High-residual-magnetism low-coercive-force double-phase composite magnet and preparation method thereof

Abstract

The invention relates to a high-residual-magnetism low-coercive-force double-phase composite magnet and a preparation method thereof. The high-residual-magnetism low-coercive-force two-phase composite magnet is composed of a hard magnetic phase and a soft magnetic phase, the hard magnetic phase is an alloy phase with the chemical general formula (Nd1-aREa) x (Fe1-bCob) 100-x-y (B1-cMc) y, RE is a light rare earth element, M is a metal element, and the atomic composition ratios a, b, c, x and y meet the following inequalities: 0 < = a < = 0.1, 0 < = b < = 0.1, 0 < = c < = 0.15, 12 < = x < = 13.5, 6 < = y < = 7; the soft magnetic phase is an alpha-Fe phase; in terms of the total mass percentage of the magnet, the content of the alpha-Fe soft magnetic phase is 30-50%, and the balance is the hard magnetic phase. The inherent contradiction that high residual magnetism and low coercive force of a double-phase composite magnetic material are difficult to consider at the same time is broken through by precisely regulating and controlling the material components and the phase proportion.

Description

Technical Field

[0001] This invention belongs to the field of magnetic materials technology, specifically relating to a high remanence, low coercivity two-phase composite magnet and its preparation method. Background Technology

[0002] In the field of modern electrical equipment, the development of high-performance magnetic materials is a core driving force for technological progress. Two-phase composite magnetic materials are a new type of functional material based on the exchange coupling between soft and hard magnetic phases. These materials not only possess the high anisotropy of the hard magnetic phase and the high saturation magnetization of the soft magnetic phase, but also have a theoretical magnetic energy product (BH). max Up to 1 MJ / m 3 It is about twice the size of existing single-phase NdFeB permanent magnets. It also has advantages such as low cost, high temperature stability, heat resistance and oxidation resistance due to its low rare earth element content and stable phase structure. It has become one of the current research hotspots for new magnetic materials.

[0003] Compared to single-phase magnetic materials, two-phase composite magnetic materials exhibit higher remanence and lower coercivity. They can provide a larger, constant magnetic field during magnetization and require less energy for demagnetization. Based on these superior magnetization and demagnetization characteristics, two-phase composite magnetic materials have broad application prospects in fields such as power grids, rail transportation, aerospace, and next-generation information technology. In their paper "Design and analysis of new type of magnetically controlled reactor." (Energies, 2024, 17: 2125), Liu Yang et al. used the magnetization and demagnetization characteristics of two-phase composite magnetic materials to replace the traditional electrically excited method in a novel magnetically controlled reactor. This not only resulted in significant energy savings but also offered advantages such as a simple control system, low cost, and high reliability.

[0004] In recent years, with the continuous development of new composition systems and the optimization of preparation techniques for two-phase composite magnetic materials, many excellent results have been achieved in high-performance two-phase composite magnetic materials. However, these two-phase composite magnetic materials have always faced the inherent contradiction of being unable to simultaneously achieve "high remanence" and "low coercivity." Either the remanence reaches above 0.70T while the coercivity also reaches above 1000Oe, resulting in huge energy consumption for charging and demagnetizing the two-phase composite magnetic materials, or the coercivity is below 1000Oe while the remanence is below 0.70T, making it impossible for the two-phase composite magnetic materials to provide a large constant magnetic field, which makes it difficult to meet the performance requirements of high remanence and low coercivity of two-phase composite magnetic materials for new magnetically controlled reactors. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of the difficulty in achieving both high remanence and low coercivity in existing two-phase composite magnetic materials, so as to meet the magnetic performance requirements of magnetically controlled reactors for two-phase composite magnetic materials.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A high remanence, low coercivity two-phase composite magnet, comprising a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase has the chemical formula (Nd) 1-a RE a ) x (Fe 1-b Co b ) 100-x-y (B 1-c M c ) y The alloy phase, wherein RE is a light rare earth element and M is a metallic element, and the atomic composition ratios a, b, c, x, y satisfy the following inequalities: 0≤a≤0.1, 0≤b≤0.1, 0≤c≤0.15, 12≤x≤13.5, 6≤y≤7;

[0008] The soft magnetic phase is α-Fe phase; the content of the α-Fe soft magnetic phase is 30-50% by the total mass percentage of the magnet, and the remainder is hard magnetic phase.

