Method for improving high-temperature magnetic performance of samarium-cobalt magnet

Abstract

A method for improving the high-temperature magnetic performance of a samarium-cobalt magnet comprises the steps that a metal raw material with the atomic percentage being Sm (CobalFeuCuvZrw) z is smelted, and a cast ingot is obtained; crushing the cast ingot to obtain alloy powder; carrying out die forming on the alloy powder in a magnetic field, and then carrying out cold isostatic pressing to obtain a green body; sintering the green body, and carrying out solution treatment to obtain a solid-solution-state magnet; preparing the solid-solution-state magnet into a cuboid, and grinding and polishing; the solid solution state magnet is cooled to the room temperature after being subjected to primary isothermal aging treatment, the aging temperature ranges from 800 DEG C to 850 DEG C, and the aging time ranges from 10 h to 20 h; and the samarium-cobalt magnet is placed in a magnetic field heat treatment furnace and heated to 800-850 DEG C under the vacuum degree of 10 <-3 > Pa, then an external magnetic field of 0.5-1 T is applied in the cooling process with the cooling rate of 0.5-0.9 DEG C / min till the samarium-cobalt magnet is cooled to 500 DEG C, and then the samarium-cobalt magnet is obtained after the samarium-cobalt magnet is cooled to the room temperature.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet materials technology, and in particular to a method for improving the high-temperature magnetic properties of samarium cobalt magnets. Background Technology

[0002] Rare earth permanent magnet materials are a class of permanent magnet materials with intermetallic compounds formed by rare earth metal elements and transition metal elements as the matrix. They are widely used in transportation, energy, machinery, medical, communications, and defense fields. With the rapid development of precision instruments, aerospace, and defense industries, the harsh service environments have placed higher demands on the high-temperature performance and temperature stability of rare earth permanent magnet materials. Second-generation rare earth permanent magnet materials, namely 2:17 samarium cobalt magnets, are widely used due to their excellent magnetic properties, strong temperature stability, high Curie temperature, and strong corrosion resistance. In particular, their application in defense equipment with operating temperatures above 500℃ and high stability over a wide temperature range is difficult to replace by other existing permanent magnet materials.

[0003] In permanent magnet materials, an important performance indicator for measuring magnetic properties is the maximum energy product (BH). max Coercivity H cj and remanence B r Among them, the maximum energy product (BH) is of most interest. max The coercivity test (CFT) measures the ability of permanent magnet materials to retain magnetic flux and resist demagnetization under an external field, thus assessing the overall magnetic performance of permanent magnet materials under certain conditions. The hard magnetism of 2:17 type samarium-cobalt magnets originates from their unique nanocellular structure, including a rhombic 2:17R intracellular phase, a hexagonal 1:5H pyramidal cell wall precipitate, and a plate-like Zr-rich phase perpendicular to the c-axis and penetrating the cellular structure. The high saturation magnetization of the magnet originates from its cellular main phase, the 2:17R phase. The plate-like structure is considered to provide diffusion channels for Cu to enter the 1:5 phase in the cell wall. The 1:5H cell wall phase plays a major pinning role on the domain walls during demagnetization. To a certain extent, the higher the content of the 1:5H precipitate in the magnet, the stronger the pinning effect and the higher the coercivity. The 2:17R' intermediate phase located at the edge of the 2:17R cell acts as a structural defect, increasing the local free energy and preferentially causing domain wall depinning during demagnetization, which is detrimental to improving magnetic performance. With the development of aviation technology, military technology and precision instrument technology, higher requirements have been put forward for the operating temperature range. Equipment such as all-electric aircraft magnetic bearings and rocket ion thrusters require permanent magnet materials to operate at temperatures up to 550 ℃.

[0004] The information disclosed in the background section is only for enhancing the understanding of the background of this invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] This invention provides a method for improving the high-temperature magnetic properties of samarium cobalt magnets. By applying an external magnetic field during the slow cooling process of aging, the solid-state phase transition process inside the solution-treated material is altered, promoting the redistribution of solute atoms Fe / Cu between the 2:17R and 1:5H phases. This effectively promotes the precipitation of the 1:5H cell wall phase and the decomposition of residual defects 2:17R', thereby increasing the Cu content in the 1:5H phase and significantly improving the squareness. The maximum magnetic energy product of the magnet at 550℃ increases from 6.55 to 9.37 MGOe, an improvement of 43.1%.

