A matching design method of high-performance neodymium-iron-boron diffusion base and diffusion source

Abstract

The application provides a matching design method of a high-performance neodymium-iron-boron diffusion base and a diffusion source, which comprises the following steps: forming diffusion couples by respectively combining rapidly quenched neodymium-iron-boron alloy flakes with different compositions and heavy rare earth alloy diffusion source thin strips with different compositions; obtaining neodymium-iron-boron alloy sheets after diffusion heat treatment of the different diffusion couples; evaluating diffusion effects of the heavy rare earth; selecting a neodymium-iron-boron magnet base and a diffusion source with the best diffusion effect; and finally preparing a high-performance neodymium-iron-boron diffusion magnet. The application simplifies the component design and matching process of the magnet base and the diffusion source, is conducive to reducing the research and development cost of the high-performance diffusion magnet, obtains the optimal component matching relationship of the diffusion base and the diffusion source, and prepares the high-performance neodymium-iron-boron diffusion magnet, which has great significance for the sintered neodymium-iron-boron industry and the rare earth permanent magnet material field.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth permanent magnet material production, and in particular to a matching design method for a high-performance NdFeB diffusion matrix and a diffusion source. Background Art

[0002] Third-generation rare earth permanent magnet materials, represented by NdFeB, have widespread and irreplaceable applications in high-tech fields such as wind power generation, electric new energy vehicles, energy-saving home appliances, industrial robots, and magnetic levitation trains. Coercivity, a measure of a permanent magnet's ability to resist external reverse magnetic fields or other demagnetization effects, is crucial to its service performance. However, the actual coercivity of ternary NdFeB magnets is currently less than 30% of the theoretical value. Therefore, high-coercivity, high-performance NdFeB magnets are currently a key development target.

[0003] In recent years, heavy rare earth grain boundary diffusion technology for NdFeB magnets has become an effective way to improve their coercive force. The basic idea is: a diffusion source containing heavy rare earth is attached to the surface of the magnet, and heat treatment is performed at a temperature between the melting point of the grain boundary phase and the main phase, so that the heavy rare earth elements diffuse into the interior of the magnet through the liquid grain boundary phase and are mainly distributed on the surface of the grains without entering too much into the interior of the grains, forming a heavy rare earth shell with a high anisotropy field. This "core-shell" structure can not only suppress the nucleation of reverse magnetization domains on the surface of the grains, play a role in magnetic hardening, and significantly improve the coercive force of the magnet, but also ensure the high remanence characteristics inside the grains, reduce the amount of heavy rare earth, and can prepare NdFeB magnets with both high coercive force and high magnetic energy product.

[0004] Research and technological development in heavy rare earth (HRE) grain boundary diffusion (GBD) have garnered significant attention in the industry. Diffusion sources have expanded from single HRE elements to include their oxides, fluorides, hydrides, multi-component alloys, and homogeneous multi-component mixtures. The goal of this field is to form a thin, continuous HRE shell while maximizing its penetration depth. Research has shown that HRE elements diffuse in two ways during GBD: bulk diffusion into the grain lattice and grain boundary diffusion along the grain boundaries. The bulk diffusion determines the thickness of the HRE magnetic hardening shell formed on the grain surface, while the grain boundary diffusion determines the penetration depth of the HRE into the magnet. It is the synergistic effect of these two diffusion modes that influences the performance improvement of diffused magnets. Extensive GBD practice demonstrates that different combinations of magnet matrix and diffusion source compositions lead to varying degrees of bulk diffusion and grain boundary diffusion during the diffusion process. This suggests that a certain matching relationship exists between the magnet matrix and diffusion source. Proper compositional matching between the magnet matrix and diffusion source is crucial for achieving high-performance diffused magnets.

[0005] With the popularization of NdFeB magnet grain boundary diffusion technology, the research and development stage of commercial brand magnets has paid great attention to the design of the corresponding matrix magnet grain boundary diffusion process. However, the cycle is long, and the magnet is first prepared and then the diffusion test is carried out, and then the diffusion source composition and heat treatment temperature are adjusted to complete the diffusion process design. In addition, the matching relationship between the magnet matrix and the diffusion source is a one-way match. Readjusting the magnet matrix composition will make the entire research and development design stage longer. At the same time, the magnet matrix with adjusted composition has undergone the powder metallurgy process, which is difficult to recycle and increases research and development costs.

[0006] In view of this, designing a method to quickly and effectively distinguish the behavior of "bulk diffusion" and "grain boundary diffusion" in the diffusion process of diffusion sources of different compositions and the magnet matrix, and simplifying the design and matching process of the magnet matrix and diffusion source components will be beneficial to reducing the R&D cost of high-performance diffusion magnets, obtaining the optimal matching relationship between the diffusion matrix and the diffusion source components and preparing high-performance diffusion magnets, and promoting the rapid development of the sintered NdFeB industry and the rare earth permanent magnet field. Summary of the Invention

[0007] The technical problem solved by the present invention is to provide a matching design method for a high-performance NdFeB diffusion matrix and a diffusion source, so as to overcome the problems of low efficiency, long cycle and poor matching effect between the magnet matrix and the diffusion source composition in the existing high-performance diffusion magnet formula design process.

