A dual-phase sintered NdFeB magnet and its preparation method and application

Abstract

The present invention discloses a dual-phase sintered NdFeB magnet and a preparation method and application. The main phase alloy and auxiliary phase alloy of the dual-phase sintered NdFeB magnet are sequentially processed by hydrogen breaking, airflow milling, and powder mixing methods; the hydrogen breaking method is: hydrogen absorption, and then vacuum dehydrogenation treatment is performed at 500-620°C to obtain a coarsely crushed powder; the airflow milling method is: the coarsely crushed powder obtained is finely crushed in an atmosphere with an oxygen content of less than 10ppm in the airflow mill to obtain an alloy fine powder with an average particle size of 2.0-4.5μm. The present invention increases the performance gap between the main phase and the auxiliary phase alloy by designing the composition of the dual main phases, and enhances the diffusion effect between the two. At the same time, by designing the particle size of the main phase and the auxiliary phase alloy, the diffusion efficiency between the grains is improved, and finally the "core-shell" structure has a higher anisotropy field, thereby improving the performance of the prepared magnet.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth permanent magnet material preparation, and in particular to a dual-main-phase sintered NdFeB magnet and a preparation method and application thereof. Background Art

[0002] The dual-main-phase method is a technology used to prepare rare earth permanent magnet materials. Its main purpose is to optimize its microstructure and magnetic properties by introducing two different main phases into the magnet. This method has significant advantages in improving the coercive force, remanence and maximum magnetic energy product of the magnet. In practical applications, the dual-main-phase method can effectively suppress the problem of reduced coercive force caused by the introduction of low anisotropic field phases such as cerium iron boron (Ce-Fe-B) and lanthanum iron boron (La-Fe-B). At the same time, it can also reduce the use of heavy rare earth resources and promote the sustainable development of the rare earth permanent magnet industry.

[0003] At present, the dual-main-phase method is one of the effective means to improve the performance of rare earth permanent magnets. Its core lies in improving the overall performance of the magnet by mixing two main-phase particles with different anisotropy fields. For example, by mixing (Nd, Ce)-Fe-B and (Nd, Ho, Gd, Dy)-Fe-B powders in a certain proportion, a grain structure with different intrinsic magnetism can be formed, thereby improving the coercivity and remanence; for example, in Ce-rich dual-main-phase magnets, rare earth elements diffuse between the two main-phase grains to form core-shell structure grains to enhance the coercivity. From the results reported in the article, after using the dual-main-phase method, under the condition of the same formula cost, Br and Hcj have a floating space of about 0.2kG and 1kOe respectively. Then, through component design, the goal of optimizing magnet performance or manufacturing cost can be achieved.

[0004] Although the dual-main-phase method can improve the performance of magnets to a certain extent, the changes in market demand for traditional automobiles, new energy vehicles, variable-frequency air conditioners, etc. have put forward new requirements for the performance, manufacturing cost and use of heavy rare earth resources of magnets. The traditional dual-main-phase method designs the composition of two powders. During the sintering process of the magnet, the rare earth elements diffuse between the two main phase grains, so that the two main phase grains are transformed into grains with a "core-shell" structure, thereby enhancing the coercive force. However, the mutual diffusion efficiency and diffusion degree of the two main phase grains are poor, so the improvement of coercive force is limited.

[0005] In view of this, this application is hereby filed. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a dual-main-phase sintered NdFeB magnet and a preparation method and application thereof. By designing the components of the dual-main-phases, the performance gap between the main phase and the auxiliary phase alloy is increased, and the diffusion effect between the two is enhanced. At the same time, by designing the particle size of the main phase and the auxiliary phase alloy, the diffusion efficiency between the grains is improved, and finally the "core-shell" structure has a higher anisotropy field, thereby improving the performance of the prepared magnet.

[0007] The present invention is achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a dual-phase sintered NdFeB magnet, characterized in that the main phase alloy and the auxiliary phase alloy of the dual-phase sintered NdFeB magnet are sequentially processed by hydrogen crushing, air flow milling, and powder mixing;

[0009] The hydrogen breaking method is: hydrogen absorption, followed by vacuum dehydrogenation at 500-620°C to obtain a coarsely crushed powder with an average particle size of 125-160 μm;

[0010] The method of air flow milling is as follows: the coarsely pulverized powder obtained is finely pulverized in an air flow mill in an atmosphere with an oxygen content of less than 10 ppm to obtain alloy fine powder with an average particle size of 2.0 to 4.5 μm.

