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Rotating magnetocaloric effect and thermal transport properties in sintered Nd0.8Pr0.2Co5 alloy

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Journal of Rare Earths 2020年第6期38卷 606-611页

作者： Mingxiao Zhang Kun Wang Jian Liu Lei Liu aru yan CAS Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology.Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China University of Chinese Academy of Sciences Beijing 100049China

We report microstructure,magnetocaloric effect and thermal transfer properties of highly orientated Nd0.8Pr0.2Co5 alloy prepared by powder metallurgical *** spin-reorientation transitions of easy magnetization direction,easy plane to easy cone at TSR1=206 K,easy cone to easy axis at TSR2=242 K,are *** present textured alloy exhibits a rotating entropy change of 2.6 J/(kg·K)and refrigerant capacity of 155 J/kg under a magnetic field of 2 T,and high thermal conductivity of 11 W/(m·K).The sintered Nd0.8Pr0.2Co5 alloy with good combination of excellent magnetocaloric and thermal transfer properties are promising for scientific research and practical applications as room-temperature rotating magnetic refrigeration materials.

关键词： Rotating magnetocaloric effect Rare-earth alloys Anisotropy Spin-reorientation

Zirconium content induced mitigation of mechanical anisotropy in 2:17 type SmCo magnets

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Journal of Rare Earths 2020年第2期38卷 182-187页

作者： Guanghui yan Zhuang Liu yanping Feng Weixing Xia Chaoyue Zhang Guangqing Wang aru yan University of Chinese Academy of Sciences Beijing 100049China Laboratory of Rare Earth Magnetic Functional Materials Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China CAS Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China

The mitigation of mechanical anisotropy is observed in 2:17 type SmCo magnets by adjusting the Zr content This behavior is supposed to be closely related to the density of lamellar phase,the density of which is enhanced obviously with increasing Zr *** other reasons which could cause the reduction of the mechanical anisotropy is discussed from the Zr-rich impurity phase to the atom substitutions and crystal lattice *** observation of crack in nano scale that dearly forms angles of 60° and 90° with respect to the lamellar phase,indicates that the probable cleavage planes are crystal faces(1011) and(1010).The results of investigation can deepen the understanding of mechanical anisotropy and cleavage fracture in the SmCo magnets.

关键词： 2 type SmCo magnet Mechanical anisotropy Cleavage plane Lamellar phase Rare earths

Coercivity enhancement of Ce-containing hot-deformed magnets by grain boundary diffusion of DyF_(3)

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Journal of Rare Earths 2022年第2期40卷 289-295,I0004页

作者： Bin Chen Jinyun Ju Wenzong Yin Xu Tang Renjie Chen aru yan Longquan Hou Yeyuan Du CAS Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Materials Technology and Engineering Chinese Academy of SciencesNingbo 315201China University of Chinese Academy of Sciences Beijing 100049China School of Environment and Safety Engineering North University of ChinaTaiyuan 030051China

The samples with full density were prepared by hot pressing the the melt-spun powders mixed with DyF_(3)powders of different mass fractions followed by hot-deformation *** magnetic properties and temperature dependence of coercivity were obtained by BH tracer and VSM,*** microstructure were analyzed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The coercivity of Ce-containing hot-deformed magnets is increased from 1.41 to 1.95 T by grain boundary diffusion of 3 wt%DyF_(3),and is further enhanced to 2.05 T after annealing *** thermal stability of coercivity and remanence is *** annealing condition in this work crucially plays a role in thickening the grain boundary *** analysis reveals that the continuous and thick grain boundary phase formed after DyF_(3)diffusion can weaken the magnetic coupling between grains,and suppress the platelet shaped grain size and the aspect *** Dycontaining shell structure formed by the partial diffusion of Dy into the main phase can increase the magnetic anisotropy field,which is the main reason for the coercivity *** optimizing the structure by DyF_(3)diffusion,the"dendritic-like"reverse domain is transformed into the"dot scatteredlike"reverse domain.

