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Ce substitution of Nd in FeNdB sintered magnets is very interesting for reasons of resource efficiency, sustainability and costs. However, the magnetic properties of high Ce‐content magnets are poor. This is mainly due to the lower values of intrinsic magnetic properties of Fe14Ce2B compared to Fe14Nd2B as well as the Laves phase Fe2Ce, which is formed in the grain boundaries and forms flat aggregates for higher Ce‐content. In this article, sintered magnets with 75 at% degree of substitution of the composition Fe70.9–[(Ce1−xLax)0.75Nd0.25]18.8–B5.8–M4.5 (M = Co, Ti, Al, Ga, Cu, 0 ≤ x ≤ 0.3) are produced and analyzed. It is shown that a new rare earth rich grain boundary phase is formed adding La and that the Laves phase fraction can be reduced by up to 85%. With increasing La content, the remanence and Curie temperature increase and the temperature coefficient of Hc improves. A coercivity, remanence, and maximum energy density of up to μ0Hc = 0.74 T, Jr = 0.98 T, and (BH)max = 139.9 kJ m−3 have been achieved. [ABSTRACT FROM AUTHOR]

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The effect of the chemical composition of the alloys on the magnetic properties of sintered Sm – Co – Fe – Cu – Zr magnets produced with mixing of alloy powders is studied. Elevation of (BH)max of Sm – Co – Fe – Cu – Zr magnets due to increase of the concentration of Fe to 20 wt.% requires observation of a strict proportion of the components and precision choice of the modes of heat treatment. Optimization of the chemical composition and use of step annealing with reduction of the temperature from 700 to 400°C has given sintered magnets with the following properties: Br = 11.7 – 11.9 kGs, HcB = 9 – 10 kOe, HcJ = 15 – 20 kOe, and (BH)max = 29 – 31 MGs · Oe. [ABSTRACT FROM AUTHOR]

In this study, lanthanum was applied to strip cast Ce−Fe−B alloy to improve its phase composition and microstructure. The results reveal that lanthanum doping can significantly enhance the proportion of 2 : 14 : 1 phase and improve the microstructure of Ce−Fe−B alloy. Besides, the influence of the starting alloys structure on the microstructure and magnetic properties of final multi‐phases cerium‐containing magnets was also systematically investigated. Compared to the multi‐phases magnet without lanthanum addition, a pronounced coercivity increment could be distinguished in lanthanum‐doping multi‐phases magnet, which could be attributed to the finer grain size together with ideal grain boundary. In this work, the superior performance of Hcj = 701.28 kA/m Br = 1.30 T, and (BH)max = 313.70 kJ/m3 were obtained by blending Nd−Fe−B alloy with (La0.35Ce0.65)‐Fe−B alloy to meet 25.0 wt.% lanthanum‐cerium utilization content, suggesting that the possibility to develop high abundant rare earth permanent magnetic materials. [ABSTRACT FROM AUTHOR]

SmCo5 sintered magnets with good thermal stability are mainly used in high-temperature field. In this study, two types of SmCoz powders with different nominal z values were mixed and synthesized into SmCo5 magnets by the traditional powder metallurgy method. The magnetic properties of the SmCo5 sintered magnet are maximum energy product of (BH)max = 172.29 kJ·m−3, remanence of Br = 7.47 × 105 A·m−1 and coercivity of Hci = 2.42 T. The results show that there are three coexisting phases in the magnet, which are SmCo5 phase, Sm2Co7 phase and Sm2O3 phase. The microstructural observation indicates that the average grain size in the magnet is about 8 μm, and the high coercivity of this magnet is attributed to these fine grains. X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) results indicate that the magnet has a well-aligned (00l) orientation texture. [ABSTRACT FROM AUTHOR]

RCo5 (R = rare earth) sintered magnets have good temperature stability, so it is still widely used in high temperature field. In this paper, by the method of adding liquid phase SmCo1.7 to the main phase, Sm0.7Y0.3Co5 magnet was prepared by traditional powder metallurgical process. The results show the presence of a main phase RCo5, a minor phase R2Co7, and a R-rich phase in the magnet. Contrasting the results of the XRD (X-ray diffraction) in random and oriented directions, the magnet has a well-aligned (00l) orientated texture, which is consistent with the result of the electron backscattered diffraction (EBSD). The Sm0.7Y0.3Co5 sintered magnet has good magnetic properties as remanence (Br) is 0.96 T, the coercivity (Hcj) is 1201.96 kA·m−1, and maximum magnetic energy product ((BH)max) is 175.16 kJ·m−3. [ABSTRACT FROM AUTHOR]