[0008] In view of this, the present application provides a matching design method for a high-performance NdFeB diffusion matrix and a diffusion source, comprising the following steps:

[0009] A) Batch preparation of NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source ribbons with different compositions;

[0010] B) systematically grouping and matching the NdFeB alloy quick-setting sheets and the heavy rare earth alloy diffusion source ribbons according to composition changes, and making diffusion couples with different composition matching relationships;

[0011] C) subjecting different diffusion couples to diffusion heat treatment to obtain NdFeB alloy sheets with different heavy rare earth diffusion behaviors;

[0012] D) analyzing the diffusion effect of the NdFeB alloy sheets and selecting the NdFeB alloy sheet with the best heavy rare earth diffusion effect;

[0013] E) preparing the NdFeB alloy quick-setting sheet for preparing the NdFeB alloy sheet with the best heavy rare earth diffusion effect into a magnet matrix; preparing the heavy rare earth alloy diffusion source ribbon for preparing the NdFeB alloy sheet with the best heavy rare earth diffusion effect into a diffusion source powder;

[0014] F) attaching the diffusion source powder to the surface of the magnet substrate to obtain a pretreated magnet;

[0015] G) performing diffusion heat treatment on the pretreated magnet to obtain a high-performance NdFeB diffusion magnet.

[0016] Preferably, the chemical formula of the NdFeB alloy quick-setting sheet is R1 a R2 b Fe 100-a-b-c-d-e B c M1 d M2 e , wherein R1 is selected from one or more of Pr, Nd, La and Ce, R2 is selected from one or more of Tb, Dy, Ho and Gd, M1 is selected from one or more of Co, Zr, Ni and Ti, and M2 is selected from at least one of Cu, Al, Ga and Mg; a, b, c, d and e are the mass percentages of the corresponding elements, and satisfy 25≤a≤34, 0≤b≤9, 28≤a+b≤34, 0.9≤c≤1.2, 0≤d≤3.0 and 0≤e≤2.0.

[0017] Preferably, the chemical formula of the heavy rare earth alloy diffusion source ribbon is R3 100-x-y-z R4 x M3 y L1 z , wherein M3 is selected from one or more of Fe, Cu, Al, Ga, Co, Sn and Zn, L1 is selected from one or more of H and F, x, y, z are the mass percentages of the corresponding elements, 10≤x≤90, 0≤y≤30, 0≤z≤2.

[0018] Preferably, in step A), the NdFeB alloy quick-setting sheet is obtained by throwing out a sheet from a quick-setting furnace, and the heavy rare earth alloy diffusion source strip is obtained by throwing out a strip from a quick-setting furnace or a rapid quenching furnace; the thickness of the quick-setting sheet is 200 μm to 300 μm, and the thickness of the heavy rare earth alloy diffusion source strip is 50 μm to 100 μm; the NdFeB alloy quick-setting sheet varies in composition for no less than 3 batches, and the heavy rare earth alloy diffusion source strip varies in composition for no less than 3 batches.

[0019] Preferably, in step B), the preparation of the diffusion couple is specifically as follows: NdFeB alloy quick-setting sheets with different compositions are respectively contacted and bonded with heavy rare earth alloy diffusion source ribbons with different compositions; the contact and bonding method is that the heavy rare earth alloy diffusion source ribbon is placed on the upper surface of the NdFeB alloy quick-setting sheet, and the ribbon and the quick-setting sheet are bonded using a non-aqueous adhesive; the contact area of ​​the NdFeB alloy quick-setting sheet and the heavy rare earth alloy diffusion source ribbon is the same.

[0020] Preferably, in step C), the temperature of the diffusion heat treatment is 700° C. to 1000° C., and the time of the diffusion heat treatment is 10 min to 60 min.

[0021] Preferably, in step D), the selection process is specifically as follows:

[0022] Scanning electron microscopy was used to observe the wettability of the diffusion source and the matrix in the NdFeB alloy sheet, the diffusion depth of the heavy rare earth along the diffusion surface, and the shell thickness and distribution of the heavy rare earth on the surface of the NdFeB grains.

[0023] Preferably, in step E), the preparation of the magnet matrix includes hydrogen cracking, airflow milling, orientation pressing, isostatic pressing and sintering and tempering in sequence; the magnetic field of the orientation pressing is 1.5-2.0T, the pressure of the isostatic pressing is 200-300MPa, the sintering temperature of the sintering and tempering is 1000-1100°C, the tempering temperature is 800-1000°C, and the vacuum degree is not less than 1×10 - 2 Pa, sintering time is 2 to 6 hours.

[0024] Preferably, in step F), the particle size of the diffusion source powder is 1.5 to 20 μm; the attachment method is spraying or dipping, and the diffusion source powder accounts for 0.5 wt% to 3 wt% of the pretreated magnet.

[0025] Preferably, in step G), the temperature of the diffusion heat treatment is 800-1000°C, and the vacuum degree is not less than 1×10 - 2 Pa, time is 2 to 10 hours.

