Maximum Magnetic Energy Product Research Articles

Tunning Pr to achieve ultra-high magnetic properties of anisotropic nanocrystalline (Sm,Pr)Co5 magnets

In this study, we reported on the bulk anisotropic nanocrystalline Sm1-xPrxCo5 (x = 0.2–0.6) magnets aimed at achieving excellent energy products. Through a combination of advanced processing techniques, including melt spinning, hot pressing, and hot deformation process, bulk magnets with a fine nanocrystalline structure were successfully synthesized. The results revealed that the substitution of Pr strengthened the c-axis texture and the saturation magnetization, facilitating the enhancement of remanence (Mr) and maximum magnetic energy product [(BH)max]. However, Pr substitution decreased the coercivity (Hci) due to the reduced magnetocrystalline anisotropy field. Excellent magnetic properties are obtained for Sm0.4Pr0.6Co5 magnets with the (BH)max of 23.2 MGOe and Hci of 11.8 kOe. The prepared (Sm,Pr)Co5 magnets with different Pr contents have essentially the same microstructure with RECo5 main phase grains of about 400 nm in diameter and fine dispersed rare earth-rich nanoprecipitates. Our findings can provide reliable reference for manufacturing nanocrystalline permanent magnet materials and promote the development of rare earth permanent magnet new materials.

A high magnetic energy product obtained in hot-deformed Nd-Fe-B magnet by chemical plating Fe-Co bilayer films

This study investigates a novel method, chemical plating, with the goal of integrating nano-sized ferromagnetic materials into hot-deformed Nd-Fe-B magnets, potentially enhancing their magnetic properties. Coating Fe-Co double layers on Nd-Fe-B magnetic powder resulted in a significant improvement in the remanence over 10 %, increasing from 1.37 to 1.45 T, as well as an increase in the maximum magnetic energy product from 45.95 to 52.02 MGOe in hot-deformed Nd-Fe-B magnets. Microstructure observations revealed that the coarse non-oriented grains at the interface of powder ribbons were suppressed and the texture of grain alignment in the interior of powder ribbons was enhanced after the coating of Fe-Co. Additionally, there was a noticeable increase in the concentrations of ferromagnetic elements in intergranular phases. The reduced coarse grain regions, the enhanced grain alignment and the increased ferromagnetic intergranular phases are considered to be the main reasons for the enhancement of remanence and maximum magnetic energy product in hot-deformed magnets.

Construction of Tb-rich shells via novel interdiffusion approach to tackle coercivity-remanence trade-off

The strategic introduction and efficient utilization of heavy rare earth elements within Nd-Fe-B-based permanent magnets are instrumental in achieving an optimal balance between remanence (Br) and high coercivity (Hcj). Herein, we propose a novel interdiffusion approach based on hydrogen decrepitation (HD) for the cost-effective and high-performance sintered Nd-Fe-B magnets. With the aim of generating continuous Tb-rich shells on the grain surface, which favors high Br and high Hcj, strip cast (SC) flakes homogeneously mixed with 0.9 wt% Tb were processed by the HD. It is shown that the formation of (Nd, Tb)-Fe-B by the interdiffusion of Nd-Fe-B and Tb during de-hydrogenation, as well as the interdiffusion of Nd-Fe-B and (Nd, Tb)-Fe-B during sintering and tempering, is the key to the construction of Tb-rich shells. As a result, a magnet (Mag-Tb&HD) with maximum magnetic energy product ((BH)max) of 52.21 MGOe was achieved, which is superior to magnet prepared form SC flakes containing 0.9 wt% Tb (Mag-Tb&SC, (BH)max=49.36 MGOe) and the magnet prepared by adding 0.9 wt% Tb to the jet milling (Mag-Tb&JM, (BH)max=50.41 MGOe).

Vacuum processing temperature effect on highly coercive recycled NdFeB permanent magnets with Pr-based alloy addition

This study presents a modified method for recycling NdFeB scrap magnets, producing up to 100 kg of recycled sintered NdFeB magnets per batch. By adding a Pr-based alloy to N40H-grade NdFeB scrap and optimizing vacuum sintering and heat treatment conditions, we enhanced the magnetic properties and corrosion resistance of the recycled magnets. Various analyses, including BH Tracer measurements, FE-EPMA, accelerated corrosion tests, and C/N/O content analysis, evaluated differences in magnetic properties, microstructure, corrosion resistance, and impurity content. Optimal recycling involved vacuum sintering at 1085 °C, followed by heat treatments at 900 °C and 470 °C. Recycled magnets with PrCoGa alloy showed superior properties, such as an intrinsic coercivity (iHc) of 1414 kA/m, remanence (Br) of 1.290 T, and a maximum magnetic energy product ((BH)max) of 315.4 kJ/m, meeting N40H standards. Accelerated corrosion tests also indicated enhanced corrosion resistance in recycled magnets with Pr90Co8Ga2 alloy. This research offers a commercially viable approach for NdFeB magnet and rare earth element recycling.

