A method for preparing a grain boundary diffusion source and a high-performance and high-abundance rare earth magnet

Abstract

The present invention discloses a grain boundary diffusion source and a preparation method of a high-performance and high-abundance rare earth magnet. The grain boundary diffusion source comprises (HRE x La 1‑x ) 68 (M 1‑y Ga y ) 32 alloy powder, where HRE is selected from one or more of Dy or Tb, and M is selected from one or more of Fe, Co, Al, Ca, Cu, Ni, Ge, Zr, Ti, Nb, Mo, Hf, Ta or W; wherein, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, x(HRE)+x(La)=68 at.%, x(M)+x(Ga)=32 at.%. In the grain boundary diffusion source of the present invention, partial substitution of Ce atoms by La atoms in the grain boundary can reduce or even inhibit the formation of the CeFe2 phase, which is helpful for the diffusion of Tb / Dy elements. The La element will form an Ia3_-RE2O3 grain boundary phase, and the wettability of this phase is easy to form a smooth and complete intergranular phase, which is beneficial to weakening the exchange coupling effect between adjacent main phase grains, thereby improving the coercivity of the magnet; the RE6(Fe,M) 14 phase generated after the diffusion of the Ga element can reduce the content of α-Fe in the grain boundary phase, thereby improving the coercivity of the magnet, and the RE6(Fe,M) 14 phase has antiferromagnetic properties, which can improve the coercivity of the magnet; the price of the La element is much lower than that of the Tb element, and the cost is low.

Description

Technical Field

[0001] The invention belongs to the field of rare earth permanent magnetic material preparation, and in particular relates to a method for preparing a grain boundary diffusion source and a high-performance and high-abundance rare earth magnet. Background Art

[0002] Nd-Fe-B magnets have many advantages such as strong magnetism and small size. With the continuous development of high-tech industries such as new energy vehicles and robots, the demand for high-performance Nd-Fe-B magnets continues to increase, which has led to the excessive use of low-abundance rare earth metals Nd, Dy and Tb. Finding replacements for these key elements has become urgent and important.

[0003] The rare earth element Ce has a high content and a low price, and has not been effectively utilized in the production of Nd-Fe-B magnets. Therefore, using part of the high-abundance rare earth Ce to replace Nd will be an important way to explore the sustainable development of the comprehensive utilization of rare earth metals; however, compared with Nd-Fe-B magnets, the intrinsic magnetic properties of Ce2Fe14B are much lower than those of Nd2Fe14B. Ce replacing Nd will lead to a strong magnetic dilution effect, which reduces the permanent magnetic properties of the magnet, especially the coercive force.

[0004] The recently developed grain boundary diffusion technology can increase the coercivity of the magnet without reducing the remanence and magnetic energy product of the magnet. Therefore, people try to use grain boundary diffusion technology to improve the coercivity of Ce-containing magnets. Considering the role and cost of the diffusion source, various types of diffusion sources have been developed for GBDP, such as oxides, hydrides, fluorides, alloys and pure metals.

[0005] However, as the diffusion proceeds, CeFe2 phase is easily formed in the grain boundaries of Nd-Fe-B magnets with a higher Ce content. The presence of CeFe2 phase will change the solid-liquid diffusion interface into a solid-solid diffusion interface. At the same time, the presence of CeFe2 phase will also change the chemical gradient between the intergranular phase and the main phase grains. As the chemical gradient decreases, the exchange of rare earth atoms further slows down, thereby hindering the diffusion of the diffusion source in the magnet, resulting in insufficient increment of the grain boundary diffusion performance of the Ce magnet.

[0006] On the other hand, during the diffusion process, although the content of diffusion source elements in the CeFe2 phase is lower than that in the rare earth-rich phase, the CeFe2 phase will still consume a certain amount of diffusion sources. For traditional diffusion sources, under the premise of the same amount of diffusion source, the performance increment of the Ce-containing magnet is insufficient and the coercive force of the magnet is insufficient. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a method for preparing a grain boundary diffusion source and a high-performance and high-abundance rare earth magnet, which can improve the coercive force of the Ce-containing NdFeB magnet while maintaining the remanence and maximum magnetic energy product of the magnet at a low cost.

[0008] To achieve the above object, the technical solution adopted by the present invention is: a grain boundary diffusion source, including (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Alloy powder, wherein the HRE is one or more selected from Dy or Tb, and the M is one or more selected from Fe, Co, Al, Ca, Cu, Ni, Ge, Zr, Ti, Nb, Mo, Hf, Ta or W; wherein 0≤x≤1, 0≤y≤1, x(HRE)+x(La)=68at.%, x(M)+x(Ga)=32at.%.

[0009] A method for preparing a high-performance and high-abundance rare earth magnet comprises the following steps:

[0010] S1: preparing a high-abundance rare earth NdFeB blank containing Ce element for grain boundary diffusion treatment;

[0011] S2 processes the sintered NdFeB blank into a substrate treated with grain boundary diffusion and undergoes surface treatment;

[0012] S3: preparing a slurry of a grain boundary diffusion source, and then attaching the slurry of the grain boundary diffusion source to a diffusion magnet substrate to form a grain boundary diffusion layer;

[0013] S4: transferring the magnet to be diffused with the grain boundary diffusion layer formed thereon to a sintering furnace for diffusion heat treatment to obtain a diffused magnet.

