Rare earth permanent magnet, method for producing the same, and electric machine

Abstract

The application provides a rare earth permanent magnet, which comprises a main phase and a grain boundary phase, the main phase is dispersed in the grain boundary phase, the main phase comprises a core and a shell layer covering the core, and the shell layer and the grain boundary phase have graphene. The rare earth permanent magnet has excellent mechanical properties and magnetic properties, and has high comprehensive utilization rate of rare earth resources and low preparation cost. The application also provides a preparation method of the rare earth permanent magnet and a motor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of permanent magnet materials, in particular to a rare earth permanent magnet, a preparation method thereof and a motor. BACKGROUND

[0002] The rare earth permanent magnet has the advantages of high magnetic energy product, high coercivity, relatively low price and sufficient raw material reserves, and is widely used in industry and agriculture. At present, the rare earth permanent magnet is difficult to simultaneously achieve high coercivity, high durability and bending strength without any treatment. For example, the magnetic performance of the rare earth permanent magnet is improved by adding a precious rare earth element, but the mechanical performance is not improved. Therefore, the rare earth permanent magnet needs to be further researched and developed. SUMMARY

[0003] Therefore, the present application provides a rare earth permanent magnet, a preparation method thereof and a motor, the rare earth permanent magnet has excellent magnetic performance, good mechanical performance and improved comprehensive performance, which helps to improve the use performance of the electrode.

[0004] In a first aspect, the present application provides a rare earth permanent magnet, which comprises a main phase and a grain boundary phase, the main phase is dispersed in the grain boundary phase, the main phase comprises a core and a shell layer covering the core, the shell layer and the grain boundary phase have graphene, the core comprises RL 1 a RH 1 b Fe c Co d B e , RL 1 comprises at least one of Pr and Nd, RH 1 comprises at least one of La, Ce, Sm, Gd, Ho and Y, a, b, c, d, e are weight fractions, 7.91≤a≤10.03, 18.98≤b≤20.79, 64.72≤c≤72.28, 0≤d≤2.33, 0.83≤e≤1.23, the shell layer comprises RL 2 f RL 3 g RH 2 h Fe i Co j B k M 1 l C m , RL 2 comprises at least one of La, Ce, Sm, Gd, Ho and Y, RL 3 comprises at least one of Pr and Nd, RH 2M 1 M, f, g, h, i, j, k, l, m are weight fractions, 21.64≤f+g+h≤32.64, 3.83≤g≤8.1, 6.66≤h≤8.97, 40.554≤i≤65.014, 0≤j≤2.1, 0.25≤k≤0.49, 11.5≤l≤20.58, 1.596≤m≤2.736, the grain boundary phase comprises RL 4 o RL 5 p RH 3 q Fe r Co s M 2 t C u , RL 4 M, RL 5 M, RH 3 M, M 2 M, o, p, q, r, s, t, u are weight fractions, and 19.39≤o+p+q≤33.857, 2.08≤p≤6.815, 9.52≤q≤14.946, 24.458≤r≤61.895, 0≤s≤1.92, 16.435≤t≤34.305, 2.28≤u≤4.56.

[0005] Optionally, in the core, 8≤a≤10, 19≤b≤20.5, 65.7≤c≤71, 0.5≤d≤1.8, 0.9≤e≤1.1.

[0006] Optionally, in the shell, 21.8≤f+g+h≤32.5, 3.9≤g≤7.8, 6.7≤h≤8.8, 42.5≤i≤63.72, 0.2≤j≤1.9, 0.28≤k≤0.45, 11.8≤l≤20.3, 1.6≤m≤2.5.

[0007] Optionally, in the grain boundary phase, 19.5≤o+p+q≤33.5, 2.2≤p≤6.7, 9.7≤q≤14.5, 25.7≤r≤60.8, 0.2≤s≤1.7, 16.5≤t≤34, 2.4≤u≤4.

[0008] Optionally, a ratio of a mass content of the rare earth element in the shell layer to a mass content of the rare earth element in the core is (0.744-1.093):1.

[0009] Optionally, a thickness of the shell layer is 0.1-8.5 μm.

[0010] Optionally, a mass content of the grain boundary phase in the rare earth permanent magnet is 20%-40%, and a mass content of the main phase is 60%-80%.

[0011] In a second aspect, the application provides a preparation method of a rare earth permanent magnet, comprising:

[0012] mixing the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material, and then performing magnetic field orientation compression molding and sintering to obtain a rare earth permanent magnet blank, wherein the first main phase alloy raw material comprises R 1 a' Fe b' Co c' B d' , R 1 comprises at least one of Pr and Nd, a', b', c' and d' are weight fractions, 25.5≤a'≤29.5, 66.4≤b'≤73.6, 0≤c'≤2, 0.9≤d'≤1.2, the second main phase alloy raw material comprises R 2 e' Fe f' Co g' B h' , R 2 comprises at least one of La, Ce, Sm, Gd, Ho and Y, e', f', g' and h' are weight fractions, 27.5≤e'≤31.5, 63.85≤f'≤71.7, 0≤g'≤2.5, 0.8≤h'≤1.25, and the grain boundary phase alloy raw material comprises R 3 i' Fe j' Co k' M 3 l' , R 3 comprises at least one of La, Ce, Sm, Pr and Nd, M 3 comprises at least one of Zr, Ga, Cu, Sn, Al and Zn, i', j', k' and l' are weight fractions, 19≤i'≤25.2, 44.9≤j'≤71, 0≤k'≤4, 10≤l'≤25;

[0013] The grain boundary diffusion material is arranged on the surface of the rare earth permanent magnet blank, and the grain boundary diffusion material comprises a diffusion alloy material and modified graphene, the modified graphene comprises graphene and a zinc alloy layer covering the graphene, the diffusion alloy material comprises R 4 m' R 5 n' Fe o' M 4 p' , R 4 comprises at least one of Pr and Nd, R 5 comprises at least one of Dy and Tb, M 4 comprises at least one of Ga, Cu, Sn, Al and Zn, m', n', o', p' are weight fractions, 5.2≤m'≤14.5, 23.8≤n'≤31.8, 28.85≤o'≤55.5, 15.5≤p'≤24, the zinc alloy layer comprises Zn q' Al r' Si s' Ti t' , q', r', s', t' are weight fractions, 61.8≤q'≤84.87, 14.1≤r'≤34.4, 0.9≤s'≤2.2, 0.13≤t'≤0.7;

[0014] The rare earth permanent magnet is prepared after hot pressing, diffusion treatment and tempering treatment.

[0015] Optionally, before the grain boundary diffusion material is arranged on the surface of the rare earth permanent magnet blank, the method further comprises: mixing the graphene with a zinc alloy material, and obtaining the modified graphene after ball milling.

[0016] Further, the average particle size of the zinc alloy material is 58nm-80nm.

[0017] Further, the average particle size of the modified graphene is 10nm-25nm.

[0018] Further, the ball-to-material ratio in the ball milling is (5-10):1, the rotation speed is 160r / min-180r / min, and the time is 6h-10h.

[0019] Further, the ball milling is carried out in an inert atmosphere or under vacuum.

[0020] Optionally, in the diffusion alloy raw material, 6≤m'≤14, 24≤n'≤31, 30.7≤o'≤53.4, and 16≤p'≤23.

[0021] Optionally, the mass content of the modified graphene in the grain boundary diffusion material is 10%-23%.

[0022] Optionally, the mass content of the graphene in the modified graphene is 19%-38%.

[0023] Optionally, the ratio of the mass of the second main phase alloy raw material to the sum of the mass of the first main phase alloy raw material and the mass of the second main phase alloy raw material is 50%-69%.

[0024] Optionally, the ratio of the mass of the grain boundary phase alloy raw material to the sum of the mass of the first main phase alloy raw material, the mass of the second main phase alloy raw material and the mass of the grain boundary phase alloy raw material is 5%-17%.

[0025] Optionally, the magnetic field orientation compression forming comprises processing at a magnetic field of 1.5T-3.5T, at a pressure of 170MPa-210MPa for 60s-150s.

[0026] Optionally, the sintering comprises processing at 1030℃-1090℃ for 4h-5.5h.

[0027] Optionally, the hot pressing comprises processing at 550℃-800℃, 80MPa-150MPa and a vacuum degree of 10 -3 Pa-10 -2 Pa for 30min-150min.

[0028] Optionally, the diffusion processing comprises processing at 600℃-1000℃ and a vacuum degree of 10 -5 Pa-10 -2 Pa for 2h-12h.

[0029] Optionally, the tempering processing comprises processing at 400℃-600℃ and a vacuum degree of 10 -5 Pa-10 -2 Pa for 2.5h-10h.

[0030] Optionally, the sintering further comprises pre-tempering processing, and the pre-tempering processing comprises processing at 890℃-950℃ for 2.5h-5h, and then processing at 480℃-520℃ for 3.5h-8h.

[0031] In a third aspect, the application provides an electric machine comprising the rare earth permanent magnet of the first aspect or the rare earth permanent magnet prepared by the preparation method of the second aspect.

[0032] The rare earth permanent magnet provided by the application has excellent magnetic and mechanical properties, and the use amount of valuable rare earth metals is reduced, the rare earth resources can be comprehensively utilized, the preparation cost is low, and the use is beneficial; the electrode with the rare earth permanent magnet has excellent comprehensive performance and long service life. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A structure diagram of a rare earth permanent magnet provided for an embodiment of the present application.

[0034] Figure 2 A flow chart of a preparation method of a rare earth permanent magnet provided for an embodiment of the present application.

[0035] Figure 3 A scanning electron microscope (SEM) image of a rare earth permanent magnet prepared for example 1. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0037] The present application provides a rare earth permanent magnet, the rare earth permanent magnet comprising a main phase and a grain boundary phase, the main phase being dispersed in the grain boundary phase, the main phase comprising a core and a shell layer covering the core, the shell layer and the grain boundary phase having graphene, the core comprising RL 1 a RH 1 b Fe c Co d B e , RL 1 comprising at least one of Pr and Nd, RH 1 comprising at least one of La, Ce, Sm, Gd, Ho and Y, a, b, c, d, e are parts by weight, 7.91≤a≤10.03, 18.98≤b≤20.79, 64.72≤c≤72.28, 0≤d≤2.33, 0.83≤e≤1.23, the shell layer comprising RL 2 f RL 3 g RH 2 h Fe i Co j B k M 1 l C m , RL 2 comprising at least one of La, Ce, Sm, Gd, Ho and Y, RL 3 comprising at least one of Pr and Nd, RH 2 comprising at least one of Dy and Tb, M 1at least one of Zr, Ga, Cu and Sn, and Al, Zn, Si and Ti, f, g, h, i, j, k, l, m are weight fractions, 21.64≤f+g+h≤32.64, 3.83≤g≤8.1, 6.66≤h≤8.97, 40.554≤i≤65.014, 0≤j≤2.1, 0.25≤k≤0.49, 11.5≤l≤20.58, 1.596≤m≤2.736, the grain boundary phase includes RL 4 o RL 5 p RH 3 q Fe r Co s M 2 t C u , RL 4 at least one of La, Ce and Sm, RL 5 at least one of Pr and Nd, RH 3 at least one of Dy and Tb, M 2 at least one of Zr, Ga, Cu and Sn, and Al, Zn, Si and Ti, o, p, q, r, s, t, u are weight fractions, and 19.39≤o+p+q≤33.857, 2.08≤p≤6.815, 9.52≤q≤14.946, 24.458≤r≤61.895, 0≤s≤1.92, 16.435≤t≤34.305, 2.28≤u≤4.56. Please refer to Figure 1 FIG. 1 is a structural schematic diagram of a rare earth permanent magnet according to an embodiment of the present application, wherein the rare earth permanent magnet 100 includes a main phase 10 and a grain boundary phase 20, the main phase 10 is dispersed in the grain boundary phase 20, and the main phase 10 includes a core 11 and a shell layer 12 covering the core 11.

[0038] In the present application, the main phase is dispersed in the grain boundary phase, that is, the grain boundary phase isolates and / or coats the main phase, and the main phase is a core-shell structure, which improves the magnetocrystalline anisotropy field of the core in the main phase, reduces the magnetic exchange coupling effect between the core grains in the main phase, and inhibits the generation of the reverse magnetization domain, thereby significantly enhancing the coercivity and high-temperature external field durability of the overall rare earth permanent magnet, while the remanence performance of the rare earth permanent magnet can be ensured to the greatest extent; the shell layer and the grain boundary phase have graphene uniformly dispersed therein, which effectively improves the mechanical properties of the rare earth permanent magnet, such as bending resistance, and is beneficial to improving the processability of the rare earth permanent magnet; the shell layer of the main phase is a rare earth-rich phase with a high magnetocrystalline anisotropy field, which can efficiently improve the coercivity of the rare earth permanent magnet, so that the rare earth permanent magnet has excellent magnetic properties and mechanical properties; at the same time, the rare earth permanent magnet contains a large amount of high-abundance rare earth elements (such as La, Ce, Sm, etc.), which can reduce the cost of the rare earth permanent magnet while ensuring the magnetic properties of the rare earth permanent magnet.

[0039] In the present application, the core includes RL 1 a RH 1 b Fe c Co d B e , RL 1 includes at least one of Pr and Nd, RH 1 includes at least one of La, Ce, Sm, Gd, Ho and Y, a, b, c, d, e are weight fractions, 7.91≤a≤10.03, 18.98≤b≤20.79, 64.72≤c≤72.28, 0≤d≤2.33, 0.83≤e≤1.23. Specifically, a can be but is not limited to 7.91, 8, 8.15, 8.38, 8.67, 8.93, 9.05, 9.32, 9.59, 9.81, 9.95, 10, 10.02, etc. Specifically, b can be but is not limited to 19, 19.24, 19.47, 19.73, 19.91, 20, 20.5, 20.66. Specifically, c can be but is not limited to 64.72, 65.64, 67.85, 68.18, 69.75, 70.5, 71, 72.1, etc. Specifically, d can be but is not limited to 0, 0.5, 0.72, 0.98, 1.32, 1.59, 1.8, 1.9, 2, 2.21, etc. Specifically, e can be but is not limited to 0.83, 0.85, 0.9, 1, 1.03, 1.1, 1.13, 1.2, etc. In an embodiment of the present application, in the core, 8≤a≤10, 19≤b≤20.5, 65.7≤c≤71, 0.5≤d≤1.8, 0.9≤e≤1.1, which is conducive to further improving the coercivity of the rare earth permanent magnet without affecting the remanence (remanence).