[0026] The present application provides a matching design method for a high-performance NdFeB diffusion matrix and a diffusion source, which uses NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion sources as basic raw materials. Since the quick-setting sheets are flaky crystals with continuous grain boundary phases, it is convenient to observe and analyze the metallurgical reaction behavior of the diffusion-introduced elements with the main phase grains and grain boundary phases. Therefore, the diffusion couple composed of the NdFeB alloy quick-setting sheets and the heavy rare earth alloy diffusion source thin strips proposed in the present invention is an excellent sample carrier for analyzing the diffusion effect of heavy rare earths; directly using the diffusion couple composed of the NdFeB alloy quick-setting sheets and the heavy rare earth alloy diffusion source thin strips to conduct diffusion tests and evaluate the NdFeB alloy sheets generated therefrom can eliminate the errors introduced in the magnet matrix preparation process, has high repeatability, and is convenient for formulating evaluation standards , and thanks to the continuous grain boundary phase of the NdFeB alloy quick-solidification sheet, the diffusion temperature of the diffusion couple can be reduced, the diffusion time of the diffusion couple can be shortened, the evaluation cycle can be greatly shortened, the accuracy of the evaluation of the heavy rare earth diffusion effect can be improved, and the design and matching process of the magnet matrix and the diffusion source composition can be simplified; the present invention evaluates the diffusion effect of the heavy rare earth and the matching relationship between the NdFeB matrix and the diffusion source composition design by analyzing the diffusion depth of the heavy rare earth along the diffusion surface in the NdFeB alloy sheet and the shell thickness and distribution of the heavy rare earth on the surface of the NdFeB grain, and further prepares the NdFeB matrix and diffusion source of specific composition, which has high feasibility, and the performance of the finally prepared diffusion magnet is highly consistent with the evaluation expectations, and the matching design work of the NdFeB diffusion matrix and the diffusion source composition can be completed quickly and efficiently.

[0027] On the other hand, the matching design method provided by the present invention can directly melt and recover NdFeB alloy quick-setting sheets that do not meet the requirements, and a new batch of quick-setting sheets can be re-prepared after adjusting the element ratio, thereby greatly improving the utilization rate of raw materials and reducing the matching design cost of the NdFeB magnet matrix and the diffusion source. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Scanning electron microscope microstructure of the NdFeB alloy sheet designed to match Example 1;

[0029] Figure 2 Schematic diagram of diffusion couple matching in this application. DETAILED DESCRIPTION

[0030] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0031] In response to the development and bottleneck problems of high-performance diffusion magnets in the prior art, the present application provides a matching design method for a high-performance NdFeB diffusion matrix and a diffusion source. The method is based on a large number of NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source strips. After matching the diffusion couples, a thermal diffusion treatment is performed, and then the obtained NdFeB alloy sheet is analyzed to obtain the best diffusion couple. Finally, the quick-setting sheet and the diffusion source are prepared into a pre-treated magnet, and a diffusion heat treatment is performed to obtain a high-performance NdFeB diffusion magnet. This method has a good matching effect, high efficiency and short cycle. Specifically, the present invention provides a matching design method for a high-performance NdFeB diffusion matrix and a diffusion source, comprising the following steps:

[0032] A) Batch preparation of NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source ribbons with different compositions;

[0033] B) systematically grouping and matching the NdFeB alloy quick-setting sheets and the heavy rare earth alloy diffusion source ribbons according to composition changes, and making diffusion couples with different composition matching relationships;

[0034] C) subjecting different diffusion couples to diffusion heat treatment to obtain NdFeB alloy sheets with different heavy rare earth diffusion behaviors;

[0035] D) analyzing the diffusion effect of the NdFeB alloy sheets and selecting the NdFeB alloy sheet with the best heavy rare earth diffusion effect;

[0036] E) preparing the NdFeB alloy quick-setting sheet for preparing the NdFeB alloy sheet with the best heavy rare earth diffusion effect into a magnet matrix; preparing the heavy rare earth alloy diffusion source ribbon for preparing the NdFeB alloy sheet with the best heavy rare earth diffusion effect into a diffusion source powder;

[0037] F) attaching the diffusion source powder to the surface of the magnet substrate to obtain a pretreated magnet;

[0038] G) performing diffusion heat treatment on the pretreated magnet to obtain a high-performance NdFeB diffusion magnet.

[0039] The present application provides a matching design method for NdFeB diffusion matrix and diffusion source, which first prepares NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source ribbons of different compositions in batches; in the present application, the NdFeB alloy quick-setting sheets are obtained by throwing sheets from a quick-setting furnace, and the heavy rare earth alloy diffusion source ribbons are obtained by throwing strips from a quick-setting furnace or a rapid quenching furnace; the thickness of the quick-setting sheets is 200-300 μm, and the thickness of the heavy rare earth alloy diffusion source ribbon is 50-100 μm; the quick-setting sheets of the above size are convenient for observing and analyzing the metallurgical reaction behavior of the diffusion-introduced elements with the main phase grains and grain boundaries.