关键词： Ce-containing hot-deformed magnet Coercivity Grain boundary phase Dy-containing shell structure Rare earths

Effects of Nd-Ga intergranular addition on microstructure and magnetic properties of heavy-rare-earth-free Nd-Fe-B sintered magnets

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Journal of Rare Earths 2022年第6期40卷 924-929,I0003页

作者： Jinhao Zhu Guangfei Ding Lei Jin Zhehuan Jin Bo Zheng Shuai Guo Renjie Chen aru yan CAS Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application TechnologyNingbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China University of Chinese Academy of Sciences Beijing 100049China

In this study,we propose an approach of grain boundary modification that can significantly increase the coercivity of the B-lean Nd-Fe-B sintered magnets by intergranular addition of *** coercivity is substantially enhanced from 1.51 to 2.04 T through optimizing the microstructure and adjusting the phase composition for the grain boundary phase in the annealed *** matrix grains are covered by a continuous thin grain boundary phase accompanying the formation of intermetallic Nd_(6)Fe_(13)Ga *** analysis of magnetic behaviors above Curie temperature confirms that the grain boundary phase of annealed Nd-Ga doped magnets appears to be non-ferromagnetic,facilitating the intergrain exchange *** observation in grain boundary area indicates that some surface of the matrix grain is dissolved in the formation process of the Nd_(6)Fe_(13)Ga *** gives rise to a decrease in the proportion of matrix grains and saturation magnetization of the *** detailed relationship between magnetic properties and microstructure is discussed based on these results.

关键词： Nd-Fe-B sintered Magnet Magnetic properties Grain boundary Microstructures Rare earths

Effect of yttrium substitution on magnetic properties and service performances of Nd-Fe-B sintered magnets

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Journal of Rare Earths 2023年第1期41卷 116-121页

作者： Xiaodong Fan Shuai Guo Guangfei Ding Sining Fan Zhehuan Jin Renjie Chen Shukai Zhang aru yan CAS Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Material Technology and EngineeringChinese Academy of SciencesNingbo 315201China Chinalco Shandong Yinuowei Strong Magnetic Material Co. LtdTaian 271600China

We successfully fabricated partial Y substituted NdY-Fe-B magnets with nominal compositions of(Nd_(1-x)Y_(x))_(13.80)Fe_(ba1)Al_(0.24)Cu_(0.1)B_(6.04)(at%,x=0,0.1,0.2,0.3,0.4) by powder metallurgy process and the magnetic properties as well as service performances of the magnets were also systematically *** phase constituents of the magnets have no obvious variation within the whole range of Y content,while the main phase grains form in-situ core-shell structure where Y gathers in the core and Nd mainly distributes in the *** with pure Nd-Fe-B magnets,the magnetic performances of Y substituted magnets slightly decrease on account of the poor intrinsic magnetic properties of Y_(2)Fe_(14)***,the μ_(O)M_(r),μ_(O)H_(cj) and(BH)_(max) of the 20 at% Y magnet still remain at a high level of 1.325 kG,1.173 kOe and 342.884 kj/m^(3),which approaches the performances of commercial N45-grade *** service performances of Y substituted magnets indicate that though the surface corrosion products and Vickers hardness of the NdY-Fe-B magnets increase to a certain extent compared to Nd-Fe-B,the magnets with Y substitution still display relatively good service ***,on the basis of sacrificing little partial magnetic and service performances,Y substituted Nd can still prepare NdY-Fe-B medium-grade *** this way,we achieve the balanced utilization of rare earth resources,which has significant meanings for the industry and scientific research.