[0009] Preferably, the light rare earth element RE is one or more of Y, La, Ce, and Pr.

[0010] Preferably, the metallic element M is one or more of Al, Nb, and Zr.

[0011] Preferably, the magnet has the following magnetic properties at room temperature: remanence B r ≥0.70T, coercivity H c ≤700Oe.

[0012] Preferably, the average particle size of the hard magnetic phase is 100 μm to 200 μm, and the average particle size of the soft magnetic phase is 100 nm to 250 nm.

[0013] Based on the same inventive concept, this invention also proposes a method for preparing the aforementioned high remanence and low coercivity two-phase composite magnet, comprising the following steps:

[0014] According to the hard magnetic phase composition and proportion, Nd, RE, Fe, Co, B and M raw materials are weighed and induction melted under inert gas protection to obtain master alloy ingots;

[0015] The master alloy ingot is remelted and subjected to rapid melt quenching under argon protection to obtain a nanocrystalline rapid quenching alloy strip.

[0016] The fast-quenched alloy strip is crushed and sieved to obtain hard magnetic alloy powder with an average particle size of 100μm to 200μm.

[0017] The hard magnetic alloy powder is uniformly mixed with α-Fe powder with an average particle size of 100nm to 250nm in the specified ratio to obtain a mixed powder.

[0018] The mixed powder is placed in an electric field-assisted hot pressing device and subjected to hot pressing-hot deformation treatment to obtain a hot-deformed magnet.

[0019] The heat-deformed magnet is heat-treated in a vacuum or inert atmosphere to obtain a two-phase composite magnet with high remanence and low coercivity.

[0020] Preferably, the melt quenching rate is 16–20 m / s.

[0021] Preferably, the electric field-assisted hot pressing device applies a current of 1000 to 4000 A.

[0022] Preferably, in the hot pressing-hot deformation treatment, the heating rate is ≥100K / min, the hot deformation temperature is 625~700℃, the pressure is 90~100MPa, the deformation rate is 0.04% / s, and the deformation amount is 75%.

[0023] Preferably, the heating rate of the heat treatment is 10-20 K / min, the heat treatment temperature is 650-900℃, and the holding time is 1-3 h.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The present invention proposes a high remanence, low coercivity two-phase composite magnet, which is composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase has the chemical formula (Nd) 1-a RE a ) x (Fe 1-b Co b ) 100-x-y (B 1-c M c ) y The alloy phase, wherein RE is a light rare earth element and M is a metallic element, and the atomic composition ratios a, b, c, x, and y satisfy the following inequalities: 0 ≤ a ≤ 0.1, 0 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.15, 12 ≤ x ≤ 13.5, 6 ≤ y ≤ 7; the soft magnetic phase is α-Fe phase; based on the total mass percentage of the magnet, the content of the α-Fe soft magnetic phase is 30-50%, with the remainder being hard magnetic phase. By precisely controlling the material composition and phase ratio, the inherent contradiction of "high remanence and low coercivity being difficult to achieve simultaneously" in two-phase composite magnetic materials is overcome. On the one hand, the hard magnetic phase is designed to be of a specific chemical formula (Nd... 1-aRE a ) x (Fe 1-b Co b ) 100-x-y (B 1-c M c ) y In alloy phases, introducing light rare earth element RE to partially replace Nd can reduce the anisotropic field of the hard magnetic phase, doping with Co enhances ferromagnetic exchange coupling, and introducing metallic element M improves the compactness of the hard magnetic phase, optimizing the remanence and coercivity of the hard magnetic phase, thereby achieving overall magnetic property control of the magnet; on the other hand, controlling the α-Fe soft magnetic phase content to 30-50% strengthens the exchange coupling between the soft and hard magnetic phases, ultimately achieving a magnet with both high remanence (B) and high magnetism (B). r ≥0.70T) and low coercivity (H c ≤700Oe).

