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Magnetostriction of 〈100〉 oriented Fe–Ga rods with large diameter

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Rare Metals 2015年第7期34卷 472-476页

作者： Ji-Heng Li Xue-Xu Gao Xi-Ming xiao xiao-qian bao Mao-Cai Zhang State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

The Fe83Ga17 alloy rods with h100 i preferential orientation was prepared by directional solidification *** dimension of oriented Fe83Ga17 rods is large up to 40 mm greater than diameter in previous investigations of3–10 *** growth direction of columnar grain is nearly parallel to the solidification direction of *** deviation angle between axial direction and h100 i direction of columnar crystal was investigated by method of electron backscattering diffraction, and the deviation is smaller than10°.The large columnar grain and h100 i preferential orientation along axial direction of rods could be attributed to the calm solid–liquid interface during solidification process that is difficultly formed due to electromagnetism agitation in induction heating zone-melting *** corresponding magnetostriction is large up to 290 9 10-6under pre-compressive press of 15 MPa.

关键词： Fe–Ga alloys Directional solidification Crystallog

Enhancement of ductility and improvement of abnormal Goss grain growth of magnetostrictive Fe–Ga rolled alloys

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International Journal of Minerals,Metallurgy and Materials 2018年第4期25卷 444-452页

作者： Ji-heng Li Chao Yuan Xing Mu xiao-qian bao Xue-xu Gao State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

The influences of initial microstructures on the mechanical properties and the recrystallization texture of magnetostrictive 0.1 at% Nb C-doped Fe83 Ga17 alloys were investigated. The directionally solidified columnar-grained structure substantially enhanced the tensile elongation at intermediate temperatures by suppressing fracture along the transverse boundaries. Compared with tensile elongations of 1.0% at 300℃ and 12.0% at 500℃ of the hot-forged equiaxed-grained alloys, the columnar-grained alloys exhibited substantially increased tensile elongations of 21.6% at 300℃ and 46.6% at 500℃. In the slabs for rolling, the introduction of 〈001〉-oriented columnar grains also promotes the secondary recrystallization of Goss grains in the finally annealed sheets, resulting in an improvement of the saturation magnetostriction. For the columnar-grained specimens, the inhomogeneous microstructure and disadvantage in number and size of Goss grains are improved in the primarily annealed sheets, which is beneficial to the abnormal growth of Goss grains during the final annealing process.

关键词： magnetostriction iron-gallium alloys columnar grain ductility abnormal grain growth

Particle interaction during magnetization reversal process of anisotropic Sm_2Fe_(17)N_x powders

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Rare Metals 2018年第10期37卷 875-880页

作者： Ci-Fu Lu Xiu-Feng Hong xiao-qian bao Xue-Xu Gao Jie Zhu State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

The particle interaction during magnetization reversal process is important for the applications and magnetic properties improvement of Sm2Fe17Nx powders. In this paper, an anisotropic Sm2Fe17Nx powder free of α- Fe was prepared by ball milling. The magnetically soft Sm2Fe17 powders with different particle sizes were added into the α-Fe-free SmaFe17Nx powder as easy nucleation sites, and the effects of these magnetically soft phases on the magnetization reversal process were investigated quantitatively. It is found that the squareness of Sm2Fe17Nx powder decreases obviously with the increasing number of Sm2Fe17 particle and the demagnetization curves can be divided into two stages. The magnetization reversal process suggests that the addition of magnetically soft powder should only reduce the coercivity of a specific part of Sm2Fe17Nx particles and the reversed domain walls cannot move easily across neighboring Sm2Fe17Nx particles. Based on the observed magnetization reversal process, the mechanical properties of magnetically soft phase should be considered in the preparation of anisotropic Sm2Fe17Nx powders.

关键词： Rare earth permanent magnets Sm2Fe17Nx Magnetic domain behavior

Texture-based magnetostriction calculation of oriented polycrystalline cobalt ferrites

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Rare Metals 2018年第5期37卷 421-426页

作者： Ji-Quan Wang Ji-Heng Li Chao Yuan xiao-qian bao Xue-Xu Gao State Key Laboratory of Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083China

Oriented polycrystalline cobalt ferrites with different alignments were prepared via a ceramic method. The maximum magnetostriction λs up to -270×10^-6 was achieved for oriented samples, when the oriented magnetic field was above 1.0 T. Textures of all samples were determined by electron back-scattered diffraction （EBSD） technique and were used to calculate magnetostriction values of oriented polycrystalline cobalt ferrite samples. Results show that a preferred 〈001〉 orientation has been obtained within oriented sample. Calculation was done by considering the magnetostriction value as the sum of the content in volume fraction-weighted single-crystal behavior along [100], [110], [210], [310], [311], [211] and [111] directions. The calculated magnetostriction values when compared with experimentally obtained values show identical behavior as a function of applied magnetization orientation field. Good consistency of change rules between calculated values and measured ones illustrates the successful application of this method in predicting magnetostriction values of polycrystalline materials.

