Effect of heat treatment on the properties of Metglas foils, and laminated magnetoelectric composites made thereof

Annealing of magnetostrictive Metglas foils, subsequently incorporated into laminated Metglas/Pb(Zr, Ti)O₃ magnetoelectric (ME) composites, is shown to result in improved magnetic properties, as well as ME coefficients. Annealing of the foils at 350 °C resulted in partial crystallization, without oxidation or magnetic cluster formation that would reduce the magnetization. Laminate composites made with these annealed Metglas foils had improved ME coefficients.     

Crystallization,embrittlement and fracture morphology of annealed Fe81B13.5Si3.5C2

Crystallization of Fe₈₁B_13.5Si_3.5C₂ (Metglas 2605SC) was investigated using angular dispersive X-ray diffractometry and energy dispersive X-ray diffractometry. Transition temperatures were determined by annealing an array of specimens from 0 to 97 h at temperatures ranging from 140 to 490° C. Samples of Metglas 2605SC began to transform in about 2.2 h at 365° C. Crystallization temperatures and products were compared to those previously reported in the literature. In addition, the embrittlement behaviour of the alloy was investigated and the fracture topographies of the as-received and annealed samples were examined and categorized using scanning electron microscopy. The Metglas tended to embrittle easily within short periods of annealing at temperatures as low as 240° C.     

A New Magnetoelectric Composite with Enhanced Magnetoelectric Coefficient and Lower Resonance Frequency

This study reports large magnetoelectric (ME) effect by attaching Ni and Metglas magnetostrictive layers to one free end of piezoelectric Pb(Zr,Ti)O3 (PZT) cantilever. By this structure, the influences of the bonding layer can be weakened so as to get relatively high ME voltage coefficient (α_ME) at resonance frequency. And the cantilever structural magnetostrictive material can supply stronger magnetic force to the PZT plate instead of the shear force in traditional structure, leading to an enhancement of α_ME at resonance frequency and generate a new resonance frequency of bending mode which is lower. Also, it can be used without bias field due to the built-in dc magnetic bias field between Ni and Metglas layers. Hence, it can obtain a larger α_ME at a lower resonance frequency at zero bias. The resonant α_ME at zero bias of the new composite reaches 50 V/cm?Oe which is about 1.5~2 times as large as that of the traditional one. Besides, it greatly enhances the α_ME in a frequency range between two resonance frequencies. When we changed the length and thickness of Ni or Metglas layers, the results changed with them. Both the length and thickness have the optimum number to get a maximal α_ME. We also find if Ni and Metglas layers are not side to side aligned, α_ME at zero bias will decrease a lot.     

Magnetoelectric bending-mode structure based on Metglas/Pb(Zr,Ti)O₃ fiber laminates

A magnetoelectric (ME) bending-mode structure based on Metglas/Pb(Zr,Ti)O(3) fiber laminates has been studied. This bending mode had a fundamental resonance (FBR) of about 210 Hz, which was much lower than that of the longitudinal mode. Near the FBR, the ME voltage coefficient was about 400 V/cm·Oe. Magnetic sensors based on this bending mode had an equivalent magnetic noise floor of ≤ 0.3 pT/√Hz at f = 210 Hz.     

Amorphous ribbon domain refinement by scribing

Domain control has been applied to amorphous metal ribbon by mechanical and laser scribing. Mechanically scribed lines were made using a number 88 tungsten carbide scriber with minimum applied pressure. The scribing interval was varied from 0.6 to 10 mm. Laser scribing was performed by using a well-focusedQ-switch YAG laser. The laser power level and scribing interval were varied to obtain optimal magnetics properties. Core loss reductions of 20-25 percent were measured for mechanically and laser scribed Metglas 2605S-2 ribbon. A mechanism of domain refinement is suggested.     

