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Enhanced mechanical properties of giant magnetostrictive Tb-Dy-Fe alloy via constructing semi-coherent interface between matrix phase and ductile grain boundary phase

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JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY 2024年第000期175卷 185-193页

作者： Li, Jiheng Zhou, Zhiguang Han, Zhaopeng Yang, Zijing Bao, Xiaoqian gao, xuexu Univ Sci & Technol Beijing State Key Lab Adv Met & Mat Beijing 100083 Peoples R China Beijing Res Inst Mech & Elect Techno Co Ltd CSM Beijing 100083 Peoples R China

Giant magnetostrictive Tb-Dy-Fe alloys in the form of thin sheets or fine wires are required in precision micro-actuators and sensors. However, Tb-Dy-Fe alloys are too brittle to undergo machining and application. In the present work, we investigated the effects of diffusing the Dy 36 Cu 64 alloy into the grain boundary phases of the -oriented Tb0.30Dy0.70Fe1.95 alloy to modify the microstructural, mechanical, and magnetostrictive properties. Microstructural analysis revealed the introduction of Cu into the grain boundary phase through the diffusion treatment, transforming the brittle rare earth (RE)-rich grain boundary phase into a ductile (Tb,Dy)Cu grain boundary phase and changing the non-coherent interface to a semi-coherent one between the (Tb,Dy)Fe(2 )matrix phase and the grain boundary phase without affecting the microstructure of the matrix phase. The as-diffused Tb0.30Dy0.70Fe1.95 alloy exhibited significantly improved mechanical properties, with its tensile strength, bending strength, and fracture toughness at room temperature increasing to 44.6 MPa, 106.8 MPa, and 2.36 MPa m(1/2), respectively, which were 2, 2.4, and 1.5 times those of the non-diffused sample. This was attributed to the formation of ductile (Tb,Dy)Cu grain boundary phase and semi-coherent interfaces. Furthermore, the magnetostrictive strain of the as-diffused Tb0.30Dy0.70Fe1.95 alloy reached 1448 ppm, suggesting that there was minimal impact on the magnetostrictive properties, due to the small influence of grain boundary diffusion on the matrix phase.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

关键词： Tb-Dy-Fe alloys Magnetostriction Mechanical performance Grain boundary diffusion Semi-coherent interface TBDYFE STRENGTH NB CO CU

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Microstructure evolution and coercivity mechanism of hydrogenation-disproportionation-desorption-recombination(HDDR) treated Nd-Fe-B strip cast alloys

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Journal of Rare Earths 2022年第5期40卷 792-799,I0005页

作者： Bin Ma Xiaoqian Bao Aizhi Sun Jiheng Li xuexu gao State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing 100083China

In this paper,we systematically investigated the microstructure evolution and coercivity mechanism of hydrogenation-disproportionation-desorption-recombination(HDDR)treated Nd-Fe-B strip cast alloys by transmission electron microscopy(TEM)and three-dimensional atom probe(3 DAP)*** rodlike NdH_(2+x) phases with diameters of 10-20 nm are embedded intoα-Fe matrix,which hereditarily leads to textured grains in HDDR *** migration of NdH_(2+x) from Nd-rich region toα-Fe matrix during hydrogen absorption process contributes to the uniform redistribution of Nd-rich phases after HDDR treatment The HDDR alloy with single domain grain sizes of 200-300 nm exhibits relatively low coercivity of 1.01 T that arises from pinning magnetic domain *** weak c-axis orientation of HDDR alloy results in a lower reverse magnetic field(coercivity)to reduce remanence to ***,the direct contact of Nd_(2)Fe_(14)B grains and the high concentration of ferromagnetic elements(Fe content≈66.06 at%,Co content≈0.91 at%)in Nd-rich grain boundary layer lead to strong magnetostatic coupling effect among Nd_(2) Fe_(14)B *** nano-sized a-Fe inside Nd_(2) Fe_(14)B matrix makes the magnetization reversal easily and decreases the coercivity of HDDR alloy.

关键词： Nd-Fe-B strip Cast HDDR treatmemt Microstructure evolution Coercivity mechanism Three-dimensional atom probe Rare earths

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Effect of Ga addition on the magnetic properties and microstructure of nanocrystalline Nd_(12.3)Fe_(81.7)B_(6.0) ribbons

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Rare Metals 2011年第5期30卷 447-452页

作者： BAO Xiaoqian GUO Xiaoyan GUO Jianchun gao xuexu State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China Shandong Jinma Industrial Group Co. Ltd. Rizhao 276826 China

Nd 12.3 Fe 81.7 x Ga x B 6.0 （x = 0-1.8） ribbons were prepared by melt spinning at 22 m/s and subsequent annealing treatment. The influences of Ga addition and annealing conditions on the magnetic properties and microstructure of the nanocrystalline alloys were systematically investigated. After being annealed at 620℃ for 20 min, the J r and H ci increased from 0.85 T and 582.6 kA/m for Ga-free sample to 0.97 T and 734.6 kA/m for the x = 0.9 sample, respectively. The （BH） max for the x = 0.9 sample increased by about 40% from 96.3 to 135.5 kJ/m 3 compared with that of the Ga-free one. The significant improvement of magnetic properties originated from the refinement of grains in the samples by introducing Ga, which led to a stronger exchange coupling between the neighboring grains in comparison with that in Ga-free samples. The microstructure and magnetic properties of the samples depended strongly on annealing parameters, while the sensitivity of micro-structure to annealing conditions could be significantly suppressed by the addition of Ga element.

