Structure and magnetostriction of Tb_(0.4)Nd_(0.6)(Fe_(0.8)Co_(0.2))_(1.90) alloy prepared by solid-state synthesis

Mechanical alloying (MA) and subsequent solid sintering process was used to prepare the Nd-containing magnetostrictive Tb0.4Nd0.6(Fe0.8Co0.2)1.90 alloy. The structure, thermal stability and phase transformation were investigated as functions of composition, milling process and annealing temperature. An amorphous phase was formed by high-energy ball milling for 5 h with the ball-to-powder weight ratio of 20:1, which crystallized into MgCu2-type and PuNi3-type crystalline structure with different annealing temperatures. The magnetoelastic properties were investigated by means of a standard strain technique. The high Nd-content (Tb,Nd)(Fe,Co)2 Laves phase for the composition Tb0.4Nd0.6(Fe0.8Co0.2)1.90 was synthesized by MA process plus annealing at 500 ℃ for 30 min.

Relationship between crystal growth mode, preferred orientation and magnetostriction of (Tb_(0.3)Dy_(0.7))Fe_(1.95) alloys

The relationship between crystal growth mode, preferred orientation and magnetostrictive properties of （Tb0.3Dy0.7）Fe1.95 alloys was investigated at different directional solidification rates. The results showed that preferred orientation had a strong influence on the characteristics of （Tb0.3Dy0.7）Fe1.95 alloys. At lower solidification rates, the sample with 〈110〉 preferred orientation showed larger low-field magnetostriction and apparent compressive stress effect. The excessive solidification rate resulted in failure of preferred orientation and a poor magnetostrictive performance. With an increase in solidification rates, the crystal growth modes changed gradually from cellular and primary dendrite morphology to developed dendritic morphology. In addition, domain configurations were observed using magnetic force microscopy, and the change of magnetostrictive properties was interpreted in terms of revealing the domain configurations.

THE SYNTHESIS AND MAGNETOSTRICTION OF P_ (rx) Ce_(1-x) Fe_2 COMPOUNDS

The synthesis and magnetic properties of Pr xCe 1 x Fe 2 have been investigated. The forma tion of Pr xCe 1 x Fe 2 is found to depend strongly on annealing temperature. Pure single phase compound can be synthesized at ambient pressure when x≤0 5. The main phase of the Laves structure can still be observed up to x=0 8. Magnetostriction increases with in creasing x and a largest saturation magnetostriction 200 ppm is observed for x=0.5.

Influence of Magnetic Heat Treatment and Compressive Stress on Jump Effect of Magnetostriction of Tb_(0.3)Dy_(0.7)Fe_(1.95) Alloy

The 〈 110 〉 -oriented TTb0.3Dy0.7Fe1.95 polycrystalline alloy was magnetically annealed, and its influence on jump effect of magnetostriction was investigated. In the vacuum superconductive high magnetic field equipment, 〈 110 〉 -oriented Tb0.3Dy0.7Fe1.95 polycrystalline alloy of the directional solidification was annealed at 623 and 723 K for 5 min under the magnetic field vertical to specimen axis. It is found that magnetic annealing can enhance the jump effect under compressive stress, and increase the saturated magnetostriction coefficient λs, the λs of the magnetic annealing specimens at 623 K under 8.1 MPa is attained to 1950 × 10^-6, Magnetic annealing increases the maximum of dynamic magnetostriction coefficient, d33^max, as well as the magnetic field for d33^max under 8.1 MPa.

Effect of Ho-doping on microstructure and magnetostriction of TbDyFe alloys

Tb0.3Dy0.7HoxFe1.95（x=0.00, 0.05, 0.10, 0.15, 0.20, 0.35, 0.50, 0.65） quaternary alloys were prepared by arc-melting and followed by annealing.The phases present and structure of the alloys were determined using a D8-Advance X-ray diffractometer.The magnetostriction of the alloys was studied by standard strain gauge technique.The dependence of Ho content on the structure, magnetostriction and density of the alloys was investigated in detail.The research results showed that Ho-doping did not change MgCu2-type cubic Laves structure in Tb0.3Dy0.7Fe1.95.When Ho content x≤0.2, rich rare earth phase presented in the alloys increased and magnetostriction of the alloys reduced evidently with increasing x, but for alloys with x〉0.2, the content of rich rare earth phase started to reduce and the magnetostriction increased quickly, especially at low magnetic field in the alloy with x=0.65 due to separation of rich rare earth phases on the surface of the alloy.

