Iron-gallium Alloys Research Articles

Characterization and energy-based model of the magnetomechanical behavior ofpolycrystalline iron–gallium alloys

The actuation and sensing behavior of a typical polycrystallineFe81.6Ga18.4 alloy sample grown using free stand zone melt (FSZM) manufacturing processes wascharacterized and its cross-section texture was determined at three transverse stationsusing electron back-scattering diffraction (EBSD). An attempt was made to model theactuation and sensing behavior of the polycrystalline magnetostrictive sample from itscross-section texture by treating the polycrystal as composed of multiple grains of singlecrystals, each with a different orientation to the loading axis. The polycrystallinemagnetomechanical behavior was modeled as the sum of the volume fraction weightedsingle-crystal behavior along the [100], [110], [210], [310], [111], [211] and [311] directions,which are modeled using the energy-based approach discussed in Armstrong (1997 J. Appl.Phys. 81 2321) and Atulasimha (2006 PhD Thesis Aerospace Engineering, University ofMaryland).

Corrosion studies of single crystals of iron–gallium alloys in aqueous environments

Iron–gallium (Fe–Ga) alloys have attracted lot of attention for use in sensor and actuator applications due to an excellent combination of large low-field magnetostriction, high mechanical strength, good ductility and low cost. This paper reports the very first measurement of the corrosion behavior of single crystals of Fe–Ga alloys. The corrosion behaviors of single crystals of Fe–15 at.% Ga, Fe–20 at.% Ga and Fe–27.5 at.% Ga alloys were studied in acidic (0.1 M HCl), basic (0.1 M NaOH) and simulated seawater (3.5 wt.% NaCl) environments. Dependence of corrosion rates on the crystal orientation is also examined. The polarization resistance technique was used for measuring the corrosion potentials and corrosion rates. The corrosion rate of single crystals of Fe–Ga alloys in 0.1 M HCl aqueous solution is higher than that in 3.5 wt.% NaCl aqueous solutions. The corrosion rate of single crystals of Fe–Ga alloys is least in 0.1 M NaOH aqueous solutions.

Magnetic Circuit for Stress-Based Magnetic Force Control Using Iron-Gallium Alloy

We propose a stress-based magnetic force control method using the inverse magnetostrictive effect. A basic magnetic circuit consists of iron yokes, permanent magnets, and magnetostrictive material by which compressive stress applied to the material is converted to variations in the magnetic force. The characteristics of the force, such as bias, variation and sensitivity, depend on the inverse magnetostrictive properties of the material. In this paper we investigate the suitability of Galfenol, iron-gallium alloy, which has large permeability and high saturation. Measurements of the relations between stress and strain, flux density, and magnetic force in series and parallel magnetic circuit with a rod of Galfenol or Terfenol-D under compression show the advantages of Galfenol and clarify the design criteria for the magnetic circuit in future applications

Magnetomechanical performance of directionally solidified Fe–Ga alloys

Iron-gallium alloys can produce magnetostrictions of ∼400ppm and might serve as mechanically robust actuator/sensing materials. However, for polycrystalline Fe–Ga alloys, the magnetostrictive performance decreases with the increasing deviations from the ideal ⟨100⟩ texture. In this paper, three directionally solidified Fe–Ga alloys with gallium contents of 17, 18.4, and 19.5at.% were characterized at ambient temperature. These specimens exhibit high d33 and magnetic permeability when subjected to applied magnetic fields, indicating their suitability for light weight actuator applications but not for high force applications due to their low saturation magnetostriction and hence low blocking force. All the alloys produce significant changes in magnetization, around 0.7Ms–0.8Ms when subjected to cyclic compressive stresses of 51MPa, making them promising candidate materials for sensing and energy harvesting applications. However, eddy current effects may easily become a problem when such materials are subjected to a high frequency vibration or magnetic field due to their intrinsic high magnetic permeability.

