Y-containing rare earth permanent magnet with high mechanical service stability, and preparation method and application thereof

Abstract

The application discloses a yttrium-containing rare earth permanent magnet with high mechanical service stability and a preparation method and application thereof. The preparation method comprises the following steps: uniformly mixing yttrium-containing main alloy magnetic powder and rare earth oxides, and sequentially performing magnetic field orientation forming, cold isostatic pressing, vacuum sintering and tempering heat treatment to obtain the yttrium-containing rare earth permanent magnet with high mechanical service stability. The prepared yttrium-containing rare earth permanent magnet comprises main phase grains and grain boundaries uniformly wrapped around the main phase grains, the main phase grains have yttrium-rich cores and R2-rich shells, and yttrium-rich oxide particles are uniformly and dispersedly distributed in the grain boundaries, and the composition of the yttrium-rich oxide particles is (R1 (1‑x) Y x ) y Fe 100‑w‑y‑ z M w B z ·(0.001~0.1)R22O3. The application realizes grain boundary structure optimization and microstructure strengthening, and significantly improves the magnetic performance and mechanical stability of the permanent magnet.

Description

Technical Field

[0001] This invention belongs to the field of rare earth permanent magnet material preparation, specifically relating to a yttrium-containing rare earth permanent magnet with high mechanical service stability, its preparation method and application. Background Technology

[0002] Rare earth permanent magnet materials are widely used in key fields such as new energy vehicle drive motors, wind turbines, high-end servo systems, and aerospace equipment due to their excellent magnetic energy product, coercivity, and high magnetization. Among them, sintered neodymium iron boron (Nd-Fe-B) permanent magnets are currently the best-performing and most widely used rare earth permanent magnet materials. However, with the development of social productivity, the application fields of sintered Nd-Fe-B are constantly expanding. Under complex service environments, traditional Nd-Fe-B permanent magnets suffer from problems such as fragile mechanical properties, easy propagation of microcracks, and insufficient long-term service stability, which seriously restricts their application expansion in high-reliability fields.

[0003] In existing technologies, improvements to the service stability of magnets are mainly achieved through grain boundary phase regulation and microstructure refinement. Grain boundary phase regulation refers to optimizing grain boundary wettability through alloying elements such as Cu, Al, and Ga to improve interfacial bonding strength. However, this regulation method often leads to uneven distribution of alloying elements and significant agglomeration, making it difficult to balance the magnetic and mechanical properties of the magnet. Microstructure refinement refers to refining grains through methods such as hot deformation, rapid solidification, and nanocrystallization to suppress crack propagation. However, excessively fine grains can easily lead to unstable coercivity or decreased magnetization orientation.

[0004] Yttrium (Y), a rare earth element, possesses strong oxygen affinity, high ductility, and a stabilizing effect on grain boundary phases. With an atomic radius close to that of light rare earth elements, Yttrium can, to some extent, replace neodymium (Nd) or praseodymium (Pr), thereby reducing raw material costs. Simultaneously, Y exhibits a strong chemical affinity for oxygen, which can promote the segregation and redistribution of oxygen at grain boundaries through thermodynamic forces, thereby altering the chemical composition and interfacial energy of the grain boundaries. Traditional external oxide particle strengthening strategies often employ the direct incorporation of alloy ceramic powders such as zirconium oxide (ZrO2) and alumina (Al2O3). However, the interfacial bonding between these oxides and the matrix is ​​weak, easily forming pores or stress concentration zones during sintering, and even becoming crack initiation sources, leading to a decline in mechanical properties. Furthermore, the chemical inertness of these oxides makes it difficult for them to undergo interfacial reactions with rare earth elements, hindering the synergistic control of microstructure homogenization and grain boundary strengthening at the microscale. For example, existing research has employed the incorporation of diamagnetic nano-ceramic particles to improve mechanical processing properties, but this sacrifices some magnetic properties. Summary of the Invention

[0005] The main objective of this invention is to provide a yttrium-containing rare-earth permanent magnet with high mechanical service stability, its manufacturing method, and its application, so as to overcome the defects of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] The first aspect of the present invention provides a method for manufacturing a yttrium-containing rare earth permanent magnet with high mechanical service stability, comprising: uniformly mixing a yttrium-containing main alloy with a rare earth oxide and then sequentially performing magnetic field orientation forming, cold isostatic pressing, vacuum sintering and tempering heat treatment.