[0026] The present invention discloses a method for preparing a high-remanence, low-coercivity two-phase composite magnet. This method employs an electric field-assisted hot pressing-hot deformation process instead of the conventional molybdenum wire heating hot pressing-hot deformation process. By applying current, rapid heating is achieved, shortening the high-temperature residence time of the magnet and effectively suppressing abnormal grain growth. Simultaneously, combined with hot deformation, the exchange coupling between the soft and hard magnetic phases is enhanced, and anisotropy is optimized, significantly improving the remanence of the two-phase composite magnet and reducing its coercivity. Adding a post-deformation treatment step after the hot pressing-hot deformation process optimizes the magnet's microstructure, reduces internal defects and anisotropic fields, thereby significantly reducing coercivity while maintaining a substantially unchanged remanence. Detailed Implementation

[0027] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0028] This invention provides a high remanence, low coercivity two-phase composite magnet, composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase has the chemical formula (Nd) 1-a RE a ) x (Fe 1-b Co b ) 100-x-y (B 1-c M c ) yThe alloy phase, where RE represents light rare earth elements and M represents metallic elements, has atomic composition ratios a, b, c, x, and y that satisfy the following inequalities: 0 ≤ a ≤ 0.1, 0 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.15, 12 ≤ x ≤ 13.5, and 6 ≤ y ≤ 7. The soft magnetic phase is α-Fe; by mass percentage, the content of the α-Fe soft magnetic phase is 30–50%, with the remainder being the hard magnetic phase. The two-phase composite magnet exhibits the following magnetic properties at room temperature: remanence B r ≥0.70T, coercivity H c ≤700Oe.

[0029] Furthermore, the light rare earth element RE is one or more of Y, La, Ce, and Pr;

[0030] The metallic element M is one or more of Al, Nb, and Zr.

[0031] The average particle size of the hard magnetic phase is 100 μm to 200 μm, and the average particle size of the soft magnetic phase is 100 nm to 250 nm.

[0032] The preparation method of the above-mentioned two-phase composite magnet includes the following steps:

[0033] ① Raw material smelting: Weigh Nd, RE, Fe, Co, B and M raw materials according to the general chemical formula of the hard magnetic phase used in the two-phase composite magnet, and carry out induction smelting under inert gas protection to obtain master alloy ingot;

[0034] ② Rapid melt quenching: The master alloy ingot is remelted and rapidly quenched under argon protection to obtain a nanocrystalline rapid-quenched alloy strip. To ensure the formation of a nanocrystalline phase within the strip during rapid melt quenching, the quenching rate is 16–20 m / s;

[0035] ③ Powder making: The fast-quenched alloy strip is crushed and sieved to obtain hard magnetic alloy powder with an average particle size of 100μm~200μm;

[0036] ④ Powder mixing: Hard magnetic alloy powder and α-Fe powder with an average particle size of 100nm to 250nm are mixed uniformly in a certain proportion to obtain mixed powder. Mixing soft and hard magnetic powders within this particle size range is beneficial to improving the exchange coupling effect between soft and hard magnetic phases, improving the remanence enhancement effect, and increasing remanence.

[0037] ⑤ Electric Field Assisted Hot Pressing-Hot Deformation: The mixed powder is subjected to hot pressing-hot deformation treatment in an electric field assisted hot pressing device to obtain a hot-deformed magnet. To ensure extremely rapid heating, the current is 1000–4000 A, at which point the heating rate is ≥100 K / min. This shortens the time the magnet is in a high-temperature state, prevents abnormal grain growth, enhances the exchange coupling between the soft and hard magnetic phases, and is beneficial to improving remanence. The hot deformation temperature is 625–700℃, the pressure is 90–100 MPa, the deformation rate is 0.04% / s, and the deformation amount is 75%. Under these hot deformation parameters, the two-phase composite magnet exhibits excellent anisotropy, which is beneficial to obtaining greater remanence.

[0038] ⑥ Post-deformation treatment: The hot-deformed magnet is heat-treated in a vacuum or inert atmosphere at a heating rate of 10–20 K / min, a holding temperature of 650–900℃, and a holding time of 1–3 h. Finally, it is cooled in the furnace to obtain the final two-phase composite magnet. These heat treatment parameters can appropriately weaken the anisotropic field of the hot-deformed magnet, significantly reduce the coercivity while maintaining the remanence basically unchanged, and achieve a balance between high remanence and low coercivity.