Magnetostriction of ternary Fe–Ga–X (X=C,V,Cr,Mn,Co,Rh) alloys

Binary iron-gallium (Galfenol) alloys have large magnetostrictions over a wide temperature range. Single crystal measurements show that additions of 2at.% or greater of 3d and 4d transition elements with fewer (V, Cr, Mo, Mn) and more (Co, Ni, Rh) valence electrons than Fe, all reduce the saturation magnetostriction. Kawamiya and Adachi [J. Magn. Magn. Mater. 31–34, 145 (1983)] reported that the D03 structure is stabilized by 3d transition elements with electron∕atom ratios both less than iron and greater than iron. If D03 ordering decreases the magnetostriction, the maximum magnetostriction should be largest for the (more disordered) binary Fe–Ga alloys as observed. Notably, addition of small amounts of C (0.07, 0.08, and 0.14at.%) increases the magnetostriction of the slow cooled binary alloy to values comparable to the rapidly quenched alloy. We assume that small atom (C, B, N) additions enter interstitially and inhibit ordering, thus maximizing the magnetostriction without quenching.

Machining of iron–gallium alloy for microactuator

We study the micromachining of iron–gallium alloy for use in a microactuator. Iron–gallium (Galfenol) is an iron-based magnetostrictive material with magnetostriction exceeding 200 ppm, Young's modulus of 70 GPa, and distinctive ductile and machinable properties. An actuator made by small Galfenol component therefore should be simple, robust against external forces and drivable at low voltage. A rod of Galfenol (Fe 81.6Ga 18.4) prepared by the free stand zone melting technique was machined to create pillars of l mm 2 by an ultra precision cutting technique to study the suitability of Galfenol in micro components. Comparison of strain gage measurements for the pillars and non-machined specimens verifies the magnetostriction, with variation arising from the grain distribution that is not significantly dispelled by the milling process. Measurement of displacements by a Laser Doppler vibrometer supports our results and discussion. The successful fabrication of pillars of 0.7 and 0.5 mm 2 and length 5 mm shows the forgiveness of the material under high-speed cutting, and its potential in miniaturization.

Ｆｅ‐Ｇａ合金（Ｇａｌｆｅｎｏｌ）を用いたマイクロ磁歪振動子

Micro magnetostrictive vibrator using Iron-Gallium alloy (Galfenol) was investigated. Galfenol is an iron-based magnetostrictive material with the magnetostriction more than 200 ppm, high permeability μr > 100 and Young's modulus of 70 GPa. The material is machinable to free of the shape by conventional cutting process, and sustainable for tensile, bending, and impact. Micro actuator using Galfenol equipped with iron yoke and winding coil, therefore, has advantages over PZT type, in simple, low voltage driving, high robustness and wide temperature operation range. This paper describes the performance of a micro vibrator improved to our previous prototype, in configuration, material, and fabrication process. The vibrator using stress-annealed Galfenol machined to the rod of 1mm diameter was observed the displacement of 1.2μm, high bandwidth of 30 kHz and high tensile robustnesswithstanding suspended weight of 500g. The vibrator was also verified useful as speaker which can generate clearsound from the power of a portable music player.

Ｆｅ‐Ｇａ合金（Ｇａｌｆｅｎｏｌ）と非磁性材料の積層型ユニモルフアクチュエータ

We investigate a bending actuator based on unimorph, lamination of Galfenol (Iron-gallium alloy) and non-magnetic material. The Galfenol U-shape yoke bonded with stainless plates (lamination) is wound coils, and iscomposed close magnetic loop with connected an iron plate. The magnetostriction in longitude direction is constrained by the stainless, thus, the lamination yields bending deformation with the current induced. The advantage of the actuator is simple, compact and ease of assembling including winding coil, and high tolerance against bending, tensileand impact. We machined the yoke from a plate of 1mm thickness of Galfenol of Research grade using ultra highprecision cutting technique. The prototype with lamination thickness of 1mm was observed the displacement 13 μm and 1st resonance 1.6 kHz, and the high bending (tensile) tolerance withstanding suspended weight of 500g.

Sensing Behavior of Varied Stoichiometry Single Crystal Fe-Ga

Iron-Gallium (Fe-Ga) alloys are promising materials for sensing applications. However, the mechanical and magnetic properties of these materials vary significantly with the percentage of gallium, which motivates this study on the effect of stoichiometry on the behavior of Fe-Ga alloys. Major loop compressive tests (loading to 110MPa and unloading, at magnetic fields ranging from 0 to 891 Oe) were performed on single crystal 19 and 24% Ga samples with longitudinal axis in the [100] direction. The effect of% Ga on the magnetomechanical properties is discussed. Furthermore, the magnetic interaction between the Fe-Ga sample and the remainder of the magnetic circuit is modeled.