Coercivity enhancement of sintered NdFeB magnets by powder Refinement, lubricant increment and Hydrogen-Containing sintering manufacturing

This study investigates powder refinement, lubricant increment, and hydrogen-containing sintering procedures to develop high coercivity in NdFeB magnets. To improve the intrinsic coercivity iHc of sintered NdFeB magnets, it is proposed to control the average particle size and distribution of the magnetic powder by increasing the classification wheel speed of the jet mill during the jet milling process. Additionally, the incremental addition of lubricant is carried out in the additive mixing stage after the magnetic powder is refined. Through the increase of lubricant, the amount of lubricant is enough to completely cover the surface of the powder; hence, the alignment of the powder in the magnetic field forming process is improved, thereby increasing the maximum magnetic energy product (BH)max of the magnet. However, the magnetic properties of the magnet are improved through the refinement of the powder and the increase of the lubricant, but it also leads to the residue of impurities inside the magnet, which actually deteriorates the iHc. Different from the traditional process, this study moved the dehydrogenation procedure to the sintering process, thus reducing the residue of impurities inside the magnet, which is beneficial to the improvement of the magnetic properties of the magnet. Herein, we report a new commercial-scale process (100 kg batches) integrating all the above-modified procedures that reached the best experimental results of iHc = 20.79 kOe, (BH)max = 44.46 MGOe and BHH = 65.25 (i.e., BHH= iHc + (BH)max). The iHc, (BH)max, and BHH of the NdFeB magnet obtained by the new process proposed in this study are 16.47 %, 0.33 %, and 5 % higher than the traditional process, respectively. As a result, iHc has been greatly improved, making NdFeB magnets more conducive to meeting a wide variety of end-user applications, including high-coercivity (>20 kOe) sintered magnets suitable for equipment operating in high-temperature environments.

Effect of Nd-M (M = Al/Co) alloys addition on microstructures and magnetic properties of hot deformed CeFeB magnets

In this study, the magnetic properties, thermal stabilities, elemental distributions and phase transition temperatures of hot deformed CeFeB magnets were investigated by adding 20 wt% of Nd85Al15 and Nd64Co36 alloys, respectively. The results revealed that the addition of low melting point alloys efficiently enhanced the comprehensive magnetic performance and thermal stability of the CeFeB magnets. The optimal magnetic properties were obtained with the addition of 20 wt% Nd85Al15. Compared to the original sample, the coercivity increased from 104 kA/m to 604 kA/m, and the maximum magnetic energy product increased from 8 kJ/m3 to 34 kJ/m3. The incorporation of Nd-Al/Co alloys effectively reduced the area fraction of the coarse grain region and facilitated a more uniform distribution of the RE-rich phase. TEM observations demonstrated that Nd partially replaced Ce, leading to the formation of (Nd, Ce)2Fe14B hard magnetic phase. Additionally, the analysis of the M–T curves indicated the presence of two Curie temperature points for Nd85Al15 and Nd64Co36 added CeFeB hot deformed magnets. The addition of Nd85Al15 improved the fluidity of the RE-rich phase, thereby enhancing the coercivity. Conversely, the incorporation of Nd64Co36 resulted in the entry of Co elements into the main phase, contributing to improved thermal stability.

Effects of Misalignment of c-axis on the Properties of Hydrogenation-Disproportionation-Desorption-Recombination Particles.

