THE EFFECT STRESS ON THE MAGNETOSTRICTION IN TWIN- FREE SINGLE CRYSTALS Tb_y Dy_(1-y) (Fe_(1-x) T_x)_2 (T=Al,Mn)

Magnetostriction at room temperature under various conditions of compressive prestress and applied fields in Tb yDy 1-y (Fe 1-x T x) 2 (T=Al,Mn) twin-free single crystals were investigated. The substitution of Al or Mn for Fe lowers the magnetostriction un-der ordinary temperature and pressure, but it also decreases the saturation field, which enables these materials with potential benefits for applications.

Fabrication,magnetostriction properties and applications of Tb-Dy-Fe alloys:a review

As an excellent giant-magnetostrictive material, Tb-Dy-Fe alloys(based on Tb0.27-0.30Dy0.73-0.70Fe1.9-2Laves compound) can be applied in many engineering fields, such as sonar transducer systems, sensors, and micro-actuators. However, the cost of the rare earth elements Tb and Dy is too high to be widely applied for the materials. Nowadays, there are two different ways to substitute for these alloying elements. One is to partially replace Tb or Dy by cheaper rare earth elements, such as Pr, Nd, Sm and Ho; and the other is to use non-rare earth elements, such as Co, Al, Mn, Si, Ce, B, Be and C, to substitute Fe to form single MgCu_2-type Laves phase and a certain amount of Re-rich phase, which can reduce the brittleness and improve the corrosion resistance of the alloy. This paper systemically introduces the development, the fabrication methods and the corresponding preferred growth directions of Tb-Dy-Fe alloys. In addition, the effects of alloying elements and heat treatment on magnetostrictive and mechanical properties of Tb-Dy-Fe alloys are also reviewed, respectively. Finally, some possible applications of Tb-Dy-Fe alloys are presented.

MEASUREMENTAL RESEARCH ON THE MAGNETOMECHANICAL COUPLING PROPERTIES OF RARERARTH GIANT MAGNETOSTRICTION MATERIALS

The physical modelanditsequivalentcircuitoftestapparatusissetup by meansofimpedanceanalysis method. The magnetostriction coefficient, magnetomechanicalcoupling coefficient,frequency and anti- frequency of TbxDy1 - xFe2 - z(0 27 ≤x ≤0 3 ,0 ≤z ≤0 1) rod are measured. Somecoupling problems with mechanicalstress and electromagnetic field such as flux leakage in magnetic path are discussed. The comparing calculated with tested resultsshowsthe accuracyof measurementand thesimplification of model.

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.

Magnetostriction of Pseudobinary Compounds Pr_(0.15)Tb_xDy_(0.85-x)Fe_2(x=0 to 0.85)

The compound ingots of Pr0.15TbxDy0.85-xFe2 (x=0 to 0.85) were prepared by arc melting in a water Cu boat using arc furnace under a purified Ar atmosphere. Appropriate annealing (850℃, 100 h) can obtain single Laves phase compound. The magnetostriction for these systems will rise obviously when partially substituted Tb or Dy by Pr.

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

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.

Influence of Tb on easy magnetization direction and magnetostriction of PrFe1.9 alloy

The crystal structures, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase Pr1-xTbxFe1.9 compounds are investigated in a temperature range between 5 K and 300 K. High resolution synchrotron x-ray diffraction(XRD) analysis shows that different proportions of Tb in Pr1-xTbxFe1.9 alloys can result in different easy magnetization directions(EMD) below 70 K, i.e., [100] with x = 0.0, and [111] with x ≥ 0.1. This indicates Tb substitution can lead the EMD to change from [100] to [111] with x rising from 0.0 up to 0.1. The Tb substitution for Pr reduces the saturation magnetization Ms and the magnetostriction to their minimum value when x = 0.6, but it can increase low-field(0 ≤ H ≤9 kOe, the unit 1 Oe = 79.5775 A·m-1) magnetostriction when x = 0.8 and 1.0 at 5 K. This can be attributed to the larger magnetostriction of PrFe1.9 than that of TbFe1.9, as well as the decrease of the resulting anisotropy due to Tb substitution at low temperatures.