[0011] In a specific embodiment, the composition of the main phase alloy is (R, Ce) a Fe 100-a-b-c M b B c , R is PrNd alloy or Nd metal, and M includes at least one of Cu, Al, Zr, Co, and Ga.

[0012] In a specific embodiment, the composition of the auxiliary phase alloy is (X, Ce) a Fe 100-a-b-c M b B c , X includes at least one of heavy rare earth elements such as Ho, Gd, Dy, etc., and M includes at least one of Cu, Al, Zr, Co, and Ga.

[0013] In a specific embodiment, 31≤a≤32, 0.1≤b≤1.8, and 0.8≤c≤1.

[0014] The composition and performance gap between the main phase alloy selected and designed by the present invention and the auxiliary phase alloy is large, and the magnet prepared by the invention has high performance, which is related to the anisotropy of each magnet component. The larger the difference in magnet performance, the greater the anisotropy, and the higher the Hcj of the prepared magnet. This is because the two main phase particles diffuse with each other during sintering or aging, and the main phase particles with different anisotropy fields are converted into main grains with a "core-shell" structure. The greater the difference in the composition of the two main phase grains during the process, the better the diffusion effect.

[0015] In a specific embodiment, the main phase alloy and the auxiliary phase alloy are both prepared by smelting.

[0016] In a specific embodiment, the mass ratio of the main phase alloy to the auxiliary phase alloy is 3-4:1-2.

[0017] In a specific embodiment, the average particle size of the main phase alloy is 3 to 4.1 μm.

[0018] In a specific embodiment, the average particle size of the auxiliary phase alloy is 2.5-3 μm.

[0019] In the alloy size selected and designed by the present invention, the main phase alloy particle size is larger and the auxiliary phase alloy particle size is smaller. Compared with the large-sized main phase alloy, the small-sized auxiliary phase alloy grains are easier to melt and exchange components or diffuse with the large-sized main phase grains. The concentration of heavy rare earth in the surface shell structure of the obtained main phase grains of the magnet is higher than the concentration of the main and auxiliary phase alloys with normal particle sizes. Therefore, reducing the auxiliary phase alloy particle size can greatly improve the diffusion efficiency of the grains, and ultimately make the "core-shell" structure have a higher anisotropy field.

[0020] In a second aspect, the present invention provides a dual-phase sintered NdFeB magnet, which is prepared by the preparation method, and the composition of the dual-phase sintered NdFeB magnet is (R, X, Ce) a Fe 100-a-b-c M b B c ;

[0021] Among them, R is PrNd alloy or Nd metal, X includes at least one of heavy rare earth elements such as Ho, Gd, Dy, etc., M includes at least one of Cu, Al, Zr, Co, Ga, and 31≤a≤32, 0.1≤b≤1.8, and 0.8≤c≤1.

[0022] In a third aspect, the present invention also provides the use of the above-mentioned dual-phase sintered NdFeB magnet or the dual-phase sintered NdFeB magnet prepared according to the method of the present invention in humanoid robots, instruments and meters, household appliances, motors, wind power generation, mobile phones, communication equipment, rotating machinery or sporting goods.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1. A dual-main-phase sintered NdFeB magnet, a preparation method and an application thereof are provided in an embodiment of the present invention. By designing the composition of the dual-main-phase, the performance gap between the main-phase and auxiliary-phase alloys is increased, and the diffusion effect between the two is enhanced. At the same time, by designing the particle size of the main-phase and auxiliary-phase alloys, the diffusion efficiency between the grains is improved, and finally the "core-shell" structure has a higher anisotropy field, thereby improving the performance of the prepared magnet;

[0025] 2. A dual-main-phase sintered NdFeB magnet, a preparation method and an application provided by an embodiment of the present invention has a large difference between the composition and performance of the main phase alloy and the auxiliary phase alloy, and the prepared magnet has high performance, which is related to the anisotropy of each magnet component. The greater the difference in magnet performance, the greater the anisotropy, and the higher the Hcj of the prepared magnet; this is because the two main phase particles diffuse with each other during sintering or aging, and the main phase particles with different anisotropy fields are converted into main grains with a "core-shell" structure. The greater the difference in the composition of the two main phase grains during the process, the better the diffusion effect;

[0026] 3. An embodiment of the present invention provides a dual-main-phase sintered NdFeB magnet and a preparation method and application thereof. The main phase alloy has a larger particle size and the auxiliary phase alloy has a smaller particle size. Compared with the large-sized main phase alloy, the small-sized auxiliary phase alloy grains are easier to melt and exchange components or diffuse with the large-sized main phase grains. The concentration of heavy rare earths in the surface shell structure of the main phase grains of the obtained magnet is higher than that of the main and auxiliary phase alloys of normal particle size. Therefore, reducing the particle size of the auxiliary phase alloy can greatly improve the diffusion efficiency of the grains, and ultimately make the "core-shell" structure have a higher anisotropy field. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0028] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details need not be employed to practice the present invention. In other embodiments, in order to avoid confusing the present invention, well-known materials or methods are not specifically described.