[0014] Furthermore, in step S3, the grain boundary diffusion source slurry is attached to the diffusion magnet substrate to form a grain boundary diffusion layer by coating, screen printing and suspended plasma spraying.

[0015] Further, the steps of preparing the grain boundary diffusion source slurry are as follows:

[0016] S20) putting the adhesive into the liquid dispersant and stirring to dissolve;

[0017] S21) placing the dissolved colloid into a glove box, opening the nitrogen outlet valve of the glove box, opening the nitrogen inlet valve, and allowing nitrogen to exhaust the air in the glove box to reduce the oxygen content to less than 0.01%;

[0018] S22) adding grain boundary diffusion source powder and protective layer powder with a particle size of 3-4um into the colloid in multiple times, stirring evenly each time until all the powders are added, and then extending the stirring time for 5 minutes to obtain a grain boundary diffusion source slurry after the powder is completely covered by the colloid, wherein the mass percentage of the grain boundary diffusion source powder in the slurry is 1%-90%.

[0019] Furthermore, in step 3, two slurries with different contents of grain boundary diffusion sources are prepared, and then the two slurries with different contents of grain boundary diffusion sources are sequentially attached to the diffusion magnet substrate to form a double-layer grain boundary diffusion layer;

[0020] Among them, the slurry of the first grain boundary diffusion source is (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 , 0≤x≤0.3, 0≤y≤0.3, x(HRE)+x(La)=68at.%, x(M)+x(Ga)=32at.%;

[0021] The second grain boundary diffusion source slurry is (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 , 0.7≤x≤1, 0.7≤x≤1, x(HRE)+x(La)=68at.%, x(M)+x(Ga)=32at.%.

[0022] Furthermore, the mass ratio between the two grain boundary diffusion source slurries with different contents in the double-layer grain boundary diffusion layer is 1:2.

[0023] Furthermore, a functional protection layer prepared by a functional protection slurry is attached to the double-layer grain boundary diffusion layer to form a grain boundary diffusion composite layer on the diffusion magnet substrate.

[0024] Furthermore, the material of the functional protective slurry is selected from a metal powder of Group IVB, Group VB, Group VIB or Group VIIB of the periodic table of Mo, W, Nb, Ta, Ti, Hf, Zr, Ti, V, Re, or an alloy powder of the above materials, or one or more of the oxides, fluorides, hydrides, chlorides or nitrates of the above materials.

[0025] Further, the steps of preparing the grain boundary diffusion source powder are as follows:

[0026] S30) According to (HRE x La 1-x ) 68 (M1-y Ga y ) 32 The mass percentage of each component is used for batching, and before batching, the oxide layer of the surface of HRE and La needs to be removed by a shot blasting machine;

[0027] S31) adding all raw materials into the quick-setting furnace, flushing the furnace cavity with argon gas, and then evacuating the furnace cavity to a vacuum degree less than or equal to 3×10 -3 Pa, then filled with argon as a protective gas for smelting, and finally the molten alloy was poured through a tundish onto a rotating water-cooled copper roller to obtain (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Quick-setting tablets;

[0028] S32) The obtained (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The quick-setting sheet is transferred to a hydrogen rupture tank, and then the hydrogen rupture tank is placed in a hydrogen rupture furnace for hydrogen rupture treatment to obtain (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Hydrogen broken coarse powder;

[0029] S33) will (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The hydrogen-crushed coarse powder was transferred to a special tank for jet mill in the glove box, and then jet milled at a speed of 4500 to obtain a particle size of 3-4um (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Diffusion source powder.

[0030] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0031] 1) (HRE of the present invention x La 1-x ) 68 (M 1-y Ga y )32 Grain boundary diffusion source, the partial substitution of La atoms for Ce in the grain boundary can reduce or even inhibit the formation of CeFe2 phase, thereby increasing the diffusion depth and facilitating the diffusion of Tb / Dy elements; at the same time, La tends to combine with oxygen in the grain boundary to form Ia3_-RE2O3 grain boundary phase. The wettability of this phase makes it easy to form a smooth and complete intergranular phase, which is beneficial to weaken the exchange coupling between adjacent main phase grains and thus improve the coercive force of the magnet.

[0032] In addition, Ga element diffuses into the grain boundary and generates RE6(Fe,M) 14 phase, which can effectively reduce the α-Fe content in the grain boundary phase, thereby reducing the exchange coupling between the α-Fe phase and the main phase grains to increase the coercive force of the magnet, and RE6(Fe,M) 14 The phase has antiferromagnetic properties and can act as a pinning center in the triangular grain boundary, thereby increasing the coercive force of the magnet.

[0033] 2) The high-performance and high-abundance rare earth magnet prepared by the present invention replaces a part of the Tb element by the La element. Since the La element is a high-abundance rare earth element, its price is much lower than that of the Tb element. Therefore, it has the advantage of low cost while maintaining good hard magnetic properties of the magnet, and can effectively utilize high-abundance rare earth metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The technical solution of the present invention is further described below in conjunction with the accompanying drawings:

[0035] Figure 1 This is a schematic diagram of a process for preparing a high-performance and high-abundance rare earth magnet in one embodiment of the present invention;

[0036] Figure 2 It is a schematic diagram of the structure of the composite diffusion layer after diffusion on the magnet to be diffused in the second embodiment of the present invention;

[0037] Figure 3 In one embodiment of the present invention, TbH x Diffusion source and (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Diffusion depth comparison of composite diffusion sources;