[0040] In the present application, the shell layer has graphene, the shell layer comprises RL 2 f RL 3 g RH 2 h Fe i Co j B k M 1 l C m , RL 2 comprises at least one of La, Ce, Sm, Gd, Ho and Y, RL 3 comprises at least one of Pr and Nd, RH 2 comprises at least one of Dy and Tb, M 1 comprises at least one of Zr, Ga, Cu and Sn and Al, Zn, Si and Ti, f, g, h, i, j, k, l, m are parts by weight, 21.64≤f+g+h≤32.64, 3.83≤g≤8.1, 6.66≤h≤8.97, 40.554≤i≤65.014, 0≤j≤2.1, 0.25≤k≤0.49, 11.5≤l≤20.58, 1.596≤m≤2.736. It can be understood that M 1Al, Zn, Si and Ti, and further comprising at least one of Zr, Ga, Cu and Sn. Specifically, f+g+h can be, but is not limited to, 21.64, 21.8, 23.7, 25.5, 27.24, 28.37, 30.26, 32.5, etc. Specifically, g can be, but is not limited to, 3.83, 3.9, 3.95, 4, 4.25, 5.72, 6.94, 7, 7.34, 7.8, 8, etc. Specifically, h can be, but is not limited to, 6.7, 6.9, 7, 7.2, 7.6, 7.9, 8, 8.2, 8.5, 8.8, 8.9, etc. Specifically, i can be, but is not limited to, 40.554, 42.5, 43.2, 47.8, 50.5, 55.7, 58.1, 60.4, 63.3, 63.72, 65, etc. Specifically, j can be, but is not limited to, 0, 0.2, 0.7, 1, 1.3, 1.5, 1.7, 1.9, 2, 2.1, etc. Specifically, k can be, but is not limited to, 0.28, 0.3, 0.34, 0.37, 0.4, 0.45, 0.47, etc. Specifically, l can be, but is not limited to, 11.8, 12.5, 14, 15.6, 17.3, 18.9, 20, 20.3, 20.5, etc. Specifically, m can be, but is not limited to, 1.6, 1.841, 1.95, 2, 2.245, 2.5, 2.67, etc. In an embodiment of the present application, in the shell layer, 21.8≤f+g+h≤32.5, 3.9≤g≤7.8, 6.7≤h≤8.8, 42.5≤i≤63.72, 0.2≤j≤1.9, 0.28≤k≤0.45, 11.8≤l≤20.3, 1.6≤m≤2.5, which is conducive to further improving the coercive force and mechanical properties of the rare earth permanent magnet without affecting the residual magnetism.

[0041] In an embodiment of the present application, the shell layer comprises 0.061-0.098 parts by weight of Si. Specifically, the shell layer can comprise, but is not limited to, 0.065 parts, 0.07 parts, 0.083 parts, 0.09 parts or 0.095 parts by weight of Si. In an embodiment, the shell layer can comprise 0.07-0.09 parts by weight of Si, which further improves the performance of the rare earth permanent magnet.

[0042] In an embodiment of the present application, the shell layer comprises 0.0091-0.0312 parts by weight of Ti. Specifically, the shell layer can comprise, but is not limited to, 0.01 parts, 0.015 parts, 0.02 parts, 0.027 parts, 0.03 parts or 0.031 parts by weight of Ti. In an embodiment, the shell layer can comprise 0.01-0.03 parts by weight of Ti, which further improves the performance of the rare earth permanent magnet.

[0043] In an embodiment of the present application, the shell layer contains Dy2Fe 14 at least one of B phase and Tb2Fe 14 at least one of B phase and Pr2Fe 14 at least one of B phase and Nd2Fe 14 at least one of B phase, so as to further improve the crystalline magnetic anisotropy constant of the main phase surface and weaken the decline of magnetic performance caused by high-abundance rare earth elements (such as Ce).

[0044] In an embodiment of the present application, the ratio of the mass content of rare earth elements in the shell layer to the mass content of rare earth elements in the core is (0.744-1.093):1, which is beneficial to further improve the magnetic performance of the rare earth permanent magnet. Specifically, the ratio of the mass content of rare earth elements in the shell layer to the mass content of rare earth elements in the core can be but is not limited to 0.75:1, 0.8:1, 0.807:1, 0.83:1, 0.85:1, 0.885:1, 0.9:1, 0.93:1, 0.97:1, 1:1, 1.083:1, 1.09:1, etc. In an embodiment, the ratio of the mass content of rare earth elements in the shell layer to the mass content of rare earth elements in the core can be (0.807-1.083):1. In another embodiment, the ratio of the mass content of rare earth elements in the shell layer to the mass content of rare earth elements in the core can be (0.85-1):1. In yet another embodiment, the ratio of the mass content of rare earth elements in the shell layer to the mass content of rare earth elements in the core can be (0.862-0.991):1.

[0045] In an embodiment of the present application, the thickness of the shell layer is 0.1 μm-8.5 μm, which can improve the magnetic crystalline anisotropy field of the main phase, reduce the magnetic exchange coupling effect between the main phases, and improve the coercivity of the permanent magnet. Specifically, the thickness of the shell layer can be but is not limited to 0.2 μm, 0.5 μm, 1 μm, 1.7 μm, 2.5 μm, 4 μm, 5 μm, 6 μm, 7.4 μm, 8 μm, etc. In an embodiment, the thickness of the shell layer can be 1 μm-7.4 μm. In another embodiment, the thickness of the shell layer can be 1.2 μm-7 μm. In yet another embodiment, the thickness of the shell layer can be 1.8 μm-6 μm.

[0046] In the present application, the shell layer can partially or completely cover the core. In an embodiment of the present application, the covering rate of the shell layer is greater than or equal to 60%. Specifically, the covering rate of the shell layer can be, but is not limited to, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc. The covering rate of the shell layer is the percentage of the surface area of the core covered by the shell layer to the total surface area of the core. In an embodiment, the shell layer completely covers the core, i.e., the covering rate of the shell layer is 100%, which can further improve the magnetic performance of the rare earth permanent magnet. In another embodiment, more than 90% of the total number of the core is completely covered by the shell layer.

[0047] In the present application, the grain boundary phase has graphene, and the grain boundary phase includes RL 4 o RL 5 p RH 3 q Fe r Co s M 2 t C u , RL 4 includes at least one of La, Ce and Sm, RL 5 includes at least one of Pr and Nd, RH 3 includes at least one of Dy and Tb, M 2 includes at least one of Zr, Ga, Cu and Sn, and Al, Zn, Si and Ti, o, p, q, r, s, t, u are weight fractions, and 19.39≤o+p+q≤33.857, 2.08≤p≤6.815, 9.52≤q≤14.946, 24.458≤r≤61.895, 0≤s≤1.92, 16.435≤t≤34.305, 2.28≤u≤4.56. It can be understood that M 2Al, Zn, Si and Ti, and further including at least one of Zr, Ga, Cu and Sn. Specifically, o+p+q can be, but is not limited to, 19.5, 20, 20.7, 22.9, 25, 27.3, 29.5, 30, 33.5, 33.8, etc. Specifically, p can be, but is not limited to, 2.2, 2.7, 3, 3.5, 4, 4.8, 5, 5.2, 6, 6.7, 6.8, etc. Specifically, q can be, but is not limited to, 9.7, 10, 10.3, 11.5, 12, 12.7, 13, 14.5, 14.8, etc. Specifically, r can be, but is not limited to, 25, 25.7, 27.5, 30, 38.1, 47, 50, 55, 60.8, 61, etc. Specifically, s can be, but is not limited to, 0, 0.2, 0.5, 0.8, 1, 1.3, 1.5, 1.7, 1.8, etc. Specifically, t can be, but is not limited to, 16.5, 18, 20, 23.8, 28.1, 30.5, 34, etc. Specifically, u can be, but is not limited to, 2.3, 2.4, 3.1, 3.7, 4, 4.3, etc. In an embodiment of the present application, in the grain boundary phase, 19.5≤o+p+q≤33.5, 2.2≤p≤6.7, 9.7≤q≤14.5, 25.7≤r≤60.8, 0.2≤s≤1.7, 16.5≤t≤34, 2.4≤u≤4, which is conducive to further improving the coercivity and mechanical properties of the rare earth permanent magnet without affecting the residual magnetism.

[0048] In an embodiment of the present application, the grain boundary phase includes 0.087-0.164 parts by weight of Si. Specifically, the grain boundary phase can include, but is not limited to, 0.09 parts, 0.1 parts, 0.13 parts, 0.15 parts or 0.16 parts by weight of Si. In an example, the grain boundary phase can include 0.09-0.15 parts by weight of Si, further improving the performance of the rare earth permanent magnet.

[0049] In an embodiment of the present application, the grain boundary phase includes 0.0091-0.0312 parts by weight of Ti. Specifically, the grain boundary phase can include, but is not limited to, 0.02 parts, 0.03 parts, 0.035 parts, 0.04 parts or 0.05 parts by weight of Ti. In an example, the grain boundary phase can include 0.02-0.05 parts by weight of Ti, further improving the performance of the rare earth permanent magnet.

[0050] In an embodiment of the present application, the mass content of the grain boundary phase in the rare earth permanent magnet is 20%-40%, and the mass content of the main phase is 60%-80%, further improving the magnetic properties and mechanical properties of the rare earth permanent magnet. Specifically, the mass content of the grain boundary phase in the rare earth permanent magnet can be, but is not limited to, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 37%, 40%, etc.; the mass content of the main phase in the rare earth permanent magnet can be, but is not limited to, 60%, 63%, 65%, 67%, 70%, 72%, 75%, 78%, 80%, etc. In an embodiment, the mass content of the grain boundary phase in the rare earth permanent magnet is 22%-37%, and the mass content of the main phase is 63%-78%. In another embodiment, the mass content of the grain boundary phase in the rare earth permanent magnet is 25%-35%, and the mass content of the main phase is 65%-75%.

[0051] In the present application, the Co element in the rare earth permanent magnet can increase the Curie temperature, reduce the temperature coefficient of coercivity, and improve the temperature stability of the permanent magnet.

[0052] In the present application, at least one of the core, the shell layer and the grain boundary phase of the rare earth permanent magnet can contain trace impurity elements. These impurity elements can be brought by the metal raw materials. Specifically, the impurity elements can include, but are not limited to, at least one of Ca, Ni, Mn, Mg, Cr, Er, W, Mo, Ca, N, O, S and P.

[0053] In an embodiment of the present application, the thickness of the rare earth permanent magnet is 1mm-10mm, which is conducive to the performance of the magnetic properties and mechanical properties of the rare earth permanent magnet. Specifically, the thickness of the rare earth permanent magnet can be, but is not limited to, 1mm, 3mm, 5mm, 6mm, 7mm, 10mm, etc. In an embodiment, the thickness of the rare earth permanent magnet can be 2mm-7mm. In an embodiment of the present application, the rare earth permanent magnet can have a sheet structure, which is conducive to the performance of the magnetic properties and mechanical properties of the rare earth permanent magnet.

[0054] In an embodiment of the present application, the remanence of the rare earth permanent magnet is greater than or equal to 12.56 kGs, the intrinsic coercivity is greater than or equal to 24.63 kOe, the magnetic flux irreversible loss at 7 kOe, 180℃ for 10 h is less than or equal to 10.96%, and the bending strength is greater than or equal to 295 MPa. The rare earth permanent magnet has excellent magnetic properties and mechanical properties, which is beneficial to the use of the rare earth permanent magnet. In an embodiment of the present application, the remanence of the rare earth permanent magnet can be 12.92-13.03 kGs, the intrinsic coercivity can be 28.23-29.74 kOe, the magnetic flux irreversible loss at 7 kOe, 180℃ for 10 h can be 5.44%-6.8%, and the bending strength can be 364-394 MPa. In an embodiment of the present application, the remanence of the rare earth permanent magnet can be 12.92-13.03 kGs, the intrinsic coercivity can be 29.32-29.74 kOe, the magnetic flux irreversible loss at 7 kOe, 180℃ for 10 h can be 5.44%-6%, and the bending strength can be 370-394 MPa.

[0055] The present application also provides a permanent magnet comprising the rare earth permanent magnet in any of the above embodiments and a grain boundary diffusion layer arranged on at least one surface of the rare earth permanent magnet. In an embodiment of the present application, the thickness of the grain boundary diffusion layer can be 5-15 μm, which can avoid affecting the magnetic properties of the rare earth permanent magnet. Specifically, the thickness of the grain boundary diffusion layer can be, but is not limited to, 5 μm, 7 μm, 10 μm, 12 μm, 14 μm, 15 μm, etc. In the present application, the grain boundary diffusion layer on the surface of the rare earth permanent magnet can be removed and recycled to realize the reuse of the grain boundary diffusion layer material.

[0056] The present application also provides a preparation method of a rare earth permanent magnet, comprising mixing a first main phase alloy raw material, a second main phase alloy raw material and a grain boundary phase alloy raw material, and performing magnetic field orientation compression molding and sintering to obtain a rare earth permanent magnet blank, wherein the first main phase alloy raw material comprises R 1 a' Fe b' Co c' B d' , R 1 at least one of Pr and Nd, a', b', c' and d' are weight fractions, 25.5≤a'≤29.5, 66.4≤b'≤73.6, 0≤c'≤2, 0.9≤d'≤1.2, the second main phase alloy raw material comprises R 2 e' Fe f' Co g' B h' , R 2The alloy comprises at least one of La, Ce, Sm, Gd, Ho, and Y, where e', f', g', and h' are parts by weight, with 27.5 ≤ e' ≤ 31.5, 63.85 ≤ f' ≤ 71.7, 0 ≤ g' ≤ 2.5, and 0.8 ≤ h' ≤ 1.25. The grain boundary phase alloying material includes R. 3 i' Fe j' Co k' M 3 l' R 3 Including at least one of La, Ce, Sm, Pr and Nd, M 3 The rare earth permanent magnet blank contains at least one of Zr, Ga, Cu, Sn, Al, and Zn, where i', j', k', and l' are parts by weight, 19 ≤ i' ≤ 25.2, 44.9 ≤ j' ≤ 71, 0 ≤ k' ≤ 4, and 10 ≤ l' ≤ 25. A grain boundary diffusion material is disposed on the surface of the rare earth permanent magnet blank. The grain boundary diffusion material includes a diffusion alloy material and modified graphene. The modified graphene includes graphene and a zinc alloy layer coating the graphene. The diffusion alloy material includes R... 4 m' R 5 n' Fe o' M 4 p' R 4 Including at least one of Pr and Nd, R 5 Including at least one of Dy and Tb, M 4 Includes at least one of Ga, Cu, Sn, Al, and Zn, where m', n', o', and p' are parts by weight, with 5.2 ≤ m' ≤ 14.5, 23.8 ≤ n' ≤ 31.8, 28.85 ≤ o' ≤ 55.5, and 15.5 ≤ p' ≤ 24. The zinc alloy layer includes Zn. q' Al r' Si s' Ti t' q', r', s', and t' are weight parts, 61.8≤q'≤84.87, 14.1≤r'≤34.4, 0.9≤s'≤2.2, and 0.13≤t'≤0.7; rare earth permanent magnets are obtained after hot pressing, diffusion treatment, and tempering treatment.