[0040] The composition of the NdFeB alloy quick-setting sheet is a NdFeB alloy well known to those skilled in the art. For example, the chemical formula of the NdFeB alloy quick-setting sheet is R1 a R2 b Fe 100-a-b-c-d-e B c M1 d M2 e , wherein R1 is selected from one or more of Pr, Nd, La and Ce, R2 is selected from one or more of Tb, Dy, Ho and Gd, M1 is selected from one or more of Co, Zr, Ni and Ti, and M2 is selected from at least one of Cu, Al, Ga and Mg; a, b, c, d and e are the mass percentages of the corresponding elements, and satisfy 25≤a≤34, 0≤b≤9, 28≤a+b≤34, 0.9≤c≤1.2, 0≤d≤3.0, and 0≤e≤2.0. The composition of the heavy rare earth alloy diffusion source ribbon is a heavy rare earth alloy diffusion source well known to those skilled in the art. For example, the chemical formula of the heavy rare earth alloy diffusion source ribbon is R3 100-x-y-z R4 x M3 y L1 z , wherein M3 is selected from one or more of Fe, Cu, Al, Ga, Co, Sn and Zn, L1 is selected from one or more of H and F, x, y, z are the mass percentages of the corresponding elements, 10≤x≤90, 0≤y≤30, 0≤z≤2.

[0041] For the accuracy of the research, the NdFeB alloy quick-setting sheets described in this application have no less than 3 batches of composition changes, and the heavy rare earth alloy diffusion source strips have no less than 3 batches of composition changes; different batches of the NdFeB alloy quick-setting sheets and the heavy rare earth alloy diffusion source strips can be adjusted according to the composition of their respective alloy elements.

[0042] This application then systematically groups and matches the above-mentioned NdFeB quick-setting sheets and heavy rare earth alloy diffusion source ribbons according to composition changes, and makes diffusion couples with different composition matching relationships; in this application, the process of preparing the diffusion couple is specifically as follows: NdFeB alloy quick-setting sheets with different compositions are respectively contacted and bonded with heavy rare earth alloy diffusion source ribbons with different compositions; the contact bonding method is that the heavy rare earth alloy diffusion source ribbon is placed on the upper surface of the NdFeB alloy quick-setting sheet, and the ribbon and the quick-setting sheet are bonded using a non-aqueous adhesive; the contact area between the NdFeB alloy quick-setting sheet and the heavy rare earth alloy diffusion source ribbon is the same. The formation of the diffusion couple is conducive to the subsequent diffusion heat treatment, and then the subsequent diffusion behavior is studied, focusing on observing the effect of the contact interface on the heavy rare earth elements in the heavy rare earth alloy diffusion source ribbon entering the NdFeB alloy quick-setting sheet during subsequent diffusion. In this application, the alloying elements in the NdFeB quick-setting sheet can be randomly selected, and the alloying elements in the heavy rare earth alloy diffusion source ribbon can also be randomly selected. After the alloying elements of the two are randomly selected, a system group matching is performed. In order to ensure sufficient research, the system group matching needs to ensure that each NdFeB quick-setting sheet is matched with the heavy rare earth alloy diffusion source ribbon. The specific method is as follows: Figure 2 Example shown.

[0043] According to the present invention, after the above-mentioned multiple matched diffusion couples are prepared, they are subjected to diffusion heat treatment to obtain multiple NdFeB alloy sheets with different heavy rare earth diffusion behavior conditions; the diffusion heat treatment is a diffusion heat treatment well known to those skilled in the art, and can be specifically carried out in a vacuum heat treatment furnace, the temperature of the diffusion heat treatment is 700°C to 1000°C, and the time of the diffusion heat treatment is 10min to 60min; more specifically, the temperature of the diffusion heat treatment is 800°C to 900°C, and the time of the diffusion heat treatment is 20min to 40min.

[0044] This application then analyzes the diffusion depth of heavy rare earth in the above-mentioned NdFeB alloy sheet and the thickness and distribution of the heavy rare earth shell on the surface of the NdFeB grains, and selects the NdFeB alloy sheet with the best heavy rare earth diffusion effect; the above-mentioned analysis process is carried out in a manner familiar to those skilled in the art, and the selection process is specifically: using a scanning electron microscope to observe the wettability of the diffusion source and the matrix in the NdFeB alloy sheet, the diffusion depth of the heavy rare earth along the diffusion surface, and the thickness and distribution of the heavy rare earth shell on the surface of the NdFeB grains. The deeper the diffusion depth, the better the diffusion effect; the more obvious the heavy rare earth shell, the better the diffusion effect; the more uniform the distribution of the heavy rare earth in the entire NdFeB alloy sheet, the better the diffusion effect.