[0038] Figure 4 In one embodiment of the present invention, TbH is 800um x Diffusion source and (HRE x La 1-x ) 68 (M 1-y Ga y )32 intergranular phase ratio of composite diffusion sources;

[0039] Among them: 1. magnet to be diffused; 2. functional protection layer; 3. first diffusion layer; 4. second diffusion layer. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0041] The present invention provides a method for preparing a grain boundary diffusion source and a high-performance and high-abundance rare earth magnet, so as to solve the problem in the prior art that CeFe2 phase is easily formed in the grain boundary of a Nd-Fe-B magnet with a higher Ce content, which hinders the diffusion of the diffusion source in the magnet, resulting in insufficient increase in the grain boundary diffusion performance of the Ce magnet, and at the same time, the CeFe2 phase consumes a certain amount of diffusion source, resulting in insufficient coercive force of the magnet.

[0042] To facilitate understanding, the specific process in the embodiments of the present application is described below.

[0043] A grain boundary diffusion source according to an embodiment of the present invention comprises (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Alloy powder, wherein the HRE is one or more selected from Dy or Tb, and the M is one or more selected from Fe, Co, Al, Ca, Cu, Ni, Ge, Zr, Ti, Nb, Mo, Hf, Ta or W; wherein x satisfies 0≤x≤1, y satisfies 0≤y≤1, x(HRE)+x(La)=68at.%, x(M)+x(Ga)=32at.%.

[0044] Wherein, the (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Alloy powder is: (HRE 1-x La x ) 68 Ni 16 Ga 16 、(HRE 1- xLa x ) 68 Al 16 Ga 16 、(HRE 1-x La x ) 68 Cu 16 Ga 16 、(HRE 1-x La x ) 68 Ti 16 Ga 16 .

[0045] In the present invention, light rare earth elements La, La 3+ The ionic radius is the largest among all rare earth atoms. La is more inclined to enter the grain boundary. The partial substitution of La atoms for Ce in the grain boundary can reduce or even inhibit the formation of CeFe2 phase, thereby increasing the diffusion depth and facilitating the diffusion of Tb / Dy elements. At the same time, La tends to combine with oxygen in the grain boundary to form Ia3_-RE2O3 grain boundary phase. The wettability of this phase makes it easy to form a smooth and complete intergranular phase, which is beneficial to weakening the exchange coupling between adjacent main phase grains and thus improving the coercive force of the magnet.

[0046] As La diffuses, the CeFe2 phase is suppressed from forming, and the α-Fe content of the grain boundary phase gradually increases. The presence of excessive α-Fe phase will form an exchange coupling effect with the main phase grains to reduce the coercive force of the magnet; therefore, the present invention introduces Ga element into the diffusion source alloy containing Tb / Dy and La. Ga element diffuses into the grain boundary and generates RE6(Fe,M) 14 The formation of this phase can effectively reduce the α-Fe content in the grain boundary phase, thereby reducing the exchange coupling between the α-Fe phase and the main phase grains to increase the coercive force of the magnet, and RE6(Fe,M) 14 The phase has antiferromagnetic properties and can act as a pinning center in the triangular grain boundary, thereby increasing the coercive force of the magnet.

[0047] In the embodiment of the present invention, the (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The alloy powder can be prepared into a slurry and then used alone as a diffusion source, and directly attached to the surface of the magnet for grain boundary diffusion through processes such as coating, screen printing, and suspended plasma spraying.

[0048] Also available in two different contents (HRE x La 1-x )68 (M 1-y Ga y ) 32 The slurry and the functional protection slurry are made into a composite diffusion layer on the surface of the magnet and then diffused at the grain boundary.

[0049] Among them, the first grain boundary diffusion source slurry is (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 , x satisfies 0≤x≤0.3, y satisfies 0≤y≤0.3, x(HRE)+x(La)=68at.%, ​​x(M)+x(Ga)=32at.%. The La element content in the first grain boundary diffusion source slurry is relatively high between 1.0 and 0.7, and the HRE and Ga contents are relatively low between 0 and 0.3.

[0050] In the grain boundary diffusion of Ce-containing magnets, the first layer of grain boundary diffusion source slurry mainly uses La element to reduce or inhibit the formation of CeFe2 phase, and improve the diffusion depth and diffusion mobility of the diffusion source in the magnet.

[0051] The second grain boundary diffusion source slurry is (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 , where x satisfies 0.7≤x≤1, y satisfies 0.7≤x≤1, x(HRE)+x(La)=68at.%, ​​x(M)+x(Ga)=32at.%. The La element content in the second grain boundary diffusion source slurry is less than 0-0.3, and the HRE and Ga contents are relatively high between 1.0 and 0.7. The second grain boundary diffusion source slurry mainly utilizes HRE and Ga elements to improve the coercive force of the magnet.

[0052] In the present invention, the preparation method of the grain boundary diffusion source slurry is as follows:

[0053] S20) putting the adhesive into the liquid dispersant and stirring to dissolve;

[0054] S21) placing the dissolved colloid into a glove box, opening the nitrogen outlet valve of the glove box, opening the nitrogen inlet valve, and allowing nitrogen to exhaust the air in the glove box to reduce the oxygen content to less than 0.01%;

[0055] S22) adding grain boundary diffusion source powder and protective layer powder with a particle size of 3-4um into the colloid in multiple times, stirring evenly each time until all the powders are added, and then extending the stirring time for 5 minutes to obtain a grain boundary diffusion source slurry after the powder is completely covered by the colloid, wherein the mass percentage of the grain boundary diffusion source powder in the slurry is 1%-90%.