[0057] Please see Figure 2 The flowchart below shows a method for preparing a rare-earth permanent magnet according to an embodiment of this application, including:

[0058] S101: The first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material are mixed, and then shaped and sintered by magnetic field orientation to obtain a rare earth permanent magnet blank.

[0059] S102: A grain boundary diffusion material is placed on the surface of a rare earth permanent magnet blank. The grain boundary diffusion material includes a diffusion alloy material and modified graphene. The modified graphene includes graphene and a zinc alloy layer coating the graphene.

[0060] S103: Rare earth permanent magnets are produced by hot pressing, diffusion treatment and tempering treatment.

[0061] The rare earth permanent magnet preparation method provided in this application uses first main phase alloy raw materials, second main phase alloy raw materials, and grain boundary phase alloy raw materials containing a large amount of high-abundance rare earth elements (such as La, Ce, Sm, etc.), which reduces the cost of rare earth permanent magnets. Simultaneously, the diffusion alloy material in the grain boundary diffusion material has different properties from graphene. Graphene has poor interfacial wettability. By modifying graphene with zinc alloy material, the modified graphene has suitable density and wettability. During hot pressing, this increases the interfacial bonding force between the modified graphene and the diffusion alloy material, improves the diffusion kinetic energy of the molten diffusion alloy material, and allows graphene to diffuse into the interior of the rare earth permanent magnet blank along with the diffusion alloy material and be uniformly distributed in the grain boundaries, thus better playing the role of grain boundary modification. The modified graphene and diffusion alloy material enter the grain boundaries, where R... 5 Or R 4 It undergoes a substitution reaction with at least one of Pr and Nd or at least one of La and Ce in the alloy raw material, forming Dy2Fe on the surface of the main phase. 14 B and Tb2Fe 14 At least one of B, Pr2Fe 14 B and Nd2Fe 14 At least one of B is generated, i.e., a shell is formed, resulting in a core-shell structured main phase, which increases the crystal magnetic anisotropy constant of the main phase surface. Furthermore, the rare earth element-enriched shell can reduce or eliminate the defect of easy demagnetization of the magnet grain boundary phase, suppress the formation of antimagnetic domains, and compensate for MM2Fe. 14 The decrease in magnetic properties caused by B effectively improves the coercivity of the entire magnet while having a relatively small impact on remanence. Therefore, the preparation method provided in this application can improve the coercivity, high-temperature field durability, and mechanical properties of rare earth permanent magnets without affecting the remanence properties, thereby obtaining rare earth permanent magnets with excellent comprehensive performance.

[0062] In S101, a rare earth permanent magnet blank is prepared by mixing the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material, pressing them into shape by magnetic field orientation and sintering.

[0063] In this application, the first main phase alloying material includes R 1 a' Fe b' Co c' B d' R1 including at least one of Pr and Nd, a', b', c', d' are weight fractions, 25.5≤a'≤29.5, 66.4≤b'≤73.6, 0≤c'≤2, 0.9≤d'≤1.2. Specifically, a' can be but is not limited to 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, etc. Specifically, b' can be but is not limited to 66.5, 67, 68, 69, 70, 72, 73, etc. Specifically, c' can be but is not limited to 0, 0.5, 1, 1.5, 2, etc. Specifically, d' can be but is not limited to 1, 1.05, 1.1, 1.15, 1.2, etc.

[0064] In the present application, the second main phase alloy raw material includes R 2 e' Fe f' Co g' B h' , R 2 including at least one of La, Ce, Sm, Gd, Ho and Y, e', f', g', h' are weight fractions, 27.5≤e'≤31.5, 63.85≤f'≤71.7, 0≤g'≤2.5, 0.8≤h'≤1.25. Specifically, e' can be but is not limited to 27.8, 28, 28.5, 29, 29.2, 30, 31, etc. Specifically, f' can be but is not limited to 63.85, 65.5, 67.2, 68.9, 69, 70, 71, etc. Specifically, g' can be but is not limited to 0, 0.5, 1, 1.5, 2, etc. Specifically, h' can be but is not limited to 0.9, 1, 1.1, 1.2, etc.

[0065] In the present application, the grain boundary phase alloy raw material includes R 3 i' Fe j' Co k' M 3 l' , R 3 including at least one of La, Ce, Sm, Pr and Nd, M 3 including at least one of Zr, Ga, Cu, Sn, Al and Zn, i', j', k', l' are weight fractions, 19≤i'≤25.2, 44.9≤j'≤71, 0≤k'≤4, 10≤l'≤25. Specifically, i' can be but is not limited to 20, 21, 22, 23, 24, 25, etc. Specifically, j' can be but is not limited to 45, 50.2, 53.6, 57.8, 61.3, 65.9, 69.6, 70, etc. Specifically, l' can be but is not limited to 12, 15, 17, 20, 23, 24, etc.

[0066] In an embodiment of the present application, the mixing of the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material comprises separately melting the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material to obtain first main phase alloy raw material ingots or rapidly solidified sheets, second main phase alloy raw material ingots or rapidly solidified sheets and grain boundary phase alloy raw material ingots or rapidly solidified sheets; and mixing the first main phase alloy raw material ingots or rapidly solidified sheets, the second main phase alloy raw material ingots or rapidly solidified sheets and the grain boundary phase alloy raw material ingots or rapidly solidified sheets. In another embodiment of the present application, the mixing of the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material comprises separately melting the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material to obtain first main phase alloy raw material ingots or rapidly solidified sheets, second main phase alloy raw material ingots or rapidly solidified sheets and grain boundary phase alloy raw material ingots or rapidly solidified sheets; mixing the first main phase alloy raw material ingots or rapidly solidified sheets, the second main phase alloy raw material ingots or rapidly solidified sheets and the grain boundary phase alloy raw material ingots or rapidly solidified sheets, and then crushing and powdering. In yet another embodiment of the present application, the mixing of the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material comprises separately melting the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material to obtain first main phase alloy raw material ingots or rapidly solidified sheets, second main phase alloy raw material ingots or rapidly solidified sheets and grain boundary phase alloy raw material ingots or rapidly solidified sheets; crushing and powdering the first main phase alloy raw material ingots or rapidly solidified sheets, the second main phase alloy raw material ingots or rapidly solidified sheets and the grain boundary phase alloy raw material ingots or rapidly solidified sheets to obtain the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material; and mixing the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material.

[0067] In the present application, the rapid quenching thin slice can be obtained by using a method well known to those skilled in the art. In an embodiment, the rapid quenching thin slice can be prepared by using a rapid quenching ribbon process, and the spinning speed (for example, the linear speed of the copper roller surface) can be 1 m / s-2.5 m / s (for example, 1 m / s, 1.2 m / s, 1.5 m / s, 1.9 m / s, 2 m / s, 2.3 m / s, etc.). In the present application, the crushing can be performed by using a method well known to those skilled in the art, as long as the obtained ingot or ribbon can be fully crushed to obtain a crushed powder. Specifically, the hydrogen crushing method can be used. In an embodiment, the hydrogen crushing process includes hydrogen absorption at 0.1 MPa-1.5 MPa (for example, 0.2 MPa, 0.5 MPa, 0.8 MPa, 1 MPa, 1.3 MPa, etc.) hydrogen pressure for 1 h-3 h (for example, 1 h, 1.5 h, 2 h, 2.5 h, 2.8 h, etc.) at 15°C-25°C (for example, 17°C, 18°C, 20°C, 23°C, 24°C, etc.), and hydrogen desorption at 500°C-650°C (for example, 525°C, 550°C, 570°C, 600°C, 630°C, etc.) for 4 h-8 h (for example, 4.5 h, 5 h, 6 h, 7 h, 8 h, etc.). In the present application, the powdering can be performed by using a method well known to those skilled in the art, as long as the hydrogen crushed powder can be prepared into an alloy powder with a target particle size. The jet milling method can be used, and an antioxidant needs to be added before jet milling. Specifically, the antioxidant can include but is not limited to a neodymium-iron-boron special antioxidant, for example, a neodymium-iron-boron special antioxidant with a trade name of KM-01 purchased from Beijing Junce Feng Science and Technology Development Co., Ltd. In an embodiment, the hydrogen crushed powder is 100 parts, and the antioxidant is 0.03 parts-0.15 parts (for example, 0.05 parts, 0.08 parts, 0.1 parts, 0.13 parts, etc.) by weight fraction. In an embodiment, the powdering can obtain an alloy powder with an average particle size of 2 μm-4.5 μm (for example, 2.5 μm, 3 μm, 3.2 μm, 3.5 μm, 3.7 μm, 4 μm, etc.). In the present application, the alloy powder can be mixed with a lubricant to improve the dispersibility of the alloy powder. For example, the alloy powder of the first main phase alloy raw material, the alloy powder of the second main phase alloy raw material, and the alloy powder of the grain boundary phase alloy raw material can be mixed with the lubricant respectively, and then all mixed together; or the alloy powder of the first main phase alloy raw material, the alloy powder of the second main phase alloy raw material, and the alloy powder of the grain boundary phase alloy raw material can be mixed together, and then mixed with the lubricant. In an embodiment, the alloy powder is 100 parts, and the lubricant is 0.02 parts-0.2 parts (for example, 0.05 parts, 0.08 parts, 0.1 parts, 0.13 parts, 0.15 parts, 0.19 parts, etc.) by weight fraction. Specifically, the lubricant can include but is not limited to at least one of gasoline, oleic acid, stearic acid, polyethylene glycol, sorbitan, and glyceryl stearate.

[0068] In an embodiment of the present application, the ratio of the mass of the second main phase alloy raw material to the sum of the mass of the first main phase alloy raw material and the mass of the second main phase alloy raw material is 50%-69%. It can be understood that the mass of the first main phase alloy raw material is m1, the mass of the first main phase alloy raw material is m2, and m2 / (m1+m2) is 50%-69%, which is beneficial to obtain a rare earth permanent magnet with excellent comprehensive performance. Specifically, the ratio of the mass of the second main phase alloy raw material to the sum of the mass of the first main phase alloy raw material and the mass of the second main phase alloy raw material can be but is not limited to 50%, 53%, 55%, 57%, 60%, 63%, 65%, 68%, etc.

[0069] In an embodiment of the present application, the ratio of the mass of the grain boundary phase alloy raw material to the sum of the mass of the first main phase alloy raw material, the mass of the second main phase alloy raw material and the mass of the grain boundary phase alloy raw material is 5%-17%. It can be understood that the mass of the first main phase alloy raw material is m1, the mass of the first main phase alloy raw material is m2, and the mass of the grain boundary phase alloy raw material is m3, and m3 / (m1+m2+m3) is 5%-17%, which is beneficial to obtain a rare earth permanent magnet with excellent comprehensive performance. Specifically, the ratio of the mass of the grain boundary phase alloy raw material to the sum of the mass of the first main phase alloy raw material, the mass of the second main phase alloy raw material and the mass of the grain boundary phase alloy raw material can be but is not limited to 5%, 7%, 10%, 13%, 15%, 17%, etc.

[0070] In an embodiment of the present application, the magnetic field orientation compression molding includes processing at a pressure of 170MPa-210MPa (such as 170MPa, 180MPa, 190MPa, 200MPa, 210MPa, etc.) for 60s-150s (such as 60s, 80s, 100s, 115s, 130s, 145s, etc.) under a magnetic field of 1.5T-3.5T (such as 1.5T, 2T, 2.3T, 2.5T, 2.8T, 3T, 3.3T, etc.), which is beneficial to the molding of the rare earth permanent magnet blank and ensures the magnetic properties of the prepared rare earth permanent magnet.

[0071] In an embodiment of the present application, the sintering includes processing at 1030°C-1090°C for 4h-5.5h. Specifically, the temperature of sintering can be but is not limited to 1030°C, 1040°C, 1050°C, 1060°C, 1070°C, 1080°C, etc., and the time of sintering can be but is not limited to 4h, 4.5h, 5h, 5.5h, etc.

[0072] In an embodiment of the present application, the sintering is followed by a pre-tempering treatment. The pre-tempering treatment improves the performance of the rare earth permanent magnet. In an embodiment of the present application, the pre-tempering treatment comprises a treatment at 890-950°C (e.g. 900°C, 910°C, 920°C, 930°C, 940°C, etc.) for 2.5-5h (e.g. 3h, 3.5h, 4h, 4.5h, etc.), followed by a treatment at 480-520°C (e.g. 490°C, 500°C, 510°C, 515°C, etc.) for 3.5-8h (e.g. 4h, 4.5h, 5h, 6h, 7h, 8h, etc.). This is beneficial for the flow and distribution of the Nd-rich phase between the main phase, thus improving the performance of the rare earth permanent magnet. In the present application, the rare earth permanent magnet blank can also be machined to obtain a structure with a desired shape and size.

[0073] In an embodiment of the present application, the thickness of the rare earth permanent magnet blank can be 1-10mm, which is beneficial for the subsequent diffusion of the grain boundary diffusion material. Specifically, the thickness of the rare earth permanent magnet blank can be, but is not limited to, 1mm, 2mm, 5mm, 7mm, 8mm, etc. In an embodiment, the thickness of the rare earth permanent magnet blank can be 2-7mm. In an embodiment of the present application, the rare earth permanent magnet blank can be in a sheet structure, which is beneficial for the subsequent diffusion of the grain boundary diffusion material.