[0008] The composition of the yttrium-containing main alloy is (R1) (1-x) Y x ) y Fe 100-w-y-z M w B z R1 includes any one or more combinations of La, Ce, Pr, Nd, Dy, Tb, Gd, and Ho, and M includes any one or more combinations of Co, Al, Cu, Ga, Nb, Zr, and Ti, and the atomic percentage content satisfies 0 < w ≤ 5, 0 < x ≤ 1, 13 ≤ y ≤ 16, and 5 ≤ z ≤ 6.

[0009] The rare earth oxide contains rare earth element R2, which includes any one or a combination of two or more elements selected from Pr, Nd, Dy, Tb, and Ho.

[0010] Furthermore, during the vacuum sintering process, the yttrium-containing main alloy and rare earth oxides can undergo an in-situ metallurgical substitution reaction to generate Y-rich oxide particles and release active R2 atoms. The active R2 atoms diffuse to the surface of the grains, thereby giving the main phase grains of the permanent magnet a Y-rich core and an R2-rich shell, and Y-rich oxide particles are uniformly dispersed in the grain boundaries. The particle size of the Y-rich oxide particles is <4μm, and the atomic percentage content of Y element is >20%.

[0011] A second aspect of the present invention provides a yttrium-containing rare-earth permanent magnet with high mechanical service stability, prepared by the aforementioned method, wherein the composition of the yttrium-containing rare-earth permanent magnet is (R1... (1-x) Y x ) y Fe 100-w-y-z M w B z • (0.001~0.1)R22O3, the yttrium rare earth permanent magnet includes a main phase grain and grain boundaries uniformly surrounding the main phase grain. The main phase grain has a Y-rich core and an R2-rich shell, and Y-rich oxide particles are uniformly dispersed in the grain boundaries. The particle size of the Y-rich oxide particles is <4μm, and the atomic percentage content of Y element is >20%, wherein 0 < w ≤ 5, 0 < x ≤ 1, 13 ≤ y ≤ 16, and 5 ≤ z ≤ 6.

[0012] The third aspect of the present invention provides the application of the yttrium rare earth permanent magnet with high mechanical service stability in the fields of new energy vehicle drive motors, wind turbines or high-end servo system equipment.

[0013] Compared with the prior art, the present invention has at least the following beneficial effects:

[0014] (1) This invention introduces rare earth oxide powder into the yttrium rare earth main alloy and induces the in-situ metallurgical reaction between Y element and rare earth oxide during liquid phase sintering, thereby realizing the in-situ dispersion generation of Y-rich oxide particles and overcoming the problems of uneven phase distribution and poor interfacial bonding of traditional alloy oxide particles.

[0015] (2) The active rare earth elements released during the reaction process provided by the present invention can form a rare earth enriched shell on the surface of the main phase grains, constructing a core-shell structure with a high anisotropic field, and realizing the synergistic improvement of the mechanical properties and coercivity of yttrium rare earth permanent magnets.

[0016] (3) The preparation process provided by the present invention is compatible with the existing sintered NdFeB system. It is easy to operate and has good consistency and stability. The resulting yttrium rare earth permanent magnet has higher mechanical service stability and reliability under complex working conditions. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a SEM microstructure diagram of the yttrium rare earth permanent magnet in Embodiment 1 of the present invention. Detailed Implementation

[0019] In view of the problems existing in the above-mentioned prior art, after in-depth research, we provide yttrium-containing rare earth permanent magnets with high mechanical service stability, as well as their manufacturing method and applications. The main approach is to optimize the grain boundary structure and strengthen the microstructure through the in-situ metallurgical reaction mechanism of yttrium and rare earth oxides, while ensuring the high energy product and excellent magnetic properties of the magnets. This significantly improves the mechanical stability and crack resistance of sintered NdFeB permanent magnets.

[0020] The first aspect of the present invention provides a method for manufacturing a yttrium-containing rare earth permanent magnet with high mechanical service stability, comprising: uniformly mixing a yttrium-containing main alloy with a rare earth oxide and then sequentially performing magnetic field orientation forming, cold isostatic pressing, vacuum sintering and tempering heat treatment.

