magnet to the total area of ​​that cross-section. The size of the observation area was, for example, 40 μm × 40 μm and 75 μm × 75 μm; the magnification was 2000–5000 times. Similarly, the percentage of the area of ​​all R6T13M1 phases within the cross-section of the NdFeB magnet to the total area of ​​that cross-section could also be obtained using a similar method. Figure 1 and Figure 2 As shown, the triangular region grain boundary phase marked by △ is R6T. 13 M1 phase, the triangular region marked with ◇ is a Fe-rich high M phase; the triangular region marked with ○ is a Cu-rich phase. The compositional analysis of each grain boundary phase yielded the test results.

[0121] The magnetic properties of the magnet were measured using a BH curve measuring instrument (NIM-200).

[0122] The magnetic performance test data of Examples 1-5 and Comparative Example 1 are as follows:

[0123]

[0124] The microstructural test results of Examples 1-5 are as follows:

[0125] Example 1: Neodymium iron boron magnets include main phase grains, thin-layer grain boundary phases, and triangular grain boundary phases. Thin-layer grain boundary phases refer to the grain boundary phases formed between two adjacent main phase grains, while triangular grain boundary phases refer to the grain boundary phases surrounded by three or more main phase grains.

[0126] The area of ​​all triangular grain boundary phases within the cross-section of the neodymium iron boron magnet accounts for 7.3% of the total cross-sectional area. The triangular grain boundary phases include R6T… 13 M1 phase, all R6T within the cross-section of the neodymium iron boron magnet 13 The area of ​​phase M1 accounts for 6.25% of the total area of ​​the cross section.

[0127] The triangular grain boundary phase includes a Fe-rich high-M phase, and the Gd / R ratio in the Fe-rich high-M phase is 5.2%.

[0128] Triangular grain boundary phases include R6T 13 M1 phase, R6T 13 The Gd / R ratio in the M1 phase is 7.92%.

[0129] The triangular grain boundary phase also includes a Cu-rich phase, and the Gd / R ratio in the Cu-rich phase is 4.5%.

[0130] Example 2: Neodymium iron boron magnets include main phase grains, thin-layer grain boundary phases, and triangular grain boundary phases. Thin-layer grain boundary phases refer to the grain boundary phases formed between two adjacent main phase grains, while triangular grain boundary phases refer to the grain boundary phases surrounded by three or more main phase grains.

[0131] The area of ​​all triangular grain boundary phases within the cross-section of the neodymium iron boron magnet accounts for 6.22% of the total cross-sectional area. The triangular grain boundary phases include R6T... 13 M1 phase, all R6T within the cross-section of the neodymium iron boron magnet 13 The area of ​​phase M1 accounts for 5.60% of the total area of ​​the cross section.

[0132] The triangular grain boundary phase includes a Fe-rich high-M phase, and the Gd / R ratio in the Fe-rich high-M phase is 10.11%.

[0133] Example 3: Neodymium iron boron magnets include main phase grains, thin-layer grain boundary phases, and triangular grain boundary phases. Thin-layer grain boundary phases refer to the grain boundary phases formed between two adjacent main phase grains, while triangular grain boundary phases refer to the grain boundary phases surrounded by three or more main phase grains.

[0134] The area of ​​all triangular grain boundary phases within the cross-section of the neodymium iron boron magnet accounts for 7.11% of the total cross-sectional area. The triangular grain boundary phases include R6T... 13 M1 phase, all R6T within the cross-section of the neodymium iron boron magnet 13 The area of ​​phase M1 accounts for 6.10% of the total area of ​​the cross section.

[0135] Triangular grain boundary phases include R6T 13 M1 phase, R6T 13 The Gd / R ratio in the M1 phase is 8.63%.

[0136] The triangular grain boundary phase also includes a Cu-rich phase, and the Gd / R ratio in the Cu-rich phase is 6.21%.

[0137] The triangular grain boundary phase includes a Fe-rich high-M phase, and the Gd / R ratio in the Fe-rich high-M phase is 8.80%.

[0138] Example 4: Neodymium iron boron magnets include main phase grains, thin-layer grain boundary phases, and triangular grain boundary phases. Thin-layer grain boundary phases refer to the grain boundary phases formed between two adjacent main phase grains, while triangular grain boundary phases refer to the grain boundary phases surrounded by three or more main phase grains.