[0074] In S102, the grain boundary diffusion material comprises a diffusion alloy material, and the diffusion alloy material comprises R 4 m' R 5 n' Fe o' M 4 p' , R 4 comprises at least one of Pr and Nd, R 5 comprises at least one of Dy and Tb, M 4m', n', o', p' are weight fractions, 5.2≤m'≤14.5, 23.8≤n'≤31.8, 28.85≤o'≤55.5, 15.5≤p'. Specifically, m' can be but is not limited to 5.5, 6, 6.8, 7.4, 8.5, 9, 10.7, 12, 13, 14, etc. Specifically, n' can be but is not limited to 24, 25.7, 28.1, 29.5, 30, 31, etc. Specifically, o' can be but is not limited to 29, 30.7, 32.5, 35.7, 40.1, 45.4, 48.5, 50, 53.4, 53.7, etc. Specifically, p' can be but is not limited to 16, 17.5, 19, 20.3, 21.5, 23, etc. In an embodiment of the present application, in the diffusion alloy raw material, 6≤m'≤14, 24≤n'≤31, 30.7≤o'≤53.4, 16≤p'≤23, which is further conducive to obtaining a rare earth permanent magnet with high coercivity and good mechanical properties at low cost and with less impact on the residual magnetism. The grain boundary diffusion material further comprises modified graphene, and the modified graphene comprises graphene and a zinc alloy layer covering the graphene, and the zinc alloy layer comprises Zn q' Al r' Si s' Ti t' q', r', s', t' are weight fractions, 61.8≤q'≤84.87, 14.1≤r'≤34.4, 0.9≤s'≤2.2, 0.13≤t'≤0.7. Specifically, q' can be but is not limited to 62, 65, 68, 70.5, 74.8, 78.1, 80.5, 82.7, etc. Specifically, r' can be but is not limited to 15, 18.5, 20.7, 22.3, 25.5, 29.1, 30.5, 33.6, etc. Specifically, s' can be but is not limited to 1, 1.2, 1.5, 1.8, 2, 2.1, etc. Specifically, t' can be but is not limited to 0.2, 0.35, 0.5, 0.62, 0.7, etc.

[0075] In the related art, structural defects are prone to exist at the junction of the main phase and the grain boundary phase of the rare earth permanent magnet, and the area of the structural defects is the nucleation center of the reverse magnetization domain, which is prone to cause demagnetization of the magnet; the grain boundary phase alloy raw material provided in the present application has low-melting-point metal elements, which can reduce the melting point of the grain boundary phase, so that the grain boundary phase alloy raw material melts to become a diffusion channel of the grain boundary diffusion material when it is subjected to subsequent diffusion process treatment, the grain boundary diffusion material diffuses along the low-melting-point grain boundary phase, reduces or eliminates the defect that the grain boundary impurity phase of the magnet is prone to demagnetization, and inhibits the generation of the reverse magnetization domain.

[0076] In an embodiment of the present application, the step of disposing the grain boundary diffusion material on the surface of the rare earth permanent magnet blank further comprises: mixing graphene with zinc alloy material, and obtaining modified graphene after ball milling. Graphene is a two-dimensional atomic crystal structure of hexagonal honeycomb structure formed by sp2 hybridization of carbon atoms, which has ultra-high Young's modulus and tensile strength, and thus is an ideal reinforcing phase that can improve the mechanical properties of the rare earth permanent magnet. When graphene is directly used as a grain boundary diffusion material, graphene is difficult to diffuse into the interior of the rare earth permanent magnet, and even if it enters, it is difficult to disperse uniformly, and the improvement of the mechanical properties is limited. Understandably, the zinc alloy material is Zn q' Al r' Si s' Ti t' The zinc alloy material in the present application belongs to a low-melting-point alloy system, has good casting performance, and does not affect the magnetic properties of the rare earth permanent magnet. By coating graphene with zinc alloy material, modified graphene is formed, the overall density of graphene is improved, the interface wettability between graphene and the diffusion alloy material is improved, graphene can fully contact with the diffusion alloy material, the interface bonding between graphene and the diffusion alloy material is improved, graphene can diffuse into the interior of the rare earth permanent magnet blank with the diffusion alloy material and be uniformly distributed in the grain boundary, thereby significantly improving the mechanical properties of the rare earth permanent magnet.

[0077] In an embodiment of the present application, the ball-to-material ratio in ball milling is (5-10):1, the rotation speed is 160r / min-180r / min, and the time is 6h-10h, which is conducive to the coating of zinc alloy on graphene, improves the coating uniformity and coating efficiency, and does not damage the material structure, so that graphene can effectively play a role. In the ball milling process, the zinc alloy material has good ductility and can be flaked, which increases the specific surface area of the inclusion graphene, embeds the graphene sheet layer on the surface of the zinc alloy material, and realizes firm combination. Specifically, the ball-to-material ratio in ball milling can be, but is not limited to, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc., the rotation speed can be, but is not limited to, 160r / min, 165r / min, 170r / min, 175r / min, 180r / min, etc., and the time can be, but is not limited to, 6h, 7h, 8h, 9h, 10h, etc. In an embodiment of the present application, ball milling can be carried out in an inert atmosphere (such as argon) or under vacuum conditions.

[0078] In an embodiment of the present application, the zinc alloy material can be prepared by a rapid solidification atomization method. In an embodiment, the zinc alloy material is prepared by mixing the elements in the zinc alloy material according to the ratio, heating to 485-518°C for smelting, using an inert gas (such as argon) as a protective atmosphere during the smelting process, and using a gas atomization method with a cooling speed of 103-105K / s and an atomization pressure of 20-50MPa. The atomization medium can be argon. The above method can be used to prepare a zinc alloy material with small particle size, low melting point, uniform composition, fast melting speed, and good wettability.

[0079] In an embodiment of the present application, the average particle size of the zinc alloy material is 58-80nm, which is beneficial for coating the graphene. Specifically, the average particle size of the zinc alloy material can be, but is not limited to, 60nm, 65nm, 68nm, 70nm, 73nm, 75nm, 79nm, etc. In an embodiment, the average particle size of the zinc alloy material can be 60-78nm.

[0080] In an embodiment of the present application, the melting point of the zinc alloy material is less than or equal to 650°C. That is, the melting point of the zinc alloy layer is less than or equal to 650°C, which forms a molten state during diffusion, promotes the diffusion of graphene, and is beneficial for further improving the mechanical properties of the rare earth permanent magnet without affecting the magnetic properties of the rare earth permanent magnet.

[0081] In an embodiment of the present application, the average particle size of the graphene is 6-23nm, which is beneficial for coating the zinc alloy material. Specifically, the average particle size of the graphene can be, but is not limited to, 6nm, 10nm, 13nm, 15nm, 17nm, 20nm, or 23nm, etc. In an embodiment, the average particle size of the graphene can be 10-20nm.

[0082] In an embodiment of the present application, the average particle size of the modified graphene is 10-25nm, which is beneficial for further improving the mechanical properties of the rare earth permanent magnet, improving the uniform dispersion of the rare earth permanent magnet, and reducing the preparation cost and process difficulty. Specifically, the average particle size of the modified graphene can be, but is not limited to, 10nm, 12nm, 15nm, 18nm, 20nm, 23nm, etc. In an embodiment, the average particle size of the modified graphene can be 15-23nm.

[0083] In an embodiment of the present application, the mass content of the graphene in the modified graphene is 19-38%, which is further beneficial for improving the mechanical properties of the rare earth permanent magnet. Specifically, the mass content of the graphene in the modified graphene can be, but is not limited to, 20%, 23%, 25%, 27%, 30%, 33%, 35%, or 37%, etc.

[0084] In an embodiment of the present application, the mass content of the modified graphene in the grain boundary diffusion material is 10%-23%. Specifically, the mass content of the modified graphene in the grain boundary diffusion material can be, but is not limited to, 10%, 13%, 15%, 18%, 20%, 22%, etc. In an embodiment, the mass content of the modified graphene in the grain boundary diffusion material is 12%-22%.

[0085] In an embodiment of the present application, the diffusion alloy material can be prepared by a melt rapid quenching method. In an embodiment, the rapid quenching speed can be 18 m / s-28 m / s. In another embodiment, the rapid quenching speed can be 19 m / s-26 m / s. In a specific embodiment, the diffusion alloy material is prepared by a rapid quenching speed of 18 m / s-28 m / s after ingredients are prepared and mixed according to the proportion of each element in the diffusion alloy material.

[0086] In an embodiment of the present application, the average particle size of the diffusion alloy material is 30 nm-85 nm, which is beneficial to uniform mixing and dispersion of the modified graphene, and at the same time, the melting and adhering effect of the rare earth permanent magnet blank is good, the preparation difficulty is small, and the preparation cost is low. Specifically, the average particle size of the diffusion alloy material can be, but is not limited to, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 75 nm, 80 nm, etc. In an embodiment, the average particle size of the diffusion alloy material can be 35 nm-80 nm.

[0087] In an embodiment of the present application, the melting point of the diffusion alloy material is less than or equal to 650℃, which forms a molten state in the diffusion process, promotes the diffusion of graphene, is beneficial to further improving the mechanical properties of the rare earth permanent magnet, and does not affect the magnetic properties of the rare earth permanent magnet. In an embodiment, the melting point of the diffusion alloy material can be 450℃-650℃.

[0088] In the present application, the rare earth permanent magnet blank has oppositely arranged first and second surfaces, and the grain boundary diffusion material can be arranged on the first surface, the second surface, or both the first and second surfaces, and a rare earth permanent magnet with excellent comprehensive performance can be obtained. The mixing method of the diffusion alloy material and the modified graphene is not limited in the present application, for example, mechanical stirring, ball milling, etc. can be used; the form of the grain boundary diffusion material covering the surface of the rare earth permanent magnet blank is not limited, for example, coating, spraying, coating, dipping, suspension adhesion, barrel plating electrophoresis, etc. In an embodiment, the grain boundary diffusion material can be directly coated on the first and second surfaces of the rare earth permanent magnet blank, which is simple to operate and can reduce the preparation cost.

[0089] In an embodiment of the present application, the surface of the rare earth permanent magnet blank can be treated before the grain boundary diffusion material is provided. Specifically, the surface treatment can be, but is not limited to, pickling or mechanical polishing. In an embodiment, the pickling can use a 0.3wt% nitric acid solution.

[0090] In S103, the rare earth permanent magnet with excellent magnetic properties and good mechanical properties is prepared after the hot pressing and diffusion treatment.

[0091] In an embodiment of the present application, the hot pressing includes a temperature of 550-800°C (such as 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, etc.), a pressure of 80-150MPa (such as 80MPa, 85MPa, 90MPa, 100MPa, 120MPa, 140MPa, etc.), and a vacuum degree of 10 -3 Pa-10 -2 Pa for 30-150min (such as 50min, 70min, 90min, 100min, 120min, etc.). In an embodiment of the present application, the pressure direction of the hot pressing is parallel to the easy magnetization axis direction of the rare earth permanent magnet blank. The presence of the hot pressing pressure in the present application increases the diffusion kinetic energy of the molten diffusion alloy material, which can be distributed between the main phase grains along the grain boundary diffusion channel, improve the orientation degree of the main phase, improve the remanence, and thus improve the performance of the rare earth permanent magnet.

[0092] In an embodiment of the present application, the diffusion treatment includes a temperature of 600-1000°C (such as 650°C, 700°C, 800°C, 900°C, 950°C, 1000°C, etc.), and a vacuum degree of 10 -5 Pa-10 -2 Pa for 2-12h (such as 3h, 5h, 7h, 8h, 10h, 11h, etc.), which is conducive to the melting of the grain boundary diffusion material and does not affect the properties of the rare earth permanent magnet blank.

[0093] In an embodiment of the present application, the tempering treatment includes a temperature of 400-600°C (such as 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, etc.), and a vacuum degree of 10 -5 Pa-10 -2 Pa for 2.5-10h (such as 3h, 5h, 7h, 8h, 10h, etc.), which is conducive to further homogenizing the structure, eliminating defects, and improving the coercivity.

[0094] In the present application, impurities such as oxides, carbides, and nitrides can be introduced during the preparation of the rare earth permanent magnet to form grain boundary impurity phases.

[0095] In the present application, the grain boundary diffusion material is sufficient to form a grain boundary diffusion layer on the surface of the rare earth permanent magnet after diffusion treatment. The grain boundary diffusion layer can be removed or thinned according to the needs to obtain the final rare earth permanent magnet. It can be understood that the material of the grain boundary diffusion layer is the grain boundary diffusion material.

[0096] In the present application, the preparation method of the rare earth permanent magnet can be used to prepare the rare earth permanent magnet of any of the above embodiments.

[0097] In an embodiment of the present application, the mass content of the modified graphene in the shell layer of the main phase of the rare earth permanent magnet is 2.57%-4.91%. Specifically, the mass content of the modified graphene in the shell layer of the main phase of the rare earth permanent magnet can be, but is not limited to, 2.57%, 2.73%, 2.89%, 3.05%, 3.27%, 3.45%, 3.7%, 3.91%, 4.3%, 4.56% or 4.8% and the like. In an embodiment, the mass content of the modified graphene in the shell layer of the main phase of the rare earth permanent magnet can be 2.7%-4.5%. In another embodiment, the mass content of the modified graphene in the shell layer of the main phase of the rare earth permanent magnet can be 3%-4.8%.

[0098] In an embodiment of the present application, the mass content of the modified graphene in the grain boundary phase of the rare earth permanent magnet is 2.03%-3.23%. Specifically, the mass content of the modified graphene in the grain boundary phase of the rare earth permanent magnet can be, but is not limited to, 2.03%, 2.1%, 2.25%, 2.47%, 2.6%, 2.82%, 2.95%, 3%, 3.15% or 3.2% and the like. In an embodiment, the mass content of the modified graphene in the grain boundary phase of the rare earth permanent magnet is 2.2%-3.1%. In another embodiment, the mass content of the modified graphene in the grain boundary phase of the rare earth permanent magnet is 2.5%-3%.

[0099] The present application also provides an electric machine comprising the rare earth permanent magnet of the first aspect or the rare earth permanent magnet prepared by the preparation method of the second aspect. The permanent magnet drive electric machine has a long service life and excellent comprehensive performance, and can be applied to the communication technology industry (such as mobile phone vibration motor, loudspeaker and the like), medical equipment field (such as nuclear magnetic resonance instrument and the like), automobile field (such as power steering motor, electric vehicle motor), new energy field (such as wind driven generator and the like).

[0100] The effects of the technical solutions of the present application are further described below through specific examples.

[0101] Example 1

[0102] The formula of Pr 26 Fe 71.9 Co 0.5The raw material of B1 was treated by tape casting at a copper roll surface linear velocity of 1.1 m / s, the obtained tape was hydrogenated at 0.12 MPa hydrogen pressure and 22°C for 1.5 h, and then dehydrogenated at 510°C for 4.2 h to obtain first hydrogenated powder. Then 100 parts by weight of the first hydrogenated powder was uniformly mixed with 0.035 parts by weight of neodymium-iron-boron antioxidant (Beijing Junce Feng Science and Technology Development Co., Ltd., brand KM-01), followed by grinding by air flow mill to prepare micro powder with an average particle size of 2.1 μm, to obtain first main phase alloy raw material.