Structure, Magnetic Properties and Magnetostriction of Pr_xTb_(1-x)(Fe_(0.6)Co_(0.4))_(1.9) Alloys

The structure, magnetic properties and magnetostriction of PrxTb1-x(Fe0.6Co0.4)1.9 alloys were investigated. It was found that PrxTb1-x(Fe0.6Co0.4)1.9 alloys with x<0.4 were composed of single cubic Laves phase, while a mass of PuNi3-type phase appeared when the Pr concentration was higher than 0.4. The magnetization measurement showed that there were two different magnetic phases in Pr0.2Tb0.8(Fe0.6Co0.4)1.9 alloys. The saturation magnetostriction of Pr0.2Tb0.8(Fe0.6Co0.4)1.9 alloys at 900 kA·m-1 is 1765×10-6, which was higher than that of Tb0.27Dy0.73Fe2(1600×10-6). The spontaneous magnetostriction λ111 showed a maximum value at x=0.3.

Magnetostriction and Acoustics Properties of Tb_(1-x)Dy_x (Fe_(1-y)Mn_y)_(1.95) Alloys and Their Application to Sonar Transducers

The magnetostriction and acoustics properties of Tb1-x xDyx (Fe1-yMny) 1.95 alloys and their application to sonar transducers were studied. The following results were obtained from experiments. When the applied magnetic field intensity is ≥ 800 kA·m-1, the magnetostrictive coefficients are (1300- 1800)× 10-6. The electromechanical coupling factors are 0.84-0.93, the sound velocities 2168-2856 m·s-1 and the Young's modulus (5.06- 7.26) ×10 N·m-2. A sonar transducer made of the alloy rod, which has a total length of 300 mm and a total weight of 2 kg, is characterized by 2.4 kHz specified resonant frequency, 1 kHz frequency band, 173 kB current response and 45% electroacoustic efficiency.

Structure,magnetization, and magnetostriction of Sm-R-Fe (R=Pr,Nd) thin films

The structure, magnetization, and magnetostriction of Sm0.9Pr0.1Fex and Sm1-xNdxFel.9 thin films have been investigated using X-ray diffraction, vibrating sample magnetometer, and optical cantilever method. It is found that the structure of Sm0.9Pr0.1Fex thin films consists of an Sm-Pr-Fe amorphous phase when x≤2.69 and that of Sm1-xNdxFel.9 thin films consists of an Sm-Nd-Fe amorphous phase. The in-plane magnetization of Sm0.91Pr0.1Fex thin films increases with increase in the Fe content, and low values of the in-plane coercivity occur in the range of 1.62≤ x≤ 2.28. The magnetostriction value of Sm0.91Pr0.1Fex thin films increases with increasing the Fe content when x ≤ 1.94 and decreases when x 〉 1.94. The in-plane magnetostriction of Sm1-xNdxFe1.9 thin films under low magnetic fields has been improved by the substitution of Nd for Sm when x = 0.2.

Magnetic properties and magnetostriction of PrxNd_(1-x)Fe_(1.9)(0≤x≤1.0) alloys at low temperature