[0039] Example 1

[0040] This embodiment provides a high remanence, low coercivity two-phase composite magnet, composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase is (Nd) 0.98 Pr 0.02 ) 13.12 (Fe 0.95 Co 0.05 ) 80 (B 0.86 Al 0.04 Nb 0.06 Zr 0.04 ) 6.88 The alloy phase consists of an α-Fe soft magnetic phase; by mass percentage, the α-Fe soft magnetic phase accounts for 50%, with the remainder being a hard magnetic phase.

[0041] The preparation method of the above-mentioned two-phase composite magnet includes the following steps:

[0042] ① Raw material smelting: Weigh Nd, Pr, Fe, Co, B, Al, Nb and Zr raw materials according to the atomic percentages stated in the above general chemical formula for hard magnetic phase, and carry out induction smelting under inert gas protection to obtain master alloy ingots;

[0043] ② Rapid melt quenching: The master alloy ingot is remelted and rapid melt quenching is carried out under argon protection at a quenching rate of 20 m / s to obtain nanocrystalline rapid quenching alloy strip;

[0044] ③ Powder making: The fast-quenched alloy strip is crushed and sieved to obtain hard magnetic alloy powder with an average particle size of 100μm;

[0045] ④ Powder mixing: Hard magnetic alloy powder and α-Fe powder with an average particle size of 100nm are mixed uniformly in a certain proportion to obtain mixed powder;

[0046] ⑤ Electric field assisted hot pressing-hot deformation: The mixed powder is subjected to hot pressing-hot deformation treatment in an electric field assisted hot pressing equipment. The current is 1000A, the heating rate is 100K / min, the hot deformation temperature is 625℃, the pressure is 90MPa, the deformation rate is 0.04% / s, and the deformation amount is 75%, to obtain a hot deformed magnet.

[0047] ⑥ Post-deformation treatment: The hot-deformed magnet is heat-treated in a vacuum or inert atmosphere at a heating rate of 10K / min, a holding temperature of 800℃, and a holding time of 1h. Finally, it is cooled in the furnace to obtain the final two-phase composite magnet.

[0048] Example 2

[0049] This embodiment provides a high remanence, low coercivity two-phase composite magnet, composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase is (Nd) 0.98 Pr 0.02 ) 13.12 (Fe 0.95 Co 0.05 ) 80 (B 0.86 Al 0.04 Nb 0.06 Zr 0.04 ) 6.88 The alloy phase consists of an α-Fe soft magnetic phase; by mass percentage, the α-Fe soft magnetic phase accounts for 40%, with the remainder being a hard magnetic phase.

[0050] The preparation method of the above-mentioned two-phase composite magnet includes the following steps:

[0051] ① Raw material smelting: Same as in Example 1;

[0052] ② Rapid quenching of melt: Same as in Example 1;

[0053] ③ Powder preparation: Same as in Example 1;

[0054] ④ Mixing powder: Same as in Example 1;

[0055] ⑤ Electric field assisted hot pressing-hot deformation: Same as Example 1;

[0056] ⑥ Post-deformation treatment: Same as in Example 1.

[0057] Example 3

[0058] This embodiment provides a high remanence, low coercivity two-phase composite magnet, composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase is (Nd) 0.98Pr 0.02 ) 13.12 (Fe 0.95 Co 0.05 ) 80 (B 0.86 Al 0.04 Nb 0.06 Zr 0.04 ) 6.88 The alloy phase consists of an α-Fe soft magnetic phase; by mass percentage, the α-Fe soft magnetic phase accounts for 30%, with the remainder being a hard magnetic phase.

[0059] The preparation method of the above-mentioned two-phase composite magnet includes the following steps:

[0060] ① Raw material smelting: Same as in Example 1;

[0061] ② Rapid quenching of melt: Same as in Example 1;

[0062] ③ Powder preparation: Same as in Example 1;

[0063] ④ Mixing powder: Same as in Example 1;

[0064] ⑤ Electric field assisted hot pressing-hot deformation: Same as Example 1;

[0065] ⑥ Post-deformation treatment: Same as in Example 1.