关键词： Y substitution Magnetic properties Service performances Nd-Fe-B sintered Magnets Rare earths

Sandwiched structure of hot-deformed Nd-Fe-B permanent magnets processed by Nd-Cu eutectic alloys diffusion

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Journal of Rare Earths 2021年第8期39卷 993-997页

作者： Longquan Hou Jinyun Ju Xu Tang Renjie Chen Wenzong Yin aru yan Bin Chen Yeyuan Du Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Material Technology and EngineeringChinese Academy of SciencesNingbo 315201China Anhui Key Laboratory of Metal Materials and Processing School of Materials Science and EngineeringAnhui University of TechnologyMaanshan 243002China

A series of sandwiched structures with different near-surface mass fractions x(x=3 wt%,4 wt%,5 wt%)was employed to develop high-coercivity hot-deformed Nd-Fe-B magnets by the addition of 2 wt%Nd-Cu eutectic alloys via adjusting the middle thickness and near-surface *** designed magnet with a pronounced composite structure shows a 23% increase in coercivity with a 6% loss of remanence by adjusting the sandwiched structure at 4 wt% Nd-Cu eutectic alloys in the near-surface *** results indicate that the near-surface Nd-Cu-rich "shell" structure can effectively suppress the magnetization reversal of overall magnets,enhancing the *** the help of loading stress,Nd-Cu liquid enriched at the near-surface regions of the sample is infiltrated into the Nd-Cu-lean middle region,resulting in a concentration *** characterizations further demonstrate that the infiltrated Nd-Cu eutectic plays a critical role in inhibiting grain growth and intergranular magnetic *** optimized microstructure features suppress the reversed magnetization process,which makes a positive contribution to coercivity.

关键词： Nd-Fe-B Hot-deformed magnet Sandwiched structure Rare earths

A comparative study of NdY-Fe-B magnet and NdCe-Fe-B magnet

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Journal of Rare Earths 2022年第9期40卷 1480-1487,I0006页

Low cost and high abundance rare earth elements Y and Ce have attracted tremendous interests of the industrial and scientific societies for fabricating the highly cost-performance efficient rare earth permanent ***,the effect of separate replacement of Nd by Y or Ce on the performances of NdFeB-type magnet under the same atomic ratio and preparation conditions is still *** this work,we systematically investigated the magnetic properties,thermal stabilities and service performances of(Nd_(0.8)Y_(0.2))_(13.80)Fe_(bal)Al_(0.24)Cu_(0.1)B_(6.04)(atomic fraction,denoted as 20 Y)and(Nd_(0.8)Ce_(0.2))_(13.80)Fe_(bal)Al_(0.24)Cu_(0.1)B_(6.04)(atomic fraction,denoted as 20 Ce)*** results demonstrate that theμ_(0)M_(r),μ_(0)H_(c)and(BH)_(max)of 20 Y magnet are respectively 1.325 T,1.173 T and 343.467 kJ/m^(3),which are comprehensively higher than those of 20 Ce magnet(μ_(0)M_(r)=1.310 T,μ_(0)H_(c)=0.948 T,(BH)_(max)=321.105 kJ/m^(3)).Moreover,the 20 Y magnet has higher thermal stability compared with 20 Ce magnet which is favorable for the magnetic performances at elevated *** investigation of micro structure and elemental distribution indicates that the excellent magnetic performance s of NdY-Fe-B magnet can be attributed not only to the preferable intrinsic properties4πM_(s),H_(s)and T_(c)of Y_(2)Fe_(14)B,but also to the in-situ co re-shell structure of the 2:14:1 matrix phase grain with Yrich core and Nd-rich shell,along with the thicker grain boundary layer between the adjacent matrix phase grains in NdY-Fe-B ***,the 20 Y magnet exhibits better mechanical property and higher corrosion resistance than 20 Ce magnet,which are helpful for prolonging the service life of the magnet in practical application.