The time changes in the magnetization of the magnets (Pr0.51Dy0.49)13(Fe0.64Co0.36)80B7 and (Pr0.51Dy0.49)13(Fe0.64Co0.36)79Cu1B7 (at %) sintered at 160°C are studied. Alloying of the Pr–Dy–Fe–Co–B materials with copper is shown to cause a decrease in the magnetization losses in time. [ABSTRACT FROM AUTHOR]

Aiming at the comprehensive utilization of the rare-earth resources and the preparation of the high-performance low-cost Nd–Fe–B magnets, sintered magnets with different Ce substitution amounts of 17.2 wt%, 24.8 wt% and 31.8 wt% were prepared by intergranular-alloy method. The influence of substitution of Ce for Nd on their microstructure and magnetic properties in this work was detailedly investigated. The results indicated that the remanence (Br) and the maximum energy product ((BH)max) of the sintered magnets decreased monotonically with the increase in Ce substitution. However, the obvious enhancement of coercivity (Hcj) was also observed, which was mainly due to the improvement of microstructure and the smooth, continuous grain boundary (GB). It can be found that a reasonable Ce substitution of 24.8 wt% for the sintered magnets could promote the refinement of microstructure, leading to the realization of superior magnetic properties. It is expected that the investigations could be beneficial to offer a feasible method for preparing the high-performance low-cost Ce-doped magnets. [ABSTRACT FROM AUTHOR]

Highlights • The main phase rose from 0 to 48% with partially La substitution in Ce-Fe-B alloy. • The (BH) max of 34.76 MGOe was obtained with 32 wt% La-Ce substitution for Pr-Nd. • The H cj of magnets slightly decreased from 6.49 kOe to 6.16 kOe with La addition. Abstract In this paper, the Ce-Fe-B and (La, Ce)-Fe-B strips were prepared by strip-casting technique and the multi-phases RE-Fe-B (RE = La, Ce, Pr and Nd) magnets were fabricated by dual-alloy method with (Pr, Nd)-Fe-B alloy. The effects of La substitution for Ce on the microstructure of Ce-Fe-B strip-casting alloy were investigated, especially for the formability of 2:14:1 phase. The results showed that the proportion of RE 2 Fe 14 B phase significantly increased from 0.0% to 48.0% and the CeFe 2 phase drastically decreased from 67.1% to 38.1% with La substitution for 35 wt% Ce in Ce-Fe-B strip-casting alloy. It could be attributed to the enlarged temperature gap between the formation of 2:14:1 phase and Ce 2 Fe 17 phase, which was beneficial for the formability of 2:14:1 phase. Owing to the rise of the proportion of the 2:14:1 phase, the remanence (B r) and maximum energy product ((BH) max) of dual-alloy magnets increased from 11.49 kGs, 28.68 MGOe to 12.38 kGs, 34.76 MGOe with respect to 32.0 wt% Ce or La-Ce substitution content for Pr-Nd, respectively. Meanwhile, the coercivity (H cj) slightly decreased from 6.49 kOe to 6.16 kOe, which was caused by the decrease of H A (54.09 kOe → 42.37 kOe) and the deterioration of microstructure of the magnet. This work indicated that the cost-effective La-contained RE-Fe-B permanent magnets could be prepared by dual-alloy method. [ABSTRACT FROM AUTHOR]

CeCo5-based magnets have recently attracted much attention due to their moderate magnetic performance and low cost. Nevertheless, there have been few studies on the effects of Ce content on the magnetic properties and microstructures of CeCo5-based magnets. In response to this, the magnetic properties of sintered bulk magnets with nominal compositions of Ce(Co0.73Cu0.135Fe0.135)z (z = 4.95, 5.15, 5.35, and 5.55), prepared by the conventional powder metallurgy method, were investigated here. Based on experimental findings, it was shown that Ce(Co0.73Cu0.135Fe0.135)5.15 sintered bulk magnets had comprehensive magnetic properties—maximum energy product of 80 kJ m− 3 (10 MGOe) and intrinsic coercivity (Hcj) of 452 kA m− 1 (5.69 kOe)—superior to those previously reported by us. For z = 5.35 and 5.55, due to the presence of the minor Ce2Co17 phase (which has a Curie temperature (Tc) < 20 °C), magnets had low Hcj values. Based on x-ray diffraction and scanning electron microscopy observations, it was suggested that the volume fraction of the 1:5 matrix phase was the main factor determining the Hcj of CeCo5-based sintered bulk magnets obtained with different Ce contents. Furthermore, the importance of the dispersion characteristics of the Ce2O3 phase within the matrix was emphasized. Uniform dispersion of the Ce2O3 phase can significantly improve the overall magnetic performance of CeCo5-based magnets. [ABSTRACT FROM AUTHOR]