[0029] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0031] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0032] Although traditional characterization methods such as metallography and scanning electron microscopy (SEM) can provide intuitive organizational information, it is difficult to accurately capture subtle changes in non-uniform organizations and achieve a more comprehensive quantitative analysis. Electron backscatter diffraction analysis technology (EBSD) technology can realize microtexture analysis and grain orientation distribution measurement, and can quantitatively characterize the correspondence between crystal structure and orientation information and microstructural morphology, thereby more accurately analyzing the relationship between material microstructural characteristics and performance from multiple dimensions. However, facing the research needs of building quantitative relationships, there are many microstructural characteristic parameters that affect the mechanical properties of titanium alloys, and the data processing is complex and inefficient.

[0033] The dual-main-phase method can improve the performance of magnets to a certain extent, but with the changes in market demand for traditional automobiles, new energy vehicles, variable-frequency air conditioners, etc., new requirements have been put forward for the performance, manufacturing cost and use of heavy rare earth resources of magnets. The traditional dual-main-phase method designs the composition of two powders. During the sintering process of the magnet, the rare earth elements diffuse between the two main phase grains, so that the two main phase grains are transformed into grains with a "core-shell" structure, thereby enhancing the coercive force. However, the mutual diffusion efficiency and diffusion degree of the two main phase grains are poor, so the improvement of coercive force is limited.

[0034] In order to solve the above technical problems, the present invention provides a first aspect, which provides a preparation method of a dual-main-phase sintered NdFeB magnet, characterized in that the main phase alloy and the auxiliary phase alloy of the dual-main-phase sintered NdFeB magnet are processed by hydrogen crushing, air flow milling, and powder mixing in sequence;

[0035] The hydrogen cracking method is: hydrogen absorption, and then vacuum dehydrogenation treatment at 500-620°C to obtain a coarsely crushed powder with an average particle size of 125-160 μm; the main phase alloy and the auxiliary phase alloy are finely crushed to obtain an average particle size of powder;

[0036] The method of air flow milling is as follows: the coarsely pulverized powder obtained is finely pulverized in an air flow mill in an atmosphere with an oxygen content of less than 10 ppm to obtain alloy fine powder with an average particle size of 2.0 to 4.5 μm.

[0037] In a specific embodiment, the composition of the main phase alloy is (R, Ce) a Fe 100-a-b-c M b B c , R is PrNd alloy or Nd metal, and M includes at least one of Cu, Al, Zr, Co, and Ga.

[0038] In a specific embodiment, the composition of the auxiliary phase alloy is (X, Ce) a Fe 100-a-b-c M b B c, X includes at least one of heavy rare earth elements such as Ho, Gd, Dy, etc., and M includes at least one of Cu, Al, Zr, Co, and Ga.

[0039] In a specific embodiment, 31≤a≤32, 0.1≤b≤1.8, and 0.8≤c≤1.

[0040] The composition and performance gap between the main phase alloy selected and designed by the present invention and the auxiliary phase alloy is large, and the magnet prepared by the invention has high performance, which is related to the anisotropy of each magnet component. The larger the difference in magnet performance, the greater the anisotropy, and the higher the Hcj of the prepared magnet. This is because the two main phase particles diffuse with each other during sintering or aging, and the main phase particles with different anisotropy fields are converted into main grains with a "core-shell" structure. The greater the difference in the composition of the two main phase grains during the process, the better the diffusion effect.

[0041] In a specific embodiment, the main phase alloy and the auxiliary phase alloy are both prepared by smelting.

[0042] In a specific embodiment, the mass ratio of the main phase alloy to the auxiliary phase alloy is 3-4:1-2.

[0043] In a specific embodiment, the average particle size of the main phase alloy is 3 to 4.1 μm.

[0044] In a specific embodiment, the average particle size of the auxiliary phase alloy is 2.5-3 μm.