Hydrogenation-Disproportionation-Desorption-Recombination (HDDR) Nd2Fe14B particles have excellent magnetic properties, but the magnetic properties of powder are not uniform across different particle sizes. The remanence and maximum magnetic energy products of samples with a particle size of 120 μm are 14.0 kGs and 41.35 MGOe, while the products of samples with a particle size of 60 μm are only 13.3 kGs and 36.31 MGOe. The macroscopic morphology of HDDR Nd2Fe14B particles and the gradient distribution of microstructures in different micro-regions were observed. By modifying the macroscopic morphology of the particles, the poorly oriented clusters on the surface of the particles were precisely eliminated, and the remanence and maximum magnetic energy products of the particles increased to 14.5 kGs and 45 MGOe, respectively. Compared with the original particles, the samples after mechanical grinding had better grain arrangement. The effects of the nanocrystalline c-axis and field misalignment angle θ on the magnetic properties of HDDR Nd2Fe14B particles were investigated through micromagnetic simulation. The targeted removal of macroscopic defects on the particle surface contributed to a 3.6% increase in remanence and an 8.8% increase in the maximum magnetic energy product, offering a promising approach to enhance the microstructure of high-performance HDDR Nd2Fe14B particles.

Influence of preparation processes with or without long-time homogenization heat treatment on performance of Nd–Fe–B HDDR products

We investigated the influence of hydrogenation-disproportionation-desorption-recombination (HDDR) preparation processes, with or without long-time homogenization heat treatment, on the microstructure and hard magnetic properties of Nd12.7B6.5Co2.1Cr0.1Al0.5Nb0.3Ga0.5Fe77.3 powders/bonded magnets. Hard magnetic properties such as remanence (Br = 1.01 T), coercivity (Hcj = 949.39 kA/m), and maximum magnetic energy product (BH)max = 181.54 kJ/m3 were achieved for HDDR bonded magnets with homogenization heat treatment. In contrast, magnets prepared without homogenization heat treatment exhibited Br = 0.65 T, Hcj = 854.69 kA/m, and (BH)max = 66.98 kJ/m3. The notable decrease in remanence for magnets prepared without homogenization treatment is attributed to the presence of α–Fe in the parent alloy, which inhibits the hydrogenation-disproportionation process and consequently affects the orientation of the crystallographic texture. Furthermore, we fabricated bonded quadrupole magnetic rings using HDDR powder prepared with homogenization heat treatment. The study also explored the relationship between disproportionation temperature and surface magnetic field intensity for these quadrupole magnetic rings.

An efficient process for preparing regenerated magnets by dynamic recovery of Nd-Fe-B sintered magnet sludge

As a new technology for the short-process recovery of Nd–Fe–B sintered magnet sludge, the calcium thermal reduction diffusion method has attracted significant attention due to its low energy consumption, environmental friendliness, and high recovery rate. However, traditional calcium thermal reduction diffusion technology still has issues such as an insufficient reaction between the sludge and reducing agent after increasing the amount of reactants, the use of a large amount of reducing agent, and low recovery efficiency. Therefore, a novel dynamic calcium thermal reduction diffusion technology was proposed, with the calcium reduction diffusion of sludge and calcium undergoing a continuous mixing and diffusion state throughout the entire process, greatly improving the efficiency of the reaction. Compared with the traditional process, the amount of reactants was increased from a few grams to hundreds of grams, and the amount of reducing agent calcium was reduced by 25%. Subsequently, regenerated magnetic powder with a uniform particle size, good dispersion, and excellent magnetic properties was obtained. The saturation magnetization under a 3 T magnetic field was increased by 27.9% compared with the initial sludge. The maximum magnetic energy product of the magnet prepared by doping 50 wt% regenerated magnetic powder was 45 MGOe, which reached the highest level of the regenerated magnets prepared by recycling sludge. What is encouraging that this new technology had the advantage of achieving large-scale production and reducing production costs, providing a potential industrialization solution for the green and efficient recovery of Nd–Fe–B sintered magnet sludge.

Comprehensively improved magnetic performance of Nd-Fe-B magnets with high-efficiency grain boundary diffusion of heavy rare earth

Comprehensively improved magnetic performance Nd-Fe-B magnets with extremely limited amount of Heavy Rare Earth (HRE) elements are obtained to meet the increasingly demanding applications. In this work, Tb–Co thin film with uniform distribution, flat surface and strong adhesion is successfully prepared by magnetron sputtering, and the effects of Tb–Co film thickness on the magnetic properties are investigated. The magnets with optimal magnetic properties are achieved when the film thickness is about 3.5 μm, the coercivity of 1284.81 kA/m, the remanence of 1.48 T, and the maximum magnetic energy product of 437.32 kJ/m3, compared with the original magnets, enhancing by 47.9 %, 0.4 % and 5.7 %, respectively, so the magnetic properties have been comprehensively improved using little amount of HRE and Co elements. HRTEM and EPMA results revealed that Tb-rich shell distributed around the Nd2Fe14B grain. The mechanisms of the remanence and coercivity simultaneous enhancement of Nd-Fe-B magnets is elaborated in detail. Besides, the diffusion of Tb–Co thin film can enhance thermal stability of the magnets.