关键词： Magnetostriction calculation Oriented polycrystalline Cobalt ferrites Texture

Inhibition force of precipitates for promoting abnormal grain growth in magnetostrictive Fe83Ga17-(B,NbC) alloy sheets

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Rare Metals 2017年第11期36卷 886-893页

作者： Ji-Heng Li Wen-Lan Zhang Chao Yuan xiao-qian bao Xue-Xu Gao State Key Laboratory of Advanced Metals and Materials University of Science and Technology Beijing 100083 China

Inhibition force of precipitate particles for pro- moting abnormal grain growth in magnetostrictive Feg3Ga17-（B,NbC） alloy sheets was investigated in this study. After a continuous heating and a high-temperature annealing, the Fe83Gat7 ＋ 0.5 at% B alloy sheets do not occur significant abnormal grain growth. Correspondingly, textures of { 111 }〈112〉 and { 100}〈00l〉 in addition to the Goss texture are obtained in the final annealed alloy sheets. By contrast, after the same annealing processes, the size of {110} textured grains is very large in the final annealed Fe83Gaj7 ＋ 0.5 at% NbC alloy sheets due to the abnormal grain growth, which results in a sharp Goss texture. BN precipitates were introduced into Fes3Ga17 ＋ 0.2 at% B alloy sheets by nitriding annealing at 800℃ for 2 min under NH3 atmosphere. The abnormal grain growth of Goss grains is achieved in 0.2 at% B-doped Fe83Ga17 alloy sheets after a high-temperature annealing, which is attributed to the enhanced inhibition force by introducing BN precipitates. During the recrystallization annealing process, Fe2B precipitates is easy to coarsen and decom- pose at high temperature due to the low thermal stability, resulting in a decrease or even disappearance of the inhi- bition force. For NbC and BN precipitates, the thermal stability and hardness of particles are both better than those of Fe2B precipitates, leading to strong inhibition force. Because of the preferred Goss texture, the magnetostriction of 2.05 × 10-4 and 1.81 × 10 4 is obtained in the sec- ondary recrystallized Fe83Gal7 ＋ 0.5 at% NbC and Fes3Gaw ＋ 0.2 at% B alloy sheets, respectively.

关键词： Fe-Ga alloy Magnetostriction Grain growth Inhibition force Precipitates

Microstructure and magnetostrictive performance of NbC-doped <100>oriented Fe-Ga alloys

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International Journal of Minerals,Metallurgy and Materials 2015年第1期22卷 52-58页

作者： Chao Yuan Ji-heng Li Wen-lan Zhang xiao-qian bao Xue-xu Gao State Key Laboratory of Advanced Metals and Materials University of Science and Technology Beijing

The〈100〉oriented Fe83Ga17 alloy rods with various NbC contents less than 1at%were prepared by the directional solidification method at a growth rate of 720 mm·h^-1. Low NbC-content was found to affect the oriented grain growth and slightly improve the〈100〉ori-entation. Flat grain boundaries in the alloys with low NbC contents less than 0.2at%became greatly curved at higher NbC contents, and a large amount of Nb-rich precipitates were observed in the alloys with high NbC contents. Small amounts of NbC, less than 0.2at%, resulted in an increase in magnetostrictive strain due to the improvement of the〈100〉orientation, and a high magnetostrictive strain value of 335 ×10^-6 under a pre-stress of 15 MPa was obtained in the 0.1at%NbC-doped alloys. The magnetostrictive performance obviously decreased with the NbC addition higher than 0.5at%, and the strain sensitivity under no pre-stress was lower than that in the binary Fe？Ga alloy.