[0006] One method for improving the high-temperature magnetic properties of samarium cobalt magnets includes:

[0007] The first step is to determine the atomic percentage of Sm(Co). bal Fe u Cu v Zr w ) z The metal raw materials are smelted to obtain ingots, where bal = 1 - uvw, 0.10 ≤ u ≤ 0.16, 0.08 ≤ v ≤ 0.15, 0.01 ≤ w ≤ 0.03, and 7 ≤ z ≤ 7.9;

[0008] The second step is to crush the ingot to obtain alloy powder.

[0009] The third step is to mold the alloy powder in a magnetic field, and then cold isostatically press it to obtain a green blank.

[0010] The fourth step is to sinter the green blank and perform a solution treatment to obtain a solid solution magnet;

[0011] The fifth step involves shaping the solid-solution magnetic material into a cuboid and then polishing it.

[0012] The sixth step involves cooling the solid solution magnet to room temperature after a first-stage isothermal aging treatment. The aging temperature is 800–850°C, and the aging time is 10–20 hours.

[0013] The seventh step involves placing the samarium-cobalt magnet in a magnetic field heat treatment furnace under a vacuum of 10... -3 The material is heated to 800 ℃-850 ℃ under Pa, and then an external magnetic field of 0.5-1T is applied during the cooling process at a cooling rate of 0.5-0.9 ℃ / min until it cools to 500 ℃. It is then furnace cooled to room temperature to obtain a samarium cobalt magnet.

[0014] In the method for improving the high-temperature magnetic properties of samarium-cobalt magnets, in the second step, the particle size of the alloy powder is 4~6μm.

[0015] In the method for improving the high-temperature magnetic properties of samarium cobalt magnets, in the third step, the molding pressure is 150 MPa, the magnetic field strength is >1.0T, and the cold isostatic pressing pressure is 200~300 MPa.

[0016] In the method for improving the high-temperature magnetic properties of samarium cobalt magnets, in the fourth step, the green sintering temperature is 1190-1220℃, the sintering time is 0.5-3h, the solution treatment temperature is 1140-1190℃, and the sintering time is 1-8h.

[0017] In the fifth step of the method for improving the high-temperature magnetic properties of samarium cobalt magnets, the samarium cobalt magnet is made into a cuboid with its long side parallel to the c-axis direction of the samarium cobalt magnet, and then polished.

[0018] In the seventh step of the method for improving the high-temperature magnetic properties of samarium cobalt magnets, an external magnetic field of 0.5-1T is applied during the cooling process at a cooling rate of 0.5-0.9 °C / min until the temperature is cooled to 500 °C. The external magnetic field induces the directional diffusion of Fe and Cu atoms between the 2:17R intracellular phase and the 1:5H cell wall phase, thereby promoting the transformation of the residual non-equilibrium phase 2:17R′ to the 2:17R phase.

[0019] A samarium cobalt magnet, which is manufactured according to the method described above for improving the high-temperature magnetic properties of a samarium cobalt magnet.

[0020] In the aforementioned samarium cobalt magnet, at 550°C, the coercivity of the samarium cobalt magnet is at least 6.39 kOe, and the maximum energy product is at least 8.61 MGOe.