关键词： NdY-Fe-B NdCe-Fe-B Magnetic properties Thermal stabilities Service performances Rare earths

Effect of Nb doping on microstructure and magnetic properties of hot-deformed Nd-Fe-B magnets with Nd-Cu eutectic diffusion

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Journal of Materials Science & Technology 2022年第27期122卷 121-127页

作者： Tingting Song Xin Li Xu Tang Wenzong Yin yang Luo Dunbo Yu Wenlong yan Jinyun Ju Renjie Chen aru yan School of Marine Engineering Equipment Zhejiang Ocean UniversityZhoushan 316022China CAS Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Material Technology and EngineeringChinese Academy of SciencesNingbo 315201China Grirem Advanced Materials Co. Ltd.Beijing 100049China

To restrict grain growth in coarse grain regions caused by the diffusion of Nd-Cu eutectic alloys,the Nb element was introduced into the precursor alloy to regulate the microstructure of melt-spun powder and die-upset *** magnetic properties and thermal stability of die-upset magnets were appreciably improved through the addition of *** the Nb-doped diffusion die-upset magnet,the grains inside the ribbons were refined and the coarse non-oriented surface crystallite got suppressed on the interface of ribbons during the hot-deformation process to form the anisotropic ***,Nd gathers at the intergranular phases,which is considered to enforce domain wall pinning *** Nb-modified microstructure is advantageous to thermal stability and coercivity ***-resolution transmission electron microscopy images revealed that the Nb element gathered on the grain boundary and triple grain boundary to form c-Nb and h-Nb Fe B to hinder the grain growth during the hot-deformation process,which led to direct enhancement in the ***,the c-Nb and h-Nb Fe B are nonmagnetic phases that strengthened the magnetic ***,the h-Nb Fe B precipitated from the hard magnetic phase and formed crystal defects which led to remanence deterioration.

关键词： Nd-Fe-B Hot deformation Diffusion Nb-doping Coercivity

Effect of surface Nd-rich phase and oxygen content of melt-spun flakes on formation of coarse grains in hot-pressed Nd-Fe-B magnet

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Journal of Rare Earths 2021年第11期39卷 1389-1395,I0003页

作者： Yeyuan Du Wenzong Yin Renjie Chen Xu Tang Jinyun Ju Bin Chen Longquan Hou aru yan Jianhui Yuan School of Materials Engineering Shanghai Collaborative Innovation Center of Laser Advanced Manufacturing TechnologyShanghai University of Engineering ScienceShanghai 201620China Key Laboratory of Magnetic Materials and Devices.Ningbo Institute of Materials Technology and Engineering Chinese Academy of SciencesNingbo 315201China University of Chinese Academy of Sciences Beijing 100049China

Nd-Fe-B hot-pressed(HP) magnet prepared from melt-spun MQU-F flakes features coarse grains(CG)with the average size of both 200 nm(CGS) and 700 nm(CGL) at flake *** grain growth at the flake boundary of Nd2 Fe14B/α-Fe composite HP magnet before and after diffusion of low-melting-point Pr82Cu18 phase was investigated,revealing the indispensable role of surface RE-rich phase of meltspun flakes in the formation of CG in HP *** dominant role of surface oxygen content of melt-spun flakes in the formation of CGL has been clarified with etching *** HP magnet prepared from the etched flakes with dramatically decreased oxygen content exhibits the CG regions merely with homoge neous equiaxed CGS at flake ***,the coercivity(μ0 Hc) shows significant increase while remanent magnetization(μ0 Mr) inappreciable *** investigation with sieving method reveals the elimination of CGL via removal of the fine Nd-Fe-B flakes smaller than 54 μm due to their much higher oxygen content,confirming the dominant role of oxygen content in the formation of *** quantitative analysis on the magnetic properties of the above HP magnets reveals the monotonic increase of coercivity(μ0 Hc) and negligible change of remanent magnetization(μ0 Mr) with decreased oxygen contents of Nd-Fe-B *** maximum value of coercivity(μ0 Hc) increases from2.26 to 2.47 T as the oxygen content decreases from 0.1692 wt% to 0.079 wt%.

关键词： Coarse grain Hot pressing Nd-Fe-B Oxygen content Nd-rich phase Rare earths