[0021] The composition of the yttrium-containing main alloy is (R1) (1-x) Y x ) y Fe 100-w-y-z M w B z R1 includes any one or more combinations of La, Ce, Pr, Nd, Dy, Tb, Gd, and Ho, and M includes any one or more combinations of Co, Al, Cu, Ga, Nb, Zr, and Ti, and the atomic percentage content satisfies 0 < w ≤ 5, 0 < x ≤ 1, 13 ≤ y ≤ 16, and 5 ≤ z ≤ 6.

[0022] The rare earth oxide contains rare earth element R2, which includes any one or a combination of two or more elements selected from Pr, Nd, Dy, Tb, and Ho.

[0023] Furthermore, during the vacuum sintering process, the yttrium-containing main alloy and rare earth oxides can undergo an in-situ metallurgical substitution reaction to generate Y-rich oxide particles and release active R2 atoms. The active R2 atoms diffuse to the surface of the grains, thereby giving the main phase grains of the permanent magnet a Y-rich core and an R2-rich shell, and Y-rich oxide particles are uniformly dispersed in the grain boundaries. The particle size of the Y-rich oxide particles is <4μm, and the atomic percentage content of Y element is >20%.

[0024] Furthermore, the preferred value of x in the yttrium-containing main alloy is 0.05 ≤ x ≤ 0.6. When the Y content is too low, insufficient Y-rich oxides are formed in the grain boundaries, making it difficult to achieve a significant strengthening effect; when the Y content is too high, it will lead to the main phase Nd2Fe 14 As the B ratio decreases, the remanence decreases.

[0025] In some embodiments, the mass ratio of the yttrium-containing main alloy to rare earth oxides is 0.1 to 10:100. If the amount of rare earth oxides added is too low, the in-situ metallurgical substitution reaction will be difficult to carry out fully; if the amount of rare earth oxides added is too high, oxide agglomeration will form, destroying the grain boundary continuity and causing the yttrium-containing rare earth permanent magnet to become brittle.

[0026] In some embodiments, the yttrium-containing main alloy and rare earth oxides are mixed uniformly in powder form.

[0027] In some embodiments, the average particle size of the rare earth oxide is 0.1~3µm. If the rare earth oxide particles are too large, it can easily lead to uneven dispersion and stress concentration; if the particles are too small, the reaction can be insufficient, weakening the strengthening effect.

[0028] Furthermore, the average particle size of the rare earth oxide is 1µm.

[0029] In some embodiments, the rare earth oxide is selected from R22O3 type oxides.

[0030] In some embodiments, the method for manufacturing the yttrium-containing rare-earth permanent magnet with high mechanical service stability specifically includes: according to (R1 (1-x) Y x ) y Fe 100-w-y-z M w B z The raw materials are prepared according to the specified ratio, and after being melted under the protection of inert gas, they are cast onto rotating rollers to obtain a rapidly solidified alloy sheet. The rapidly solidified alloy sheet is then subjected to hydrogen crushing and air jet milling to obtain yttrium-containing main alloy powder.

[0031] Furthermore, the average thickness of the rapid-solidifying alloy sheet is 0.1~0.5mm.

[0032] Furthermore, the particle size distribution parameter (SMD) of the air jet mill is 1~10 μm.

[0033] Furthermore, the rotational speed of the roller is 12~24 rpm.

[0034] Furthermore, the heating temperature before hydrogen crushing and absorption is 250~450 ℃, and the hydrogen pressure is 80~120 MPa.

[0035] Furthermore, the sorting wheel speed of the air jet mill is 3000~8000 rpm.

[0036] In some embodiments, the method for manufacturing the yttrium-containing rare-earth permanent magnet with high mechanical service stability specifically includes: performing magnetic field orientation molding under a magnetic field of 1.5~2T to obtain a molded blank, and performing cold isostatic pressing under a pressure of 100~200MPa to obtain a magnet blank. In this invention, if the magnetic field strength is too low, it will lead to insufficient orientation of the main phase grains; if the magnetic field strength is too high, it will cause uneven molding density of the blank. If the cold isostatic pressing pressure is insufficient, it will cause the blank to be loose; if the cold isostatic pressing pressure is too high, it will easily cause the blank to break.