[0045] In the preferred alloy size selected and designed by the present invention, the main phase alloy particle size is larger and the auxiliary phase alloy particle size is smaller. Compared with the large-sized main phase alloy, the small-sized auxiliary phase alloy grains are easier to melt and exchange components or diffuse with the large-sized main phase grains. The concentration of heavy rare earth in the surface shell structure of the obtained main phase grains of the magnet is higher than the concentration of the main and auxiliary phase alloys of normal particle size. Therefore, reducing the auxiliary phase alloy particle size can greatly improve the diffusion efficiency of the grains, and ultimately make the "core-shell" structure have a higher anisotropy field.

[0046] In a second aspect, the present invention provides a dual-phase sintered NdFeB magnet, which is prepared by the preparation method, and the composition of the dual-phase sintered NdFeB magnet is (R, X, Ce) a Fe 100-a-b-c M b B c ;

[0047] Among them, R is PrNd alloy or Nd metal, X includes at least one of heavy rare earth elements such as Ho, Gd, Dy, etc., M includes at least one of Cu, Al, Zr, Co, Ga, and 31≤a≤32, 0.1≤b≤1.8, and 0.8≤c≤1.

[0048] In a third aspect, the present invention also provides the use of the above-mentioned dual-phase sintered NdFeB magnet or the dual-phase sintered NdFeB magnet prepared according to the method of the present invention in humanoid robots, instruments and meters, household appliances, motors, wind power generation, mobile phones, communication equipment, rotating machinery or sporting goods.

[0049] Example 1

[0050] The embodiment of the present invention provides a method for preparing a dual-phase sintered NdFeB magnet, comprising the following steps:

[0051] (1) Place the main phase alloy raw materials and auxiliary phase alloy raw materials into a vacuum melting furnace at about 5×10 -2 The alloys are vacuum melted at a temperature of 1500-1550° C. in a vacuum of 1500-1550° C.; the molten liquids obtained by the melting are then cast by a thin strip continuous casting method to obtain main phase alloy flakes and auxiliary phase alloy flakes;

[0052] The main phase alloy sheet composition is: (Nd 16.5 Ce 15 ) 31.5 Fe 66.72 A l0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 1 main phase alloy slice);

[0053] The auxiliary phase alloy sheet composition is: (Nd 26.5 Ho 5 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 1 auxiliary phase alloy sheet);

[0054] (2) Hydrogen crushing process: At room temperature, the main phase alloy flakes and the auxiliary phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0055] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in a jet mill in an atmosphere with an oxygen content of less than 10 ppm to obtain a main phase alloy powder with an average particle size of 4.1 μm and an auxiliary phase alloy powder with an average particle size of 4.1 μm;

[0056] (4) Molding process: The main phase alloy powder and the auxiliary phase alloy powder are mixed in a ratio of 3:2, pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0057] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet with a composition of Nd 31.5 Ho 2 Ce 9 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 .

[0058] Magnetic properties test: The remanence of the magnet is 12.65KGs and the coercive force is 16.23KOe.

[0059] Example 2

[0060] The embodiment of the present invention provides a method for preparing a dual-phase sintered NdFeB magnet, comprising the following steps:

[0061] (1) placing a main phase alloy raw material and a subsidiary phase alloy raw material into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain a main phase alloy sheet and a subsidiary phase alloy sheet;

[0062] The main phase alloy sheet composition is: (Nd 20 Ce 11.25 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 main phase alloy slice);

[0063] The auxiliary phase alloy sheet composition is: (Nd 21.5 Ho 10 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 auxiliary phase alloy sheet);

[0064] (2) Hydrogen crushing process: At room temperature, the main phase alloy flakes and the auxiliary phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0065] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in a jet mill in an atmosphere with an oxygen content of less than 10 ppm to obtain a main phase alloy powder with an average particle size of 4.1 μm and an auxiliary phase alloy powder with an average particle size of 4.1 μm;

[0066] (4) Molding process: The main phase alloy powder and the auxiliary phase alloy powder are mixed in a ratio of 4:1, pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0067] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet with a composition of Nd 31.5 Ho 2 Ce 9 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 .

[0068] Magnetic properties test: The remanence of the magnet is 12.64KGs and the coercive force is 16.62KOe.