The effect of annealing of a (Pr0.41Ce0.12Dy0.47)13.46(Fe0.64Co0.36)80.3B6.24 alloy at 1000°C on its microstructure and the properties of sintered magnets made of it has been studied. In the annealed state, the composition of the main magnetic phase (Pr,Dy)2(Fe,Co)14B changes sharply (dysprosium content changes), the residual induction of the sintered magnets made of the annealed alloy increases by 6%, and the coercive force determined from magnetization increases by 8.5%. The volume content of the main magnetic phase R2(Fe,Co)14B in sintered magnets (Nb,Dy)-(Fe,Co)-B and (Pr,Dy)-(Fe,Co)-B is found. The content of this phase in neodymium-based magnets is approximately half as much. [ABSTRACT FROM AUTHOR]

In this work the finite elements method is used to simulate, by micromagnetic modeling, the magnetic behavior of sintered anisotropic magnets. Hysteresis loops were simulated for different grain sizes in an oriented multigrain sample. By keeping out other parameters that contribute to the magnetic microstructure, such as the sample size, the grain morphology and the grain boundaries mismatch, it has been found that the grain size affects the magnetic properties only if the grains are exchange-decoupled. In this case, as the grain size decreases, a decrease in the nucleation field of a reverse magnetic domain is observed and an increase in the coercive field due to the pinning of the magnetic domain walls at the grain boundaries. [ABSTRACT FROM AUTHOR]

• High entropy design for RE 2 Fe 14 B with five rare earth elements La/Ce/Pr/Nd/Y. • The magnets have a high RE 2 Fe 14 B melting temperature, less REFe 2 and fine grains. • (BH) max reached 33.48 MGOe with 60 wt% La/Ce/Y substituted Pr/Nd. • Pr/Nd-lean sintered magnets were prepared with single main phase process. In this study, single main phase (SMP) magnets with high-entropy RE 2 Fe 14 B were prepared, which contained La, Ce, Pr, Nd and Y. The microstructure and properties of the magnets were studied. The results show that the magnets with high entropy design have a higher melting temperature (T m) of RE 2 Fe 14 B (1189.5℃), less REFe 2 and finer grains (mean grain size: 4.51 μm) compared with binary main phase (BMP) magnets of (LaCe)-Fe-B mixed with (PrNd)-Fe-B. This is mainly due to the high entropy effect, lattice distortion effect and sluggish diffusion from the high-entropy RE 2 Fe 14 B, as well as the synergism of the rare earth (RE) elements. The properties of the magnets are enhanced, especially the magnetic properties. Maximum energy product (BH) max of 33.48 MGOe is achieved with only 40 wt% Pr/Nd in total RE. This work provides a valuable method to obtain RE-Fe-B magnets with high cost performance. [ABSTRACT FROM AUTHOR]

In recent years, significant research efforts were undertaken to enhance coercivity ( H _cj ) of Nd-Fe-B sintered magnets. One of the methods is Dy diffusion, which is very effective in improving H _cj while maintaining the same level of remanence ( B _r ). Experiments reported in this work revealed that Dy diffusion differently affected H _cj of Nd-Fe-B sintered magnets at three diffusion stages: (1) from 0 to 4 h of Dy diffusion, H _cj increased rapidly from 32.3 to 36.5 kOe as Dy content increased rapidly from 0 to 0.27 wt%; (2) from 4 to 24 h, when Dy content changed from 0.27 to 0.56wt%, H _cj increased from 36.5 to 38.7 kOe; (3) from 24 to 30 h, H _cj and Dy content barely changed. Thus, extending Dy diffusion time beyond 24 h period would not yield any improvements. From 0 to 30 h, B _r slightly decreased from 12.40 to 12.22 kGs. During Dy diffusion, intergranular grain boundaries became continuous and homogeneous, and some micro-defects were repaired. As a result, from 0 to 24 h, H _cj enhanced significantly while B _r barely changed. Thus, the Nd-Fe-B sintered magnets with high properties ( B _r = 12.22 kGs, H _cj = 38.9 kOe and ( BH ) _max = 36.87 MGOe) were obtained.