[0066] Example 4

[0067] This embodiment provides a high remanence, low coercivity two-phase composite magnet, composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase is (Nd) 0.90 Y 0.05 La 0.05 ) 12 (Fe 0.90 Co 0.10 ) 82 (B 0.95 Al 0.05 The alloy phase consists of 6 alloy phases, with the soft magnetic phase being α-Fe phase. By mass percentage, the content of α-Fe soft magnetic phase is 50%, and the remainder is hard magnetic phase.

[0068] The preparation method of the above-mentioned two-phase composite magnet includes the following steps:

[0069] ① Raw material smelting: Weigh Nd, Y, La, Fe, Co, B and Al raw materials according to the atomic percentages stated in the above general chemical formula for hard magnetic phases, and perform induction smelting under inert gas protection to obtain master alloy ingots;

[0070] ② Rapid melt quenching: The master alloy ingot is remelted and rapid melt quenching is carried out under argon protection at a quenching rate of 16 m / s to obtain nanocrystalline rapid quenching alloy strip;

[0071] ③ Powder making: The fast-quenched alloy strip is crushed and sieved to obtain hard magnetic alloy powder with an average particle size of 200μm;

[0072] ④ Powder mixing: Hard magnetic alloy powder and α-Fe powder with an average particle size of 250nm are mixed uniformly in a certain proportion to obtain mixed powder;

[0073] ⑤ Electric field assisted hot pressing-hot deformation: The mixed powder is subjected to hot pressing-hot deformation treatment in an electric field assisted hot pressing equipment. The current is 4000A, the heating rate is 200K / min, the hot deformation temperature is 700℃, the pressure is 100MPa, the deformation rate is 0.04% / s, and the deformation amount is 75%, to obtain a hot deformed magnet.

[0074] ⑥ Post-deformation treatment: The hot-deformed magnet is heat-treated in a vacuum or inert atmosphere at a heating rate of 20K / min, a holding temperature of 900℃, and a holding time of 1h. Finally, it is cooled in the furnace to obtain the final two-phase composite magnet.

[0075] Example 5

[0076] This embodiment provides a high remanence, low coercivity two-phase composite magnet, composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase is (Nd) 0.91 Y 0.03 La 0.03 Ce 0.03 ) 12 (Fe 0.90 Co 0.10 ) 82 (B 0.90 Nb 0.05 Zr 0.05 The alloy phase consists of 6 alloy phases, with the soft magnetic phase being α-Fe phase. By mass percentage, the content of α-Fe soft magnetic phase is 50%, and the remainder is hard magnetic phase.

[0077] The preparation method of the above-mentioned two-phase composite magnet includes the following steps:

[0078] ① Raw material smelting: Weigh Nd, Y, La, Ce, Fe, Co, B, Nb and Zr raw materials according to the atomic percentages stated in the above general formula for hard magnetic phase chemical composition, and perform induction smelting under inert gas protection to obtain master alloy ingots;

[0079] ② Rapid melt quenching: The master alloy ingot is remelted and rapid melt quenching is carried out under argon protection at a quenching rate of 18 m / s to obtain nanocrystalline rapid quenching alloy strip;

[0080] ③ Powder making: The fast-quenched alloy strip is crushed and sieved to obtain hard magnetic alloy powder with an average particle size of 150μm;

[0081] ④ Powder mixing: Hard magnetic alloy powder and α-Fe powder with an average particle size of 200nm are mixed uniformly in a certain proportion to obtain mixed powder;

[0082] ⑤ Electric field assisted hot pressing-hot deformation: The mixed powder is subjected to hot pressing-hot deformation treatment in an electric field assisted hot pressing equipment. The current is 1000A, the heating rate is 100K / min, the hot deformation temperature is 625℃, the pressure is 90MPa, the deformation rate is 0.04% / s, and the deformation amount is 75%, to obtain a hot deformed magnet.

[0083] ⑥ Post-deformation treatment: The hot-deformed magnet is heat-treated in a vacuum or inert atmosphere at a heating rate of 10K / min, a holding temperature of 650℃, and a holding time of 3h. Finally, it is cooled in the furnace to obtain the final two-phase composite magnet.