Multiple enhancement on the magnetic and electric properties of SrM hexaferrites by phase-change perovskite additives

M−type strontium (SrM) hexaferrites, which possess a high saturation magnetization, coercivity, and maximum magnetic energy product, have been widely used as permanent magnets in electric machines. However, emerging high-speed and high-power electric machines put forward higher requirements on the loss characteristics of ferrites at high frequencies and high temperatures. Here, the effects of two phase-change perovskite additives, barium titanate (BTO) and BTO-based ceramic with a positive temperature coefficient (PTCC), on the magnetic properties, electrical properties, and their temperature dependence of SrM hexaferrite are reported. The spatial concentration distribution and diffusion kinetics of the perovskite additives are investigated, showing their accumulation at the grain boundaries and gradual diffusion into the crystallites. Due to the high melting points, the addition of BTO and PTCC at the grain boundaries hinder the grain growth and reduce the grain size. Due to the strong pinning effect of the impurities near the grain boundaries and the reduction of grain size, enhancement in coercivity up to 10 % as well as an increase of 225 % in resistivity are observed. More interestingly, a positive temperature dependence of the resistivity is achieved by adding various amounts of PTCC. These results demonstrate the capability of phase-change perovskite additives to achieve simultaneous enhancement in multiple electromagnetic and temperature properties of SrM hexaferrite.

Significantly improved magnetic properties and thermal stability for sintered Nd-Fe-B magnets via grain boundary diffusion of DyCo alloy

Improving the coercivity in high temperature applications is one of the critical issues of NdFeB-based magnets. In this work, DyCo alloy is selected as the diffusion source for grain boundary infiltration to prepare high coercivity NdFeB magnets with excellent thermal stability. Increasing the diffusion temperature until 950 °C is beneficial in elevating the coercivity. Magnetic hardening enhancement of interfacial region contributed by the formation of (Nd, Dy)2Fe14B shell and the elevated magnetic isolation effect between adjacent matrix phase grains are responsible to the coercivity improvement. The optimum magnetic properties with the coercivity of 1573 kA/m, the remanence of 1.33 T, and the maximum magnetic energy product of 338 kJ/m3 can be achieved at 900 °C. The significant increase of Curie temperature to 51 K is attributed to the higher exchange energy between Co-Co and Fe-Co. Moreover, the thermal stability including the temperature coefficient of remanence α and coercivity β are all improved considerably.

High-performance anisotropic SmCo-based magnet with novel microstructure

A novel microstructure of magnetically anisotropic SmCo-based magnet with high-performance is reported. The magnet consists of SmCo7-H (TbCu7-hexagonal type), Sm2Co17–H (Th2Ni17-hexagonal type) and SmCo3-R (SmCo3-rhombohedral type) phases. The maximum magnetic energy product of the magnet is 231.69 kJ/m3, and the intrinsic coercivity is 1005.47 kA/m. An outstanding intrinsic coercivity temperature coefficient (β) of −0.125%/K between 298 and 773 K is obtained, which is very close to the β of commercial high-temperature Sm2Co17-based sintered magnets. The initial magnetization curve indicates that the coercivity mechanism is controlled by a domain wall pinning mechanism. The SmCo3-R lamellar phase may be a potential pinning center or self-pinning center. The microstructure of the magnet is different from that of any previous SmCo-based magnets. These findings provide a new idea for preparing high-performance SmCo-based permanent magnets.

Preparation and magnetic properties of magnetically anisotropic 2:17-type SmCo alloy spherical particles

This study utilized the irregular Sm(Co0.69Fe0.22Cu0.07Zr0.02)8.1 alloy powder as the primary material, combining the solid/liquid interface de-wetting effect and abnormal grain growth method for preparing the 1:7-type SmCo spherical single crystal powder. Through aging heat treatment, the anisotropic 2:17-type SmCo alloy spherical permanent magnetic powder with size distribution of 30–130 μm was successfully obtained. The study explored the spheroidization mechanism and single crystal growth rule of Sm(Co0.69Fe0.22Cu0.07Zr0.02)8.1 alloy powder, as well as the impact of solution-aging magnetic hardening treatment on the permanent magnet properties. The optimized permanent magnetic properties of the resulting 2:17-type SmCo alloy spherical powder were coercivity Hic = 1244 kA/m, and maximum magnetic energy product (BH)max = 224.5 kJ/m3 at room temperature. The anisotropic 2:17-type SmCo alloy spherical magnetic powder prepared using this method exhibits significant potential applications in the production of bonded magnets.