[0056] In addition, the preparation process of the functional protection slurry is the same as that of the grain boundary diffusion source slurry. The functional protection layer prepared by the functional protection slurry in the present invention is a high temperature resistant and oxidation resistant coating. The coating material is selected from a metal powder of Group IVB, Group VB, Group VIB or Group VIIB of the periodic table of Mo, W, Nb, Ta, Ti, Hf, Zr, Ti, V, Re, or an alloy powder of the above materials, or one or more of the oxides, fluorides, hydrides, chlorides or nitrates of the above materials, wherein the film thickness of the functional protection layer 3 is 5-15um.

[0057] based on Figure 1 In one embodiment of the present invention, the steps of the method for preparing a high-performance and high-abundance rare earth magnet are as follows:

[0058] S1: preparing a high-abundance rare earth NdFeB blank containing Ce element for grain boundary diffusion treatment;

[0059] S2 processes the sintered NdFeB blank into a substrate treated with grain boundary diffusion and undergoes surface treatment;

[0060] S3: preparing a slurry of a grain boundary diffusion source, attaching two slurries of grain boundary diffusion sources with different contents on a diffusion magnet substrate in sequence to form a double-layer grain boundary diffusion layer, and then attaching a functional protection layer prepared by a functional protection slurry on the double-layer grain boundary diffusion layer to form a grain boundary diffusion composite layer;

[0061] S4: transferring the magnet to be diffused with the grain boundary diffusion composite layer formed thereon to a sintering furnace for diffusion heat treatment to obtain a diffused magnet.

[0062] Among them, the slurry of the first grain boundary diffusion source is (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 , 0≤x≤0.3, 0≤y≤0.3, x(HRE)+x(La)=68at.%, x(M)+x(Ga)=32at.%;

[0063] The second grain boundary diffusion source slurry is (HRE x La 1-x ) 68 (M 1-y Ga y )32 , 0.7≤x≤1, 0.7≤x≤1, x(HRE)+x(La)=68at.%, x(M)+x(Ga)=32at.%.

[0064] The preparation method in the above embodiment is to diffuse the magnet by preparing a grain boundary diffusion source and a functional protection layer with two different contents.

[0065] Several specific embodiments are listed below to specifically describe the method for preparing a high-performance and high-abundance rare earth magnet disclosed in the present invention and the performance of the prepared magnet.

[0066] Example 1

[0067] 1) Using Tb, La, Cu, and Ga with a purity of 99.9% by mass as raw materials, according to the atomic percentage (Tb 1-x La x ) 68 Cu 16 Ga 16 (x=0.1, 0.2, 0.3, 0.4, 0.5) are used for batching. Before batching, the oxide layers on the surfaces of Tb and La need to be removed by a shot blasting machine.

[0068] 2) Add all the raw materials into the quick-setting furnace, flush the furnace cavity with argon, and then evacuate to a vacuum degree less than or equal to 3×10 -3 Pa, and then filled with argon as a protective gas for smelting, and finally the molten alloy was poured through a tundish onto a rotating water-cooled copper roller to obtain (Tb 1-x La x ) 68 Cu 16 Ga 16 (x=0.1, 0.2, 0.3, 0.4, 0.5) quick-setting tablets.

[0069] 3) The obtained (Tb 1-x La x ) 68 Cu 16 Ga 16 (x = 0.1, 0.2, 0.3, 0.4, 0.5) The quick-setting sheet was transferred to the material tank, and then the material tank was placed in a hydrogen cracking furnace for hydrogen cracking to obtain (Tb 1-x La x ) 68 Cu 16 Ga 16 (x=0.1, 0.2, 0.3, 0.4, 0.5) hydrogen-crushed coarse powder; wherein, during the hydrogen-crushing process, the hydrogen absorption temperature is 300°C, the hydrogen absorption pressure is 0.091Pa, the hydrogen absorption time is 2h, the dehydrogenation temperature is 350°C, and the dehydrogenation time is 1h.

[0070] 4) The obtained (Tb 1-x La x ) 68 Cu 16 Ga 16 The hydrogen-broken coarse powder (x = 0.1, 0.2, 0.3, 0.4, 0.5) was transferred to a special tank for jet mill in a glove box, and then jet milled at a speed of 4500. Finally, a particle size of 4.1 um (Tb 1-x La x ) 68 Cu 16 Ga 16 (x=0.1, 0.2, 0.3, 0.4, 0.5) diffusion source powder.

[0071] 5) A high-abundance rare earth NdFeB blank containing Ce element for grain boundary diffusion treatment is prepared, wherein the components are composed by mass percentage, including: Pr-Nd: 21.1%, Ce: 7.9%, Al: 0.30%, Co: 1.0%, B: 0.95%, Cu: 0.1%, Ga: 0.2%, Zr: 0.2% and the balance Fe, and then it is prepared according to the existing rare earth magnet smelting, belt throwing, hydrogen crushing, air flow grinding, orientation pressing, sintering and heat treatment processes.

[0072] 6) The processed sintered magnet is processed into a square magnet of 10mm*10mm*4mm, with the 4mm direction being the magnetic field orientation direction. After the processed magnet is surface cleaned, the magnetic properties are tested using a Mianyang Bipolar 264Y permanent magnet property automatic measuring instrument. The measuring temperature is 20°C, and the measuring results are Br: 13.41kGs, Hcj: 10.18kOe, (BH)max: 42.48MGOe, SQ: 95.48%.