(Ce,Nd)-Fe-B sintered magnets were prepared by the addition of NdH x powders in Ce 9 Nd 4.5 Fe 80 B 6.5 powders. The coercivity is rather low in Ce 9 Nd 4.5 Fe 80 B 6.5 magnets, and Ce element prefers to distribute at the outer-layer of main phase (Ce,Nd) 2 Fe 14 B. The investigation of scanning electron microscope shows that the addition of NdH x powders leads to the increase of Nd content at grain outer-layer of main phase owing to the element diffusion. Magnetization reversal undergoes the nucleation of reversed domain wall at grain outer-later, and the addition of NdH x powders leads to the increase in the nucleation field of reversed domain, giving rise to the significant improvement of coercivity. The larger amount addition of NdH x powders leads to the increase in the amount of intergranular phase, resulting in the decreases of the remanence, the squareness of demagnetization curve and the maximum energy product. [ABSTRACT FROM AUTHOR]

Computer simulations of the magnetizing process have been carried out by applying a numerical model to the theory of magnetization and demagnetization for magnetic materials. The numerical model (written using the Python programming language) is able to calculate the magnetization/demagnetization of the permanent magnet material according to its $B$ – H$ curves. This numerical model is combined with an existing finite-element method (FEM) model in which the result of computations is the approximated potential value in the FEM mesh. The aim of this paper was to develop a tool able to simulate the behavior of an anisotropic sintered permanent magnet during the demagnetization process. The permanent magnet material that has been studied in this paper is sintered Nd–Fe–B and it was modeled taking into account an average misalignment angle related to the magnet easy axis. This model also takes into account different demagnetizing field directions, such as a demagnetizing field perpendicular to the orientation direction, which is often ignored. It is shown that even a demagnetizing field perpendicular to the magnetization direction can produce visible demagnetization effects. A Gaussian distribution of the average misalignment angle in the permanent magnet material is also taken into account as well as its variation. Demag curves have been calculated varying the misalignment angle and the intensity and direction of the external magnetic field. The simulation results are in perfect agreement with the {1}/{\cos \theta} law. The model can be applied in many magnetization and magnetic tuning applications. [ABSTRACT FROM PUBLISHER]

Sintered Nd-Fe-B magnets are some of the strongest magnetic materials showing magnetic properties. Blending addition is frequently performed in order to improve the magnetic properties of these materials. In this work, high-melting point Ni and low-melting point Cu were added to NdFeB ingot by blending. As a result of structural analysis, it was observed that 0.2 wt% Cu + Ni addition improved the structure of the material; on the other hand, excessive addition resulted in porosity. It was also observed that 0.2 wt% addition improved the magnetic properties, and Curie temperature increased with increasing addition ratio. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present improvements in the investigation of magnetic microstructures by the colloid-scanning electron microscopy (colloid-SEM) technique. Good spatial resolution and surface sensitivity of the technique are demonstrated. Clear improvements in the study of magnetic domains on inclined planes were achieved. The presented improvements are also found to be of large significance in investigations for the identification of magnetic minerals in rocks. [Copyright &y& Elsevier]

Zinc stearate additions have been used to increase the remanence of sintered Nd-Fe-B magnets produced by the powder metallurgy without powder pressing. Zinc stearate acts as an internal lubricant, i.e., it decreases the friction forces between the particles and favors an increase in the degree of texture of the powders, which is induced by the magnetic field. It is shown that the density and the magnetic hysteresis characteristics of sintered magnets produced using additions of 0.15 wt % zinc stearate exceeds the corresponding values obtained for magnets produced without this addition at a filling density of powders in containers of more than 2.9 and 3.0 g/cm in dry and wet states, respectively. Using additions of zinc stearate in the amount of 0.15% with respect to the weight of the powder, magnets with a density of 7.55 g/cm, B = 14.02 kG, H = 7.91 kOe, and ( BH) = 46.1 MG Oe have been produced. [ABSTRACT FROM AUTHOR]

The effect of cobalt content in sintered magnets of the Nd(Pr) - Dy - Fe - Co - B system on the sintering temperature, at which the density is equal to 99% of the maximum value and the coercive force H is the highest, is determined. The main components forming the liquid phase in sintering of the materials are determined. It is shown that the addition of (Pr, Dy)(Fe, Co)B intermetallic to alloy (Pr, Dy) - (FeCo) ( y ≈ 0.5) during the operation of fine milling of sintered magnets has a positive effect on the value of H. [ABSTRACT FROM AUTHOR]