The crystal structure,magnetic and magnetostrictive properties of high-pressure synthesized Prx Nd1-xFe1.9（0≤x≤1.0） alloys were studied.The alloys exhibit single cubic Laves phase with MgCu 2-type structure.The initial magnetization curve reveals that Pr0.2Nd0.8Fe1.9 has a minimum magnetocrystalline anisotropy at 5 K.The magnetostriction curve at 5 K shows that Pr0.2Nd0.8Fe1.9 has a very good low-field magnetostrictive property,and the magnetostriction of the PrxNd1-xFe1.9 alloy in high magnetic field is attributable mainly to Pr.The temperature dependence of the magnetostriction（λ ｜｜） at the field of 5 kOe shows that the substitution of Nd reduces the K 1 remarkably,and the values of λ｜｜ of Pr0.2Nd0.8Fe1.9 and Pr0.8Nd0.2Fe1.9 alloys are nearly five times larger than that of the PrFe 1.9 alloy below 50 K;the λ｜｜ of Pr0.8Nd0.2Fe1.9 reaches up to 1082 ppm at 100 K,which makes it a potential candidate for application in this temperature range.

Large magnetostriction of Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites in a wide temperature range

We report the magnetostrictive performance of the Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites.Measurement of M?ssbauer spectra and the XRD results indicate that the easy magnetic direction of the Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)compound is along<111>direction with spontaneous magnetostrictionλ111 of1900 ppm.The<111>-oriented Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites with particle volume fractions of20 vol%-55 vol%were prepared.Magnetization measurements demonstrate that the composite is highly anisotropic.The raw material cost of Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)is about 85%of that of the Terfenol-D(Tb_(0.3)Dy_(0.7)Fe_(2))composition.Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composites possess comparable magnetostriction with those composites made of Tb_(0.3)Dy_(0.7)Fe_(2)particles.At room temperature,the magnetostrictionλ_Ⅱof the Nd_(0.2)Tb_(0.3)Dy_(0.5)Fe_(1.93)/epoxy composite reaches 420 ppm at a low field of 80 kA/m and about1000 ppm at 239 kA/m.In addition,the composite exhibits a large saturation magnetostrictionλ_Ⅱover1200 ppm from 300 to 100 K,suggesting its potential applications as a low-cost magnetostrictive material in a wide temperature range.Therefore,the current study offers an opportunity to widen the operating temperature range of the magnetostrictive composite.

X-ray diffraction analysis by Rietveld refinement of FeAl alloys doped with terbium and its correlation with magnetostriction

Fe_(81)Al_(19) polycrystalline alloys doped with Tb(0-0.25 at%) were obtained by arc melting.The introduction of Tb favors the formation of columnar grains in the micro structure of the alloys,which develops a texture in the [100]crystal direction.Microstructural examination shows that the alloys are composed in great proportion by the disordered body-centered cubic(bcc),A2 phase and by a small proportion of the ordered bcc,B2 phase.As a consequence of doping with Tb,the lattice parameter increases,so the calculated apparent crystallite size increases,indicating a decrease in dislocation density and therefore in microstrains.The change in the magnetostriction with the magnetic field,dλ_(T)/dH,is directly related to strain anisotropy that can favor the iron easy magnetization axis on the [100] direction.An increase in total magnetostriction is found in the doped alloys with a maximum of 90 × 10^(-6) at 300 K for the alloy containing 0.027 at% Tb.This enhancement is a threefold value of the undoped alloy,which is attributed to the smaller maximum strain value and the preferential orientation formation by the columnar grains.

Research on microstructure and magnetostriction of Fe_(83)Ga_(17)Dy_x alloys

The crystal structure,microstructure and the magnetostriction of Fe83Ga17Dyx(x=0,0.2,0.4,0.6) series alloys were studied.The results showed that the influence of the Dy on the crystal structure of the alloy was very small but the effect on the microstructure was significant when different contents of Dy were added into the Fe83Ga17 alloy,respectively.Meanwhile,the magnetostriction of Fe83Ga17Dy0.2 alloy was greatly enhanced,the magnetostriction λ value reached 300×10-6 at 400(kA/m) magnetic field.