[0103] The raw material with a formula of La 16 Sm 12 Fe 70 Co 0.5 B 0.9 was treated by tape casting at a copper roll surface linear velocity of 1.15 m / s, the obtained tape was hydrogenated at 0.13 MPa hydrogen pressure and 23°C for 1.6 h, and then dehydrogenated at 515°C for 4.3 h to obtain second hydrogenated powder. Then 100 parts by weight of the second hydrogenated powder was uniformly mixed with 0.04 parts by weight of neodymium-iron-boron antioxidant, followed by grinding by air flow mill to prepare micro powder with an average particle size of 2.2 μm, to obtain second main phase alloy raw material.

[0104] The raw material with a formula of La 12 Sm8Fe 66.4 Co1Zr 12 was treated by tape casting at a copper roll surface linear velocity of 1.2 m / s, the obtained tape was hydrogenated at 0.14 MPa hydrogen pressure and 24°C for 1.7 h, and then dehydrogenated at 520°C for 4.4 h to obtain third hydrogenated powder. Then 100 parts by weight of the third hydrogenated powder was uniformly mixed with 0.045 parts by weight of neodymium-iron-boron antioxidant, followed by grinding by air flow mill to prepare micro powder with an average particle size of 2.3 μm, to obtain grain boundary phase alloy raw material.

[0105] 48 parts by weight of the first main phase alloy raw material and 52 parts by weight of the second main phase alloy raw material were uniformly mixed to obtain main phase alloy powder. 92 parts by weight of the main phase alloy powder and 8 parts by weight of the grain boundary phase alloy powder were uniformly mixed to obtain rare earth permanent magnet raw material. 100 parts by weight of the rare earth permanent magnet raw material was uniformly mixed with 0.03 parts by weight of gasoline (Haotian Chemical Co., Ltd., brand YS-06) to obtain rare earth permanent magnet blank alloy powder.

[0106] The rare earth permanent magnet blank alloy powder is formed in a constant magnetic field of 1.6T, and then is subjected to isostatic pressing at 175MPa for 62s; then is sintered at 1035℃ for 4.2h; and then is subjected to pre-tempering treatment, including first-tempering at 855℃ for 2.5h, and second-tempering at 482℃ for 3.5h, to obtain a rare earth permanent magnet blank. The rare earth permanent magnet blank is mechanically processed into a cuboid with a length of 17mm, a width of 14mm, and a thickness of 2mm.

[0107] A low-melting point zinc alloy with a formula of Zn 82.25 Al 16 Si1Ti 0.15 is prepared by a rapid solidification atomization method, a cooling speed of the atomization method is 104K / s, an atomization pressure is 25MPa, and a microfine powder with an average particle size of 60nm is obtained, to obtain a zinc alloy material. The zinc alloy material is mixed with graphene and placed in a ball mill, the ball milling is carried out under the protection of inert gas argon, a low-speed ball milling ball material ratio is 6:1, a rotating speed is 165r / min, and a ball milling time is 7h, to obtain modified graphene with an average particle size of 15nm, and a mass content of the graphene in the modified graphene is 20%.

[0108] Raw materials with a formula of Pr6Dy 24 Fe 53.4 Al 16 are smelted at 600℃, diffusion alloy thin strips are prepared at a rapid quenching speed of 19m / s, and then are ground by ball milling to obtain microfine powder with an average particle size of 35nm, to obtain a diffusion alloy material. The diffusion alloy material is mixed with modified graphene to obtain a grain boundary diffusion material, and a mass content of the modified graphene in the grain boundary diffusion material is 12%.

[0109] The rare earth permanent magnet blank is subjected to sand blasting treatment, the grain boundary diffusion material is uniformly coated on upper and lower surfaces of the rare earth permanent magnet blank, and then is placed in a hot pressing mold. The hot pressing mold is placed in a vacuum hot pressing furnace, and is subjected to hot pressing at a vacuum degree of 8×10 -2 Pa, a pressing temperature of 550℃, and a pressure of 80Mpa, and is kept for 30min, and a pressure direction is parallel to an easy magnetization axis direction. Then, the grain boundary diffusion is carried out at a vacuum degree of 5×10 -2 Pa and a diffusion temperature of 850℃ for 8h. Then, tempering treatment is carried out at a temperature of 410℃ for 2.5h, a vacuum degree of 4×10 -2 Pa, to obtain a rare earth permanent magnet A1. A core of a main phase of the rare earth permanent magnet A1 is composed of Pr8La 11 Sm8Fe 70.9 Co 0.5 B 0.9 , and a shell layer of the main phase is composed of La6Sm 5.2 Pr 3.9Dy 6.7 Fe 63.54 Co 0.2 B 0.28 Zr3Al5Zn 3.8 Si 0.07 Ti 0.01 C 1.6 The grain boundary phase is composed of La5Sm 2.6 Pr 2.2 Dy 9.7 Fe 60.59 Co 0.2 Zr4Al5Zn 7.5 Si 0.09 Ti 0.02 C 2.4 The mass content of rare earth elements in the shell of the main phase is 0.807 times that in the core of the main phase, and the thickness of the shell is 1μm-3.3μm. The mass content of grain boundary phase in the rare earth permanent magnet A1 is 22%.

[0110] The rare-earth permanent magnet A1 was cut, and the cut surface underwent appropriate surface treatment. Its microstructure was then observed under an electron scanning microscope. The results are as follows: Figure 3 As shown, it can be clearly seen that its main phase is divided into the kernel ( Figure 3 31) and shell ( Figure 3 32 in the middle), and grain boundary phase ( Figure 3 33) Isolate and / or cover adjacent main phases.

[0111] Example 2

[0112] Similar to Example 1, except that the rare earth permanent magnet blank is machined into a cuboid with a length of 17 mm, a width of 14 mm, and a thickness of 10 mm. The remaining processes are the same as in Example 1, yielding rare earth permanent magnet A2. The core composition of the main phase of rare earth permanent magnet A2 is Pr8La. 11 Sm8Fe 70.9 Co 0.5 B 0.9 The shell composition of the main phase is La6Sm 5.2 Pr 3.9 Dy 6.7 Fe 63.54 Co 0. 2B 0.28 Zr3Al5Zn 3.8 Si 0.07 Ti 0.01 C 1.6 The grain boundary phase is composed of La5Sm 2.6 Pr 2.2 Dy 9.7 Fe 60.59 Co 0.2Zr4Al5Zn 7.5 Si 0.0 9Ti 0.02 C 2.4 The mass content of rare earth elements in the shell of the main phase is 0.807 times that in the core of the main phase, the thickness of the shell is 0.6-2.7 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet A2 is 20%.

[0113] Example 3

[0114] The raw material with the formula of Nd 28 Fe 68.8 Co 1.5 B 1.1 is subjected to tape casting at a copper roll surface linear velocity of 2.3 m / s, the obtained tape is hydrogenated at 1.4 MPa hydrogen pressure and 24°C for 2.8 h, and then dehydrogenated at 648°C for 7.8 h to obtain first hydrogen-fragmented powder. Then 100 parts by weight of the first hydrogen-fragmented powder is mixed with 0.12 parts by weight of neodymium-iron-boron antioxidant, and then ground by air jet mill to obtain fine powder with an average particle size of 4.3 μm, thereby obtaining first main phase alloy raw material.

[0115] The raw material with the formula of Ce 14 Gd 16 Fe 66.2 Co2B 1.2 is subjected to tape casting at a copper roll surface linear velocity of 2.4 m / s, the obtained tape is hydrogenated at 1.3 MPa hydrogen pressure and 23°C for 2.9 h, and then dehydrogenated at 649°C for 7.9 h to obtain second hydrogen-fragmented powder. Then 100 parts by weight of the second hydrogen-fragmented powder is mixed with 0.13 parts by weight of neodymium-iron-boron antioxidant, and then ground by air jet mill to obtain fine powder with an average particle size of 4.4 μm, thereby obtaining second main phase alloy raw material.

[0116] The raw material with the formula of Ce 13 Pr 12 Fe 47.4 Co3Ga 24 is subjected to tape casting at a copper roll surface linear velocity of 2.5 m / s, the obtained tape is hydrogenated at 1.5 MPa hydrogen pressure and 25°C for 3 h, and then dehydrogenated at 650°C for 8 h to obtain third hydrogen-fragmented powder. Then 100 parts by weight of the third hydrogen-fragmented powder is mixed with 0.15 parts by weight of neodymium-iron-boron antioxidant, and then ground by air jet mill to obtain fine powder with an average particle size of 4.5 μm, thereby obtaining grain boundary phase alloy raw material.

[0117] 33 parts by weight of the first main phase alloy raw material and 67 parts by weight of the second main phase alloy raw material are uniformly mixed to obtain a main phase alloy powder. 84 parts by weight of the main phase alloy powder and 16 parts by weight of the grain boundary phase alloy powder are uniformly mixed to obtain a rare earth permanent magnet raw material. 100 parts by weight of the rare earth permanent magnet raw material is uniformly mixed with 0.02 parts by weight of oleic acid (Haotian Chemical Co., Ltd.) to obtain a rare earth permanent magnet blank alloy powder.

[0118] The rare earth permanent magnet blank alloy powder is formed in a constant magnetic field of 3.5T, and then is subjected to isostatic pressing at 210MPa for 150s. Then, the rare earth permanent magnet blank alloy powder is sintered at 1090℃ for 4.5h, and then is subjected to pre-tempering treatment, including first tempering at 950℃ for 3h, and second tempering at 520℃ for 4h, to obtain a rare earth permanent magnet blank. The rare earth permanent magnet blank is mechanically processed into a cuboid with a length of 14mm, a width of 12mm, and a thickness of 7mm.

[0119] A low-melting-point zinc alloy with a formula of Zn 62.8 Al 34 Si2Ti 0.6 is prepared by a rapid solidification atomization method, a cooling speed of the atomization method is 105K / s, an atomization pressure is 48MPa, a micro-powder with an average particle size of 78nm is obtained, and a zinc alloy material is obtained. The zinc alloy material is mixed with graphene and placed in a ball mill, the ball milling is carried out under the protection of inert gas argon, the low-speed ball milling ball material ratio is 9:1, the rotating speed is 175r / min, and the ball milling time is 9h, a modified graphene with an average particle size of 23nm is prepared, and the mass content of the graphene in the modified graphene is 37%.

[0120] Raw materials with a formula of Nd 14 Tb 31 Fe 31.4 Ga 23 are smelted at 850℃, a diffusion alloy thin strip is prepared at a rapid quenching speed of 26m / s, then is ground by ball milling, a micro-powder with an average particle size of 80nm is prepared, and a diffusion alloy material is obtained. The diffusion alloy material is mixed with the modified graphene to obtain a grain boundary diffusion material, and the mass content of the modified graphene in the grain boundary diffusion material is 22%.

[0121] After the rare earth permanent magnet blank is pickled with 0.3wt% nitric acid aqueous solution, the grain boundary diffusion material is uniformly coated on the upper and lower surfaces of the rare earth permanent magnet blank, and then is placed in a hot pressing mold. The hot pressing mold is placed in a vacuum hot pressing furnace, and is subjected to hot pressing at a vacuum degree of 1×10 -2 Pa, a pressing temperature of 800℃, and a pressure of 150Mpa, and is kept for 150min, and the pressure direction is parallel to the direction of the easy magnetization axis. Then, the grain boundary diffusion material is subjected to hot pressing at a vacuum degree of 1×10 -5Pa, the diffusion temperature is 600°C, and the grain boundary diffusion is performed for 12 hours. Then, tempering treatment is performed at a temperature of 400°C for 10 hours under a vacuum degree of 1 x 10 -2 Pa, to obtain a rare earth permanent magnet A3. The core of the main phase of the rare earth permanent magnet A3 is composed of Nd 10 Ce 12 Gd8Fe 66.4 Co 1.8 B 1.1 The shell layer of the main phase is composed of Ce7Gd 8.9 Pr 3.8 Nd4Tb 8.8 Fe 41.53 Co 1.9 B 0.45 Ga8Al6Zn 6.3 Si 0.09 Ti 0.03 C 2.5 The grain boundary phase is composed of Ce 7.3 Pr3Nd 3.8 Tb 14.5 Fe 30.8 Co 1.7 Ga 14 Al 12 Zn8Si 0.15 Ti 0.05 C4, the mass content of the rare earth element in the shell layer of the main phase is 1.083 times the mass content of the rare earth element in the core of the main phase, the thickness of the shell layer is 1.5 μm-3 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet A3 is 37%.

[0122] Example 4

[0123] The process is substantially the same as that of Example 3, except that 50 parts by weight of the first main phase alloy raw material and 50 parts by weight of the second main phase alloy raw material are uniformly mixed to obtain a main phase alloy powder, and the remaining process is the same as that of Example 3, to obtain a rare earth permanent magnet A4. The core of the main phase of the rare earth permanent magnet A4 is composed of Nd 9.93 Ce 8.9 Gd 10.08 Fe 67.49 Co 1.75 B 1.15 The shell layer of the main phase is composed of Nd 6.1 Ce 7.18 Gd 3.2 Pr2Tb 8.7 Fe 47.02 Co 1.72 B 0.46 Ga 8.4 Al 7.2 Zn 4.8 Si 0.09 Ti0.03 C 2.4 , the grain boundary phase is composed of Ce 7.3 Pr3Nd 3.8 Tb 14.5 Fe 30.8 Co 1.7 Ga 14 Al 12 Zn8Si 0.15 Ti 0.05 C4, the mass content of rare earth elements in the shell layer of the main phase is 1.093 times that in the core of the main phase, the thickness of the shell layer is 1.5 μm-2.5 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet A4 is 38%.

[0124] Example 5

[0125] The process is substantially the same as that in Example 3, except that 95 parts by weight of the main phase alloy powder and 5 parts by weight of the grain boundary phase alloy powder are uniformly mixed to obtain a rare earth permanent magnet raw material, and the remaining process is the same as that in Example 3 to obtain a rare earth permanent magnet A5. The core of the main phase of the rare earth permanent magnet A5 is composed of Nd 10 Ce 12 Gd8Fe 66.4 Co 1.8 B 1.1 , the shell layer of the main phase is composed of Nd 6.94 Ce 7.998 Gd 3.2 Pr 1.06 Tb 8.742 Fe 49.872 Co 1.458 B 0.44 Ga 12.39 Al 1.54 Si 0.09 Ti 0.03 Zn 2.876 C 2.664 , the grain boundary phase is composed of Ce 5.33 Pr 2.92 Nd 3.83 Tb 14.57 Fe 38.77 Co 1.23 Ga 20.65 Al 2.57 Si 0.15 Ti 0.045 Zn 4.79 C 4.44 , the mass content of rare earth elements in the shell layer of the main phase is 1.028 times that in the core of the main phase, the thickness of the shell layer is 1 μm-2 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet A5 is 36%.