[0021] Compared with existing technologies, this invention has the following advantages: During the slow aging cooling process, an external magnetic field parallel to the c-axis of the magnet is applied. This external magnetic field provides additional static magnetic energy, improving the redistribution efficiency of Fe and Cu between the 2:17R intracellular phase and the 1:5H precipitated phase. This promotes the transformation of the 2:17R' intermediate phase to the 2:17R equilibrium phase, effectively reducing the volume fraction of residual defects in 2:17R', and significantly increasing the maximum magnetic energy product of the samarium-cobalt magnet at 550°C. The preparation process of this invention is simple, and the prepared samarium-cobalt magnet exhibits a very high maximum magnetic energy product at 550°C, meeting the operating temperature and service characteristics requirements of advanced equipment such as magnetic motors, aerospace accelerators, and aircraft generator detectors. This is of great significance for the development of related magnetic devices. Attached Figure Description

[0022] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0023] In the attached diagram:

[0024] Figure 1 This is a heat treatment schematic diagram of a method for improving the high-temperature magnetic properties of a samarium-cobalt magnet according to an embodiment of this disclosure;

[0025] Figure 2 The Sm(Co) obtained in Example 1 with and without magnetic field heat treatment are examples. bal. Fe 0.149 Cu 0.14 Zr 0.02 ) 7.6 Comparison of hysteresis loops of magnets;

[0026] Figure 3(a) shows the Sm(Co) obtained in Example 1 with and without magnetic field heat treatment. bal. Fe 0.149 Cu 0.14 Zr 0.02 ) 7.6 The XRD diagram of the magnet, Figure 3(b) is an enlarged view of the (024) peak in Figure 3(a); the wider the half width at half maximum (WHM) of the (024) peak, the lower the order of the 2:17R phase and the more residual defects 2:17R'.

[0027] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0028] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0029] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0030] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0031] like Figure 1 As shown in Figure 3(b), the method for improving the high-temperature magnetic properties of samarium cobalt magnets includes the following steps:

[0032] The first step is to determine the atomic percentage of Sm(Co). bal Fe u Cu v Zr w ) z The metal raw materials are smelted to obtain ingots, where bal = 1 - uvw, 0.10 ≤ u ≤ 0.16, 0.08 ≤ v ≤ 0.15, 0.01 ≤ w ≤ 0.03, and 7 ≤ z ≤ 7.9;

[0033] The second step is to crush the ingot to obtain alloy powder.

[0034] The third step is to mold the alloy powder in a magnetic field, and then cold isostatically press it to obtain a green blank.

[0035] The fourth step is to sinter the green blank and perform a solution treatment to obtain a solid solution magnet;

[0036] The fifth step involves forming the solid solution magnet into a cuboid whose long side is parallel to the c-axis direction of the samarium cobalt magnet, and then grinding and polishing it.

[0037] The sixth step involves cooling the solid solution magnet to room temperature after a first-stage isothermal aging treatment. The aging temperature is 800–850°C, and the aging time is 10–20 hours.

[0038] The seventh step involves placing the samarium-cobalt magnet in a magnetic field heat treatment furnace under a vacuum of 10... -3The material is heated to 800 ℃-850 ℃ under Pa, and then an external magnetic field of 0.5-1T is applied during the cooling process at a cooling rate of 0.5-0.9 ℃ / min until it cools to 500 ℃. It is then furnace cooled to room temperature to obtain a samarium cobalt magnet.

[0039] In the method for improving the high-temperature magnetic properties of samarium-cobalt magnets, in the second step, the particle size of the alloy powder is 4~6μm.

[0040] In the method for improving the high-temperature magnetic properties of samarium cobalt magnets, in the third step, the molding pressure is 150 MPa, the magnetic field strength is >1.0T, and the cold isostatic pressing pressure is 200~300 MPa.

[0041] In the method for improving the high-temperature magnetic properties of samarium cobalt magnets, in the fourth step, the green sintering temperature is 1190-1220℃, the sintering time is 0.5-3h, the solution treatment temperature is 1140-1190℃, and the sintering time is 1-8h.

[0042] In the fifth step of the method for improving the high-temperature magnetic properties of samarium cobalt magnets, the solid solution magnet is made into a cuboid whose long side is parallel to the c-axis direction of the samarium cobalt magnet, and then polished.

[0043] In the seventh step of the method for improving the high-temperature magnetic properties of samarium cobalt magnets, an external magnetic field of 0.5-1T is applied during the cooling process at a cooling rate of 0.5-0.9 °C / min until the temperature is cooled to 500 °C. The external magnetic field promotes the directional diffusion of Fe and Cu atoms between the 2:17R intracellular phase and the 1:5H cell wall phase, and promotes the transformation of the residual non-equilibrium phase 2:17R′ to the 2:17R phase.