[0045] On the basis of selecting the NdFeB alloy sheet with the best heavy rare earth diffusion effect, the NdFeB quick-setting sheet of the sheet is used as the matrix, and the heavy rare earth diffusion source thin strip is used as the diffusion powder to prepare the pretreated magnet; the preparation process of the matrix is ​​specifically as follows: the NdFeB alloy quick-setting sheet is subjected to hydrogen cracking and air flow milling in sequence, and then oriented pressing, isostatic pressing and sintering and tempering in sequence; the magnetic field of the oriented pressing is 1.5-2.0T, the pressure of the isostatic pressing is 200-300MPa, the sintering temperature of the sintering and tempering is 1000-1100℃, the tempering temperature is 800-1000℃, and the vacuum degree is not less than 1×10 -2 Pa, and the sintering time is 2 to 6 hours. The specific preparation process of the diffusion source powder is: hydrogen crushing and air flow grinding are carried out on the heavy rare earth alloy diffusion source ribbon in sequence to obtain the diffusion source powder, and the particle size of the diffusion source powder is 1.5 to 2.0 μm. The pre-treated magnet is to attach the diffusion source powder to the surface of the magnet substrate, and the attachment is specifically carried out by spraying or dipping. The diffusion source powder is 0.5wt% to 3wt% of the pre-treated magnet, and more specifically, the diffusion source powder is 1.0 to 2.0wt% of the pre-treated magnet; too much content of the diffusion source powder will cause serious damage to the magnetic properties such as the remanence of the diffusion magnet, and too little will lead to a small increase in the performance such as coercive force after diffusion, and the expected diffusion effect cannot be achieved.

[0046] Finally, the pre-treated magnet is subjected to diffusion heat treatment to obtain a high-performance NdFeB diffusion magnet. The temperature of the diffusion heat treatment is 800-1000°C and the vacuum degree is not less than 1×10 -2 Pa, and the time is 2 to 12 hours; more specifically, the temperature of the diffusion heat treatment is 850 to 950° C., and the time is 5 to 10 hours.

[0047] The present invention is a technical method summarized through extensive practice. Compared with the existing technology, it has the following obvious outstanding substantial features and significant advantages:

[0048] 1) Since the driving force of diffusion comes from the concentration gradient (Fick's law), the effective detection and observation depth of heavy rare earth element diffusion in NdFeB alloy is usually less than 1000μm, of which the depth that is easy to distinguish and observe is usually less than 400μm. The thickness of NdFeB alloy quick-setting sheets is usually between 200 and 400μm, and the quick-setting sheets are plate-like crystals with continuous grain boundary phases, which facilitates the observation and analysis of the metallurgical reaction behavior of the elements introduced by diffusion with the main phase grains and grain boundary phases. Therefore, the diffusion couple composed of NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source thin ribbons proposed in the present invention is an excellent sample carrier that can be used to analyze the diffusion effect of heavy rare earth elements;

[0049] 2) The traditional way of evaluating the matching relationship and diffusion effect of the NdFeB matrix and the diffusion source is greatly affected by the process environment during the preparation of the magnet matrix, such as oxygen control, magnetic powder particle size, etc., which leads to large fluctuations or deviations in the evaluation results. The present invention proposes to directly use a diffusion couple composed of a NdFeB alloy quick-setting sheet and a heavy rare earth alloy diffusion source thin strip to conduct a diffusion test, and evaluate the resulting NdFeB alloy sheet. This can eliminate the errors introduced in the magnet matrix preparation process, has high repeatability, and is convenient for formulating evaluation standards. In addition, thanks to the continuous grain boundary phase of the NdFeB alloy quick-setting sheet, the diffusion temperature of the diffusion couple can be reduced, the diffusion time of the diffusion couple can be shortened, the evaluation cycle can be greatly shortened, the accuracy of the heavy rare earth diffusion effect evaluation can be improved, and the design and matching process of the magnet matrix and diffusion source composition can be simplified;

[0050] 3) The traditional method of evaluating the matching relationship and diffusion effect between the NdFeB matrix and the diffusion source is that the magnet matrix prepared during the evaluation process does not meet the matching requirements or has poor diffusion effect. Because it has undergone a powder metallurgy process and introduced multiple elements such as oxygen, carbon, and nitrogen, it is difficult to recycle. However, the method proposed in the present invention can directly smelt and recycle the NdFeB alloy quick-setting sheets that do not meet the requirements. After adjusting the element ratio, a new batch of quick-setting sheets can be prepared, which greatly improves the utilization rate of raw materials and reduces the design cost of matching the NdFeB magnet matrix and the diffusion source.

[0051] 4) The present invention evaluates the diffusion effect of heavy rare earth and the matching relationship between the NdFeB matrix and the diffusion source composition design by analyzing the diffusion depth of heavy rare earth along the diffusion surface in NdFeB alloy sheets and the shell thickness and distribution of heavy rare earth on the surface of NdFeB grains, and further prepares NdFeB matrix and diffusion source with specific composition. The feasibility is high, and the performance of the finally prepared diffusion magnet is highly consistent with the evaluation expectations, and the matching design work of the NdFeB diffusion matrix and diffusion source composition can be completed quickly and efficiently.