[0139] The area of ​​all triangular grain boundary phases within the cross-section of the neodymium iron boron magnet accounts for 6.50% of the total cross-sectional area. The triangular grain boundary phases include R6T… 13 M1 phase, all R6T within the cross-section of the neodymium iron boron magnet 13 The area of ​​phase M1 accounts for 5.64% of the total area of ​​the cross section.

[0140] Triangular grain boundary phases include R6T 13 M1 phase, R6T 13 The Gd / R ratio in the M1 phase is 8.81%.

[0141] Example 5: Neodymium iron boron magnets include main phase grains, thin-layer grain boundary phases, and triangular grain boundary phases. Thin-layer grain boundary phases refer to the grain boundary phases formed between two adjacent main phase grains, while triangular grain boundary phases refer to the grain boundary phases surrounded by three or more main phase grains.

[0142] The area of ​​all triangular grain boundary phases within the cross-section of the neodymium iron boron magnet accounts for 6.10% of the total cross-sectional area. The triangular grain boundary phases include R6T… 13 M1 phase, all R6T within the cross-section of the neodymium iron boron magnet 13 The area of ​​phase M1 accounts for 5.50% of the total area of ​​the cross section.

[0143] The triangular grain boundary phase also includes a Cu-rich phase, and the Gd / R ratio in the Cu-rich phase is 6.00%.

[0144] The triangular grain boundary phase includes a Fe-rich high-M phase, and the Gd / R ratio in the Fe-rich high-M phase is 4.2%.

[0145] Comparative Example 1: Neodymium iron boron magnets include main phase grains, thin-layer grain boundary phases, and triangular grain boundary phases. Thin-layer grain boundary phases refer to the grain boundary phases formed between two adjacent main phase grains, while triangular grain boundary phases refer to the grain boundary phases surrounded by three or more main phase grains.

[0146] The area of ​​all triangular grain boundary phases within the cross-section of the neodymium iron boron magnet accounts for 5.20% of the total cross-sectional area. The triangular grain boundary phases include R6T... 13 M1 phase, all R6T within the cross-section of the neodymium iron boron magnet 13 The area of ​​phase M1 accounts for 5.12% of the total area of ​​the cross section, R6T 13 The ratio of the atomic percentage of R1 to the atomic percentage of R in the M1 phase, R1 / R, is 9.2%.

[0147] The technical solution of this application adds Gd or Ce to partially replace the light rare earth elements Pr and Nd. In systems with low B content, adjusting the distribution of Gd or Ce in the grain boundary phase after adding a certain amount of Gd or Ce is one of the key factors in this application. Furthermore, the inventors discovered that Gd tends to enter the triangular grain boundary phase with higher Fe content in the intergranular phase. Therefore, by adjusting the content of elements such as Cu and Ga combined with a three-stage tempering process, the technical solution of this application can precisely control the proportion of Gd in the triangular grain boundary phase, reduce the Gd / R value in the Fe-rich, high-M phase, and reduce R6T. 13 The Gd / R value in the M1 phase decreases the Gd / R value in the Cu-rich phase, thereby increasing the proportion of Pr and Nd elements in each phase. This increase in proportion is beneficial to the demagnetizing coupling effect, thus producing magnets with good coercivity, remanence and squareness.

[0148] While numerous embodiments of this application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of this application. It should be understood that various alternatives to the embodiments of this application described herein may be employed in the practice of this application. The appended claims are intended to define the scope of protection of this application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A neodymium iron boron magnet, characterized in that, The neodymium iron boron magnet contains the following components: R: 28~33wt%, B: 0.85~0.94wt%, Co: 0.05~0.6wt%, Cu: 0.25~0.5wt%, Ga: 0.3~0.45 wt%, M1: 0.05~1.1wt%, M2: 0.1~0.5 wt%, Fe: 63.2~69 wt%; Wherein, R is a rare earth element, R includes at least PrNd, the content of PrNd is ≤28.5wt%, and R includes R1, R1 is Gd, the content of R1 is 3~7 wt%, and R does not include Dy and Tb; M1 is selected from at least one element of Al and Sn; M2 is selected from at least one element among Zr, Ti and Nb; The neodymium iron boron magnet comprises a main phase grain, a thin layer of grain boundary phase, and a triangular grain boundary phase. The distribution of the triangular grain boundary phase satisfies the following condition: the area of ​​all triangular grain boundary phases within the cross-section of the neodymium iron boron magnet accounts for 6% to 8.5% of the total cross-sectional area; the triangular grain boundary phase includes R6T... 13 Phase M1, where M is selected from one or more of Al, Cu, Ga, Ti, Sn, Zr, and Nb, T is selected from one or two of Fe and Co, and R6T 13 The ratio of the atomic percentage of R1 to the atomic percentage of R in the M1 phase, R1 / R, is 6.0% to 9.0%; the triangular grain boundary phase also includes a Fe-rich high-M phase, and the ratio of the atomic percentage of R1 to the atomic percentage of R in the Fe-rich high-M phase, R1 / R, is 4.0% to 11.0%.