Fabrication and application prospects of Pr–Fe–B/Alnico nanocomposite alloys

The potentials of rare earth-based nanocomposite alloys have never been realized due to strict microstructural constraints. Owing to the easy demagnetization it is challenging to increase the soft magnetic phase content. To avoid the easy demagnetization, Pr–Fe–B/Alnico magnets were fabricated and reported in this manuscript. The content of the Alnico phase is increased from 0 to 25 wt%, while the content of Pr element is reduced to below the sub-stoichiometry of the 2:14:1 main phase. The maximum magnetic energy product, which is the figure-of-merit for permanent magnets, is increased from 122 kJ/m3 for the standard alloy to 146 kJ/m3 for the alloy with 15 wt% Alnico which shows a significant improvement considering the fact that the Curie point of the magnet is also increased by ∼66 K. The special microstructure contains distinctly and heterogeneously distributed 2:14:1 and Alnico phases. The dimensions of neither the 2:14:1 nor the Alnico phases meet the dimensional requirements of the nanocomposite magnets, but still the smooth demagnetization curves are noted for the alloys. The behavior of effective anisotropy, the performance of the magnets in applied magnetic field and the magnetic interactions among the various constituent grains were quantitatively studied by reversible susceptibility, irreversible susceptibility and recoil loop openness. This study may provide some guiding principles for the development of nanocomposite magnetic alloys with excellent magnetic properties by using much less RE elements.

Dependences of Magnetic Properties on the Grain Size and Hard/Soft Magnetic Phase Volume Ratio for Ce2Fe14B/α-Fe and Nd2Fe14B/α-Fe Nanocomposites.

The magnetic properties of magnetic nanocomposites consisting of hard and soft magnetic phases are dependent not only on the intrinsic properties but also on the grain structure and volume ratio of the two phases. In this study, we performed a systematic micromagnetic simulation on the magnetic properties of Ce2Fe14B/α-Fe and Nd2Fe14B/α-Fe nanocomposites. The volume fractions of the hard magnetic Nd2Fe14B or Ce2Fe14B phase were varied from 80% to 40%, and the grain sizes of the hard magnetic phase and the soft magnetic α-Fe phase were changed independently from 10 nm to 40 nm. The results show that when the grain size of both hard and soft phases is 10 nm and the volume fraction of the hard phase is 70%, the highest maximum magnetic energy product can be obtained in both Ce2Fe14B/α-Fe and Nd2Fe14B/α-Fe nanocomposites. The hard magnetic properties of Ce2Fe14B/α-Fe nanocomposite decrease significantly when the volume fraction of the α-Fe phase exceeds 30%. However, for the Nd2Fe14B/α-Fe system, this situation only occurs when the α-Fe volume fraction exceeds 40%. The reason for this is not only because of the low anisotropic field and the smaller exchange coupling length between the soft and hard magnetic phases, but also because of the lower saturation magnetization of the hard phase. The grain size has greater effects on the magnetic properties compared to the volume fraction of the hard magnetic phase. The main reason is that as the grain size increases, the remanence of the nanocomposite decreases sharply, which also leads to a rapid decrease in the maximum magnetic energy product. The simulation results on the effects of phase ratio and grain size have been verified by experiments on melt-spun Ce2Fe14B/α-Fe alloys with various compositions prepared by melt-spinning followed by annealing for various lengths of time. Due to the influence of demagnetization energy, the hard magnetic phase with high saturation magnetization is preferred for the preparation of high-performance nanocomposite magnets.