[0069] Example 3

[0070] The embodiment of the present invention provides a method for preparing a dual-phase sintered NdFeB magnet, comprising the following steps:

[0071] (1) placing a main phase alloy raw material and a subsidiary phase alloy raw material into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain a main phase alloy sheet and a subsidiary phase alloy sheet;

[0072] The main phase alloy sheet composition is: (Nd 20 Ce 11.25 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 main phase alloy slice);

[0073] The auxiliary phase alloy sheet composition is: (Nd 21.5 Ho 10 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5Zr 0.25 B 0.92 (No. 2 auxiliary phase alloy sheet);

[0074] (2) Hydrogen crushing process: At room temperature, the main phase alloy flakes and the auxiliary phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0075] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in a jet mill in an atmosphere with an oxygen content of less than 10 ppm to obtain a main phase alloy powder with an average particle size of 4.1 μm and an auxiliary phase alloy powder with an average particle size of 3 μm;

[0076] (4) Molding process: The main phase alloy powder and the auxiliary phase alloy powder are mixed in a ratio of 4:1, pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0077] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet with a composition of Nd 31.5 Ho 2 Ce 9 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 .

[0078] Magnetic properties test: The remanence of the magnet is 12.62KGs and the coercive force is 17.36KOe.

[0079] Example 4

[0080] The embodiment of the present invention provides a method for preparing a dual-phase sintered NdFeB magnet, comprising the following steps:

[0081] (1) placing a main phase alloy raw material and a subsidiary phase alloy raw material into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain a main phase alloy sheet and a subsidiary phase alloy sheet;

[0082] The main phase alloy sheet composition is: (Nd 20 Ce 11.25 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B0.92 (No. 2 main phase alloy slice);

[0083] The auxiliary phase alloy sheet composition is: (Nd 21.5 Ho 10 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 auxiliary phase alloy sheet);

[0084] (2) Hydrogen crushing process: At room temperature, the main phase alloy flakes and the auxiliary phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0085] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in a jet mill in an atmosphere with an oxygen content of less than 10 ppm to obtain a main phase alloy powder with an average particle size of 4.1 μm and an auxiliary phase alloy powder with an average particle size of 2.5 μm;

[0086] (4) Molding process: The main phase alloy powder and the auxiliary phase alloy powder are mixed in a ratio of 4:1, pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0087] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet with a composition of Nd 31.5 Ho 2 Ce 9 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 .

[0088] Magnetic properties test: The remanence of the magnet is 12.65KGs and the coercive force is 17.87KOe.

[0089] Example 5

[0090] The embodiment of the present invention provides a method for preparing a dual-phase sintered NdFeB magnet, comprising the following steps:

[0091] (1) placing a main phase alloy raw material and a subsidiary phase alloy raw material into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain a main phase alloy sheet and a subsidiary phase alloy sheet;

[0092] The main phase alloy sheet composition is: (Nd 20 Ce 11.25 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 main phase alloy slice);

[0093] The auxiliary phase alloy sheet composition is: (Nd 21.5 Ho 10 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 auxiliary phase alloy sheet);

[0094] (2) Hydrogen crushing process: At room temperature, the main phase alloy flakes and the auxiliary phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0095] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in a jet mill in an atmosphere with an oxygen content of less than 10 ppm to obtain a main phase alloy powder with an average particle size of 4.1 μm and an auxiliary phase alloy powder with an average particle size of 2 μm;

[0096] (4) Molding process: The main phase alloy powder and the auxiliary phase alloy powder are mixed in a ratio of 4:1, pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0097] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet with a composition of Nd 31.5 Ho 2 Ce 9 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 .

[0098] Magnetic properties test: The remanence of the magnet is 12.64KGs and the coercive force is 16.83KOe.

[0099] Example 6

[0100] The embodiment of the present invention provides a method for preparing a dual-phase sintered NdFeB magnet, comprising the following steps:

[0101] (1) placing a main phase alloy raw material and a subsidiary phase alloy raw material into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain a main phase alloy sheet and a subsidiary phase alloy sheet;

[0102] The main phase alloy sheet composition is: (Nd 20 Ce 11.25 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 main phase alloy slice);

[0103] The auxiliary phase alloy sheet composition is: (Nd 21.5 Ho 10 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 auxiliary phase alloy sheet);

[0104] (2) Hydrogen crushing process: At room temperature, the main phase alloy flakes and the auxiliary phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0105] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in a jet mill in an atmosphere with an oxygen content of less than 10 ppm to obtain a main phase alloy powder with an average particle size of 3 μm and an auxiliary phase alloy powder with an average particle size of 4.1 μm;

[0106] (4) Molding process: The main phase alloy powder and the auxiliary phase alloy powder are mixed in a ratio of 4:1, pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0107] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet with a composition of Nd 31.5 Ho 2 Ce 9 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 .