2. The neodymium iron boron magnet according to claim 1, characterized in that, The content of R is 29.5~33 wt%.

3. The neodymium iron boron magnet according to claim 1 or 2, characterized in that, The composition of the neodymium iron boron magnet includes at least one of the following characteristics: a. Al: 0.5~1.1 wt% b. Ti: 0.15~0.3wt%.

4. The neodymium iron boron magnet according to claim 1 or 2, characterized in that, The distribution of the triangular grain boundary phase satisfies the following condition: the area of ​​all triangular grain boundary phases in the cross section of the NdFeB magnet accounts for 7% to 8.5% of the total area of ​​the cross section.

5. The neodymium iron boron magnet according to claim 4, characterized in that, The triangular region grain boundary phase includes R6T. 13 M1 phase, the R6T 13 The distribution of the M1 phase satisfies the following condition: all R6T phases within the cross-section of the neodymium iron boron magnet... 13 The area of ​​phase M1 accounts for 5.5% to 7% of the total area of ​​the cross section.

6. The neodymium iron boron magnet according to claim 5, characterized in that, All R6T within the cross-section of the neodymium iron boron magnet 13 The area of ​​phase M1 accounts for 6% to 7% of the total area of ​​the cross section.

7. The neodymium iron boron magnet according to claim 1 or 2, characterized in that, The triangular region grain boundary phase of the neodymium iron boron magnet includes at least one of the following characteristics: a. The ratio of the atomic percentage of R1 to the atomic percentage of R in the Fe-rich high-M phase, R1 / R, is 4.0%~9.0%; b. The triangular grain boundary phase includes R6T. 13 M1 phase, and R6T 13 The ratio of the atomic percentage of R1 to the atomic percentage of R in the M1 phase, R1 / R, is 6.0%~8.5%; c. The triangular grain boundary phase includes a Cu-rich phase, and the ratio of the atomic percentage of R1 to the atomic percentage of R in the Cu-rich phase, R1 / R, is 4.0% to 6.5%.

8. The neodymium iron boron magnet according to claim 7, characterized in that, The ratio of the atomic percentage of R1 to the atomic percentage of R in the Cu-rich phase, R1 / R, is 4.0% to 6.0%.

9. A method for preparing a neodymium iron boron magnet according to any one of claims 1-8, characterized in that, include: 1) The pre-configured raw material alloy is processed into rapidly solidified alloy sheets using a rapid solidification process; 2) The rapidly solidified alloy sheet obtained in step 1) is hydrogen-milled and then subjected to air jet milling with the addition of additives to obtain alloy powder. The average particle size D50 of the alloy powder is 3~5μm. 3) Press the alloy powder obtained in step 2) into a compact under magnetic field orientation with a magnetic field strength of 1.4-2.5T to obtain a compact, or obtain a compact through a second isostatic pressing treatment; 4) Place the pressed blank obtained in step 3) into a sintering furnace and sinter and age it in a vacuum or inert atmosphere to finally obtain a neodymium iron boron magnet; The aging process is a three-stage aging process: the first stage aging temperature is 800~950℃, and the holding time is 0.5~4h; the second stage aging temperature is 450~550℃, and the holding time is 2~10h; the third stage aging temperature is 600~700℃, and the holding time is 2~10h.

10. The preparation method according to claim 9, characterized in that, In step 4), the aging process further includes: cooling to 150~250℃ after the second aging, with a cooling rate of 3~8℃ / min; and cooling to room temperature after the third aging, with a cooling rate of 3~8℃ / min.

11. The preparation method according to claim 9 or 10, characterized in that, In step 1), the rapid solidification process includes melting the alloy raw materials in a vacuum induction melting furnace at a melting temperature of 1400-1500℃, and casting the molten liquid onto a copper roller to obtain a rapid solidification alloy sheet of 0.15-0.4mm.

12. The preparation method according to claim 9 or 10, characterized in that, In step 4), the sintering process parameters include: sintering temperature of 1030~1120℃ and sintering time of 4~12h.

13. The preparation method according to claim 12, characterized in that, The sintering time is 6~12h.

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