[0126] Example 6

[0127] A raw material having a composition of Pr 27 Fe 70.35 Co1B 1.05 was subjected to a spin casting treatment at a copper roll surface linear velocity of 1 m / s. The resultant spin-cast sheet was hydrogen-absorbed at 0.1 MPa hydrogen pressure for 3 h at 15°C, and then hydrogen- desorbed at 500°C for 8 h to obtain first hydrogen-fragmented powder. Then, 100 parts by weight of the first hydrogen-fragmented powder was mixed with 0.03 parts by weight of a neodymium-iron-boron antioxidant, and then ground by an air jet mill to produce fine powder having an average particle diameter of 2 μm, to obtain a first main phase alloy raw material.

[0128] A raw material having a composition of La 12 Ho 17 Fe 68.4 Co1B1 was subjected to a spin casting treatment at a copper roll surface linear velocity of 1.9 m / s. The resultant spin-cast sheet was hydrogen-absorbed at 1.5 MPa hydrogen pressure for 1 h at 25°C, and then hydrogen-desorbed at 650°C for 4 h to obtain second hydrogen-fragmented powder. Then, 100 parts by weight of the second hydrogen-fragmented powder was mixed with 0.15 parts by weight of a neodymium-iron-boron antioxidant, and then ground by an air jet mill to produce fine powder having an average particle diameter of 4.5 μm, to obtain a second main phase alloy raw material.

[0129] A raw material having a composition of Ce 10 Nd 12 Fe 60.4 Co2Cu 15 was subjected to a spin casting treatment at a copper roll surface linear velocity of 2.5 m / s. The resultant spin-cast sheet was hydrogen-absorbed at 1.2 MPa hydrogen pressure for 1.5 h at 22°C, and then hydrogen-desorbed at 600°C for 5 h to obtain third hydrogen-fragmented powder. Then, 100 parts by weight of the third hydrogen-fragmented powder was mixed with 0.14 parts by weight of a neodymium-iron-boron antioxidant, and then ground by an air jet mill to produce fine powder having an average particle diameter of 4 μm, to obtain a grain boundary phase alloy raw material.

[0130] Forty-five parts by weight of the first main phase alloy raw material and 55 parts by weight of the second main phase alloy raw material were mixed uniformly to obtain a main phase alloy powder. Eighty-six parts by weight of the main phase alloy powder and 14 parts by weight of the grain boundary phase alloy powder were mixed uniformly to obtain a rare earth permanent magnet raw material. One hundred parts by weight of the rare earth permanent magnet raw material was mixed with 0.2 parts by weight of glyceryl stearate (Haotian Chemical Co.) to obtain a rare earth permanent magnet green alloy powder.

[0131] The rare earth permanent magnet blank alloy powder is shaped in a constant magnetic field of 1.5T, and then is subjected to isostatic pressing at 170MPa for 60s. Then the shaped product is sintered at 1030℃ for 5.5h, and then is subjected to pre-tempering treatment, including first-tempering at 850℃ for 5h, and second-tempering at 480℃ for 8h, to obtain a rare earth permanent magnet blank. The rare earth permanent magnet blank is mechanically processed into a cuboid with a length of 16mm, a width of 14mm, and a thickness of 5mm.

[0132] A low-melting point zinc alloy with a formula of Zn 79.5 Al 18 Si 1.5 Ti 0.4 is prepared by a rapid solidification atomization method, a cooling speed of the atomization method is 103K / s, an atomization pressure is 45MPa, and a microfine powder with an average particle size of 65nm is obtained, to obtain a zinc alloy material. The zinc alloy material is mixed with graphene and is placed in a ball mill, the ball milling is carried out under the protection of inert gas argon, a low-speed ball milling ball material ratio is 7:1, a rotating speed is 170r / min, and a ball milling time is 8h, to obtain modified graphene with an average particle size of 20nm, and a mass content of the graphene in the modified graphene is 29%.

[0133] Raw materials with a formula of Pr 10 Dy 25 Fe 45.4 Cu 19 are smelted at 620℃, a diffusion alloy thin strip is prepared by rapid quenching at a speed of 20m / s, and then is ground by ball milling to obtain a microfine powder with an average particle size of 40nm, to obtain a diffusion alloy material. The diffusion alloy material is mixed with modified graphene to obtain a grain boundary diffusion material, and a mass content of the modified graphene in the grain boundary diffusion material is 20%.

[0134] After a rare earth permanent magnet blank is pickled by using 0.3wt% nitric acid aqueous solution, the grain boundary diffusion material is uniformly coated on upper and lower surfaces of the rare earth permanent magnet blank, and then is placed in a hot pressing mold. The hot pressing mold is placed in a vacuum hot pressing furnace, and is subjected to hot pressing at a vacuum degree of 1×10 -3 Pa, a pressing temperature of 560℃, and a pressure of 90Mpa, and is kept for 40min, and a pressure direction is parallel to an easy magnetization axis direction. Then the grain boundary diffusion is carried out at a vacuum degree of 1×10 -2 Pa and a diffusion temperature of 1000℃ for 2h. Then tempering treatment is carried out at a temperature of 600℃ for 5h, a vacuum degree of 1×10 -5 Pa, to obtain a rare earth permanent magnet A6. A core composition of a main phase of the rare earth permanent magnet A6 is Pr9La 13 Ho 7.5 Fe 67.8Co1B1, the shell composition of the main phase is Pr4Ho5La2Ce3Nd4Dy7Fe 55.8 Co1B 0.4 Cu4Al7Zn4Si 0.08 Ti 0.02 C2, the grain boundary phase composition is Ce5Nd3Pr 3.79 Dy 10 Fe 55.38 Co1Cu4Al6Zn8Si 0.1 Ti 0.03 In C3, the mass content of rare earth elements in the shell of the main phase is 0.847 times that in the core of the main phase, and the thickness of the shell is 1μm-2μm. The mass content of grain boundary phase in rare earth permanent magnet A6 is 25%.

[0135] Example 7

[0136] The formula is Nd 25.5 Fe 73 B 0.9 The raw material was subjected to a strip spinning process at a surface linear velocity of 1.5 m / s on a copper roller. The resulting strip was then subjected to hydrogen absorption at 20°C for 1.2 h under a hydrogen pressure of 1.2 MPa, followed by dehydrogenation at 531°C for 5 h to obtain the first hydrogen-rich powder. 100 parts by weight of the first hydrogen-rich powder were then mixed uniformly with 0.05 parts by weight of NdFeB antioxidant, and subsequently ground using an air jet mill to produce a fine powder with an average particle size of 2.5 μm, thus obtaining the first main phase alloy raw material.

[0137] The formula is Ce 11 Y 16.5 Fe 71.1 B 0.8 The raw material was subjected to a copper roller surface linear velocity of 1.9 m / s for strip spinning. The resulting strip was then subjected to hydrogen absorption at 23°C for 1.5 h under a hydrogen pressure of 1.3 MPa, followed by dehydrogenation at 523°C for 5.2 h to obtain the second hydrogen-rich powder. 100 parts by weight of the second hydrogen-rich powder were then mixed uniformly with 0.051 parts by weight of NdFeB antioxidant, and subsequently ground using an air jet mill to produce a fine powder with an average particle size of 2.6 μm, thus obtaining the second main phase alloy raw material.

[0138] The formula is Ce 10 Sm9Fe 70.4 Sn 10The raw material of the formula of Nd 90.5% Tb 5% Fe 4% Sn 0.5% was melt-spun at a copper roll surface linear velocity of 1.7 m / s. The obtained melt-spun sheet was hydrogenated at 24 ℃ for 1.3 h under a hydrogen pressure of 1.4 MPa, and then dehydrogenated at 525 ℃ for 5.3 h to obtain a third hydrogen decrepitated powder. Then, 100 parts by weight of the third hydrogen decrepitated powder was uniformly mixed with 0.052 parts by weight of a neodymium-iron-boron antioxidant, followed by grinding by an air flow mill to obtain a fine powder having an average particle size of 2.7 μm, thereby obtaining a grain boundary phase alloy raw material.

[0139] The first main phase alloy raw material and the second main phase alloy raw material were uniformly mixed to obtain a main phase alloy powder. The main phase alloy powder and the grain boundary phase alloy powder were uniformly mixed to obtain a rare earth permanent magnet raw material. The rare earth permanent magnet raw material and the sorbitan (Haitian Chemical Co., Ltd.) were uniformly mixed to obtain a rare earth permanent magnet blank alloy powder.

[0140] The rare earth permanent magnet blank alloy powder was formed in a constant magnetic field of 2 T, and then subjected to isostatic pressing at 180 MPa for 100 s. Then, the rare earth permanent magnet blank alloy powder was sintered at 1080 ℃ for 4 h, and then subjected to pre-tempering treatment, including first tempering at 860 ℃ for 3 h, and second tempering at 490 ℃ for 4 h, thereby obtaining a rare earth permanent magnet blank. The rare earth permanent magnet blank was mechanically processed into a cuboid having a length of 15 mm, a width of 11 mm, and a thickness of 10 mm.

[0141] A low-melting-point zinc alloy having a formula of Zn 84.27 Al 14.1 Si 0.9 Ti 0.13 was prepared by a rapid solidification atomization method. The cooling speed of the atomization method was 105 K / s, and the atomization pressure was 20 MPa. A fine powder having an average particle size of 58 nm was obtained, thereby obtaining a zinc alloy material. The zinc alloy material and graphene were mixed and placed in a ball mill. The ball milling was carried out under the protection of an inert gas argon. The low-speed ball milling ball material ratio was 5:1, the rotation speed was 160 r / min, and the ball milling time was 6 h. Modified graphene having an average particle size of 10 nm was obtained. The mass content of graphene in the modified graphene was 19%.

[0142] A raw material having a formula of Nd 5.2 Tb 23.8 Fe 54.9 Sn 15.5 was melt-spun at 650 ℃ at a rapid quenching speed of 18 m / s to obtain a diffusion alloy thin strip. The diffusion alloy thin strip was ground by a ball mill to obtain a fine powder having an average particle size of 30 nm, thereby obtaining a diffusion alloy material. The diffusion alloy material and modified graphene were mixed to obtain a grain boundary diffusion material. The mass content of modified graphene in the grain boundary diffusion material was 10%.

[0143] After the rare earth permanent magnet blank is pickled with 0.3wt% nitric acid aqueous solution, the grain boundary diffusion material is uniformly coated on the upper and lower surfaces of the rare earth permanent magnet blank, and then the blank is put into a hot-pressing mold. The hot-pressing mold is put into a vacuum hot-pressing furnace, and hot-pressing is carried out under the conditions of a vacuum degree of 5x10 -2 Pa, a pressing temperature of 570°C, a pressure of 100Mpa, and a pressure holding time of 100min, and the pressure direction is parallel to the direction of the easy magnetization axis. Then, vacuum annealing is carried out under the conditions of a vacuum degree of 5x10 -3 Pa and a diffusion temperature of 700°C for 6.5h. Subsequently, tempering treatment is carried out under the conditions of a temperature of 450°C, a time of 7.5h, and a vacuum degree of 8x10 -3 Pa, to obtain a rare earth permanent magnet A7. The core of the main phase of the rare earth permanent magnet A7 is composed of Nd 7.91 Ce 10 Y 8.98 Fe 71.58 B 0.83 , and the shell of the main phase is composed of Sm2Ce4Y 5.15 Nd 3.83 Tb 6.66 Fe 64.2439 B 0.25 Sn5Al4Zn 2.5 Si 0.061 Ti 0.0091 C 1.596 , and the grain boundary phase is composed of Ce3Sm 4.79 Nd 2.08 Tb 9.52 Fe 61.095 Sn 5.435 Al7Zn4Si 0.087 Ti 0.013 C 2.28 The mass content of the rare earth elements in the shell of the main phase is 0.805 times that of the rare earth elements in the core of the main phase, the thickness of the shell is 0.1μm-1μm, and the mass content of the grain boundary phase in the rare earth permanent magnet A7 is 20%.

[0144] Example 8

[0145] The raw material with a formula of Pr 29.5 Fe 66.7 Co2B 1.2 is subjected to tape casting at a copper roll surface linear velocity of 1.8m / s. The obtained tape is hydrogenated at 15°C under a hydrogen pressure of 1.2Mpa for 1.8h, and then dehydrogenated at 508°C for 7h to obtain first hydrogen-fragmented powder. Then, 100 parts by weight of the first hydrogen-fragmented powder is uniformly mixed with 0.1 part by weight of neodymium-iron-boron antioxidant, and then ground by an air flow mill to obtain micro-powder with an average particle size of 3.9μm, to obtain first main phase alloy raw material.

[0146] The raw material with the formula of Gd 14 Y 17.5 Fe 64.15 Co 2.5 B 1.25 was subjected to a spinning process at a copper roll surface linear velocity of 1.9 m / s. The obtained spinning sheet was hydrogenated at 1.4 MPa hydrogen pressure at 17°C for 1.9 h, and then dehydrogenated at 509°C for 7.2 h to obtain second hydrogenation powder. Then, 100 parts by weight of the second hydrogenation powder was uniformly mixed with 0.12 parts by weight of a neodymium-iron-boron antioxidant, followed by grinding by an air flow mill to produce fine powder with an average particle size of 4.2 μm, to obtain a second main phase alloy raw material.

[0147] The raw material with the formula of La 13 Ce 12.2 Fe 45.2 Co4Sn4Al6Zn 15 was subjected to a spinning process at a copper roll surface linear velocity of 2 m / s. The obtained spinning sheet was hydrogenated at 1.5 MPa hydrogen pressure at 19°C for 2 h, and then dehydrogenated at 511°C for 7.3 h to obtain third hydrogenation powder. Then, 100 parts by weight of the third hydrogenation powder was uniformly mixed with 0.13 parts by weight of a neodymium-iron-boron antioxidant, followed by grinding by an air flow mill to produce fine powder with an average particle size of 4.5 μm, to obtain a grain boundary phase alloy raw material.