Magnetostrictive Vibration Sensor based on Iron-Gallium Alloy

ABSTRACTThis work characterizes magnetostrictive single crystal Fe84Ga16 (Galfenol) as static and dynamic sensor in bending mode. Galfenol patch bonded to a cantilevered aluminum beam was characterized for static and dynamic loading of the beam. A figure of merit has been defined and sensor parameters have been obtained for different stress conditions and Galfenol patch thickness. Issues related to application in static and dynamic sensing have been discussed.

Bending of Iron-Gallium (Galfenol) Alloys for Sensor Applications

ABSTRACTThis project investigates the magnetomechanical sensing behavior of iron-gallium alloys in response to applied bending loads to identify the relevant design criteria for novel magnetostrictive sensor applications. A series of experiments are conducted on the magnetic induction response of cantilevered beams to dynamic bending loads. Analytic models of the system are formulated from both the constitutive magnetostriction equations and a free energy derivation. Both the experimental and analytical results show a change of as much as 0.3 T of induction can be measured in the samples in response to relatively small applied forces, with the output magnetic signal appearing at twice the frequency of beam vibration.

Energy-based constitutive Model for Magnetostrictive Materials and its Application to Iron-Gallium Alloys

ABSTRACTAn energy-based constitutive model that can simulate the performance of magnetostrictive actuators and sensors along any of the crystallographic orientations was developed. This model was validated by comparing its predictions with experimental actuator characteristics (λ-H and B-H curves) along the <100> and <110> directions as well as sensor characteristics (B-σ curves) along the <100> direction of single crystal FeGa samples with ∼18-19 at. % Ga. These experimental characteristics were obtained using 6.35 mm (1/4 inch) diameter and 25.4 mm (1 inch) long, oriented single crystal rods grown using the Bridgman method by the DOE Ames Lab.

Tensile properties of magnetostrictive iron–gallium alloys

Iron–gallium alloys can produce magnetostrictions of ∼400 ppm and might function as mechanically robust actuator/sensing materials. Single crystal specimens of Fe-17 at.% Ga were tested in tension at room temperature. Specimens with a [1 1 0] tensile axis orientation exhibited {1 1 0}〈1 1 1〉 slip and an ultimate tensile strength of 580 MPa through 1.6% elongation. The Young’s modulus was 160 GPa in the loading direction with a Poisson’s ratio of −0.37 on the (1 0 0) major face. A specimen with a [1 0 0] tensile axis orientation exhibited {2 1 1}〈1 1 1〉 slip and discontinuous yielding. A maximum tensile strength of 515 MPa was observed with fracture occurring after 2% elongation. The Young’s modulus was 65 GPa in the loading direction with a Poisson’s ratio of 0.45 on the (0 0 1) major face. A sizeable elastic anisotropy of 19.9 was identified for Fe-27.2 at.% Ga accompanied by a Poisson’s ratio of −0.75 to produce a large in-plane auxetic behavior.

Electrical resistance of liquid iron-gallium alloys

Electrical resistance of liquid iron-gallium alloys

Spin-wave stiffness and electronic structure of iron-aluminium and iron-gallium alloys

The spin-wave stiffness D of a series of ferromagnetic iron-aluminium and iron-gallium alloys has been measured by the neutron small-angle scattering technique. The experimental results are compared with the predictions of both a localized moment model and a simple band model, and it is found that both models are in fair agreement with the experimental measurements. The results of the fit to the band model suggest that in the iron-aluminium alloys the aluminium does not donate electrons to the 3d band of the alloy, while in the iron-gallium alloys each gallium atom contributes about one electron, which enters predominantly the spin-up sub-band.

Magnetization of Iron-Gallium and Iron-Arsenic Alloys

The magnetizations of bcc α-phase iron-gallium and iron-arsenic alloys have been measured by a force technique between room temperature and 8°K. Customary extrapolation procedures were used to obtain mean atomic magnetic moments from these data. The linear rate of decrease of mean moment with solute concentration was found to be 1.428±0.095μB per atom for the iron-gallium system and 1.403±0.143μB per atom for the iron-arsenic system. This is in contrast with the usual behavior of nontransition metal solutes which are generally considered to dilute a constant iron moment.