[0044] A samarium cobalt magnet, which is manufactured according to the method described above for improving the high-temperature magnetic properties of a samarium cobalt magnet.

[0045] In the aforementioned samarium cobalt magnet, at 550°C, the coercivity of the samarium cobalt magnet is at least 6.39 kOe, and the maximum energy product is at least 8.61 MGOe.

[0046] In one embodiment, the method includes the following steps:

[0047] The first step involves melting the metal raw materials in a vacuum induction furnace according to a specific ratio to obtain an ingot. The ingot contains an atomic percentage of Sm(Co). bal Fe u Cu v Zr w ) z Samarium cobalt magnets, 0.10≤u≤0.16, 0.08≤v≤0.15, 0.01≤w≤0.03, 7≤z≤7.9;

[0048] The second step is to crush the ingot to obtain alloy powder.

[0049] The third step is to mold the alloy powder in a magnetic field, and then cold isostatically press it to obtain a green blank.

[0050] The fourth step is to sinter the green blank and perform a solution treatment to obtain a solid solution magnet;

[0051] The fifth step involves shaping the solid solution magnet into a cuboid, making its long side parallel to the c-axis direction of the samarium cobalt magnet, and then polishing it.

[0052] The sixth step involves rapidly cooling the solid solution magnet to room temperature after a first-stage isothermal aging treatment. The aging temperature is 800℃ and the aging time is 20 hours.

[0053] The seventh step involves placing the samarium-cobalt magnet in a magnetic field heat treatment furnace under a vacuum of 10... -3 The magnet was heated to 800 °C under Pa, and then an external magnetic field of 0.5 T parallel to the c-axis of the samarium cobalt magnet was applied during the cooling process at a cooling rate of 0.5-0.9 °C / min until it cooled to 500 °C. The samarium cobalt magnet was then furnace cooled to room temperature and removed.

[0054] In the first step, the samarium-cobalt magnet is in the form of Sm(Co) atomic percentage. bal Fe u Cu v Zr w ) z Where 0.10≤u≤0.16, 0.08≤v≤0.15, 0.01≤w≤0.03, and 7≤z≤7.9.

[0055] In the second step, the alloy powder particle size is 4~6 μm.

[0056] In the third step, the molding pressure is ~150 MPa, the magnetic field strength is >1.0T, and the cold isostatic pressing pressure is 200~300 MPa.

[0057] In the fourth step, the green body sintering temperature is 1190~1220℃, the sintering time is 0.5~3h, the solution treatment temperature is 1140~1190℃, and the sintering time is 1~8h.

[0058] In the fifth step, the samarium cobalt magnet is polished to make its surface smooth and to ensure that the upper and lower surfaces, which are perpendicular to the c-axis of the magnet, are parallel.

[0059] In the sixth step, the solid solution magnet is rapidly cooled to room temperature after undergoing a first-stage isothermal aging treatment. The aging temperature is 800–850°C, and the aging time is 10–20 hours.

[0060] In the seventh step, the samarium-cobalt magnet is placed in a magnetic field heat treatment furnace under a vacuum of 10... -3 The samarium-cobalt magnet was heated to 800-850 °C under Pa, and then an external magnetic field of 0.5-1 T was applied during the cooling process at a cooling rate of 0.5-0.9 °C / min until it cooled to 500 °C. After that, the furnace was cooled to room temperature and the samarium-cobalt magnet was removed.

[0061] A samarium cobalt magnet, prepared by the method described above, exhibits a coercivity of at least 6.39 kOe and a maximum energy product of at least 8.61 MGOe at 550 °C.

[0062] The samarium-cobalt magnet obtained by the aforementioned preparation method.