[0052] In order to further understand the present invention, the matching design method of the high-performance NdFeB diffusion matrix and the diffusion source provided by the present invention is described in detail below in conjunction with the embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0053] Example 1

[0054] (1) NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source ribbons with different compositions were prepared in batches by using a quick-setting furnace. The chemical formula of the NdFeB alloy quick-setting sheets is divided into Nd 29.5+f B 0.98 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.5 Fe 68.42-f, f = 0, 1, 2 are denoted as A1, A2, A3 respectively, and the chemical formula of the heavy rare earth alloy diffusion source ribbon is divided into Pr 60-g Tb 20+g Cu 20 , denote g=0, 10, 20 as B1, B2, B3 respectively;

[0055] (2) The NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source ribbons are systematically grouped and matched according to composition changes, and diffusion couples with different composition matching relationships are made;

[0056] (3) Placing different diffusion couples in a vacuum heat treatment furnace for diffusion heat treatment at a temperature of 900°C for 20 min to obtain NdFeB alloy sheets with different heavy rare earth diffusion behaviors;

[0057] (4) The diffusion depth of heavy rare earth in the NdFeB alloy sheet and the thickness and distribution of the heavy rare earth shell on the surface of the NdFeB grains were observed and analyzed using a scanning electron microscope. The results are shown in Table 1, and the NdFeB alloy sheet with the best heavy rare earth diffusion effect was selected;

[0058] (5) The NdFeB alloy quick-setting sheet used to prepare the above-mentioned NdFeB alloy sheet with the best heavy rare earth diffusion effect is subjected to hydrogen crushing and air flow milling to obtain alloy powder, which is then oriented and pressed in a 1.8T magnetic field and isostatically pressed under a pressure of 230MPa. The magnet is sent into a vacuum sintering furnace for sintering under the condition of isolation from the atmosphere. The sintering temperature is 1080℃, the sintering time is 4h, and finally tempered at 900℃ for 2h to obtain the magnet matrix; the heavy rare earth alloy diffusion source thin strip used to prepare the above-mentioned NdFeB alloy sheet with the best heavy rare earth diffusion effect is subjected to hydrogen crushing and air flow milling to obtain diffusion source powder, and the average particle size of the powder is 1.6μm;

[0059] (6) The diffusion source powder is attached to the surface of the magnet substrate by spraying to obtain a pre-treated magnet composed of a NdFeB substrate with a matching specific composition and a diffusion source, wherein the weight gain of the diffusion source powder attached to the magnet substrate is between 1.5% of the mass ratio of the pre-treated magnet;

[0060] (7) placing the pretreated magnet in a vacuum heat treatment furnace for diffusion heat treatment at a temperature of 900° C. for 6 h to obtain a final high-performance NdFeB diffusion magnet;

[0061] (8) The coercive forces of diffusion-treated magnets corresponding to different diffusion couples were compared to evaluate the effectiveness of the method. The performance of the method was tested and the coercive forces are shown in Table 1.

[0062] Table 1 Evaluation table of diffusion effects of different diffusion couples

[0063]

[0064]

[0065] It can be seen from the test results in Table 1 that this method can evaluate the diffusion depth of heavy rare earth in NdFeB alloy sheets and the thickness and distribution of heavy rare earth shell on the surface of NdFeB grains, and determine that the best diffusion couple combination is A2-B2. The performance of the finally prepared diffusion magnet is highly consistent with the evaluation expectations, which can effectively determine that the feasibility of this method is high, and the matching design work of NdFeB diffusion matrix and diffusion source composition can be completed quickly and efficiently.

[0066] The scanning electron microscope microstructure of NdFeB alloy sheet A2-B2 is shown in the figure below: Figure 1 shown.

[0067] Example 2

[0068] (1) NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source ribbons with different compositions were prepared in batches by using a quick-setting furnace. The chemical formula of the NdFeB alloy quick-setting sheets is divided into Nd 29.5 Tb 0.15 B 0.98 Cu 0.2 Ga 0.1+ h Zr 0.1 Co 0.5 Fe 68.02-h , h=0, 0.5, 1.0 are denoted as A4, A5, A6 respectively, and the chemical formula of the heavy rare earth alloy diffusion source ribbon is divided into Pr 45 Tb 15 Fe 20-i Cu 20+i , denote i=0, 10, 20 as B4, B5, B6 respectively;

[0069] (2) The NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source ribbons are systematically grouped and matched according to composition changes, and diffusion couples with different composition matching relationships are made;

[0070] (3) Placing different diffusion couples in a vacuum heat treatment furnace for diffusion heat treatment at a temperature of 900°C for 30 min to obtain NdFeB alloy sheets with different heavy rare earth diffusion behaviors;

[0071] (4) The diffusion depth of heavy rare earth in the NdFeB alloy sheet and the thickness and distribution of the heavy rare earth shell on the surface of the NdFeB grains were observed and analyzed using a scanning electron microscope. The results are shown in Table 2, and the NdFeB alloy sheet with the best heavy rare earth diffusion effect was selected;