Phase Transformation and Magnetostriction of (R-Pr)(Fe-T)_2 (R=Dy Tb; T=Co, Ni)

Structure and magnetostriction of Dy1-Prx Fe2 （0≤x≤0.5）, Dy0.6Pr0.4（Fe1-yTy）2 （0≤y≤0.6）, and Tb1-z Prz（Fe0.4Co0.6）2 （0≤z≤1.0） alloys （T=Co, Ni） have been investigated. It is found that the matrix of the alloys Dy1-xPrxFe2 is a single phase （Dy, Pr）Fe2 with MgCu2-type structure and the second phase is （Dy, Pr）Fe3 when x≤0.2. The amount of （Dy, Pr）Fe3 phase increases with increasing Pr content and becomes the main phase when x=0.4. The matrix of Dy1-x.PrxFe2 is found to be the （Dy, Pr）2Fe17 phase with Th2Zn17-type structure when x=0.5. It is found that the amount of the cubic Laves phase （Dy, Pr）（Fe, Co）2 in the Dy0.6Pr0.4（Fel-Coy）2 increases with increasing Co concentration when 0≤y≤0.6. The substitution of Ni for Fe is nearly not favorable for the formation of the cubic Laves phase （Dy, Pr）（Fe, Ni）2 in （Dy1-xPrx）Fe2. The matrix of （Tb1-z Prz）（Fe0.4Co0.6）2 is a （Tb, Pr）（Fe, Co）2 phase with the MgCu2-type cubic Laves structure and a second phase of small amount is （Tb. Pr）（Fe, Co）3 phase when z≤O.2, z=0.5 and 1.0. When 0.2<z≤0.4, the amount of the （Tb, Pr）（Fe, Co）3 phase with PuNi3-type structure increases with increasing z and becomes the main phase when z=0.4. When 0.5<z≤0.6 the amount of the （Tb, Pr）（Fe, Co）3 phase increases sharply, whereas for 0.6<z≤0.8 it decreases with increasing z. The polycrystalline magnetostriction, λ｜｜ - λ｜. at room temperature of Dyl-xPrxFe2 exhibits a peak when x=0.3. The λ｜｜ - λ｜ for Dy0.6Pr0.4（Fe1-y.My）2 （M=Co, Ni） and Tbl-zPrz（Fe0.4Co0.6）2 is also examined.

Dy substitution effect on the temperature dependences of magnetostriction in Pr_(1-x)Dy_xFe_(1.9) alloys

The temperature dependences of magnetostriction in Pr_(1 x)Dy_xFe_(1.9)(0 ≤ x ≤ 1.0) alloys between 5 K and 300 K were investigated.An unusual decrease of magnetostriction with temperature decreasing was found in Pr-rich alloys(0 ≤x≤ 0.2),due to the change of the easy magnetization direction(EMD).Dy substitution reduces the magnetostriction in high-magnetic field(10 kOe ≤ H≤90 kOe) at 5 K,while a small amount of Dy substitution(x = 0.05) is beneficial to increasing the magnetostriction in low-magnetic field between 10 K and 50 K.This makes the alloys a potential candidate for low temperature applications.

Giant Volume Magnetostriction Caused by Itinerant Electron Metamagnetic Transition and Pronounced Invar Effects in La(Fe_xSi_(1-x))_(13) Compounds

A first-order itinerant electron metamagnetic （IEM） transition above the Curie temperature Tc for ferromagnetic La（FexSi1-x）13 compounds has been confirmed by applying magnetic field. The volume change just above TC for x=0.88 is huge of about 1.5%, which is caused by a large magnetic moment induced by the IEM transition. These compounds have a possibility for practical applications as giant magnetostrictive materials. Pronounced Invar effects bring about a negative thermal expansion below TC, closely correlated with the negative mode-mode coupling among spin fluctuations.

Effect of Mn on the Magnetostriction and Magnetic Properties in Zr_(0.1)Tb_(0.9)(Fe_(1-x)Mn_x)_2 and Y_(0.1)Tb_(0.9)(Fe_(1-x)Mn_x)_2

Effect of Mn substitution for Fe in cubic Laves Zr0.1Tb0.9(Fe1-xMnx)2 and Y0.1Tb0.9(Fe1-xMnx)2 com-pounds is presented.Similar results in both systems are obtained: The structure and the magnetism of TbFe2 areboth influenced slightly by a small amount of Y or Zr substitution for Tb;With increasing x value,the latticeconstant increases monotonously;the Curie temperature decreases linearly;while saturation magnetizationincreases linearly.For the small amount of Mn substitution for Fe in both systems,magnetostriction issignificantly larger than that in the pure iron alloys.The largest magnetostriction of|γ‖-|γ|=2200×10-6at magnetic field of 2×107/4π A/mis obtained for Y0.1Tb0.9(Fe0.95Mn0.052.