关键词： iron gallium alloys magnetostriction texture niobium carbide directional solidification

Enhancement of magnetic properties and thermal stability of nanocrystalline (NdDyTb)_(12.3)(FeZrNbCu)_(81.7)B_(6.0) alloy with Co substitution

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International Journal of Minerals,Metallurgy and Materials 2009年第6期16卷 696-700页

作者： xiao-qian bao Wei Li Jie Zhu Xue-xu Gao Shou-zeng Zhou State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China College of Materials Science and Engineering Yanshan University Qirdauangdao 066004 China

The major drawbacks of Nd-Fe-B magnets are relatively low Curie temperature and poor thermal stability. Ribbons with the near stoichiometric 2：14：1 composition of Nd10.8Dy0.75Tb0.75Fe79.7-xCoxZr0.8Nb0.8Cu0.4B6.0 （x=0, 3, 6, 9, 12, 15） were prepared by rapid quenching and subsequent heat treatment. The effect of Co element on the magnetic properties, thermal stability, and microstructure of the ribbons was systematically studied by vibrating sample magnetometer （VSM）, thermal magnetic analysis, atomic force microscopy （AFM）, and transmission electron microscopy （TEM）. It was found that Co substitution was significantly effective in improving the magnetic properties and the thermal stability of nanocrystalline ribbons. Although the intrinsic coercivity decreased from 1308.7 kA/m for x=0 to 817.4 kA/m for x=15, the remanence polarization and maximum energy product increased from 0.839 T and 116.5 kJ/m^3 for the Co-free samples to 1.041 T and 155.1 kJ/m^3 for the 12at% Co-substituted samples, respectively. About 10 K increase in Curie temperature was observed for the 2：14：1 phase with 1at% Co substitution. The absolute values of temperature coefficients of induction and coercivity were significantly decreased with Co substitution, which may be attractive for high operational temperature applications. The microstructure of nanocrystalline ribbons was slightly refined with Co substitution.

关键词： nanocrystalline magnets Nd-Fe-B magnets Co substitution magnetic properties thermal stability microstructure

Magnetostriction and magnetization of <110> oriented Tb0.27Dy0.73Fe1.95 alloys with different compressive prestresses

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Rare Metals 2020年第2期39卷 176-180页

作者： Xing Mu Hai-Jun Tang Xue-Xu Gao xiao-qian bao Ji-Heng Li State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing100083China China Academy of Civil Aviation Science and Technology Beijing100028China

oriented Tb0.27Dy0.73Fe1.95 alloys were studied under different applied compressive *** saturation magnetostriction by 500×10-6 is obtained for the sample under 5 MPa than that under no applied *** understand the effect of prestress on the magnetostrictive coefficient,differential magnetostrictive coefficient,relative permeability and coercive force were studied in *** results show that the maximum differential magnetostrictive coefficient is about 37 x 10-9 m·A-1,about two times that without *** addition,the saturation magnetostriction coefficient increases gradually with the stress increasing,while the maximum differential magnetostrictive coefficient *** saturation inductions under different stresses are similar to a value of about 1.1 *** relative permeability decreases with stress increasing.

关键词： Tb-Dy-Fe Compressive prestress Magnetostriction

Secondary recrystallization of Goss texture in magnetostrictive Fe–Ga-based sheets

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Rare Metals 2020年第11期39卷 1288-1294页

作者： Chao Yuan Xue-Xu Gao Ji-Heng Li xiao-qian bao State Key Laboratory of Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

To avoid the unfavorable effect of precipitates on magnetic properties,low addition of 0.16 wt%NbC was employed in Fe_(82.5)Ga_(17.5)alloy,and 0.27 mm sheets were successfully prepared by a rolling *** Goss texture was obtained in Fe-Ga sheets by two-stage annealing *** sulfur annealing in quartz ampoules was made to produce the preferred growth of Goss texture,with a 51%increase in the observed saturation magnetostriction,from 87×10^(-6)in the Ar-annealed sheets to 132×10^(-6)in the S-annealed ***,large amounts of S-rich and Nb-rich precipitates were formed in the S-annealed ***-temperature annealing of the S-annealed sheets at 1,200℃under a flow hydrogenargon atmosphere could effectively eliminate the precipitates and promote the selective growth of(110)grains due to the low surface *** grains(~2 cm)of secondary recrystallization were achieved in the final annealed sheets,with the maximum average saturation magnetostriction of 180×10^(-6).

关键词： Fe–Ga alloy Goss texture Magnetostriction Secondary recrystallization