[0063] Example 1

[0064] Figure 1 This is a heat treatment schematic diagram illustrating a method for improving the high-temperature magnetic properties of a samarium-cobalt magnet according to an embodiment of this disclosure. The samarium-cobalt magnet in this embodiment has the chemical formula Sm(Co). bal. Fe 0.149 Cu 0.14 Zr 0.02 ) 7.6 Specifically, it includes the following steps:

[0065] Metal raw materials are placed in a vacuum induction furnace according to a certain ratio to obtain ingots;

[0066] The ingots are mechanically crushed, medium crushed, and air jet milled to obtain alloy powder with a particle size of 4~6 μm.

[0067] Alloy powder is molded in a magnetic field of >1.0T at ~150 MPa, and then cold isostatically pressed at 200~300 MPa to obtain a green blank;

[0068] The resulting green body was sintered at 1210℃ for 2 hours; then it was solution treated at 1180℃ for 2 hours and cooled to room temperature to obtain a solid solution magnet.

[0069] The solid solution treated magnet is made into a cuboid, with its long side perpendicular to the c-axis of the samarium cobalt magnet, and then polished.

[0070] The experimental magnet was placed in a muffle furnace for first-stage isothermal aging treatment, held at 800 °C for 20 h, and then rapidly cooled to room temperature.

[0071] The experimental magnet was placed in a magnetic field heat treatment furnace at a vacuum degree of 10. -3The magnet is rapidly heated to 800 °C under Pa, and then slowly cooled at a rate of 0.5 °C / min with an external magnetic field of 0.5 T parallel to the c-axis of the magnet applied until it is slowly cooled to 500 °C. The magnet is then furnace cooled to room temperature and removed to obtain the final magnet.

[0072] The final magnet underwent performance testing at 550℃. Compared with a control magnet of the same composition, subjected to slow cooling without external magnetic field treatment, and heat-treated using the same process, the magnet after magnetic field heat treatment exhibited a higher high-temperature coercivity H. cj The maximum energy product (BH) decreased from 6.82 kOe to 6.39 kOe. max It increased from 6.55 kOe to 9.37 kGOe.

[0073] Figure 2 The figures show the hysteresis loops of the experimental magnet (treated with an external magnetic field during slow cooling, marked in red) and the control magnet (treated with conventional aging, marked in black) measured at 550℃. It can be seen that the experimental magnet has a wider and larger hysteresis loop than the control magnet, which means that the squareness of the magnet was significantly improved after the external magnetic field treatment during slow cooling. The coercivity H of the magnet at 550℃ is also shown. cj The energy decreased from 6.82 kOe to 6.39 kOe, a reduction of 6.3%, while the maximum energy product increased from 6.55 to 9.37 MGOe, an increase of 43.1%.

[0074] Figure 3(a) shows the XRD patterns of the experimental magnet (treated with an external magnetic field during slow cooling, marked in red) and the control magnet (treated with conventional aging, marked in black) measured at room temperature. It can be seen that both the experimental and control magnets contain strong diffraction peaks of the 2:17R and 1:5H phases. Figure 3(b) is a magnified view of the characteristic peak {024} (38.4°) of the 2:17R phase. To estimate the degree of order of the 2:17R phase in the two magnets, the full width at half maximum (FWHM) of the characteristic peak {024} of the 2:17R phase was compared. The FWHMs of {024}-2:17R in the experimental and control magnets are ~0.390° and ~0.462°, respectively. This quantitative comparison indicates that the degree of order of the 2:17R phase in the experimental magnet is higher than that in the control magnet, meaning the former has less residual non-equilibrium phase 2:17R′. This means that the applied magnetic field can promote the transformation of the 2:17R' intermediate phase to the 2:17R equilibrium phase, effectively reducing the volume fraction of residual defects 2:17R', reducing weak pinning points during the demagnetization process, and significantly increasing the maximum magnetic energy product of the samarium cobalt magnet at 550℃.

[0075] Example 2

[0076] This embodiment is performed in essentially the same manner as Embodiment 1, except that in step 5, the solid-solution treated magnet is formed into a cuboid, with its long side parallel to the c-axis direction of the samarium-cobalt magnet. The coercivity H of the magnet... cj It has a maximum energy product (BH) of 6.62 kOe. max It is 9.10 kGOe.