[0148] The first main phase alloy raw material and the second main phase alloy raw material were uniformly mixed to obtain a main phase alloy powder. The main phase alloy powder and the grain boundary phase alloy powder were uniformly mixed to obtain a rare earth permanent magnet raw material. 100 parts by weight of the rare earth permanent magnet raw material was uniformly mixed with 0.02 parts by weight of stearic acid (Haitian Chemical Co.) to obtain a rare earth permanent magnet blank alloy powder.

[0149] The rare earth permanent magnet blank alloy powder was molded in a constant magnetic field of 2.5 T, and then subjected to isostatic pressing at 205 MPa for 130 s. Then, the rare earth permanent magnet blank was sintered at 1085°C for 4 h, and then subjected to pre-tempering, including first tempering at 875°C for 4 h, and second tempering at 515°C for 7 h, to obtain a rare earth permanent magnet blank. The rare earth permanent magnet blank was mechanically processed into a cuboid with a length of 17 mm, a width of 8 mm, and a thickness of 10 mm.

[0150] The raw material with the formula of Zn 62.1 Al 34.4 Si 2.2 Ti 0.7A low melting point zinc alloy is prepared by a rapid solidification atomization method, the cooling speed of the gas atomization method is 103 K / s, the atomization pressure is 50 MPa, a micro powder with an average particle size of 80 nm is obtained, and a zinc alloy material is obtained. The zinc alloy material is mixed with graphene and placed in a ball mill, the ball milling is carried out under the protection of inert gas argon, the low-speed ball milling ball material ratio is 10:1, the rotating speed is 180 r / min, and the ball milling time is 10 h. A modified graphene with an average particle size of 25 nm is prepared, and the mass content of graphene in the modified graphene is 38%.

[0151] The raw materials with a formula of Pr 14.5 Dy 31.8 Fe 29.1 Sn 10 Zn 14 are smelted at 670℃, and a diffusion alloy thin strip is prepared at a rapid quenching speed of 27 m / s, then the diffusion alloy thin strip is ground by ball milling to prepare a micro powder with an average particle size of 85 nm, and a diffusion alloy material is obtained. The diffusion alloy material and the modified graphene are mixed to obtain a grain boundary diffusion material, and the mass content of the modified graphene in the grain boundary diffusion material is 23%.

[0152] After the rare earth permanent magnet blank is pickled with 0.3wt% nitric acid aqueous solution, the grain boundary diffusion material is uniformly coated on the upper and lower surfaces of the rare earth permanent magnet blank, and then the rare earth permanent magnet blank is placed into a hot pressing mold. The hot pressing mold is placed into a vacuum hot pressing furnace, and hot pressing is carried out at a vacuum degree of 9×10 -2 Pa, a pressing temperature of 575℃, an applied pressure of 87Mpa, and a pressure holding time of 45min, and the pressure direction is parallel to the direction of the easy magnetization axis. Then, the grain boundary diffusion is carried out at a vacuum degree of 7×10 -2 Pa and a diffusion temperature of 915℃ for 4h. Then, tempering treatment is carried out at a temperature of 474℃ for 4.7h, a vacuum degree of 9×10 -3 Pa, and a rare earth permanent magnet A8 is obtained. The core of the main phase of the rare earth permanent magnet A8 is composed of Pr 10.03 Gd 15 Y 5.79 Fe 64.92 Co 2.33 B 1.23 , the shell layer of the main phase is composed of La5Ce 4.57 Gd3Y3Pr 8.1 Dy 8.97 Fe 40.784 Co 2.1 B 0.49 Sn4Al 10 Zn 6.4208 Si 0.098 Ti 0.0312 C 2.736 , and the grain boundary phase is composed of La5Ce 7.096 Pr6.815 Dy 14.946 Fe 24.97 Co 1.92 Sn7Al 12.777 Zn 14 Si 0.164 Ti 0.052 C 4.56 The mass content of rare earth elements in the shell layer of the main phase is 1.059 times that of the rare earth elements in the core of the main phase, the thickness of the shell layer is 6 μm-8.5 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet A8 is 40%.

[0153] Example 9

[0154] The same as Example 1, except that 60 parts by weight of the first main phase alloy raw material and 40 parts by weight of the second main phase alloy raw material are uniformly mixed to obtain a main phase alloy powder, 97 parts by weight of the main phase alloy powder and 3 parts by weight of the grain boundary phase alloy powder are uniformly mixed to obtain a rare earth permanent magnet raw material, and the remaining processes are the same as those of Example 1, thereby obtaining a rare earth permanent magnet A9. The core of the main phase of the rare earth permanent magnet A9 is composed of Pr 8.93 La7Sm 13.48 Fe 68.86 Co 0.2 B 0.835 The shell layer of the main phase is composed of La 5.66 Sm 5.43 Pr 4.83 Dy 8.61 Fe 60.08 Co 0.067 B 0.28 Zr 2.28 Al 5.36 Zn 4.29 Si 0.067 Ti 0.0094 C 2.35 The grain boundary phase is composed of La5Sm 1.46 Pr 2.81 Dy 12.85 Fe 55.66 Co 0.1 Zr 3.4 Al8Zn 6.41 Si 0.1 Ti 0.014 C 3.5 The mass content of rare earth elements in the shell layer of the main phase is 0.834 times that of the rare earth elements in the core of the main phase, the thickness of the shell layer is 0.6 μm-1.8 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet A9 is 15%.

[0155] Example 10

[0156] The same as example 1 except that 25 parts by weight of the first main phase alloy raw material and 75 parts by weight of the second main phase alloy raw material are uniformly mixed to obtain the main phase alloy powder, 80 parts by weight of the main phase alloy powder and 20 parts by weight of the grain boundary phase alloy powder are uniformly mixed to obtain the rare earth permanent magnet raw material, and the rest of the process is the same as example 1 to obtain the rare earth permanent magnet A10. The core of the main phase of the rare earth permanent magnet A10 is composed of Pr 9.69 La8Sm 11.53 Fe 66.54 Co 2.31 B 1.23 The shell layer of the main phase is composed of La 7.89 Sm 7.11 Pr 5.77 Dy 8.4 Fe 53.04 Co 0.7 B 0.25 Zr 5.36 Al 5.68 Zn 2.28 Si 0.088 Ti 0.03 C 2.72 The grain boundary phase is composed of La 7.86 Sm6Pr 4.79 Dy 10.49 Fe 49.66 Co 0.3 Zr 6.7 Al 7.1 Zn 2.85 Si 0.11 Ti 0.038 C 3.4 The mass content of rare earth elements in the shell layer of the main phase is 1 times the mass content of rare earth elements in the core of the main phase, the thickness of the shell layer is 6.2 μm-8.7 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet A10 is 41%.

[0157] Example 11

[0158] The same as example 1 except that the raw material with the formula Pr8Nd 18 Fe 71.9 Co 0.5 B1 is prepared to obtain the first main phase alloy raw material. The raw material with the formula Pr6Dy 20 Tb4Fe 53.4 Al 16 is prepared to obtain the diffusion alloy. The rest of the process is the same as example 1 to obtain the rare earth permanent magnet A11. The core of the main phase of the rare earth permanent magnet A11 is composed of Pr 2.72 Nd 6.12 La 11.06 Sm 7.94 Fe 70.026 Co0.5 B 0.934 , the shell layer of the main phase is composed of La 7.18 Sm 5.14 Nd 4.14 Pr 1.09 Dy 5.64 Tb 1.13 Fe 59.51 Co 0.45 Zr 2.95 Al 5.24 Zn 3.76 Si 0.045 Ti 0.007 C 2.66 B 0.37 , the shell layer of the main phase is composed of La 4.92 Sm 3.28 Nd 2.82 Dy 9.4 Tb 1.88 Fe 52.15 Co 0.41 Zr 4.92 Al 8.73 Zn 6.26 Si 0.076 Ti 0.01 C 4.44 , the mass content of the rare earth element in the shell layer of the main phase is 0.89 times of the mass content of the rare earth element in the core of the main phase, the thickness of the shell layer is 1.5 μm-3.5 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet A1 is 23%.

[0159] Example 12

[0160] The raw materials with the formula of Pr 29.4 Fe 66.83 Co 1.98 B 1.19 are used to obtain the first main phase alloy raw material according to the process of Example 1. The raw materials with the formula of La 11 Sm 20.4 Fe 64.29 Co 2.47 B 1.24 are used to obtain the second main phase alloy raw material according to the process of Example 1. The raw materials with the formula of La 10 Sm 9.6 Fe 52.1 Co 3.7 Zr 24 are used to obtain the grain boundary phase alloy raw material according to the process of Example 1. 28 parts by weight of the first main phase alloy raw material and 72 parts by weight of the second main phase alloy raw material are uniformly mixed to obtain the main phase alloy powder. 98 parts by weight of the main phase alloy powder and 2 parts by weight of the grain boundary phase alloy powder are uniformly mixed to obtain the rare earth permanent magnet raw material.

[0161] The raw materials with the formula of Zn 62.75Al 34 Si2Ti 0.65 The low-melting-point zinc alloy was used to obtain zinc alloy material according to the process of Example 1. Modified graphene was obtained according to the process of Example 1, with a graphene content of 15% by mass. The formulation was Pr 5.5 Dy 24 Fe 53.9 Al 16 The raw materials were used to obtain a diffusion alloy material according to the process in Example 1. The diffusion alloy material was mixed with modified graphene to obtain a grain boundary diffusion material, wherein the mass content of modified graphene in the grain boundary diffusion material was 5%.

[0162] Rare earth permanent magnet Al2 was obtained according to the process in Example 1. The core composition of the main phase of rare earth permanent magnet Al2 is Pr. 10.0 3La 10 Sm 10.79 Fe 64.92 Co 2.33 B 1.23 The shell composition of the main phase is La. 5.15 Sm6Pr 3.83 Dy 6.66 Fe 63.89 Co 0.35 B 0.25 Zr5Al4Zn 2.5 Si 0.061 Ti 0.0091 C 1.596 The grain boundary phase is composed of La4Sm 3.79 Pr 2.08 Dy 9.52 Fe 60.795 Co 0.3 Zr 5.435 Al7Zn4Si 0.087 Ti 0.013 C 2.28 The mass content of rare earth elements in the shell of the main phase is 0.702 times that in the core of the main phase, and the thickness of the shell is 0.2μm-2.3μm. The mass content of grain boundary phase in the rare earth permanent magnet A12 is 12%.

[0163] Example 13

[0164] The formula is Pr 25.6 Fe 72.82 B 0.98 The raw materials were obtained according to the process of Example 1 to obtain the first main phase alloy raw material. The formulation was La... 17 Sm 10.6 Fe 70.98 B 0.82 The raw materials were processed according to the process in Example 1 to obtain the second main phase alloy raw material. The formulation was La... 12 Sm13 Fe 62.9 Co 0.5 Zr 11 The raw material of the grain boundary phase alloy was obtained according to the process of Example 1. 53 parts by weight of the first main phase alloy raw material and 47 parts by weight of the second main phase alloy raw material were uniformly mixed to obtain a main phase alloy powder. 73 parts by weight of the main phase alloy powder and 27 parts by weight of the grain boundary phase alloy powder were uniformly mixed to obtain a rare earth permanent magnet raw material.

[0165] The low-melting-point zinc alloy with a formula of Zn 83.75 Al 14.5 Si1Ti 0.15 The zinc alloy material was obtained according to the process of Example 1. The modified graphene was obtained according to the process of Example 1, and the mass content of graphene in the modified graphene was 40%. The raw material with a formula of Pr 14.4 Dy 31.5 Fe 30.5 Al 23 The diffusion alloy material was obtained according to the process of Example 1. The diffusion alloy material and the modified graphene were mixed to obtain a grain boundary diffusion material, and the mass content of the modified graphene in the grain boundary diffusion material was 27%.

[0166] The rare earth permanent magnet A13 was obtained according to the process of Example 1. The core of the main phase of the rare earth permanent magnet A13 was composed of Pr 7.91 La 8.98 Sm 10 Fe 71.58 B 0.83 The shell layer of the main phase was composed of La 10 Sm 5.57 Pr 8.1 Dy 8.97 Fe 41.184 Co 2.1 B 0.49 Zr 8.18 Al5Zn7Si 0.098 Ti 0.031 C 2.736 The grain boundary phase was composed of La7Sm 5.096 Pr 6.815 Dy 14.946 Fe 24.97 Co 1.92 Zr 9.5 Al 10.305 Zn 14 Si 0.164 Ti 0.052 C 4.56 The mass content of rare earth elements in the shell layer of the main phase was 1.214 times the mass content of rare earth elements in the core of the main phase, the thickness of the shell layer was 5 μm-8.3 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet A13 was 42%.

[0167] Comparative Example 1

[0168] The rare earth permanent magnet blank prepared in Example 1 was directly used as the rare earth permanent magnet CA1 of Comparative Example 1.

[0169] Comparative Example 2

[0170] The process was substantially the same as that of Example 1, except that the first main phase alloy raw material, the second main phase alloy raw material and the grain boundary phase alloy raw material were not used, and a single alloy raw material was directly prepared into a rare earth permanent magnet blank, and the composition of the single alloy raw material was La 8.61 Sm 6.38 Nd 11.48 Fe 71.15 Co 0.54 B 0.87 Zr 0.96 , and the rest of the process was the same as that of Example 1 to prepare the rare earth permanent magnet CA2.

[0171] Comparative Example 3

[0172] The process was substantially the same as that of Example 1, except that the raw material with the formula Pr 9.6 Nd 29.3 Dy 10 Fe 15.5 Co 16.5 B 0.96 Al 5.5 Cu 3.2 Zr 2.4 Ga7was prepared into a tape by using a copper roller with a surface linear velocity of 1.4 m / s as the grain boundary phase alloy raw material, and the rest of the process was the same as that of Example 1 to prepare the rare earth permanent magnet CA3.

[0173] Comparative Example 4

[0174] The process was substantially the same as that of Example 1, except that the diffusion alloy material was directly used as the grain boundary diffusion material without adding the modified graphene to prepare the rare earth permanent magnet CA4. The core of the main phase of the rare earth permanent magnet CA4 was composed of Pr 11 Sm8Fe 71 Co 0.5 B 0.9 , the shell of the main phase was composed of La 8.245 Sm 5.76 Pr 4.877 Dy 6.709 Fe 65.206 Co 0.52 B 0.36 Al 4.47 Zr 3.845 , and the grain boundary phase was composed of La 6.4 Sm 4.27 Pr 2.795Dy 11.18 Fe 60.375 Co 0.53 Al 7.45 Zr 6.4 , the mass content of rare earth elements in the shell layer of the main phase is 0.948 times that of the rare earth elements in the core of the main phase, the thickness of the shell layer is 1-3 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet CA4 is 20%.

