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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

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)analyses.The rodlike NdH_(2+x) phases with diameters of 10-20 nm are embedded intoα-Fe matrix,which hereditarily leads to textured grains in HDDR alloy.The 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 motion.The weak c-axis orientation of HDDR alloy results in a lower reverse magnetic field(coercivity)to reduce remanence to 0.Moreover,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 grains.The 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

Effect of Doping of Ti and C on Crystallization and Magnetic Properties of NdPrFeB Thick Melt-Spun Ribbons

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稀有金属材料与工程 2012年第2期41卷 212-214页

作者： Peng Haijun[a] Zhang Maocai[b] bao xiaoqian[b] [a] National Engineering Research Center for Rare Earth Materials General Research Institute for Nonferrous Metals Beijing 100088 China [b] State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

结晶化过程和 NdPrFeB 厚带子的磁性上的 Ti 和 C 增加的效果被调查。结果证明 Ti 做压制形成(Nd， Pr ) 2Fe23B3 亚稳的阶段并且显著地精制合金和增加 coercivity 的谷物。在 Ti 和 C 的合作增加的情况中， coercivity 被减少，但是顽... 详细信息

结晶化过程和 NdPrFeB 厚带子的磁性上的 Ti 和 C 增加的效果被调查。结果证明 Ti 做压制形成(Nd， Pr ) 2Fe23B3 亚稳的阶段并且显著地精制合金和增加 coercivity 的谷物。在 Ti 和 C 的合作增加的情况中， coercivity 被减少，但是顽磁与 C 内容增加被提高。Jr=0.88 T 的磁性， Hcj=618 kA/m 并且(BH ) max=109.8 kJ/m3 被完成在(Nd0.4Pr0.6 ) 在最佳的退火以后的 9Fe72Ti4B11C4 带子。

关键词：稀有金属材料金属材料工程 TA2M

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 magnet.The coercivity increases from 12.3 kOe for the sample free of Pr80Al20 to16.8 kOe for the sample with 2 wt%Pr80Al20.By further increasing the Pr80Al20 content to 3 wt%,the coercivity increases slightly,but the remanence and Hk/Hcj deteriorate obviously.The 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 grains.The coercivities of the samples from the GAPP that use2 wt%Pr80Al20,Pr70Al30 and Pr60Tb20Al20 alloys,respectively,can be enhanced to a large extent.However,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 alloy.Moreover,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

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

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

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

New steelmaking process based on clean deoxidation technology

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International Journal of Minerals,Metallurgy and Materials 2024年第6期31卷 1249-1262页

作者： Zhongliang Wang Yanping bao State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China

After the converter steelmaking process,a considerable number of ferroalloys are needed to remove dissolved oxygen from the molten steel,but it also forms a lot of oxide inclusions that cannot be completely removed.At the same time,it increases the carbon emis-sions in the steel production process.After years of research,our team have developed a series of clean deoxidation technologies,includ-ing carbon deoxidation,hydrogen deoxidation,and waste plastic deoxidation of molten steel to address the aforementioned issues.In this study,thermodynamic calculations and laboratory experiments were employed to verify that carbon and hydrogen can reduce the total oxygen content in the molten steel melt to below 5×10^(-6) and 10×10^(-6),respectively.An analysis of the deoxidation mechanisms and ef-fects of polyethylene and polypropylene was also conducted.In addition,the applications of carbon deoxidation technology in different steels with the hot-state experiment and industrial production were discussed carefully.The carbon deoxidation experimental results of different steels were as follows:(1)the oxygen content of bearing steel was effectively controlled at 6.3×10^(-6) and the inclusion number density was lowered by 74.73%compared to aluminum deoxidized bearing steel;(2)the oxygen content in gear steel was reduced to 7.7×10^(-6) and a 54.49%reduction of inclusion number density was achieved with almost no inclusions larger than 5μm from the average level of industry gear steels;(3)a total oxygen content of M2 high-speed steel was as low as 3.7×10^(-6).In industrial production practice,car-bon deoxidation technique was applied in the final deoxidation stage for non-aluminum deoxidized bearing steel,and it yielded excellent results that the oxygen content was reduced to below 8×10^(-6) and the oxide inclusions in the steel mainly consist of silicates,along with small amounts of spinel and calcium aluminate.

关键词： clean deoxidation carbon deoxidation hydrogen deoxidation waste plastics deoxidation

Development and prospects of molten steel deoxidation in steelmaking process

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International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 18-32页

作者： Zhongliang Wang Yanping bao State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China

In the long traditional process of steelmaking,excess oxygen is blown into the converter,and alloying elements are used for deoxidation.This inevitably results in excessive deoxidation of products remaining within the steel liquid,affecting the cleanliness of the steel.With the increasing requirements for steel performance,reducing the oxygen content in the steel liquid and ensuring its high cleanliness is necessary.After more than a hundred years of development,the total oxygen content in steel has been reduced from approximately 100×10^(-6)to approximately 10×10^(-6),and it can be controlled below 5×10^(-6)in some steel grades.A relatively stable and mature deoxidation technology has been formed,but further reducing the oxygen content in steel is no longer significant for improving steel quality.Our research team developed a deoxidation technology for bearing steel by optimizing the entire conventional process.The technology combines silicon–manganese predeoxidation,ladle furnace diffusion deoxidation,and vacuum final deoxidation.We successfully conducted industrial experiments and produced interstitial-free steel with natural decarbonization predeoxidation.Non-aluminum deoxidation was found to control the oxygen content in bearing steel to between 4×10^(-6) and 8×10^(-6),altering the type of inclusions,eliminating large particle Ds-type inclusions,improving the flowability of the steel liquid,and deriving a higher fatigue life.The natural decarbonization predeoxidation of interstitial-free steel reduced aluminum consumption and production costs and significantly improved the quality of cast billets.

关键词： steel deoxidation deoxidizer metallurgical equipment bearing steel IF steel

Adaptation of Ocular Opponency Neurons Mediates Attention-Induced Ocular Dominance Plasticity

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Neuroscience Bulletin 2024年第3期40卷 339-349页

作者： Fangxing Song Lili Lyu Min bao CAS Key Laboratory of Behavioral Science Institute of PsychologyChinese Academy of SciencesBeijing100101China Department of Psychology University of Chinese Academy of SciencesBeijing100049China Institute of Neuroscience Key Laboratory of Primate NeurobiologyCAS Center for Excellence in Brain Science and Intelligence TechnologyChinese Academy of SciencesShanghai200031China

Previous research has shown that ocular dominance can be biased by prolonged attention to one eye.The ocular-opponency-neuron model of binocular rivalry has been proposed as a candidate account for this phenomenon.Yet direct neural evidence is still lacking.By manipulating the contrast of dichoptic testing gratings,here we measured the steady-state visually evoked potentials(SSVEPs)at the intermodulation frequencies to selectively track the activities of ocular-opponency-neurons before and after the“dichoptic-backward-movie”adaptation.One hour of adaptation caused a shift of perceptual and neural ocular dominance towards the unattended eye.More importantly,we found a decrease in the intermodulation SSVEP response after adaptation,which was significantly greater when high-contrast gratings were presented to the attended eye than when they were presented to the unattended eye.These results strongly support the view that the adaptation of ocular-opponency-neurons contributes to the ocular dominance plasticity induced by prolonged eye-based attention.

关键词： Attention Ocular dominance Opponency neuron Adaptation Steady-state visually evoked potential