[0077] Example 3

[0078] In this embodiment, the samarium-cobalt magnet has the chemical formula Sm(Co) bal. Fe 0.149 Cu 0.14 Zr 0.02 ) 7.6 Specifically, it includes the following steps:

[0079] Metal raw materials are placed in a vacuum induction furnace according to a certain ratio to obtain ingots;

[0080] The ingots are mechanically crushed, medium crushed, and air jet milled to obtain alloy powder with a particle size of 4~6 μm.

[0081] Alloy powder is molded in a magnetic field of >1.0T at ~150 MPa, and then cold isostatically pressed at 200~300 MPa to obtain a green blank;

[0082] The resulting green body was sintered at 1210℃ for 2 hours; then it was solution treated at 1180℃ for 2 hours and cooled to room temperature to obtain a solid solution magnet.

[0083] The solid solution treated magnet is made into a cuboid, with its long side perpendicular to the c-axis of the samarium cobalt magnet, and then polished.

[0084] The experimental magnet was placed in a muffle furnace for first-stage isothermal aging treatment, held at 800 °C for 15 h, and then rapidly cooled to room temperature.

[0085] The experimental magnet was placed in a magnetic field heat treatment furnace at a vacuum degree of 10. -3 The magnet is rapidly heated to 800 °C under Pa, and then slowly cooled at a rate of 0.5 °C / min with an external magnetic field of 0.5 T parallel to the c-axis of the magnet applied until it is slowly cooled to 500 °C. The magnet is then furnace cooled to room temperature and removed to obtain the final magnet.

[0086] The final state magnet was subjected to performance testing at 550℃, and the high-temperature coercivity H of the magnet was measured. cj It has a maximum energy product (BH) of 6.43 kOe. max It is 8.61 kGOe.

[0087] This example uses the minimum value of the solution treatment time parameter range to obtain the maximum magnetic energy product (BH) of the magnet.max It is 8.61 kGOe, which is lower than the maximum energy product (BH) of the magnet obtained by the optimal parameter combination in Example 1. max 9.37kGOe.

[0088] Furthermore, the external magnetic field of this invention provides additional static magnetic energy, enhances the thermodynamic driving force of phase decomposition, reduces residual defects in the magnet, and accelerates the distribution of solute atoms between the cell and the cell wall. During the slow cooling process after first-stage aging, the phase transition occurs sequentially at Curie temperatures of 2:17R and 1:5H. Applying an external magnetic field during this process provides additional driving force for the redistribution of solute atoms and the phase transition. After applying a strong magnetic field parallel to the easy magnetization axis (c-axis), at T... C -2:17R and T C Within the temperature range of -1 to 5H, the additional driving force comes from the static magnetic energy of the ferromagnetic 2:17R phase, when further cooled to T C Below -1:5H, the additional driving force comes from the magnetostatic energy difference between the 2:17R and 1:5H phases. This magnetic field-induced elemental segregation not only strengthens the saturation magnetization of the main phase but also optimizes the compositional uniformity of the cell wall phase, laying a structural foundation for subsequent improvements in magnetic properties.

[0089] Secondly, the extremely slow cooling rate (0.5 ℃ / min) prolongs the phase transition window, promoting the decomposition of defective phases. Under traditional rapid cooling or air cooling processes, the 2:17R′ intermediate phase (a non-equilibrium, low-symmetry transition phase) remains in large quantities at the cell boundaries due to kinetic freezing, becoming a preferential channel for domain wall depinning and severely impairing high-temperature coercivity and squareness. This invention significantly prolongs the atomic diffusion time within the critical precipitation temperature range of 800–500 ℃ by reducing the cooling rate to 0.5 ℃ / min, allowing the 2:17R′ phase ample opportunity to reconstruct into a thermodynamically stable 2:17R phase through an ordered transformation. XRD and hysteresis loop results show that after slow magnetic field cooling, the mass fraction of 2:17R′ is significantly reduced, while the squareness of the hysteresis loop is significantly improved, confirming the effective elimination of structural defects.