[0037] In some embodiments, the vacuum sintering temperature is 950~1150℃, and the time is 2~4h. If the vacuum sintering temperature is too low, a liquid phase cannot be formed, and the grain boundaries are not dense; if the vacuum sintering temperature is too high, it will lead to abnormal grain growth and reduce coercivity.

[0038] In some embodiments, the tempering heat treatment is performed at a temperature of 400-800°C for 2-6 hours. If the tempering heat treatment temperature is too low, the stress will be difficult to release; if it is too high, the grain boundary phase equilibrium will be disrupted.

[0039] In some more specific embodiments, the method for manufacturing the yttrium-containing rare-earth permanent magnet with high mechanical service stability specifically includes the following steps:

[0040] S1: According to (R1) (1-x) Y x ) y Fe 100-w-y-z M w B z The raw materials are prepared according to the specified ratio, and after being melted under the protection of inert gas, they are cast onto rotating rollers to obtain a rapidly solidified alloy sheet. The rapidly solidified alloy sheet is then subjected to hydrogen crushing and air jet milling to obtain yttrium-containing main alloy powder, which is then fully mixed with rare earth oxide powder to obtain mixed magnetic powder.

[0041] S2: The mixed magnetic powder is oriented by magnetic field and cold isostatically pressed to obtain a magnet blank;

[0042] S3: The magnet blank is then subjected to vacuum sintering and tempering heat treatment to obtain a yttrium rare earth permanent magnet with a core-shell structure and yttrium oxide-rich dispersed particles.

[0043] Specifically, during the vacuum sintering process, yttrium undergoes an in-situ metallurgical substitution reaction with rare earth oxides, generating Y-rich oxide particles and releasing active rare earth element atoms R2. On the one hand, the Y-rich oxide particles generated by the reaction are uniformly dispersed within the grain boundaries of the yttrium-containing rare earth permanent magnet, which can effectively pin the grain boundaries, inhibit abnormal grain growth, and prevent the propagation of microcracks under external force, thus significantly improving the mechanical service stability of the magnet. On the other hand, the replaced rare earth element atoms R2 spontaneously diffuse and accumulate on the surface of the main phase grains of the yttrium-containing rare earth permanent magnet, forming a rare earth enrichment layer and constructing a "core-shell" structure that enhances the magnetocrystalline anisotropy field, thereby improving the magnet's coercivity and maintaining high remanence.

[0044] A second aspect of the present invention provides a yttrium-containing rare-earth permanent magnet with high mechanical service stability prepared by the above method, wherein the permanent magnet composition is (R1... (1-x) Y x ) y Fe 100-w-y-z M w B z The yttrium-containing rare earth permanent magnet comprises a main phase grain and grain boundaries uniformly surrounding the main phase grain. The main phase grain has a Y-rich core and an R2-rich shell, and Y-rich oxide particles are uniformly dispersed in the grain boundaries. The particle size of the Y-rich oxide particles is <4μm, and the atomic percentage content of Y element is >20%, wherein 0 < w ≤ 5, 0 < x ≤ 1, 13 ≤ y ≤ 16, and 5 ≤ z ≤ 6.

[0045] In some implementations, the atomic percentage of Y in the Y-rich core is more than 10% higher than the atomic percentage of Y in the R2-rich shell.

[0046] In some embodiments, the particle size of the Y-rich oxide particles is 0.5~3.5 μm.

[0047] In some embodiments, the atomic percentage content of Y element in the Y-rich oxide particles is 10~40 at.

[0048] In some embodiments, the mass fraction of the Y-rich oxide particles in the grain boundary phase is 1 to 5 wt%.

[0049] In some implementations, the thickness of the R2-rich shell is 0.5~3 μm.

[0050] In some implementations, the particle size of the Y-rich core is 2~4 μm.

[0051] In some embodiments, the yttrium rare earth permanent magnet has an average bending strength of over 255 MPa and a bending strength fluctuation of less than 30 MPa.

[0052] Because the yttrium-containing rare-earth permanent magnets prepared by this invention achieve in-situ generation of Y-rich oxides and redistribution of rare-earth elements during the sintering process, the yttrium-containing rare-earth permanent magnets of this invention exhibit good compositional uniformity and microstructural stability. Through these microstructural characteristics, the yttrium-containing rare-earth permanent magnets of this invention possess significantly superior mechanical stability while improving coercivity and maintaining a high energy product.