[0084] Comparative Example 1

[0085] This comparative example provides a high remanence, low coercivity two-phase composite magnet, composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase is Nd. 13.12 (Fe 0.95 Co 0.05 ) 80 (B 0.86 Al 0.04 Nb 0.06 Zr 0.04 ) 6.88 The alloy phase consists of an α-Fe soft magnetic phase; by mass percentage, the α-Fe soft magnetic phase accounts for 50%, with the remainder being a hard magnetic phase.

[0086] The preparation method of the above-mentioned two-phase composite magnet is described in Specific Example 1.

[0087] Comparative Example 2

[0088] This embodiment provides a high remanence, low coercivity two-phase composite magnet, composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase is (Nd) 0.98 Pr 0.02 ) 13.12 Fe 80 B 6.88 The alloy phase consists of an α-Fe soft magnetic phase; by mass percentage, the α-Fe soft magnetic phase accounts for 50%, with the remainder being a hard magnetic phase.

[0089] The preparation method of the above-mentioned two-phase composite magnet is described in Specific Example 1.

[0090] Comparative Example 3

[0091] This embodiment provides a high remanence, low coercivity two-phase composite magnet, composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase is (Nd) 0.98 Pr 0.02 )13.12 (Fe 0.95 Co 0.05 ) 80 (B 0.86 Al 0.04 Nb 0.06 Zr 0.04 ) 6.88 The alloy phase consists of an α-Fe soft magnetic phase; by mass percentage, the α-Fe soft magnetic phase accounts for 50%, with the remainder being a hard magnetic phase.

[0092] The preparation method of the above-mentioned two-phase composite magnet is the same as that in specific embodiment 1, except that in step ⑤, conventional hot pressing-hot deformation is used instead of electric field assisted hot pressing-hot deformation. That is, the mixed powder is subjected to hot pressing-hot deformation treatment in a molybdenum wire heating hot pressing device, the heating rate is 10K / min, the hot deformation temperature is 625℃, the pressure is 90MPa, the deformation rate is 0.04% / s, and the deformation amount is 75%, so as to obtain a hot-deformed magnet.

[0093] Comparative Example 4

[0094] This embodiment provides a high remanence, low coercivity two-phase composite magnet, composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase is (Nd) 0.98 Pr 0.02 ) 13.12 (Fe 0.95 Co 0.05 ) 80 (B 0.86 Al 0.04 Nb 0.06 Zr 0.04 ) 6.88 The alloy phase consists of an α-Fe soft magnetic phase; by mass percentage, the α-Fe soft magnetic phase accounts for 50%, with the remainder being a hard magnetic phase.

[0095] The preparation method of the above-mentioned two-phase composite magnet is the same as that in Specific Example 1, except that step ⑥, the deformation post-processing, is not included in the preparation process.

[0096] Experimental Example

[0097] The remanence B of the high remanence and low coercivity two-phase composite magnets prepared in Examples 1-5 and Comparative Examples 1-4 was measured using a vibrating sample magnetometer (VSM). r and coercivity H c The test results are shown in Table 1.

[0098] Table 1. Test results of magnetic properties of high remanence and low coercivity two-phase composite magnets.

[0099] Group <![CDATA[Residual magnetic flux density B r (T)]]> <![CDATA[Coercive force H c (Oe)]]> Example 1 1.01 223.5 Example 2 1.03 515.0 Example 3 1.05 621.2 Example 4 0.98 218.6 Example 5 0.96 210.2 Comparative Example 1 1.02 687.5 Comparative Example 2 0.70 364.9 Comparative Example 3 0.78 423.7 Comparative Example 4 1.06 631.5