[0073] 7) Put the adhesive into the liquid dispersant and stir to dissolve the adhesive.

[0074] 8) The dissolved colloid is placed in a glove box, and the nitrogen outlet valve and nitrogen inlet valve of the glove box are opened to allow nitrogen to exhaust the air in the glove box to reduce the oxygen content to less than 0.01%.

[0075] 9) The particle size of 4.1um (Tb 1-x La x ) 68 Cu 16 Ga 16 (x = 0.1, 0.2, 0.3, 0.4, 0.5) diffusion source powder was added to the colloid several times, and stirred evenly each time until it was completely added. The stirring time was extended for 5 minutes to make the metal powder completely covered by the colloid to obtain the target slurry, wherein (Tb1-x La x ) 68 Cu 16 Ga 16 (x=0.1, 0.2, 0.3, 0.4, 0.5) The mass percentage of the diffusion source powder in the slurry is 75%.

[0076] 10) Print a layer (Tb) on the surface of the diffusion magnet substrate by screen printing 1-x La x ) 68 Cu 16 Ga 16 (x = 0.1, 0.2, 0.3, 0.4, 0.5) grain boundary diffusion layer, the (Tb 1-x La x ) 68 Cu 16 Ga 16 (x=0.1, 0.2, 0.3, 0.4, 0.5) The grain boundary diffusion layer accounts for 0.9wt.% of the substrate mass.

[0077] 11) The plated (Tb 1-x La x ) 68 Cu 16 Ga 16 (x=0.1, 0.2, 0.3, 0.4, 0.5) The magnets with grain boundary diffusion layer were dried to obtain magnets to be diffused. The drying temperature was 120℃ and the drying time was 10min.

[0078] 12) The magnet to be diffused is transferred to a sintering furnace for diffusion heat treatment to obtain a diffused magnet (Examples 1.1-1.5).

[0079] 13) The magnetic properties of the diffused magnet were tested at a temperature of 20°C.

[0080] 14) A single layer of TbHx diffusion film was deposited on the diffusion substrate using conventional screen printing as comparative example 1.1, wherein the TbHx diffusion source film accounted for 0.9 wt.% of the substrate mass.

[0081] The evaluation results of the magnetic properties at 20°C of Examples 1.1-1.5 are shown in Table 1.

[0082] Table 1 Evaluation of magnetic properties at 20°C of Examples 1.1-1.5

[0083]

[0084] As shown in Table 1, by analyzing the magnetic properties of Examples 1.1-1.5, it can be seen that (Tb 1-x La x )68 Cu 16 Ga 16 (x=0.1, 0.2, 0.3, 0.4, 0.5) After the diffusion source diffuses into the base magnet through the grain boundaries, the coercive force is greatly improved.

[0085] The remanence of the diffused magnets is lower than that of the diffused matrix, but the reduction is not large. The reason for the reduction in remanence is Tb2Fe 14 The Js value of B is lower than that of Nd2Fe 14 B and Ce2Fe 14 The Js value of B, during the diffusion heat treatment process, the Tb element will replace (Nd, Ce)2Fe 14 The Nd and Ce elements in the B grains form (Nd-Ce-Tb)2Fe 14 B grains, the magnetic dilution effect caused by the substitution of Tb elements for Nd and Ce elements reduces the remanence of the magnet; in the range of 0.3<x≤0.5, with the increase of La content in the diffusion source, the remanence of the magnet increases slightly, because part of the La / Tb elements replace the Ce element, which improves the intrinsic magnetic properties of the magnet.

[0086] For diffusion magnets, (Tb 1-x La x ) 68 Cu 16 Ga 16 (x=0.1, 0.2, 0.3, 0.4, 0.5) diffusion sources are used for diffusion. When x=0.3, the best magnetic properties can be obtained: Br=13.17kGs, Hcj=17.32kOe and (BH)max=40.78MGOe. With the increase of La content, the coercive force of the diffused magnet shows a trend of first increasing and then decreasing.

[0087] When the La content is x=0.1-0.3, the coercive force of the diffusion magnet increases with the increase of La content. The partial substitution of La atoms for Ce in the grain boundary can reduce or even inhibit the formation of CeFe2 phase, thereby increasing the diffusion depth and facilitating the diffusion of Tb elements. At the same time, La tends to combine with oxygen in the grain boundary to form Ia3_-RE2O3 grain boundary phase. The wettability of this phase makes it easy to form a smooth and complete intergranular phase, which is beneficial to weakening the exchange coupling between adjacent main phase grains and thus improving the coercive force of the magnet.

[0088] When the La content x>0.3, due to the decrease of Tb atomic concentration and the increase of La atomic concentration, a clear La gap is formed between the intergranular phase and the main phase grains. 3+ The concentration gradient makes La 3+ Enter the main phase grains to form (Nd-Ce-La-Tb)2Fe 14The B shell layer causes magnetic dilution of the main phase grains, reducing the coercive force of the magnet.

[0089] Comparing Example 1.3 with Comparative Example 1.1, it can be seen that under the premise of the same diffusion dosage, the La and Ga doped (Tb 0.7 La 0.3 ) 68 Cu 16 Ga 16 Diffusion sources can diffuse the magnet grain boundaries to achieve better coercivity improvement; at the same time, since La is a high-abundance rare earth element, its price is much lower than that of Tb, so (Tb 0.7 La 0.3 ) 68 Cu 16 Ga 16 Diffusion sources have more obvious cost advantages.