关键词： nanocrystalline alloys exchange coupling microstructure magnetic properties gallium

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Improvement of microstructure and coercivity for Nd-Fe-B sintered magnets by boundary introducing low melting point alloys

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Journal of Rare Earths 2020年第4期38卷 395-401页

作者： Shuai Cao Xiaoqian Bao Jiheng Li Haijun Yu Kunyuan Zhu xuexu gao State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

Different from the grain boundary diffusion process(GBDP),which is suitable for modifying thin magnet,a green-pressing agents permeation process(GAPP)that uses low melting point alloys was applied to the Nd-Fe-B green compact with a thickness over 15 mm to reconstruct the boundary microstructure of a sintered Nd-Fe-B *** coercivity increases from 12.3 kOe for the sample free of Pr80Al20 to16.8 kOe for the sample with 2 wt%*** further increasing the Pr80Al20 content to 3 wt%,the coercivity increases slightly,but the remanence and Hk/Hcj deteriorate *** optimal comprehensive properties of Hcj=16.8 kOe,Br=13.4 kG and Hk/Hcj=0.975 are obtained at 2 wt%Pr80Al20,since matrix phase grains are separated by relatively continuous thin grain boundary layers,which weaken the magnetic coupling between adjacent *** coercivities of the samples from the GAPP that use2 wt%Pr80Al20,Pr70Al30 and Pr60Tb20Al20 alloys,respectively,can be enhanced to a large ***,the coercivity of the magnet reconstructed with Pr80Al20 is lower than that of the sample with Pr60Tb20Al20 but is higher than that of the sample reconstructed with Pr70Cu30 ***,the coercivity of the sample from the GAPP using 2 wt%Pr80Al20 is much higher than that of the sample from the GBDP,which is due to a nearly uniform boundary microstructure from the surface to the interior of the thick magnet from the GAPP,thus providing new insights into the fabrication of thick and bulky permanent magnets with high coercivity.

关键词： Nd-Fe-B sintered magnets Green-pressing agents permeation Grain boundary diffusion Pr-Al alloys Thick and bulky magnets Rare earths

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Effect of microstructure and defects on the magnetostriction of<110> oriented TDT-110 alloys

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Journal of University of Science and Technology Beijing 2008年第1期15卷 53-57页

作者： Haijun Tang xuexu gao Wei Wu Maocai Zhang Shouzeng Zhou State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

〈110〉 oriented rods of TbDyFe giant magnetostrictive alloys have been prepared with the help of the zone melting directional solidification technique with a high temperature gradient. To acquire optimal magnetostrictive properties at low magnetic field, the TbDyFe alloys have been heat-treated at different temperatures and cooled at different rates. The relationships between the proc- ess of the heat treatment, microstructure, defects, and magnetostrictive properties of the TbDyFe materials have been studied. 2008 University of Science and Technology Beijing. All rights reserved.

关键词： TbDyFe heat treatment microstructure defect magnetostriction

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Effect of annealing time on the exchange coupling interactions and microstruc-ture of nanocomposite Pr_(7.5)Dy_1Fe_(71)Co_(15)Nb_1B_(4.5) ribbons

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Journal of University of Science and Technology Beijing 2007年第6期14卷 547-551页

作者： Xiaoqian Bao Yi Qiao xuexu gao Maocai Zhang Jie Zhu Shouzeng Zhou State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

The influence of annealing time on the magnetic properties and microstructure of nanocomposite Pr7.5Dy1Fe71Co15Nb1B4.5 ribbons was systematically investigated by the methods of vibrating sample magnetometer （VSM）, X-ray diffraction （XRD） and high resolution transmission electron microscopy （HRTEM）. Interaction domains derived from strong exchange coupling interactions between hard and soft magnetic grains were imaged using magnetic force microscopy （MFM）. Maximum remanence, intrinsic coercivity, and maximum energy product values were obtained in the ribbons annealed at 700℃ for 15 min, which were composed of Pr2（Fe, Co）14B, α-（Fe, Co）, and slight Pr2（Fe, CO）17 phases. Although Jr, Hci, and （Bn）max decreased gradually with further increase of annealing time, it is emphasized that comparatively high Jr and Hci and （BH）max were obtained in a wide annealing time period of 15 to 360 min. The shape of initial magnetization curves and hysteresis loops change as a function of annealing time, indicating different magnetization reversal routes, which can be fully explained by the corresponding microstructure.