Effect of copper on magnetostriction and mechanical properties of TbDyFe alloys

The intrinsic brittleness of the TbDyFe alloy significantly decreases its mach inability and applications.This paper aims to improve the toughness of TbDyFe alloy by adding Cu. Various alloys of the type(Tb_(0.3)Dy_(0.7))_(0.37)Fe_(0.63-χ)Cu_χ(χ=0, 0,01.0.03, 0.05, 0.08, 0.1) were fabricated by an arc melting furnace under a high purity argon atmosphere. The microstructure, magnetostrictive properties and mechanical performance were studied systematically. The results show that the (Tb,Dy)Cu phase forms in these alloys upon the addition of Cu. Correspondingly, their toughness improves, attributed to the formation of a (Tb,Dy)Cu phase. Compared to the Cu-free alloy, the fracture toughness (Kic) increases 2-3 times with increasing Cu content. However, the magnetostriction performance of these alloys declines with Cu addition, due to the low-magnetic performance of the (Tb,Dy)Cu phase at room temperature. Compared with other alloys, the alloy with the addition of 1at%Cu shows the best compromise between the saturation magnetostriction and fracture toughness.

Structure and magnetostriction of high Pr/Ce-content(Tb_(0.2)Pr_(0.8))_(1-x)Ce_(x)Fe_(1.93) Laves compounds

The light rare earth Pr/Ce-contained(Tb_(0.2)Pr_(0.8))_(1–x)Ce_(x)Fe_(1.93)(0≤x≤1.0)intermetallics were arc melted and magnetoelastic properties were investigated.The compounds of x≥0.40 are found to stabilize at ambient pressure in a single Laves phase with MgCu2-type C15 structure,which is attributed to the strong Ce 4f bonding.The mixed-valence behavior,with a support of the deviation from the linear Vegard’s law for both lattice parameter a and saturation magnetization M_(S),is observed at room temperature.The easy magnetization direction(EMD)was determined by the analysis of XRD on both magnetically aligned samples and the(440)splitting,that is,EMD lies toward<111>axis for x≤0.50 rotating to<110>for x=0.60,accompanied with the structural distortion from rhombohedral to orthorhombic.The substitution of Ce for Tb/Pr is conductive to the reduction of magnetocrystalline anisotropy,giving rise to an improvement of the low-field magnetostriction.The excellent magnetoelastic properties can be tailored by the Ce introduction,e.g.,the spontaneous magnetostriction coefficient λ_(111) as large as 1150×10^(−6) for x=0.40,and the low-field induced magnetostriction achieving a high value of λ_(a)=180×10^(−6) at 80 kA/m for x=0.60.The excellent magnetoelastic properties and the combination in high Pr-content with low cost,suggest promising prospects in applications.

Magnetostriction,composition and microstructure of Tb_(0.29)(Dy(1-x)Pr_x)_(0.71)Fe_(1.97) alloys with heat treatment

Tb0.29（Dy1–xPrx）0.71Fe1.97 （x=0, 0.1, 0.2 and 0.3） alloys prepared by the directional solidification method were treated at 1073, 1123, 1173, 1223 and 1273 K for 4 h for homogenization, respectively. The magnetostriction, micro-morphology and composition distribution were studied by the standard resistance strain gauge technique, optical microscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy （SEM-EDS）. The results indicated that heat treatment could make the microstructure of alloys homogeneous effectively and improve the magnetostriction significantly. The optimum temperature was 1223 K. Compared to the as-cast ones, the increase amplitudes of magnetostriction of the corresponding samples were 39.5%, 64.9%, 95.3% and 50.8% when x=0, 0.1, 0.2 and 0.3, respectively at the compressive stress of 2 MPa and a magnetic field of 80 kA/m. The compressive stress could also improve the magnetostriction. However, further Pr element addition and over high heat treatment temperature would lead to the excessive decomposition of PrFe2 and destroy the homogeneity, resulting in the decline of magnetostriction of alloys.