[0072] (5) The NdFeB alloy quick-setting sheet used to prepare the above-mentioned NdFeB alloy sheet with the best heavy rare earth diffusion effect is subjected to hydrogen crushing and air flow milling to obtain alloy powder, which is then oriented and pressed in a 1.8T magnetic field and isostatically pressed under a pressure of 230MPa. The magnet is sent into a vacuum sintering furnace for sintering under the condition of isolation from the atmosphere. The sintering temperature is 1080℃, the sintering time is 4h, and finally tempered at 900℃ for 2h to obtain the magnet matrix; the heavy rare earth alloy diffusion source thin strip used to prepare the above-mentioned NdFeB alloy sheet with the best heavy rare earth diffusion effect is subjected to hydrogen crushing and air flow milling to obtain diffusion source powder, and the average particle size of the powder is 1.6μm;

[0073] (6) The diffusion source powder is attached to the surface of the magnet substrate by spraying to obtain a pre-treated magnet composed of a NdFeB substrate with a matching specific composition and a diffusion source, wherein the weight increase of the diffusion source powder attached to the magnet substrate is between 1.0% of the mass ratio of the pre-treated magnet;

[0074] (7) placing the pretreated magnet in a vacuum heat treatment furnace for diffusion heat treatment at a temperature of 900° C. for 10 h to obtain a final high-performance NdFeB diffusion magnet;

[0075] (8) The coercive forces of diffusion-treated magnets corresponding to different diffusion couples were compared to evaluate the effectiveness of the method. The performance of the method was tested and the coercive forces are shown in Table 2.

[0076] Table 2 Evaluation table of diffusion effects of different diffusion couples

[0077]

[0078] It can be seen from the test results in Table 2 that this method can evaluate the diffusion depth of heavy rare earth in NdFeB alloy sheets and the thickness and distribution of heavy rare earth shell on the surface of NdFeB grains, and determine that the best diffusion couple combination is A5-B4. The performance of the finally prepared diffusion magnet is highly consistent with the evaluation expectations, which can effectively determine that the feasibility of this method is high, and the matching design work of NdFeB diffusion matrix and diffusion source composition can be completed quickly and efficiently.

[0079] Example 3

[0080] (1) NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source ribbons with different compositions were prepared in batches by using a quick-setting furnace. The chemical formula of the NdFeB alloy quick-setting sheets is divided into Nd 24+j Ce 6-j B 0.98 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.5 Fe 67.92, j = 0, 2, 4 are recorded as A7, A8, A9 respectively, and the chemical formula of the heavy rare earth alloy diffusion source ribbon is divided into Pr 60-k Dy 20+k Al 20 Ga 10 , denote g=0, 10, 20 as B7, B8, B9 respectively;

[0081] (2) The NdFeB alloy quick-setting sheets and heavy rare earth alloy diffusion source ribbons are systematically grouped and matched according to composition changes, and diffusion couples with different composition matching relationships are made;

[0082] (3) Placing different diffusion couples in a vacuum heat treatment furnace for diffusion heat treatment at a temperature of 900°C for 20 min to obtain NdFeB alloy sheets with different heavy rare earth diffusion behaviors;

[0083] (4) The diffusion depth of heavy rare earth in the NdFeB alloy sheet and the thickness and distribution of the heavy rare earth shell on the surface of the NdFeB grains were observed and analyzed using a scanning electron microscope. The results are shown in Table 3, and the NdFeB alloy sheet with the best heavy rare earth diffusion effect was selected;

[0084] (5) The NdFeB alloy quick-setting sheet used to prepare the above-mentioned NdFeB alloy sheet with the best heavy rare earth diffusion effect is subjected to hydrogen crushing and air flow milling to obtain alloy powder, which is then oriented and pressed in a 1.8T magnetic field and isostatically pressed under a pressure of 230MPa. The magnet is sent into a vacuum sintering furnace for sintering under the condition of being isolated from the atmosphere. The sintering temperature is 1070°C and the sintering time is 4h. Finally, it is tempered at 900°C for 2h to obtain the magnet matrix; the heavy rare earth alloy diffusion source thin strip used to prepare the above-mentioned NdFeB alloy sheet with the best heavy rare earth diffusion effect is subjected to hydrogen crushing and air flow milling to obtain diffusion source powder, and the average particle size of the powder is 1.6μm;

[0085] (6) The diffusion source powder is attached to the surface of the magnet substrate by spraying to obtain a pre-treated magnet composed of a NdFeB substrate with a matching specific composition and a diffusion source, wherein the weight gain of the diffusion source powder attached to the magnet substrate is between 2.5% of the mass ratio of the pre-treated magnet;

[0086] (7) placing the pretreated magnet in a vacuum heat treatment furnace for diffusion heat treatment at a temperature of 900°C for 8 hours to obtain a final high-performance NdFeB diffusion magnet;

[0087] (8) The coercive forces of diffusion-treated magnets corresponding to different diffusion couples were compared to evaluate the effectiveness of the method. The performance of the method was tested and the coercive forces are shown in Table 3.

[0088] Table 3 Evaluation table of diffusion effects of different diffusion couples

[0089]

[0090] It can be seen from the test results in Table 3 that this method can evaluate the diffusion depth of heavy rare earth in NdFeB alloy sheets and the thickness and distribution of heavy rare earth shell on the surface of NdFeB grains, and determine that the best diffusion couple combination is A8-B9. The performance of the finally prepared diffusion magnet is highly consistent with the evaluation expectations, which can effectively determine that the feasibility of this method is high, and the matching design work of NdFeB diffusion matrix and diffusion source composition can be completed quickly and efficiently.