[0108] Magnetic properties test: The remanence of the magnet is 12.59KGs and the coercive force is 16.52KOe.

[0109] Example 7

[0110] The embodiment of the present invention provides a method for preparing a dual-phase sintered NdFeB magnet, comprising the following steps:

[0111] (1) placing a main phase alloy raw material and a subsidiary phase alloy raw material into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain a main phase alloy sheet and a subsidiary phase alloy sheet;

[0112] The main phase alloy sheet composition is: (Nd 20 Ce 11.25 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 main phase alloy slice);

[0113] The auxiliary phase alloy sheet composition is: (Nd 21.5 Ho 10 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 auxiliary phase alloy sheet);

[0114] (2) Hydrogen crushing process: At room temperature, the main phase alloy flakes and the auxiliary phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0115] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in a jet mill in an atmosphere with an oxygen content of less than 10 ppm to obtain a main phase alloy powder with an average particle size of 2.5 μm and an auxiliary phase alloy powder with an average particle size of 4.1 μm;

[0116] (4) Molding process: The main phase alloy powder and the auxiliary phase alloy powder are mixed in a ratio of 4:1, pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0117] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet with a composition of Nd 31.5 Ho 2 Ce 9 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 .

[0118] Magnetic properties test: The remanence of the magnet is 12.57KGs and the coercive force is 15.24KOe.

[0119] Example 8

[0120] The embodiment of the present invention provides a method for preparing a dual-phase sintered NdFeB magnet, comprising the following steps:

[0121] (1) placing a main phase alloy raw material and a subsidiary phase alloy raw material into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain a main phase alloy sheet and a subsidiary phase alloy sheet;

[0122] The main phase alloy sheet composition is: (Nd 20 Ce 11.25 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 main phase alloy slice);

[0123] The auxiliary phase alloy sheet composition is: (Nd 21.5 Ho 10 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5Zr 0.25 B 0.92 (No. 2 auxiliary phase alloy sheet);

[0124] (2) Hydrogen crushing process: At room temperature, the main phase alloy flakes and the auxiliary phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0125] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in a jet mill in an atmosphere with an oxygen content of less than 10 ppm to obtain a main phase alloy powder with an average particle size of 2 μm and an auxiliary phase alloy powder with an average particle size of 4.1 μm;

[0126] (4) Molding process: The main phase alloy powder and the auxiliary phase alloy powder are mixed in a ratio of 4:1, pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0127] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet with a composition of Nd 31.5 Ho 2 Ce 9 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 .

[0128] Magnetic properties test: The remanence of the magnet is 12.6KGs and the coercive force is 14.71KOe.

[0129] Comparative Example 1

[0130] This comparative example provides a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0131] (1) placing the main phase alloy raw materials into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain main phase alloy sheets;

[0132] The main phase alloy sheet composition is: (Nd 16.5 Ce 15 ) 31.5 Fe 66.72 A l0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 1 main phase alloy slice);

[0133] (2) Hydrogen crushing process: At room temperature, the main phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0134] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in a jet mill in an atmosphere with an oxygen content of less than 10 ppm to obtain a main phase alloy powder with an average particle size of 4.1 μm;

[0135] (4) Molding process: The main phase alloy powder is pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0136] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet.

[0137] Magnetic properties test: The remanence of the magnet is 11.98KGs and the coercive force is 12.93KOe.

[0138] Comparative Example 2

[0139] This comparative example provides a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0140] (1) placing auxiliary phase alloy raw materials into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain auxiliary phase alloy sheets;

[0141] The auxiliary phase alloy sheet composition is: (Nd 26.5 Ho 5 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 1 auxiliary phase alloy sheet);

[0142] (2) Hydrogen crushing process: At room temperature, the auxiliary phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0143] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in an atmosphere with an oxygen content of less than 10 ppm in a jet mill to obtain auxiliary phase alloy powder with an average particle size of 4.1 μm;

[0144] (4) Molding process: The auxiliary phase alloy powder is pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0145] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet.

[0146] Magnetic properties test: The remanence of the magnet is 12.53KGs and the coercive force is 19.11KOe.