[0090] The high-performance and high-abundance rare earth magnet containing La and Ce prepared in this embodiment has the advantage of low cost while maintaining good hard magnetic properties of the magnet, can effectively utilize high-abundance rare earth metals, and realize the comprehensive and balanced utilization of rare earth resources, which is of great significance to the sustainable development of the rare earth permanent magnet industry.

[0091] Example 2

[0092] 1) Using Tb, La, Cu, and Ga with a purity of 99.9% by mass as raw materials, according to the atomic percentage (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 and(La 0.7 Tb 0.3 ) 68 Cu 22.4 Ga 9.6 Before batching, the oxide layers on the surfaces of Tb and La need to be removed by a shot blasting machine.

[0093] 2) Add the raw materials into the quick-setting furnace, flush the furnace cavity with argon gas, and then evacuate the furnace to a vacuum degree less than or equal to 3×10 -3 Pa, and then filled with argon as a protective gas for smelting, and finally the molten alloy was poured through a tundish onto a rotating water-cooled copper roller to obtain (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 and(La 0.7 Tb 0.3 ) 68 Cu 22.4 Ga 9.6Quick-setting tablets.

[0094] 3) The obtained (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 and(La 0.7 Tb 0.3 ) 68 Cu 22.4 Ga 9.6 The quick-setting sheet is transferred to a material tank, and then the material tank is placed in a hydrogen cracking furnace for hydrogen cracking to obtain (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 and(La 0.7 Tb 0.3 ) 68 Cu 22.4 Ga 9.6 The hydrogen-breaking coarse powder is prepared by hydrogen-breaking. During the hydrogen-breaking process, the hydrogen absorption temperature is 300°C, the hydrogen absorption pressure is 0.091Pa, the hydrogen absorption time is 2h, the dehydrogenation temperature is 350°C, and the dehydrogenation time is 1h.

[0095] 4) The obtained (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 and(La 0.7 Tb 0.3 ) 68 Cu 22.4 Ga 9.6 The hydrogen-crushed coarse powder was transferred to a special tank for jet mill in the glove box, and then jet milled at a speed of 4500. Finally, the particle size of 3.8-4.5um (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 and(La 0.7 Tb 0.3 ) 68 Cu 22.4 Ga 9.6 Diffusion source powder.

[0096] 5) A high-abundance rare earth NdFeB blank containing Ce element for grain boundary diffusion treatment is prepared, wherein the components are composed by mass percentage, including: Pr-Nd: 21.1%, Ce: 7.9%, Al: 0.30%, Co: 1.0%, B: 0.95%, Cu: 0.1%, Ga: 0.2%, Zr: 0.2% and the balance Fe, and the blank is prepared according to the existing rare earth magnet smelting, belt throwing, hydrogen crushing, air flow grinding, orientation pressing, sintering and heat treatment processes.

[0097] 6) The processed sintered magnet is processed into a square magnet of 10mm*10mm*4mm, with the 4mm direction being the magnetic field orientation direction. The processed magnet is subjected to surface cleaning treatment and then magnetic properties testing is performed at a measuring temperature of 20°C. The test results are: Br: 13.41kGs, Hcj: 10.18kOe, (BH)max: 42.48MGOe, SQ: 95.48%.

[0098] 7) Put the adhesive into the liquid dispersant and stir to dissolve the adhesive.

[0099] 8) The dissolved colloid is placed in a glove box, and the nitrogen outlet valve and nitrogen inlet valve of the glove box are opened to allow nitrogen to exhaust the air in the glove box to reduce the oxygen content to less than 0.01%.

[0100] 9) The particle size of 3.8-4.5um (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 Diffusion source powder is added to the colloid several times, and stirred evenly each time until it is completely added. The stirring time is then extended for 5 minutes to allow the metal powder to be completely covered by the colloid to obtain (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 Diffusion source slurry, (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 The mass percentage of the diffusion source powder in the slurry is 75%.

[0101] 10) Repeat steps 7-9 to prepare (La 0.7 Tb 0.3 ) 68 Cu 22.4 Ga 9.6 Diffusion source slurry and functional protective layer slurry, wherein the functional protective layer slurry is Al2O3 powder slurry with a particle size of 300 meshes.

[0102] 11) Print the first diffusion layer on the surface of the diffusion magnet substrate using screen printing: (La 0.7 Tb 0.3 ) 68 Cu 22.4 Ga 9.6 Diffusion source film, the (La 0.7 Tb 0.3 ) 68 Cu 22.4 Ga 9.6 The diffusion source film accounts for 0.3 wt.% of the substrate mass.

[0103] 12) After the first diffusion layer is dried, the second diffusion layer is then printed on the surface of the first diffusion layer of the diffusion magnet by screen printing: (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 Diffusion source film, the (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 The diffusion source film accounts for 0.6 wt.% of the substrate mass.

[0104] 13) Repeat the above steps to print a functional protective layer on the surface of the second diffusion layer. The thickness of the functional protective layer is 10 um.

[0105] 14) Drying the magnet coated with the composite diffusion layer film to obtain a magnet to be diffused (such as Figure 2 The drying temperature is 120°C and the drying time is 10 minutes.

[0106] 15) The magnet to be diffused is transferred to a sintering furnace for diffusion heat treatment to obtain a diffused magnet.