[0091] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0092] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A matching design method for a high-performance NdFeB diffusion matrix and a diffusion source, comprising the following steps: A) Batch preparation of NdFeB alloy rapid solidification sheets and heavy rare earth alloy diffusion source ribbons with different compositions; B) systematically grouping and matching the NdFeB alloy quick-setting sheets and the heavy rare earth alloy diffusion source ribbons according to composition changes, and making diffusion couples with different composition matching relationships; C) subjecting different diffusion couples to diffusion heat treatment to obtain NdFeB alloy sheets with different heavy rare earth diffusion behaviors; D) analyzing the diffusion effect of the NdFeB alloy sheets and selecting the NdFeB alloy sheet with the best heavy rare earth diffusion effect; The selection process is specifically as follows: Scanning electron microscopy was used to observe the wettability of the diffusion source and matrix in the NdFeB alloy sheet, the diffusion depth of heavy rare earth along the diffusion surface, and the thickness and distribution of the heavy rare earth shell on the surface of the NdFeB grains. E) preparing a NdFeB alloy quick-setting sheet for preparing the NdFeB alloy sheet with the best heavy rare earth diffusion effect into a magnet matrix; preparing a heavy rare earth alloy diffusion source ribbon for preparing the NdFeB alloy sheet with the best heavy rare earth diffusion effect into a diffusion source powder; F) attaching the diffusion source powder to the surface of the magnet substrate to obtain a pretreated magnet; the diffusion source powder accounts for 0.5 wt% to 3 wt% of the pretreated magnet; G) performing diffusion heat treatment on the pretreated magnet to obtain a high-performance NdFeB diffusion magnet; The chemical formula of the NdFeB alloy quick-setting sheet is R1 a R2 b Fe 100-a-b-c-d-e B c M1 d M2 e , wherein R1 is selected from one or more of Pr, Nd, La and Ce, R2 is selected from one or more of Tb, Dy, Ho and Gd, M1 is selected from one or more of Co, Zr, Ni and Ti, and M2 is selected from at least one of Cu, Al, Ga and Mg; a, b, c, d and e are the mass percentages of the corresponding elements, and satisfy 25≤a≤34, 0≤b≤9, 28≤a+b≤34, 0.9≤c≤1.2, 0≤d≤3.0, and 0≤e≤2.0; The chemical formula of the heavy rare earth alloy diffusion source ribbon is R3 100-x-y-z R4 x M3 y L1 z , wherein M3 is selected from one or more of Fe, Cu, Al, Ga, Co, Sn and Zn, L1 is selected from one or more of H and F, x, y, z are the mass percentages of the corresponding elements, 10≤x≤90, 0≤y≤30, 0≤z≤2.

2. The method according to claim 1, characterized in that In step A), the NdFeB alloy quick-setting sheet is obtained by spinning off a quick-setting furnace, and the heavy rare earth alloy diffusion source ribbon is obtained by spinning off a quick-setting furnace or a rapid quenching furnace; the thickness of the quick-setting sheet is 200 μm to 300 μm, and the thickness of the heavy rare earth alloy diffusion source ribbon is 50 μm to 100 μm; the NdFeB alloy quick-setting sheet varies in composition from no less than 3 batches, and the heavy rare earth alloy diffusion source ribbon varies in composition from no less than 3 batches.

3. The method according to claim 1, characterized in that In step B), the preparation of the diffusion couple is specifically as follows: NdFeB alloy quick-setting sheets with different compositions are respectively contacted and bonded with heavy rare earth alloy diffusion source ribbons with different compositions; the contact bonding method is that the heavy rare earth alloy diffusion source ribbon is placed on the upper surface of the NdFeB alloy quick-setting sheet, and the ribbon and the quick-setting sheet are bonded using a non-aqueous adhesive; the contact area of ​​the NdFeB alloy quick-setting sheet and the heavy rare earth alloy diffusion source ribbon is the same.

4. The method according to claim 1, wherein In step C), the temperature of the diffusion heat treatment is 700° C. to 1000° C., and the time of the diffusion heat treatment is 10 min to 60 min.

5. The method according to claim 1, wherein In step E), the preparation of the magnet matrix includes hydrogen cracking, air flow milling, orientation pressing, isostatic pressing and sintering and tempering in sequence; the magnetic field of the orientation pressing is 1.5-2.0T, the pressure of the isostatic pressing is 200-300MPa, the sintering temperature of the sintering and tempering is 1000-1100°C, the tempering temperature is 800-1000°C, and the vacuum degree is not less than 1×10 -2 Pa, sintering time is 2~6h.

6. The method according to claim 1, characterized in that In step F), the particle size of the diffusion source powder is 1.5-20 μm; and the attachment method is spraying or dipping.

7. The method according to claim 1, characterized in that In step G), the temperature of the diffusion heat treatment is 800-1000°C, and the vacuum degree is not less than 1×10 -2 Pa, time is 2~10h.

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