[0147] Comparative Example 3

[0148] This comparative example provides a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0149] (1) placing the main phase alloy raw materials into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain main phase alloy sheets;

[0150] The main phase alloy sheet composition is: (Nd 20 Ce 11.25 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 main phase alloy slice);

[0151] (2) Hydrogen crushing process: At room temperature, the main phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0152] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in a jet mill in an atmosphere with an oxygen content of less than 10 ppm to obtain a main phase alloy powder with an average particle size of 4.1 μm;

[0153] (4) Molding process: The main phase alloy powder is pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0154] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet.

[0155] Magnetic properties test: The remanence of the magnet is 12.79KGs and the coercive force is 12.22KOe.

[0156] Comparative Example 4

[0157] This comparative example provides a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0158] (1) placing auxiliary phase alloy raw materials into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain auxiliary phase alloy sheets;

[0159] The auxiliary phase alloy sheet composition is: (Nd 21.5 Ho 10 ) 31.5 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 (No. 2 auxiliary phase alloy sheet);

[0160] (2) Hydrogen crushing process: At room temperature, the auxiliary phase alloy flakes in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0161] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in an atmosphere with an oxygen content of less than 10 ppm in a jet mill to obtain auxiliary phase alloy powder with an average particle size of 4.1 μm;

[0162] (4) Molding process: The auxiliary phase alloy powder is pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0163] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet.

[0164] Magnetic properties test: The remanence of the magnet is 11.73KGs and the coercive force is 20.96KOe.

[0165] Comparative Example 5

[0166] This comparative example provides a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0167] (1) placing a single alloy raw material into a vacuum melting furnace and performing vacuum melting at a temperature of 1500-1550° C. in a vacuum of about 5×10-2 Pa; then casting the molten liquid obtained by the melting by a thin strip continuous casting method to obtain a single-phase alloy sheet;

[0168] The composition of single-phase alloy sheet is: Nd31.5 Ho 2 Ce 9 Fe 66.72 Al 0.15 Cu 0.1 Co 0.5 Zr 0.25 B 0.92 ;

[0169] (2) Hydrogen crushing process: at room temperature, the single-phase alloy pieces in step (1) are subjected to hydrogen absorption, and then subjected to vacuum dehydrogenation treatment at 500-620° C. to obtain coarsely crushed powder;

[0170] (3) fine pulverization: the coarsely pulverized powder in step (2) is finely pulverized in an atmosphere with an oxygen content of less than 10 ppm in a jet mill to obtain a single-phase alloy powder with an average particle size of 4.1 μm;

[0171] (4) Molding process: The single-phase alloy powder is pressed into a green body in a press with a magnetic field strength of 1.0 to 2.0 T, and then maintained at a pressure of 200 MPa for 10 seconds to obtain a molded body;

[0172] (5) Sintering process: The molded body is sintered at a temperature of 1055°C for 6 hours in a vacuum or inert gas atmosphere to obtain a NdFeB magnet.

[0173] Magnetic properties test: The remanence of the magnet is 12.58KGs and the coercive force is 15.75KOe.

[0174] The proportions and magnetic properties of Examples 1 to 8 and Comparative Examples 1 to 5 are shown in Table 1.

[0175] Table 1

[0176]

[0177]

[0178] The experimental data in Table 1 show that the magnetic properties of the magnets prepared by using dual main phases in Examples 1 and 2 of the present invention are improved by 0.87KOe and 0.48Koe, respectively, compared with the single alloy magnet of the same composition in Comparative Example 5, with Br almost unchanged.

[0179] Among them, the Hcj of Example 2 is improved more than that of Example 1. By comparison, it is found that the difference in composition and performance between the main phase alloy and the auxiliary phase alloy of Example 2 is greater than that of Example 1. This is related to the anisotropy of each magnet component. The greater the difference in magnet performance, the greater the anisotropy, the higher the Hcj of the prepared magnet, and the higher the magnet performance. This is related to the principle of the dual-main phase method. The two main phase particles will diffuse with each other during sintering or aging, and the main phase particles with different anisotropy fields will be converted into main grains with a "core-shell" structure. The greater the difference in composition of the two main phase grains in the process, the better the diffusion effect. In the present invention, the difference in composition and performance of the two main phase alloys and the auxiliary phase alloys in Example 2 is greater than that in Example 1, so the magnet performance in Example 2 is improved more.