Magnetostriction and hysteresis of <110> oriented TbDyHoFe_(1.95) alloy

(Tb0.36Dy0.64)1-xHoxFe1.95 magnetostrictive alloys with 【110】 orientation were prepared by zone melting directionally solidified method.The magnetostrictive performance and hysteresis of 【110】 aligned polycrystalline(Tb0.36Dy0 64)1-xHoxFe1.95 were investigated under applied magnetic field H(0【H【4 kOe) in the temperature range from-60 to 80 oC with 0,5 and 10 MPa pre-stress.The(Tb0.36Dy0.64)1-x HoxFe1.95 alloys(x【0.3) have the character of giant magnetostriction from-60 to 80 oC.An obvious magnetostrictive "jump" effect was observed in these samples from-60 to 80 oC.The pre-stress and temperature dependence of the Wh was also examined.Between the temperature range from-60 to 80 oC,the magnetostriction increased with temperature decreased,while the magnetostriction hysteresis decreased,with the pre-stress increased,but the magnetostriction and the magnetostrictive hysteresis increased.

Thermal expansion anomaly and spontaneous magnetostriction of Gd_2Fe_(17) compound

Materials with negative thermal expansion have many practical applications. However, these materials are known in only several oxide systems, and when the negative thermal expansion occurs, the contraction is usually small and limited to a narrow temperature range beyond room temperature. For obtaining a compound with negative thermal expansion in broad temperature range, the structural and magnetic properties of Gd2Fe17 compound were investigated by means of X-ray diffraction and magnetization measurements. The Gd2Fe17 compound annealed at 1050 oC had a Th2Zn17-type structure. There existed an anisotropic strong spontaneous magnetostriction and a negative thermal expansion in Gd2Fe17 compound. The average thermal expansion coefficients was =–7.40×10–6/K in the temperature range of 294–453 K and =–1.80×10–5/K in 453–534 K, respectively. The spontaneous magnetostrictive deformation ωS decreased from 4.34×10–3 to near zero with temperature increasing from 294 to 572 K. The spontaneous linear deformation λc was much larger than λa at the same temperature below about 500 K.

Effect of cerium on structure,magnetism and magnetostriction of Fe_(81)Ga_(19) alloy

FeGa alloy is a new kind of magnetostrictive material, and rare-earth cerium can improve its magnetostrictive property.（Fe（81）Ga（19））（100-x）Cex（x = 0, 0.3 at%, 0.7 at%, 1 at%） samples were prepared by doping cerium in Fe（81）Ga（19） alloy. Their microstructures and phases were studied, and valence electronic structures were investigated. Electromagnetic parameters, such as coercivity, saturation magnetization,remnant magnetization and saturation magnetostrictive coefficients（λs） of every sample were measured.Cerium atoms are distributed at grain boundaries, and the Ce-doped alloys remain the A2 structure of FeGa alloy. When x is 0.7, the value of saturation magnetism is 217.08 emu/g, which is the maximum in the Ce-doped samples. The equivalent half length of single bond is the maximum also, and reaches to0.11380 nm. At the same time, the number of covalent electrons is 3.5672, and is the minimum of the Cedoped samples. Its As is the largest in the four samples. The change of As results in the change of equivalent half length of single bond in Ce-doped alloy.

基于Matlab的超磁致伸缩骨传导振子设计平台研发

针对声学领域中利用稀土超磁致伸缩材料(GMM)设计的微型骨传导振子结构设计计算复杂的问题,提出设计一款稀土超磁致伸缩骨传导振子的结构设计平台。在稀土超磁致伸缩换能器设计理论的基础上,利用Matlab强大的数据处理能力和GUI图形用户界面功能搭建了骨传导振子的设计平台。该平台可以对骨传导振子内部的GMM棒、激励线圈、预压力机构等部件进行设计计算,还可对骨传导振子的性能指标进行检验。该平台操作简单,可根据设计要求进行改变参数,有效地提高了设计效率。

Dynamic parameters of Tb-Dy-Fe giant magnetostrictive alloy

Tb0.3Dy0.7Fe1.90 <110> oriented rods were prepared by zone melting with unidirectional solidification.The magnetomechanical coupling factor(k33) was measured by magnetomechanical resonance under different DC bias fields up to 77.4 mT.An effective method was provided to calculate sonic velocity,elastic modulus and compliance constant through measuring resonate frequency(fr),and calculate dynamic magnetostriction(d33) via measuring magnetic permeability,magnetomechanical coupling factor(k33) and complia...