[0053] A third aspect of the present invention provides the application of the yttrium-containing rare-earth permanent magnet with high mechanical service stability in new energy vehicle drive motors, wind turbines, or high-end servo system equipment.

[0054] In summary, the method provided by this invention maintains the high energy product and excellent magnetic properties of sintered NdFeB magnets. By introducing rare earth oxide powder, it causes an in-situ metallurgical substitution reaction during sintering, forming Y-rich oxide dispersed particles and a core-shell structure of the main phase grains, thus achieving synergistic optimization of the magnet's mechanical and magnetic properties.

[0055] The following will provide a further explanation of the technical solution, its implementation process, and its principles.

[0056] For experiments not specifically described in the examples, the procedures or conditions can be performed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available. Other unmentioned raw materials and instruments are all conventionally chosen and do not involve the core technical means of this invention.

[0057] For example, the rare earth raw materials used in the embodiments and comparative examples of the present invention were purchased from Ningbo Funeng Rare Earth New Materials Co., Ltd., with a purity of 99%;

[0058] All rare earth oxide raw materials used were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of 99.9%.

[0059] The model of the vacuum melting equipment used is: Shenyang Sante Vacuum Induction Rapid Solidification Furnace ZGSN-0.003;

[0060] The model of the hydrogen crushing device used is: BQDHD-100E / J rotary hydrogen crushing furnace;

[0061] The model of the air jet mill used is: Jilin Kaier QLMR-200G air jet mill;

[0062] The model of the magnetic field orientation forming device used is: Baiqida magnetic field forming press BDM-250A;

[0063] The model of the tempering heat treatment equipment used is Qingdao Huaqi HTO-150.

[0064] Examples 1-5

[0065] The method for manufacturing yttrium rare-earth permanent magnets with high mechanical service stability specifically includes the following steps:

[0066] (1) Prepare the raw materials used in Examples 1-5 according to the composition of yttrium-containing rare earth permanent magnets and rare earth oxides, as shown in Table 1. The yttrium-containing main alloy powder and rare earth oxide powder are thoroughly mixed by vacuum melting, hydrogen crushing and air jet milling to obtain mixed magnetic powder. The thickness of the rapidly solidified alloy sheet obtained after vacuum melting is about 0.2~0.3 mm, the roller speed is 15 rpm, the hydrogen crushing temperature is 300℃, the hydrogen absorption pressure is 0.25 MPa, and the SMD of the obtained main alloy magnetic powder is about 2~3 µm.

[0067] (2) The mixed magnetic powder obtained in step (1) is subjected to magnetic field orientation molding and cold isostatic pressing to obtain a magnet blank, wherein the orientation molding magnetic field is 1.5~2.5T and the cold isostatic pressing pressure is 150MPa.

[0068] (3) The magnet blank obtained in step (2) is subjected to vacuum sintering and tempering heat treatment to obtain a yttrium rare earth permanent magnet with a core-shell structure and high mechanical service stability of yttrium oxide-rich dispersed particles. The sintering temperature is 1070℃, the sintering time is 4 hours, the tempering temperature is 485℃, and the tempering time is 3 hours.

[0069] The magnetic properties and mechanical bending resistance of the yttrium rare earth permanent magnet with high mechanical service stability obtained in step (3) were tested using a permanent magnet material testing system and a universal material testing machine. The test results are shown in Table 2, where the error bar is considered as the difference between the maximum and minimum bending resistance values.

[0070] The morphology of the yttrium rare-earth permanent magnet with high mechanical service stability was characterized using SEM-EDS. The SEM microstructure of the yttrium rare-earth permanent magnet in Example 1 of this invention is shown in the figure below. Figure 1 As shown.

[0071] Example 6

[0072] This embodiment provides a method for manufacturing a yttrium-containing rare-earth permanent magnet with high mechanical service stability, which differs from embodiments 1-5 in that the main alloy composition is Pr. 3.09 Nd 9.26 Y 0.65 Gd 0.8 Co 0.05 Cu 0.05 B5Fe 81.1 The mass ratio of Nd2O3 oxide powder to yttrium-containing main alloy was 0.1:100, the sintering temperature was 1020℃, the sintering time was 2 hours, the tempering temperature was 480℃, and the tempering time was 2 hours.