[0175] Comparative Example 5

[0176] The rare earth permanent magnet CA5 was prepared in substantially the same manner as in Example 1, except that the modified graphene with an average particle size of 11 nm was directly used as the grain boundary diffusion material without adding the diffusion alloy material. The core of the main phase of the rare earth permanent magnet CA5 was composed of Pr8La 11 Sm8Fe 70.9 Co 0.5 B 0.9 , the shell of the main phase was composed of La 9.97 Sm 7.275 Pr 3.2 Fe 59.74 Co 0.66 Zr 5.57 Al 1.74 Si 0.11 Ti 0.016 Zn9C 2.72 , the grain boundary phase was composed of La 9.28 Sm 6.19 Fe 51.83 Co 0.77 Zr 9.28 Al 2.9 Si 0.18 Ti 0.027 Zn 15 C 4.53 , the mass content of rare earth elements in the shell layer of the main phase is 0.757 times that of the rare earth elements in the core of the main phase, the thickness of the shell layer is 1-2.5 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet CA5 is 18%.

[0177] Comparative Example 6

[0178] The rare earth permanent magnet CA6 was prepared in substantially the same manner as in Example 1, except that the graphene with an average particle size of 11 nm was directly used as the grain boundary diffusion material. The core of the main phase of the rare earth permanent magnet CA6 was composed of Pr8La 11 Sm8Fe 70.9 Co 0.5 B 0.9 , the shell of the main phase was composed of La 9.97 Sm 6.91 Pr 3.2 Fe59.74 Co 0.66 B 0.36 Zr 5.57 C 13.58 The grain boundary phase is composed of La 9.28 Sm 6.19 Fe 51.83 Co 0.77 Zr 9.28 C 22.64 The mass content of rare earth elements in the shell layer of the main phase is 0.744 times that in the inner core of the main phase, the thickness of the shell layer is 1-2.5 μm, and the mass content of the grain boundary phase in the rare earth permanent magnet CA6 is 18%.

[0179] Performance detection

[0180] Remanence and coercivity detection: The remanence (Br) and intrinsic coercivity (Hcj) of the rare earth permanent magnets prepared in the above examples and comparative examples were detected at 22°C by NIM-10000H of China Institute of Metrology according to GB / T 3217-1992 test standard.

[0181] High-temperature external field durability detection: The rare earth permanent magnets prepared in the above examples and comparative examples (with a size of 33.5 mm x 13.9 mm x 5 mm) were subjected to an external magnetic field of 7 kOe at 180°C for 100 h, and then cooled to 22°C, and the magnetic flux irreversible loss (hirr) of each sample was detected by a fluxmeter.

[0182] Bending strength detection: The bending strength of the rare earth permanent magnets prepared in the above examples and comparative examples was detected at 25°C by a microcomputer-controlled electronic universal testing machine CMT5105 according to GBT228.1-2010 test standard.

[0183] The performance detection results are shown in Table 1. It can be seen that the intrinsic coercivity, demagnetization resistance and bending strength of CA1 are poor because CA1 is not diffusion modified by the grain boundary diffusion material. Compared with CA1, the intrinsic coercivity of A1-A13 is increased by a maximum of 61%, the magnetic flux irreversible loss is improved by a maximum of 74.7%, and the bending strength is increased by a maximum of 55.3%. CA2 is made of a single alloy raw material, and CA3 is made of different grain boundary phase alloy raw materials. The intrinsic coercivity, bending strength and demagnetization resistance of CA2 and CA3 are still at a low level. Compared with CA2, the intrinsic coercivity of A1 is increased by 76.6%, the magnetic flux irreversible loss is improved by 74.4%, and the bending strength is increased by 52.7%. CA4 uses diffusion alloy material as the grain boundary diffusion material, and the bending strength of CA4 is still at a low level. CA5 directly places the modified graphene on the surface of the rare earth permanent magnet blank, which can improve the bending strength, but cannot improve the intrinsic coercivity and demagnetization resistance. CA6 directly places the graphene on the surface of the rare earth permanent magnet blank, and the graphene is difficult to enter the interior of the rare earth permanent magnet blank, so the improvement of the bending strength is limited, and the intrinsic coercivity and demagnetization resistance cannot be improved. Compared with CA1-CA6, the intrinsic coercivity, demagnetization resistance and bending strength of the rare earth permanent magnet of A1-A13 are at a high level, and the comprehensive performance is excellent, which is conducive to the use of the rare earth permanent magnet.

[0184] Table 1 performance detection results

[0185] Sample No. Br (kGs) Hcj (kOe) Bending strength (MPa) Hirr (%) A1 12.98 29.83 394 5.84 A2 13 29.9 396 5.53 A3 12.99 29.32 370 5.96 A4 12.95 28.62 364 6.64 A5 12.92 28.71 366 6.8 A6 12.91 29.74 384 6 A7 12.83 27.86 346 10.96 A8 12.76 27.79 350 10.32 A9 12.87 27.95 362 7.47 A10 12.77 27.63 355 9.8 A11 12.9 28.23 382 6.08 A12 12.75 26.5 332 11.1 A13 12.7 27.5 340 11.78 CA1 13.09 18.57 255 21.9 CA2 12.98 16.89 258 22.8 CA3 12.87 20.91 237 21.5 CA4 12.78 25.72 285 12.9 CA5 13.01 20.95 309 13.36 CA6 13.03 19.15 272 13.68

[0186] The above describes the preferred embodiments of the present application, but should not be construed as limiting the scope of the present application. It should be noted that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which are also considered to be within the scope of protection of the present application.

Claims

1. A rare-earth permanent magnet, characterized in that, The rare-earth permanent magnet comprises a main phase and a grain boundary phase. The main phase is dispersed in the grain boundary phase. The main phase includes a core and a shell covering the core. The shell and the grain boundary phase contain graphene. The kernel includes RL 1 a RH 1 b Fe c Co d B e RL 1 Including at least one of Pr and Nd, RH 1 Includes at least one of La, Ce, Sm, Gd, Ho, and Y, where a, b, c, d, and e are parts by weight, 7.91 ≤ a ≤ 10.03, 18.98 ≤ b ≤ 20.79, 64.72 ≤ c ≤ 72.28, 0 ≤ d ≤ 2.33, and 0.83 ≤ e ≤ 1.

23. The shell includes RL 2 f RL 3 g RH 2 h Fe i Co j B k M 1 l C m RL 2 Including at least one of La, Ce, Sm, Gd, Ho, and Y, RL 3 Including at least one of Pr and Nd, RH 2 Including at least one of Dy and Tb, M 1 Includes at least one of Zr, Ga, Cu, and Sn, as well as Al, Zn, Si, and Ti; f, g, h, i, j, k, l, and m are parts by weight; 21.64 ≤ f + g + h ≤ 32.64, 3.83 ≤ g ≤ 8.1, 6.66 ≤ h ≤ 8.97, 40.554 ≤ i ≤ 65.014, 0 ≤ j ≤ 2.1, 0.25 ≤ k ≤ 0.49, 11.5 ≤ l ≤ 20.58, 1.596 ≤ m ≤ 2.

736. The grain boundary phase includes RL 4 o RL 5 p RH 3 q Fe r Co s M 2 t C u RL 4 Including at least one of La, Ce, and Sm, RL 5 Including at least one of Pr and Nd, RH 3 Including at least one of Dy and Tb, M 2 It includes at least one of Zr, Ga, Cu and Sn, as well as Al, Zn, Si and Ti, where o, p, q, r, s, t and u are by weight, and 19.39≤o+p+q≤33.857, 2.08≤p≤6.815, 9.52≤q≤14.946, 24.458≤r≤61.895, 0≤s≤1.92, 16.435≤t≤34.305, and 2.28≤u≤4.

56.

2. The rare earth permanent magnet as described in claim 1, characterized in that, In the kernel, 8≤a≤10, 19≤b≤20.5, 65.7≤c≤71, 0.5≤d≤1.8, and 0.9≤e≤1.

1.

3. The rare earth permanent magnet as described in claim 1, characterized in that, In the shell, 21.8≤f+g+h≤32.5, 3.9≤g≤7.8, 6.7≤h≤8.8, 42.5≤i≤63.72, 0.2≤j≤1.9, 0.28≤k≤0.45, 11.8≤l≤20.3, and 1.6≤m≤2.

5.

4. The rare earth permanent magnet as described in claim 1, characterized in that, In the grain boundary phase, 19.5≤o+p+q≤33.5, 2.2≤p≤6.7, 9.7≤q≤14.5, 25.7≤r≤60.8, 0.2≤s≤1.7, 16.5≤t≤34, and 2.4≤u≤4.

5. The rare-earth permanent magnet as described in claim 1, characterized in that, The ratio of the mass content of rare earth elements in the shell to the mass content of rare earth elements in the core is (0.744-1.093):

1.

6. The rare-earth permanent magnet as described in claim 1, characterized in that, The thickness of the shell is 0.1μm-8.5μm.

7. The rare earth permanent magnet as described in claim 1, characterized in that, The rare earth permanent magnet has a grain boundary phase content of 20%-40% and a main phase content of 60%-80%.

8. A method for preparing a rare-earth permanent magnet according to any one of claims 1-7, characterized in that, include: A rare-earth permanent magnet blank is obtained by mixing a first main phase alloy raw material, a second main phase alloy raw material, and a grain boundary phase alloy raw material, followed by magnetic field orientation pressing, molding, and sintering. The first main phase alloy raw material includes R... 1 a' Fe b' Co c' B d' R 1 The alloy comprises at least one of Pr and Nd, where a', b', c', and d' are parts by weight, 25.5 ≤ a' ≤ 29.5, 66.4 ≤ b' ≤ 73.6, 0 ≤ c' ≤ 2, and 0.9 ≤ d' ≤ 1.

2. The second main phase alloying material comprises R. 2 e' Fe f' Co g' B h' R 2 The alloy comprises at least one of La, Ce, Sm, Gd, Ho, and Y, where e', f', g', and h' are parts by weight, with 27.5 ≤ e' ≤ 31.5, 63.85 ≤ f' ≤ 71.7, 0 ≤ g' ≤ 2.5, and 0.8 ≤ h' ≤ 1.

25. The grain boundary phase alloy raw material includes R. 3 i' Fe j' Co k' M 3 l' R 3 Including at least one of La, Ce, Sm, Pr and Nd, M 3 It includes at least one of Zr, Ga, Cu, Sn, Al and Zn, where i', j', k' and l' are parts by weight, 19≤i'≤25.2, 44.9≤j'≤71, 0≤k'≤4, and 10≤l'≤25; A grain boundary diffusion material is disposed on the surface of the rare-earth permanent magnet blank. The grain boundary diffusion material includes a diffusion alloy material and modified graphene. The modified graphene includes graphene and a zinc alloy layer coating the graphene. The diffusion alloy material includes R... 4 m' R 5 n' Fe o' M 4 p' R 4 Including at least one of Pr and Nd, R 5 Including at least one of Dy and Tb, M 4 The zinc alloy comprises at least one of Ga, Cu, Sn, Al, and Zn, where m', n', o', and p' are parts by weight, with 5.2 ≤ m' ≤ 14.5, 23.8 ≤ n' ≤ 31.8, 28.85 ≤ o' ≤ 55.5, and 15.5 ≤ p' ≤ 24. The zinc alloy layer comprises Zn. q' Al r' Si s' Ti t' q', r', s', and t' are the weight parts, 61.8 ≤ q' ≤ 84.87, 14.1 ≤ r' ≤ 34.4, 0.9 ≤ s' ≤ 2.2, and 0.13 ≤ t' ≤ 0.7; Rare earth permanent magnets are obtained by hot pressing, diffusion treatment and tempering treatment.

9. The preparation method according to claim 8, characterized in that, Before the grain boundary diffusion material is disposed on the surface of the rare earth permanent magnet blank, the method further includes: The modified graphene is obtained by mixing the graphene with zinc alloy material and then ball milling it.

10. The preparation method according to claim 9, characterized in that, The average particle size of the zinc alloy material is 58nm-80nm; The modified graphene has an average particle size of 10nm-25nm.

11. The preparation method according to claim 9, characterized in that, The ball-to-material ratio in the ball mill is (5-10):1, the rotation speed is 160r / min-180r / min, and the time is 6h-10h; The ball milling is carried out under an inert atmosphere or vacuum conditions.

12. The preparation method according to claim 8, characterized in that, In the diffusion alloy raw material, 6≤m'≤14, 24≤n'≤31, 30.7≤o'≤53.4, and 16≤p'≤23.

13. The preparation method according to claim 8, characterized in that, The modified graphene in the grain boundary diffusion material has a mass content of 10%-23%; The modified graphene contains 19%-38% graphene by mass.

14. The preparation method according to claim 8, characterized in that, The ratio of the mass of the second main phase alloy raw material to the sum of the masses of the first main phase alloy raw material and the second main phase alloy raw material is 50%-69%. The ratio of the mass of the grain boundary phase alloy raw material to the sum of the masses of the first main phase alloy raw material, the second main phase alloy raw material, and the grain boundary phase alloy raw material is 5%-17%.

15. The preparation method according to claim 8, characterized in that, The magnetic field orientation pressing molding includes processing under a magnetic field of 1.5T-3.5T and a pressure of 170MPa-210MPa for 60s-150s. The sintering process includes treatment at 1030℃-1090℃ for 4-5.5 hours; The hot pressing includes temperatures of 550℃-800℃, pressures of 80MPa-150MPa, and a vacuum degree of 10. -3 Pa-10 -2 Treat under Pa conditions for 30-150 minutes; The diffusion process includes operating at 600℃-1000℃ and a vacuum degree of 10. -5 Pa-10 -2 Treatment under Pa conditions for 2-12 hours; The tempering process includes a temperature of 400℃-600℃ and a vacuum degree of 10. -5 Pa-10 -2 Treat under Pa conditions for 2.5-10 hours.

16. The preparation method according to claim 8, characterized in that, The sintering process also includes a pre-tempering treatment, which consists of treatment at 890℃-950℃ for 2.5h-5h, followed by treatment at 480℃-520℃ for 3.5h-8h.

17. An electric motor, characterized in that, This includes the rare earth permanent magnet as described in any one of claims 1-7 or the rare earth permanent magnet prepared by the preparation method described in any one of claims 8-16.

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