EFFECT OF Cr,Cu AND Co ON MAGNETOSTRICTION OF Fe-Si-B AMORPHOUS ALLOYS

The dependence of composition varied,especially C,Si,Cr,Cu and Co in four amorphousalloy systems Fe80-xCrxSi5B15.Fe80-xCrxC5B15.Fe80-xCuxSi5B15and(Fe1-xCox)82Cu0.4Si4.4B13.2upon their saturation magnetostriction at room temperature hasbeen studied.It was observed that the saturation magnetostriction of the alloys may be re-markably improved by small addition of Cu and Co.the peak value being up to 70×10-6asx=0.02 in alloys(Fe1-xCox)82Cu0.4Si4.4B13.2.

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.

Simulation on Magnetostriction Strain of Polymer-bonded Terfenol-D Composites

A model of magnetostrictive strain for polymer-bonded Terfenol-D composite is presented, which is composed of asubmodel for the average strain of Terfenol-D composite and a magnetostriction submodel for Terfenol-D particles.Simulated results show that the saturation magnetostriction λs is very closely with experimental results, althoughthere exists some difference between the calculated and the experimental results under low applied magnetic field.The saturation magnetostriction of the composites increases with the particle fraction (v1=72.5～90 vol. Pct) in thesimulated and experimental results, but the simulation result is not ideal when the particle fraction is higher than 85%.

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.

Preparation and Magnetostriction of Tb_(0.22)Dy_(0.48)Ho_(0.35)Fe_2 Alloys

Tb0.22Dy0.48Ho0.35Fe2 quaternary alloys are prepared by melting-top casting-annealing process. X-ray diffraction reveals that the alloy is single phase polycrystalline alloy with MgCu2 type cubic Laves phase structure, and (511) preferred orientation occurs in its. The magnetostriction measurements are carried out at room temperature using standard strain gauge technique in magnetic fields up to 400 kA·m-1. The results show that when the magnetic field, H, is 90 kA·m-1, the magnetostriction, λ, of Tb0.22Dy0.48Ho0.35Fe2 quaternary alloys is 260×10-6, and when the H is 210 kA·m-1, the λ is 438×10-6. When the H is 400 kA·m-1, the λ is up to the saturation value, 538×10-6. As compared with TbDyFe ternary alloys, the λ of the quaternary alloy is significantly higher when the H is less than or equal to 210 kA·m-1. When the H is 120 kA·m-1, the λ of the alloy is 333×10-6, 70×10-6 more than the ternary alloy. Research results and mechanism are discussed.

Thermal expansion anomaly and spontaneous magnetostriction of Dy_2AlFe_(14)Mn_2 compound

The structure and magnetic properties of Dy2AlFe14Mn2 compound were investigated by X-ray diffractometry and magnetization measurements.Dy2AlFe14Mn2 compound has a hexagonal Th2Ni17-type structure.Zero thermal expansion and negative thermal expansion were found in Dy2AlFe14Mn2 compound in the temperature range from 184 to 264 K,and from 264 to 383 K,respectively,by X-ray dilatometry.The spontaneous magnetostrictive deformations from 104 to 400 K were calculated.The results show that the spontaneous volume magnetostrictive deformation increases firstly with increasing temperature,and then decreases with further increasing temperature.

Structure and Magnetostriction of (Dy_(0.7)Tb_(0.3))_(0.5)Pr_(0.5)Fe_x Alloys (1.10≤x≤1.85)

The structure and magnetostriction of R0.5Pr0.5Fex （R = Dy0.7Tb0.3,1.10 ≤x≤1.85） alloys were investigated. It was found that the matrix of arc-melting R0.5Pr0.5Fex alloys is the （Dy, Tb, Pr） Fe2 phase with the MgCu2-type cubic structure and the second phase is rare earth-rich phase when x<1.25. In the range of 1.40≤x<1.55, the second phase is （Dy, Tb, Pr）Fe3 and it becomes the main phase when x >1.55. The crystalline structure of mechanically grinding R0.5Pr0.5Fex alloys is similar to that of the arc-melted alloys. The magnetostriction of the alloys increases with increasing Fe content when x ≤1.25 and decreases when x >1.25.

Anomalous thermal expansion and spontaneous magnetostriction of Gd_2Fe_(16) Cr compound

The structural and the magnetic properties of Gd 2 Fe 16 Cr compound are investigated by x-ray diffraction and magnetization measurements.The Gd 2 Fe 16 Cr compound has a rhombohedral Th 2 Zn 17-type structure.There exist an anisotropic strong spontaneous magnetostriction and a negative thermal expansion in the magnetic state of Gd 2 Fe 16 Cr compound.The average thermal expansion coefficient ā=-7.03 × 10-6 /K in a temperature range of 294-454 K and ā=-1.31 × 10-5 /K in 454-572 K are obtained.The spontaneous magnetostrictive deformation and the Curie temperature are discussed.

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.