[0073] Example 7

[0074] This embodiment provides a method for manufacturing a yttrium-containing rare-earth permanent magnet with high mechanical service stability, which differs from embodiments 1-5 in that the main alloy composition is Pr. 2.18 Nd 6.53 Y 5.8 Co 1.25 Cu 1.25 B 5.5 Fe 77.49 The mass ratio of Nd2O3 oxide powder to yttrium-containing main alloy was 3:100, the sintering temperature was 1060℃, the sintering time was 3 hours, the tempering temperature was 520℃, and the tempering time was 4 hours.

[0075] Example 8

[0076] This embodiment provides a method for manufacturing a yttrium-containing rare-earth permanent magnet with high mechanical service stability, which differs from embodiments 1-5 in that the main alloy composition is Ce. 5.04 Ho 5.04 Y 4.32 Nb 1.1 Ti 1.1 B 5.7 Fe 77.7 .

[0077] Comparative Example 1

[0078] In this comparative example, the process of preparing yttrium rare earth permanent magnets differs from that of Example 1 in that no rare earth oxide powder is used to mix with the main alloy powder, while the other preparation processes are the same as in Example 1.

[0079] Comparative Example 2

[0080] In this comparative example, the process for preparing yttrium rare earth permanent magnets differs from that in Example 1 in that the pressed blank is sintered under a vacuum of ≤5×10⁻³ Pa at a temperature of 930℃ for 1.5 hours. All other preparation steps are the same as in Example 1.

[0081] Comparative Example 3

[0082] In this comparative example, the process for preparing yttrium-containing rare-earth permanent magnets differs from that in Example 1 in that the mass ratio of rare-earth oxide powder to main alloy powder is 0.05:100. All other preparation steps are the same as in Example 1.

[0083] Comparative Example 4

[0084] In this comparative example, the process for preparing yttrium-containing rare-earth permanent magnets differs from that in Example 1 in that the mass ratio of rare-earth oxide powder to main alloy powder is 15:100. All other preparation steps are the same as in Example 1.

[0085] Comparative Example 5

[0086] In this comparative example, the process for preparing yttrium-containing rare-earth permanent magnets differs from that in Example 1 in that the main alloy composition does not contain rare-earth Y, and is composed of Pr. 2.9 Nd 11.5 Co 1.1 Cu 0.2 Ga 0.2 Ti 0.3 B 5.8 Fe 78 The other preparation steps are the same as in Example 1.

[0087] Comparative Example 6

[0088] In this comparative example, the process for preparing yttrium rare-earth permanent magnets differs from that in Example 1 in that the main alloy composition contains a higher content of rare-earth Y, with the composition being Pr. 1.3 Nd 5.1 Y8Co 1.1 Cu 0.2 Ga 0.2 Ti 0.3 B 5.8 Fe 78 The other preparation steps are the same as in Example 1.

[0089] Table 1 shows the state of the main alloy raw materials and rare earth oxides in the various embodiments and comparative examples of the present invention.

[0090] Table 2 shows the magnetic and mechanical properties of the magnets in the various embodiments and comparative examples of the present invention.

[0091] Table 3 lists the relative change rates of the atomic percentage of Y in the Y-rich core (Y core) and the atomic percentage of Y in the R2-rich shell (Y shell) of the magnet grains in various embodiments and comparative examples of the present invention, as well as the shell thickness, oxide particle size, and rare earth Y content in the oxides.

[0092] Table 1. State of main alloy raw materials and rare earth oxides in Examples 1-8 and Comparative Examples 1-6

[0093] Table 2. Magnetic and mechanical properties of magnets from Examples 1-8 and Comparative Examples 1-6

[0094] Table 3. Comparison of elements and structures in magnets of Examples 1-8 and Comparative Examples 1-6

[0095] Analysis of the experimental data in Tables 1-3 shows that the proposed method exhibits significant differences in magnetic properties, mechanical strength, and microstructure stability. Table 2 shows that Comparative Example 1 (without oxides) has a flexural strength of only 225 MPa, with drastic performance fluctuations (large error bars). Comparative Example 2, due to insufficient sintering temperature, failed to form dense liquid-phase grain boundaries, leading to further strength degradation. In contrast, the average flexural strength of Examples 1-8 is above 255 MPa, with Example 8 exceeding 330 MPa. This confirms that the Y-rich oxide particles generated through in-situ metallurgical reaction are uniformly dispersed in the grain boundary phase, effectively pinning grain boundaries and inhibiting crack propagation.