[0090] Finally, the synergistic effect of magnetic field and slow cooling enhances the magnetic energy product at 550℃, overcoming performance bottlenecks. Although a moderate increase in Cu content in the 1:5H phase may slightly reduce its pinning strength at 550℃ (causing a slight decrease in coercivity from 6.82 kOe to 6.39 kOe), the reduction of the 2:17R′ phase, the increase in the magnetization of the main phase, and the more uniform nanocellular structure significantly improve the remanence (Br) and hysteresis squareness of the magnet at high temperatures, ultimately leading to the maximum magnetic energy product (BH) at 550℃. maxThe energy density jumped from 6.55 MGOe to 9.37 MGOe, an increase of 43.1%. This performance breakthrough means that the magnet can stably output high magnetic energy in extreme high-temperature scenarios such as all-electric aircraft magnetic bearings and ion thrusters, solving the contradiction of existing Sm-Co magnets having "high coercivity but low energy product" in high-temperature applications.

[0091] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for improving the high-temperature magnetic properties of samarium-cobalt magnets, characterized in that, Includes the following steps: The first step is to determine the atomic percentage of Sm(Co). bal Fe u Cu v Zr w ) z The metal raw materials are smelted to obtain ingots, where bal = 1 - uvw, 0.10 ≤ u ≤ 0.16, 0.08 ≤ v ≤ 0.15, 0.01 ≤ w ≤ 0.03, and 7 ≤ z ≤ 7.9; The second step is to crush the ingot to obtain alloy powder. The third step is to mold the alloy powder in a magnetic field, and then cold isostatically press it to obtain a green blank. The fourth step is to sinter the green blank and perform a solution treatment to obtain a solid solution magnet; The fifth step involves shaping the solid-solution magnetic material into a cuboid and then polishing it. The sixth step involves cooling the solid solution magnet to room temperature after a first-stage isothermal aging treatment. The aging temperature is 800–850°C, and the aging time is 10–20 hours. The seventh step involves placing the samarium-cobalt magnet in a magnetic field heat treatment furnace under a vacuum of 10... -3 The material is heated to 800 ℃-850 ℃ under Pa, and then an external magnetic field of 0.5-1T is applied during the cooling process at a cooling rate of 0.5-0.9 ℃ / min until it cools to 500 ℃. It is then furnace cooled to room temperature to obtain a samarium cobalt magnet.

2. The method for improving the high-temperature magnetic properties of samarium-cobalt magnets according to claim 1, characterized in that, Preferably, in the second step, the particle size of the alloy powder is 4~6 μm.

3. The method for improving the high-temperature magnetic properties of samarium-cobalt magnets according to claim 1, characterized in that, In the third step, the molding pressure is 150 MPa, the magnetic field strength is >1.0T, and the cold isostatic pressing pressure is 200~300 MPa.

4. The method for improving the high-temperature magnetic properties of samarium-cobalt magnets according to claim 1, characterized in that, In the fourth step, the green body sintering temperature is 1190~1220℃, the sintering time is 0.5~3h, the solution treatment temperature is 1140~1190℃, and the sintering time is 1~8h.

5. A method for improving the high-temperature magnetic properties of samarium-cobalt magnets according to claim 1, characterized in that, In the fifth step, the solid solution magnet is made into a cuboid with its long side parallel to the c-axis direction of the samarium cobalt magnet, and then polished.

6. The method for improving the high-temperature magnetic properties of samarium-cobalt magnets according to claim 1, characterized in that, In the seventh step, an external magnetic field of 0.5-1T is applied during the cooling process at a cooling rate of 0.5-0.9 °C / min until the temperature is cooled to 500 °C. The external magnetic field enables the directional diffusion of Fe and Cu atoms between the 2:17R intracellular phase and the 1:5H cell wall phase, promoting the transformation of the residual non-equilibrium phase 2:17R′ to the 2:17R phase.

7. A samarium-cobalt magnet, characterized in that, It is made according to any one of claims 1-6, by a method for improving the high-temperature magnetic properties of samarium cobalt magnets.

8. The samarium-cobalt magnet according to claim 1, characterized in that, The samarium cobalt magnet has a coercivity of at least 6.39 kOe and a maximum energy product of at least 8.61 MGOe at 550°C.

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