[0180] By comparing Examples 2, 3, 4, and 5, it was found that when the particle size of the auxiliary phase alloy was reduced from 4.1 μm to 2.5 μm, the magnet obtained the highest Hcj of 17.87 Koe, which was 2.12 Koe higher than the performance of the single alloy method and 1.25 Koe higher than the performance of the traditional dual-main phase method, and the performance improvement was 2.44 times that of the traditional dual-main phase method. This is because the auxiliary phase alloy has a high heavy rare earth content, a higher Hcj, and better performance. Under the same sintering method, compared with the large-sized main phase alloy, the small-sized auxiliary phase alloy grains are easier to melt, and exchange or diffuse with the large-sized main phase grains. The heavy rare earth concentration in the shell structure of the main phase grain surface of the obtained magnet is higher than that of the main and auxiliary phase alloys of normal particle size. Therefore, reducing the particle size of the auxiliary phase alloy improves the diffusion efficiency of the grains, and ultimately makes the "core-shell" structure have a higher anisotropy field.

[0181] By comparing Examples 5, 6, 7, and 8, it is found that when the particle size of the main phase alloy is reduced from 4.1 μm to 2.5 μm, the Hcj of the magnet is reduced. When the particle size of the main phase alloy is 2.5 μm or 2 μm, its performance is worse than that of the single alloy method. This is related to grain growth. The surface of small-size grains has more defects, and its nucleation driving force is large during sintering. Therefore, under the same sintering temperature, the magnet grains are more likely to grow, and ultimately reduce the magnetic shielding effect between the main phase grains of the magnet, so that the Hcj of the magnet is reduced; on the other hand, in Examples 7 and 8, the main phase alloy grains account for a large proportion and have a smaller particle size. After the grains grow, their magnetic properties are much lower than those of the magnet prepared by the single alloy method.

[0182] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a dual-phase sintered NdFeB magnet, characterized in that: The main phase alloy and the auxiliary phase alloy of the dual-main-phase sintered NdFeB magnet are processed by hydrogen crushing and air flow grinding in sequence; The method of hydrogen cracking is: hydrogen absorption, followed by vacuum dehydrogenation at 500-620°C to obtain a coarsely crushed powder; The method of air flow milling is as follows: the coarsely pulverized powder obtained is finely pulverized in an air flow mill in an atmosphere with an oxygen content of less than 10 ppm to obtain alloy fine powder with an average particle size of 2.0 to 4.5 μm.

2. The method for preparing a dual-phase sintered NdFeB magnet according to claim 1, characterized in that: The composition of the main phase alloy is (R, Ce) a Fe 100-a-b-c M b B c , R is PrNd alloy or Nd metal, and M includes at least one of Cu, Al, Zr, Co, and Ga.

3. The method for preparing a dual-phase sintered NdFeB magnet according to claim 1, characterized in that: The composition of the auxiliary phase alloy is (X, Ce) a Fe 100-a-b-c M b B c , X includes at least one of heavy rare earth elements such as Ho, Gd, Dy, etc., and M includes at least one of Cu, Al, Zr, Co, and Ga.

4. The method for preparing a dual-phase sintered NdFeB magnet according to claim 2 or 3, characterized in that: 31≤a≤32, 0.1≤b≤1.8, 0.8≤c≤1.

5. The method for preparing a dual-phase sintered NdFeB magnet according to claim 1, characterized in that: The main phase alloy and the auxiliary phase alloy are both prepared by smelting.

6. The method for preparing a dual-phase sintered NdFeB magnet according to claim 1, characterized in that: The mass ratio of the main phase alloy to the auxiliary phase alloy is 3-4:1-2.

7. The method for preparing a dual-phase sintered NdFeB magnet according to claim 1, characterized in that: The average particle size of the main phase alloy is 3 to 4.1 μm.

8. The method for preparing a dual-phase sintered NdFeB magnet according to claim 1, characterized in that: The average particle size of the auxiliary phase alloy is 2.5-3 μm.

9. A dual-phase sintered NdFeB magnet, characterized in that: The dual-phase sintered NdFeB magnet is prepared by the preparation method according to any one of claims 1 to 8, wherein the composition of the dual-phase sintered NdFeB magnet is (R, X, Ce) a Fe 100-a-b-c M b B c ; Among them, R is PrNd alloy or Nd metal, X includes at least one of heavy rare earth elements such as Ho, Gd, Dy, etc., M includes at least one of Cu, Al, Zr, Co, Ga, and 31≤a≤32, 0.1≤b≤1.8, and 0.8≤c≤1.

10. Use of the dual-phase sintered NdFeB magnet prepared by the preparation method according to any one of claims 1 to 8 or the dual-phase sintered NdFeB magnet according to claim 9 in humanoid robots, instruments and meters, household appliances, motors, wind power generation, mobile phones, communication equipment, rotating machinery or sporting goods.

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