[0096] Regarding magnetic properties, Examples 1-8, while maintaining high remanence, exhibited significantly improved coercivity compared to Comparative Example 1 (9.16 kOe), reaching a maximum of 15.35 kOe. Combined with the elemental distribution data in Table 3, it can be observed that all the example samples formed a significant "core-shell" structural gradient, with the Y content in the core region being much higher than that in the shell (the gradient difference was mostly above 10%). This phenomenon confirms the occurrence of an in-situ substitution reaction: 2Y + R₂O₃ → Y₂O₃ + 2R. The generated Y-rich oxide particles are uniformly dispersed at the grain boundaries, effectively pinning the grain boundaries and hindering crack propagation, significantly improving the reliability and consistency of the magnet's service life. Simultaneously, the displaced active rare earth atoms spontaneously diffuse to the surface of the main phase grains, forming a rare earth-enriched shell structure, thereby significantly enhancing magnetocrystalline anisotropy and improving coercivity.

[0097] The comparative data further revealed the importance of composition and process parameters: Comparative Example 3, due to its low oxide addition (0.05%), could not induce sufficient in-situ reactions, resulting in its microstructure and properties being no different from the unadded group. In Comparative Example 4, the oxide addition was too high, and in Comparative Example 6, the Y content in the main alloy was too high, leading to severe deterioration of the magnet's magnetic properties, making it difficult to meet application requirements.

[0098] Therefore, this invention achieves a synergistic effect of grain boundary strengthening and magnetocrystalline anisotropy enhancement through the in-situ metallurgical reaction of yttrium and rare earth oxides. During sintering, the Y-rich oxide particles generated by the reaction of yttrium and rare earth oxides are uniformly distributed at the grain boundaries, effectively inhibiting abnormal grain growth and enhancing grain boundary bonding. This increases the bending strength of the magnet by approximately 20%–30% and significantly reduces the dispersion of bending performance. Furthermore, the released rare earth atoms diffuse towards the surface of the main phase grains, forming a core-shell structure with Y as the core and a rare earth-rich layer as the outer shell. This significantly enhances the magnetocrystalline anisotropy field of the grains, increasing the coercivity by approximately 40%–50% compared to samples without added oxides. Therefore, the magnet obtained by this invention maintains high remanence while possessing excellent coercivity and mechanical service stability.

[0099] In summary, this invention successfully achieved synergistic regulation of grain boundary structure optimization and rare earth element redistribution by introducing rare earth oxides into yttrium-containing rare earth main alloys and utilizing the in-situ substitution reaction between yttrium and oxides. This method not only improves the uniformity of the magnet's microstructure and interfacial bonding characteristics but also significantly enhances the magnet's coercivity and mechanical service stability. While ensuring a high magnetic energy product, it achieves a balanced optimization of magnetic and mechanical properties, demonstrating promising prospects for widespread application.

[0100] All aspects, embodiments, features, and examples of this invention should be considered illustrative in all respects and are not intended to limit the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention.

[0101] In addition, the present invention has also conducted experiments with other raw materials, process operations and process conditions described in this specification, with reference to the foregoing embodiments, and has obtained relatively ideal results in all cases.

[0102] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A method for manufacturing a yttrium-containing rare-earth permanent magnet with high mechanical service stability, characterized in that, include: After the yttrium-containing main alloy and rare earth oxides are mixed evenly, they are sequentially subjected to magnetic field orientation forming, cold isostatic pressing, vacuum sintering and tempering heat treatment. The composition of the yttrium-containing main alloy is (R1) (1-x) Y x ) y Fe 100-w-y-z M w B z R1 includes any one or more combinations of La, Ce, Pr, Nd, Dy, Tb, Gd, and Ho, and M includes any one or more combinations of Co, Al, Cu, Ga, Nb, Zr, and Ti, and the atomic percentage content satisfies 0 < w ≤ 5, 0 < x ≤ 1, 13 ≤ y ≤ 16, and 5 ≤ z ≤ 6. The rare earth oxide contains rare earth element R2, which includes any one or a combination of two or more elements selected from Pr, Nd, Dy, Tb, and Ho. Furthermore, during the vacuum sintering process, the yttrium-containing main alloy and rare earth oxides can undergo an in-situ metallurgical substitution reaction to generate yttrium-rich oxide particles and release active R2 atoms. The active R2 atoms diffuse to the surface of the grains, thereby giving the main phase grains of the permanent magnet a yttrium-rich core and an R2-rich shell, and yttrium-rich oxide particles are uniformly dispersed in the grain boundaries. The particle size of the yttrium-rich oxide particles is <4μm, and the atomic percentage content of yttrium is >20%.