关键词： nanocomposite magnets exchange coupling interaction microstructure magnetization reversal

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Effect of Cu doping and annealing treatment on the microstructure and mag-netic properties of nanocrystalline single-phase Nd-Fe-B alloys

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Journal of University of Science and Technology Beijing 2008年第6期15卷 753-757页

作者： Xiaoqian Bao xuexu gao Maocai Zhang Yi Qiao Xiaoyan Guo Jie Zhu Shouzeng Zhou State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

The effects of Cu addition and annealing treatment on the magnetic properties and microstructure of Ndl2.3Fe81.7-xCuxB6 （x=0-1.2） ribbons melt-spun and annealed were systematically investigated by the methods of vibrating sample magnetometer （VSM）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. Optimum magnetic properties were achieved by annealing melt-spun Nd12.3Fe81.5Cu0.2B6 ribbons at 550℃ for 15 min, which only contained Nd2Fe14B phase. The remanence, coercive force, and maximum energy product increase by 18.4%, 36.2%, and 49% respectively compared with those of Cu-free samples. The sig- nificant improvement in magnetic properties originates from the freer grains of the samples by introducing Cu, which leads to the stronger exchange-coupling between neighboring grains.

关键词： Nd-Fe-B magnets Cu addition annealing treatment microstructure magnetic properties

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Tailoring the mechanical anisotropy of sintered NdFeB magnets by Pr-Cu grain boundary reconstruction

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Journal of Rare Earths 2019年第4期37卷 393-397页

作者： Minghui Tang Xiaoqian Bao Xuejiao Zhang Xing Mu Kechao Lu Jiheng Li xuexu gao State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing School of Metallurgical and Ecological Engineering University of Science and Technology Beijing

Pr_(83)Cu_(17)(wt%) grain boundary reconstruction was applied to prepare sintered NdFeB magnets. The effects of addition amount and annealing on the bending strength were investigated. The results show that Pr_(83)Cu_(17) can not only effectively enhance the bending strength, but also change the mechanical anisotropy in two directions parallel and perpendicular to c-axis. The bending strength perpendicular to c-axis reaches 404 MPa in 10 wt% addition magnet, higher than 348 MPa along parallel direction. This change is attributed to the preferred distribution of boundary phases, i.e., ductile(Nd,Pr)-Fe-Cu phase along perpendicular direction to c-axis and(Nd,Pr)-Fe phase along parallel direction. Moreover, the Cu migration during 480 ℃ annealing is found to be related to this boundary phase distribution.

关键词： Mechanical properties Sintered Nd-Fe-B magnet Pr-Cu alloy Rare earths

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Giant Magnetostrictions of Tb-Dy-Fe Polycrystals with < 110 > Axial Alignment

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Journal of Materials Science & Technology 2000年第2期16卷 175-176页

作者： Shouzeng ZHOU, xuexu gao, Maocai ZHANG, Qing ZHAO and Zhenhlla SHI (State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China) State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

Preparing method and processing of Tb-Dy-Fe alloy samples with [110] axial orientation as well as their magnetostrictive properties have been studied. It has been found that the magnetostrictive strains of polycrystal samples with [110] axial orientation can reach (1550-1900) ×10~-6 in a low magnetic field less than 80 kA/m, which are equal to or somewhat better than that of the polycrystal samples with [112] axial orientation.

关键词： 110 Giant Magnetostrictions of Tb-Dy-Fe Polycrystals with Axial Alignment Fe Dy

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Effect of additive elements on exchange coupling and spin reorientation transition of nanocrystalline single-phase Nd-Fe-B alloy

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Science China(Technological Sciences) 2010年第9期53卷 2323-2327页

作者： BAO XiaoQian,gao xuexu,ZHU Jie & ZHOU ShouZeng State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing,Beijing 100083,China 1. State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

Nd12.3Fe81.7-xZrxB6.0 (x=0,1.5) and (NdDyTb)12.3(FeZrNbCu)81.7-yCoyB6.0 (y=0,12) ribbons were prepared by melt spinning at 22 m/s and subsequent *** influences of Zr,Dy/Tb and Co substitutions on magnetic properties and spin reorientation transitions of nanophase Nd2Fe14B have been systematically *** with Zr-free sample,the remanence,intrinsic coercivity and maximum energy product for Nd12.3Fe80.2Zr1.5B6.0 ribbon increase by 10.8 %,17.8 % and 60.2 %,*** significant improvement of magnetic properties originates from the finer grains of the sample by introducing Zr,which leads to the stronger exchange coupling between neighboring *** intrinsic coercivity for (DyTb)-substituted ribbon is significantly increased although the remanence is reduced,which could be compensated by the substitution of Co for *** spin reorientation temperature Tsr of nanocrystalline Nd2Fe14B alloys was determined by measuring the ac magnetic *** was found to be lower than that of bulk *** substitutions of Zr,Dy/Tb and Co result in reduction of *** smaller the grain size,the lower the Tsr will *** of spin reorientation on magnetization characteristics of nanophase Nd2Fe14B was discussed.

关键词： nanocrystalline Nd-Fe-B magnet exchange coupling spin reorientation transition magnetic properties

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