Ordered L10-FeNi (111) epitaxial thin film on Al2O3 (0001) substrate: Molecular beam epitaxy growth and characterizations

Ordered hard magnetic L10-FeNi has attracted attention as a candidate for rare-earth-free permanent magnet with a large maximum magnetic energy product. Fabricating L10-FeNi is a big challenge using conventional methods due to its low order-disorder transition temperature, 320 °C. In this work, high-quality ordered L10-FeNi films were fabricated by using molecular beam epitaxy directly on Al2O3 (0001) substrate with a two-step co-deposition method below 250 °C. The films were epitaxially grown with [111] orientation, confirmed by reflection high energy electron diffraction and x-ray diffraction patterns. An order-disorder phase transition at 320 °C was observed in temperature dependent electrical resistivity curve. The two-step molecular beam epitaxy grown film exhibited high uniaxial magnetic anisotropy constant, Ku, up to 1.15 × 106 J/m3. The obtained Ku value is comparable to previous result for FeNi along [100] growth direction, indicating an isotropic Ku. This work provides an effective molecular beam epitaxy growth method of high-quality ordered L10-FeNi (111) film for the development of the next-generation rare-earth-free permanent magnet.

Microstructure and magnetic properties of grain boundary diffused Nd-Fe-B magnets with Tb-Al-Ga alloy

The coercivity of Nd-Fe-B magnets can be effectively improved by grain boundary diffusion using low melting point alloy as diffusion source. In this work, Tb-Al-Ga alloy was used as diffusion source for grain boundary diffused Nd-Fe-B magnets. Tb-rich shell structure, potential synergistic effect of Al-Ga, interface between diffusion source and the magnets were analyzed. When the magnets were processed at 875 °C for 10 h, the coercivity increased by 123 % from 10.38 kOe to 23.15 kOe and the remanence and the maximum magnetic energy product only decreased by 3 %. Tb element mainly formed shell structure with high magneto-crystalline anisotropy field surround the main phase grains. Non-magnetic Al element was distributing around the main phase grains as network structure, which could well isolate the main phase grains. The Tb-rich shell with high magneto-crystalline anisotropy field and the non-magnetic phase with magnetic exchange decoupling between the adjacent grains contributed to substantial increase in the coercivity of the grain boundary diffused magnets. The grain boundary phase was wetted by Al element, which promoted Tb element diffused into the magnets more deeply.

Study on neutron diffraction and correlated magnetic properties of (R1−xZrx)Fe12−yMoy with low Mo concentration

In order to determine the Zr occupancy site, neutron diffraction study on (R1−xZrx)Fe12−yMoy (R = rare earth) were performed at 300 K and 573 K respectively. It is found that Zr occupies the 2a site, like the R atoms behavior. Zr is the first neighbor of Y in the periodic table, and has a similar chemic property as Y, but with a smaller atomic radius. Due to the suitable chemic property and atomic dimension, the addition of Zr at 2a site facilitates forming of the 1–12 phase, allowing more Fe atoms to enter the 8i site and decreasing Mo content from 1.5 to 0.8. As a result, Sm0.9Zr0.1(Fe0.75Co0.25)11.2Mo0.8 shows a large saturation magnetization σs of 137.6 emu/g, a high Curie temperature TC of 775 K and a strong anisotropy field Ha of 87.5 kOe, and its estimated value of maximum magnetic energy product (BH)max is up to 50.4 MGOe, favorable for permanent magnet applications. At present, almost rare-earth sintered magnets are made of Nd2Fe14B, causing the price of the raw material Nd to soar. Therefore, the development of low-cost Sm-Fe based hard magnetic materials is of particular significance.

Effect of rotation rate on the recovery of Nd–Fe–B sludge via rotation-reduction diffusion method

In recent years, calcium reduction diffusion has emerged as a new method for in situ regeneration of Nd–Fe–B sludge. In this work, rotation calcium thermal reduction diffusion technology was used for the first time to solve the issue of batch regeneration of Nd–Fe–B sludge to a certain extent, and regenerated Nd–Fe–B powder with uniform size and good dispensability was prepared. The effect of rotation rate on the properties of regenerated Nd–Fe–B powder was mainly studied. We found that the magnetic properties of the regenerated magnetic powder initially increased and then decreased with increasing rotation rate. When the rotation rate was 10 rpm, the magnetization of regenerated magnetic powder reached 138.22 emu/g, which was 10.2% higher than that of the purified sludge. The regenerated magnetic powder was doped with rare earth-rich alloy powder and high remanence alloy powder to control the composition, where the regenerated sintered magnet was prepared. The density reached 7.51 g/cm3 and the maximum magnetic energy product reached 42.87 MGOe, laying a foundation for the short-process in situ regeneration of Nd–Fe–B sludge.