2. The manufacturing method according to claim 1, characterized in that: The mass ratio of the rare earth oxide to the yttrium-containing main alloy is 0.1~10:100; And / or, the yttrium-containing main alloy and rare earth oxides are mixed uniformly in powder form; And / or, the rare earth oxide is selected from R22O3 type oxides; And / or, the average particle size of the rare earth oxide is 0.1~3µm; And / or, 0.05≤x≤0.

6.

3. The manufacturing method according to claim 1, characterized in that, Specifically, this includes: according to (R1) (1-x) Y x ) y Fe 100-w-y-z M w B z The raw materials are prepared according to the specified ratio, and after being melted under the protection of inert gas, they are cast onto rotating rollers to obtain a rapidly solidified alloy sheet. The rapidly solidified alloy sheet is then subjected to hydrogen crushing and air jet milling to obtain yttrium-containing main alloy powder.

4. The manufacturing method according to claim 3, characterized in that: The average thickness of the rapid-solidifying alloy sheet is 0.1~0.5 mm; And / or, the heating temperature before hydrogen crushing and absorption is 250~450 ℃, and the hydrogen pressure is 80~120 MPa; And / or, the particle size distribution parameter SMD of air jet milling is 1~10μm.

5. The manufacturing method according to claim 1, characterized in that, Specifically, it includes: The magnetic field orientation molding is carried out under a magnetic field of 1.5~2.5T to obtain a molding blank, and the cold isostatic pressing is carried out under a pressure of 100~200MPa to obtain a magnet blank. And / or, the vacuum sintering temperature is 950~1150℃, and the time is 2~4h; And / or, the tempering heat treatment is performed at a temperature of 400~800℃ for a time of 2~6h.

6. A yttrium-containing rare-earth permanent magnet with high mechanical service stability, prepared by any one of claims 1-5, characterized in that: The composition of the yttrium rare earth permanent magnet is (R1) (1-x) Y x ) y Fe 100-w-y-z M w B z • (0.001~0.1)R22O3, the yttrium-containing rare earth permanent magnet includes a main phase grain and grain boundaries uniformly surrounding the main phase grain. The main phase grain has a yttrium-rich core and an R2-rich shell, and yttrium-rich oxide particles are uniformly dispersed in the grain boundaries. The particle size of the yttrium-rich oxide particles is <4μm, and the atomic percentage content of yttrium is >20%, wherein 0 < w ≤ 5, 0 < x ≤ 1, 13 ≤ y ≤ 16, and 5 ≤ z ≤ 6.

7. The yttrium-containing rare-earth permanent magnet with high mechanical service stability according to claim 6, characterized in that: The atomic percentage of yttrium in the yttrium-rich core is more than 10% higher than that in the R2-rich shell. And / or, the shell thickness of the R2-rich shell is 0.5~3μm; And / or, the particle size of the yttrium-rich core is 2~4 μm.

8. The yttrium-containing rare-earth permanent magnet with high mechanical service stability according to claim 6, characterized in that: The yttrium-rich oxide particles have a particle size of 0.5~3.5μm; And / or, the atomic percentage content of yttrium in the yttrium-rich oxide particles is 10~40 at% And / or, the mass fraction of the yttrium-rich oxide particles in the grain boundary phase is 1~5 wt%.

9. The yttrium-containing rare-earth permanent magnet with high mechanical service stability according to claim 6, characterized in that: The average bending strength of the yttrium rare earth permanent magnet is above 255 MPa, and the bending strength fluctuation is less than 30 MPa.

10. The application of the yttrium-containing rare earth permanent magnet with high mechanical service stability as described in any one of claims 6-9 in new energy vehicle drive motors, wind turbine generators, or high-end servo system equipment.

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