Pressless process used for the preparation of sintered Nd-Fe-B magnets has been studied. The effect of the average particle size D, filling density ρ, and powder-texturing conditions for obtaining density ρ and desired magnetic hysteretic properties of sintered magnets has been investigated for both traditional technology (TT) and low-oxygen technology (LOT). The ρ magnitude ensuring the optimum relation between the density ρ of sintered magnets and their degree of texture was shown to be 2.5-3.0 and 2.2 g/cm for the TT and LOT, respectively. At lower ρ magnitudes, no required density of sintered magnets is reached, whereas at higher filling densities, a low level of texture and low remanence are realized. Optimum parameters of pulsed field inducing the high degree of texture in powders have been determined. The following properties were achieved for magnets prepared by pressless LOT: B ≥ 14.2 kG, H ≥ 8 kOe, and ( BH) ≥ 47.9 MG Oe. [ABSTRACT FROM AUTHOR]

The magnetic stability of RE-FeB (RE = Nd or Pr) sintered magnets above room temperature was investigated by monitoring the squareness factor (SF). At 293 ≤ T ≤ 423 K, commercial anisotropic NdFeB-based sintered magnets with a Curie temperature (Tc) of around 585 K showed no appreciable change in their squareness factors. This indicates that the SF is controlled mainly by the samples' microstructural features. Magnets with Tc > 593 K showed a tendency for improved squareness factor at higher temperatures due to the methodology employed to characterize the SF. On the other hand, PrFeCoBCuNb sintered magnets with Tc > 593 K presented a reduction in the SF with temperature rising from 298 to 373 K. [ABSTRACT FROM AUTHOR]

Abstract: To understand the mechanism of the increase in coercivity caused by post-sinter annealing of Nd–Fe–B-based magnets, we have investigated the microstructures of commercial sintered magnets by high-resolution scanning electron microscopy, transmission electron microscopy and atom probe tomography. Continuous thin layers of a Nd-rich amorphous phase were found along the grain boundaries in the post-sinter annealed sample, the chemical composition of which was determined to be Nd30Fe45Cu24.1B0.9. A fine Cu-enriched shell was also confirmed in the Nd-rich phase grain, suggesting the Nd2Fe14B grains are completely enveloped by the Cu- and Nd-enriched layers. Furthermore, a lamellar microstructure of the Cu-enriched phase was confirmed in some Nd-rich phase grains. The mechanism of the coercivity increase caused by post-sinter annealing is discussed based on these characterization results. [Copyright &y& Elsevier]

Abstract: The effect of Tb on the coercivity and impact toughness of sintered Nd–Dy–Fe–B magnets has been investigated. The results showed that the addition of Tb enhanced the intrinsic coercivity, reduced the remanence and improved the impact toughness of sintered magnets. The optimum impact toughness of sintered magnets was achieved when 1.0at% Tb was incorporated. The possible reasons for increasing the intrinsic coercivity and improving impact toughness of sintered magnets were analyzed, and the relations between the microstructure and impact toughness of sintered magnets were studied. [Copyright &y& Elsevier]

Abstract: The mechanical properties of the Nd–Fe–B-based alloys are closely related to their microstructures. It was found that the Co and Ni additions to the Nd2Fe14B (Φ) matrix phase and reduction in the amounts of rare earth (RE)-rich (n) and B-rich (η) grain boundary phases are very effective in improving the mechanical properties. The addition of a MM38.1(MM: Misch Metal)–Co46.4–Ni15.5 alloy to a ternary Nd12.8Fe79.8B7.4-type alloy by a binary powder blending technique resulted in a considerable increase in bending and compressive strength, and a significant decrease in impact strength. The solid solution hardening of the matrix phase by Co and Ni and the presence of intergranular cracks within the grain boundary phase(s) could be the main factors involved in the mechanical behaviors of these alloys. [Copyright &y& Elsevier]

Abstract: The present paper discusses the selection of process parameters for obtaining optimal magnetic properties in strontium ferrite sintered magnets. The magnetic properties have several quality characteristics, such as remanence, coercivity and energy product, etc. To consider these quality characteristics in the selection of process parameters, the Taguchi L9 design is adopted. Experimental results are provided to illustrate the proposed approach. [Copyright &y& Elsevier]