[0107] 16) The diffused magnets were tested for magnetic properties using a 264Y permanent magnet property automatic measuring instrument from Mianyang Bipolar, with the measuring temperature being 20°C.

[0108] 17) Deposit a single layer of Tb on the diffusion substrate using conventional screen printing 70 Al 15 Cu 15 The diffusion film is used as comparative example 2.1, in which the TbHx diffusion source film accounts for 0.8 wt.% of the substrate mass.

[0109] Table 2 Evaluation of magnetic properties at 20°C of the embodiments and comparative examples

[0110]

[0111] As shown in Table 2, through the magnetic property analysis of the embodiments and the comparative examples, it can be seen that the best magnetic properties that can be obtained by diffusion using a composite diffusion source are: Br = 13.27 kGs, Hcj = 19.11 kOe and (BH)max = 42.89 MGOe.

[0112] The present invention (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The coercivity increment obtained by the diffusion source is greater than that of the traditional diffusion source (TbHx, Tb 70 Al 15 Cu 15 The coercive force increment obtained; this is because, for Nd-Ce-Fe-B magnets, when using traditional diffusion sources for diffusion, due to a large number of low melting point RE-rich phases, REO X phase, Tb atoms penetrate into (Nd,Ce)2Fe through these liquid phases. 14 As the diffusion proceeds, a large number of Ce atoms migrate from the 2:14:1 main phase grains to the grain boundaries to form Ce-rich REFe2 phase. When REFe2 phase gradually becomes the dominant intergranular phase, Tb atoms migrate from the solid REFe2 phase to RE2Fe 14 The diffusion rate of the B phase will be greatly reduced. At the same time, the presence of the REFe2 phase will also change the chemical gradient between the intergranular phase and the main phase grains. As the chemical gradient decreases, the exchange of rare earth atoms will further slow down, thereby hindering the diffusion of the diffusion source in the magnet. These factors together lead to the enrichment of the Tb element on the magnet surface, and the diffusion depth is limited to below 400um.

[0113] Since Tb atoms are enriched on the magnet surface and the diffusion depth is insufficient, an inverse core-shell structure is easily formed on the surface, resulting in insufficient increment of the coercive force of the diffused magnet and greatly reducing the utilization rate of the diffusion source.

[0114] For (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Composite diffusion source, due to the high La content in the first diffusion layer (La 0.7 Tb 0.3 ) 68 Cu 22.4 Ga 9.6The melting point of the diffusion source slurry is lower. When diffusion is in progress, this layer of diffusion material first diffuses into the interior of the magnet along the grain boundary. The introduction of La element to replace Ce into the grain boundary phase through diffusion can reduce or even inhibit the formation of CeFe2 phase, thereby increasing the diffusion depth and facilitating the diffusion of Tb element. At the same time, La tends to combine with oxygen in the grain boundary to form Ia3_-RE2O3 grain boundary phase. The wettability of this phase makes it easy to form a smooth and complete intergranular phase, which is beneficial to weakening the exchange coupling between adjacent main phase grains and thus improving the coercive force of the magnet.

[0115] As diffusion continues, the second diffusion layer: (Tb 0.7 La 0.3 ) 68 Cu 9.6 Ga 22.4 The Tb, Cu, Ga and other elements in the magnet continue to penetrate into the interior of the magnet along the modified grain boundaries. A large number of Tb atoms penetrate into the RE2Fe 14 In B, (Nd-Tb)2Fe with high anisotropic fields is formed on the surface of the main phase grains. 14 B shell, greatly enhancing the coercivity of the magnet; at the same time, Ga element diffuses into the grain boundary to generate RE6(Fe,M) 14 The formation of this phase can effectively reduce the α-Fe content in the grain boundary phase, thereby reducing the exchange coupling between the α-Fe phase and the main phase grains to increase the coercive force of the magnet, and RE6(Fe,M) 14 The phase has antiferromagnetic properties and can act as a pinning center in the triangular grain boundary, thereby increasing the coercive force of the magnet.

[0116] To further illustrate (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The superiority of composite diffusion source, we have TbHx diffusion source and (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The diffusion depth of composite diffusion sources was compared, e.g. Figure 3 As shown; the results show that (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The diffusion depth of the composite diffusion source is much greater than that of the TbHx diffusion source.

[0117] like Figure 4 As shown, we also determined the TbHx diffusion source and (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The intergranular phase comparison of the composite diffusion source shows that the intergranular phase width of the latter is 3.5nm, which is larger than the 0.8nm of the traditional TbHx diffusion source; Nd2Fe 14 The direct exchange coupling length Lex of the B main phase is ≈ 2.1 nm. When the grain boundary width is less than 2.1 nm, the reversal magnetization domains can easily propagate between the main phase grains during the reversal magnetization process, resulting in a decrease in the coercive force of the magnet.

[0118] Adoption (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 After the composite diffusion source, the width of the grain boundary phase between the main phases of the magnet is greater than the exchange coupling distance of 2.1nm, which is beneficial to weaken the exchange coupling effect between neighboring main phases, thereby improving the coercive force of the magnet.