[0100] As can be seen from the magnetic property test results in Table 1, by adjusting the composition, ratio, and preparation process parameters of the α-Fe soft magnetic phase and the Nd-Fe-B hard magnetic phase, the exchange coupling effect between the hard magnetic phase and the soft magnetic phase can be precisely controlled, breaking through the magnetic property limitations of existing two-phase composite magnetic materials and obtaining materials with both high remanence (B r ≥0.70T) and low coercivity (H c A two-phase composite magnet with a coercivity of ≤700 Oe was obtained. Comparison of Example 1 and Comparative Example 1 shows that substituting some Nd with light rare earth element RE to reduce the anisotropy field of the Nd-Fe-B hard magnetic phase significantly reduces the coercivity from 687.5 Oe to 223.5 Oe while maintaining remanence at around 1.01 T. Comparison of Example 1 and Comparative Example 2 shows that by doping with trace amounts of Co and metallic elements Al, Nb, and Zr, the ferromagnetic exchange coupling within the hard magnetic phase is enhanced, optimizing the magnetic properties of the hard magnetic phase and significantly increasing the overall remanence of the two-phase composite magnet from 0.68 T to over 1.0 T. Comparison of Example 1 and Comparative Example 3 shows that using electric field-assisted hot pressing-hot deformation treatment instead of conventional molybdenum wire heating hot pressing-hot deformation treatment can increase the remanence of the two-phase composite magnet by more than 29%. Comparison of Example 1 and Comparative Example 4 shows that the post-deformation treatment process after the hot pressing-hot deformation step is beneficial for obtaining even lower coercivity.

[0101] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A two-phase composite magnet with high remanence and low coercivity, characterized in that, The magnet is composed of a hard magnetic phase and a soft magnetic phase, wherein the hard magnetic phase has the general chemical formula (Nd). 1-a RE a ) x (Fe 1-b Co b ) 100-x-y (B 1-c M c ) y The alloy phase, wherein RE is a light rare earth element and M is a metallic element, and the atomic composition ratios a, b, c, x, y satisfy the following inequalities: 0≤a≤0.1, 0≤b≤0.1, 0≤c≤0.15, 12≤x≤13.5, 6≤y≤7; The soft magnetic phase is an α-Fe phase; The α-Fe soft magnetic phase accounts for 30-50% of the total mass of the magnet, with the remainder being a hard magnetic phase.

2. The high remanence and low coercivity two-phase composite magnet according to claim 1, characterized in that, The light rare earth element RE is one or more of Y, La, Ce, and Pr.

3. The high remanence and low coercivity two-phase composite magnet according to claim 1, characterized in that, The metallic element M is one or more of Al, Nb, and Zr.

4. The high remanence and low coercivity two-phase composite magnet according to claim 1, characterized in that, The magnet has the following magnetic properties at room temperature: remanence B r ≥0.70T, coercivity H c ≤700Oe.

5. The high remanence and low coercivity two-phase composite magnet according to claim 1, characterized in that, The average particle size of the hard magnetic phase is 100 μm to 200 μm, and the average particle size of the soft magnetic phase is 100 nm to 250 nm.

6. A method for preparing a high remanence, low coercivity two-phase composite magnet according to any one of claims 1 to 5, characterized in that, Includes the following steps: According to the hard magnetic phase composition and proportion, Nd, RE, Fe, Co, B and M raw materials are weighed and induction melted under inert gas protection to obtain master alloy ingots; The master alloy ingot is remelted and subjected to rapid melt quenching under argon protection to obtain a nanocrystalline rapid quenching alloy strip. The fast-quenched alloy strip is crushed and sieved to obtain hard magnetic alloy powder with an average particle size of 100μm to 200μm. The hard magnetic alloy powder is uniformly mixed with α-Fe powder with an average particle size of 100nm to 250nm in the specified ratio to obtain a mixed powder. The mixed powder is placed in an electric field-assisted hot pressing device and subjected to hot pressing-hot deformation treatment to obtain a hot-deformed magnet. The heat-deformed magnet is heat-treated in a vacuum or inert atmosphere to obtain a two-phase composite magnet with high remanence and low coercivity.

7. The preparation method according to claim 6, characterized in that, The quenching rate of the melt is 16–20 m / s.

8. The preparation method according to claim 6, characterized in that, The electric field-assisted hot pressing device applies a current of 1000–4000 A.

9. The preparation method according to claim 6, characterized in that, In the hot pressing-hot deformation treatment, the heating rate is ≥100K / min, the hot deformation temperature is 625~700℃, the pressure is 90~100MPa, the deformation rate is 0.04% / s, and the deformation amount is 75%.

10. The preparation method according to claim 6, characterized in that, The heating rate of the heat treatment is 10-20 K / min, the heat treatment temperature is 650-900℃, and the holding time is 1-3 h.