[0119] As can be seen from the second embodiment, the present invention adopts (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The composite diffusion source can solve the problem of difficult grain boundary diffusion of Ce-containing magnets, can effectively inhibit the formation of CeFe2 phase, reduce the Fe content in the grain boundaries, and while improving the coercive force of Ce-containing NdFeB magnets, can also maintain the remanence and maximum magnetic energy product of the magnets. At the same time, the present invention prepares high-performance and high-abundance rare earth magnets containing La and Ce, which has the advantage of low cost while maintaining good hard magnetic properties of the magnets, can effectively utilize high-abundance rare earth metals, and realize the comprehensive and balanced utilization of rare earth resources, which is of great significance to the sustainable development of the rare earth permanent magnet industry.

[0120] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A grain boundary diffusion source, characterized in that: Includes (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Alloy powder, wherein the HRE is one or more selected from Dy or Tb, and the M is one or more selected from Fe, Co, Al, Ca, Cu, Ni, Ge, Zr, Ti, Nb, Mo, Hf, Ta or W; wherein 0<x<1, 0<y<1, x(HRE)+x(La)=68 at.%, x(M)+x(Ga)=32 at.%.

2. A method for preparing a high-performance and high-abundance rare earth magnet, characterized in that: The steps include: S1: preparing a high-abundance rare earth NdFeB blank containing Ce element for grain boundary diffusion treatment; S2 processes the sintered NdFeB blank into a substrate treated with grain boundary diffusion and undergoes surface treatment; S3: preparing a slurry of the grain boundary diffusion source as claimed in claim 1, and then attaching the slurry of the grain boundary diffusion source to a diffusion magnet substrate to form a grain boundary diffusion layer; S4: transferring the magnet to be diffused with the grain boundary diffusion layer formed thereon to a sintering furnace for diffusion heat treatment to obtain a diffused magnet.

3. The method for preparing a high-performance and high-abundance rare earth magnet according to claim 2, characterized in that: In step S3, the grain boundary diffusion source slurry is attached to the diffusion magnet substrate to form a grain boundary diffusion layer by coating, screen printing or suspension plasma spraying.

4. The method for preparing a high-performance and high-abundance rare earth magnet according to claim 2, characterized in that: The steps for preparing the grain boundary diffusion source slurry are as follows: S20) putting the binder into the liquid dispersant and stirring to dissolve; S21) The dissolved colloid is placed in a glove box, and the nitrogen outlet valve and nitrogen inlet valve of the glove box are opened to allow nitrogen to exhaust the air in the glove box to reduce the oxygen content to less than 0.01%; S22) respectively adding a grain boundary diffusion source powder with a particle size of 3-4 um and a protective layer powder into the same colloid in multiple times, stirring evenly each time until all the powders are added, and then extending the stirring time for 5 minutes to obtain a grain boundary diffusion source slurry after the powder is completely covered by the colloid, wherein the mass percentage of the grain boundary diffusion source powder in the slurry is 1%-90%.

5. The method for preparing a high-performance and high-abundance rare earth magnet according to claim 2, characterized in that: In step 3, two slurries with different contents of grain boundary diffusion sources are prepared, and then the two slurries with different contents of grain boundary diffusion sources are sequentially attached to the diffusion magnet substrate to form a double-layer grain boundary diffusion layer; Among them, the slurry of the first grain boundary diffusion source is (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 , 0<x≤0.3, 0<y≤0.3, x(HRE)+x(La)=68 at.%, x(M)+x(Ga)=32 at.%; The second grain boundary diffusion source slurry is (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 , 0.7≤x<1, 0.7≤y<1, x(HRE)+x(La)=68 at.%, x(M)+x(Ga)=32 at.%.

6. The method for preparing a high-performance and high-abundance rare earth magnet according to claim 5, characterized in that: The mass ratio between the two grain boundary diffusion source slurries with different contents in the double-layer grain boundary diffusion layer is 1:

2.

7. The method for preparing a high-performance and high-abundance rare earth magnet according to claim 5, characterized in that: A functional protection layer prepared by functional protection slurry is attached to the double-layer grain boundary diffusion layer to form a grain boundary diffusion composite layer on the diffusion magnet substrate.

8. The method for preparing a high-performance and high-abundance rare earth magnet according to claim 7, characterized in that: The material of the functional protection slurry is selected from a metal powder of Mo, W, Nb, Ta, Ti, Hf, Zr, Ti, V, Re or an alloy powder of the above elements, or one or more of the oxides, fluorides, hydrides, chlorides or nitrates of the above elements.

9. The method for preparing a high-performance and high-abundance rare earth magnet according to claim 4, characterized in that: The steps for preparing grain boundary diffusion source powder are as follows: S30) According to (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The mass percentage of each component is used for batching, and before batching, the oxide layer of the surface of HRE and La needs to be removed by a shot blasting machine; S31) All raw materials are added to the quick-setting furnace, and the furnace cavity is flushed with argon gas, and then evacuated to a vacuum degree less than or equal to 3×10 -3 Pa, then filled with argon as a protective gas for smelting, and finally the molten alloy was poured through a tundish onto a rotating water-cooled copper roller to obtain (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Quick-setting tablets; S32) The obtained (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The quick-setting sheet is transferred to a hydrogen rupture tank, and then the hydrogen rupture tank is placed in a hydrogen rupture furnace for hydrogen rupture treatment to obtain (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Hydrogen broken coarse powder; S33)Will (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 The hydrogen-crushed coarse powder was transferred to a special tank for jet mill in the glove box, and then jet milled at a speed of 4500 to obtain a particle size of 3-4um (HRE x La 1-x ) 68 (M 1-y Ga y ) 32 Diffusion source powder.

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