Magnetoelastic effects in amorphous Fe40Ni40P14B6alloys

The influence of compressive, tensile, and bending stresses on the magnetization processes, anisotropy energy, and remanence of an as-quenched amorphous Fe40Ni40P14B6ribbon has been studied. The magnetostriction constant has been obtained from the variation of the susceptibility with the applied compressive stress. To better understand the results, domain structures have been observed by using the Bitter technique. Our results show that the Metglas ribbon has a central region with compressive stress, while the edge regions have tensile stress. So, the influence of these regions on the magnetization processes will be very different according to the applied stress.     

Differential-mode vibrational noise cancellation structure for Metglas/Pb(Zr,Ti)O₃ fiber magnetoelectric laminates

A differential structure which has the ability to reject external vibrational noise for Metglas/Pb(Zr,Ti)O(3) (PZT) fiber-based magnetoelectric (ME) heterostructures has been studied. This type of ME structure functions better than conventional sensors as a magnetic sensor when used in an environment in which vibrational isolation is impractical. Sensors fabricated with this differential mode structure can attenuate external vibrational noise by about 10 to 20 dB at different frequencies, while simultaneously having a doubled ME voltage coefficient. Interestingly, in addition to offering a means of mitigating vibrational noise, this ME structure offers the potential to be a hybrid sensor, separating magnetic and acoustical signals.     

Kinetics of crystallization of FeB glass with electrical resistance measurements

Crystallization kinetics is measured of Metglas 2605 and Fe + 16.2 at%B (～ eutectic) alloy. For the determination of ratio transformed, data of electrical resistance changes are used, during isothermal annealings. Resistance measurement proved to be an useful method to get a quick general overlook for the crystallization process and supplies accurate activation energy values. Results can be easily used for the construction of TTT diagrams.     

On the corrosion characteristics of some commercial magnetic metallic glasses in NaCl solution

The corrosion characteristics of six commercial magnetic metallic glasses, namely Fe₇₈B₁₃Si₉ (Metglas 2605-S-2), Fe₆₇Co₁₈B₁₄Si (Metglas 2605 Co), Fe₄₀Ni₄₀B₂₀ (Vitrovac 0040), Fe₃₉Ni₃₉Mo₂(SiB)₂₀ (Vitrovac 4040), Fe₄₀Ni₃₈Mo₄B₁₈ (Metglas 2826 MB) and Fe₄₀Ni₄₀P₁₄B₆ (Metglas 2826) in which iron and boron are common base elements have been studied by immersion tests and potentiostatic techniques in various concentrations of NaCl solutions at room temperature. In exposure for up to six days, weight loss observations indicated that the corrosion rates in 3.5% NaCl were in the following increasing order: 2826 < 4040 < 0040 < 2826 MB < 2605 Co < 2605-S-2. During exposure for up to four hours under open-circuit conditions, 2826 alloy showed the noblest behaviour while 2605-S-2 was the least noble. All the alloys, except 2826, showed rapid dissolution without any passivation during anodic polarization. Phosphorus addition to Fe-Ni-B glass enhanced the active dissolution and resulted in the formation of a black prepassive film in the active region (0.2V) which becomes protective in the passive region (0.3 to 1.25V). The values ofI _crit. andI _pass. (the critical and passive current densities) decreased with a decrease of concentration from 3.5 to 0.01% NaCl, while in 0.001% NaClI _pass. slightly increased and the passivation potential range decreased. The corrosion resistance of Fe-B metallic glasses increased with metal addition in the order Co < Mo < Ni and with metalloid addition in the order Si < P.     

Development and comparative analysis of fluxgate magnetic sensor structures in PCB technology

In this paper, we present a family of fluxgate magnetic sensors on printed circuit boards (PCBs), suitable for an electronic compass. This fabrication process is simple and inexpensive and uses commercially available thin ferromagnetic materials. We developed and analyzed the prototype sensors with software tools based on the finite-element method. We developed both singleand double-axis planar fluxgate magnetic sensors as well as front-end circuitry based on second-harmonic detection. Two amorphous magnetic materials, Vitrovac 6025X (25 /spl mu/m thick) and Vitrovac 6025Z (20 /spl mu/m thick), were used as the ferromagnetic core. We found that the same structures can be made with Metglas ferromagnetic core. The double-axis fluxgate magnetic sensor has a sensitivity of about 1.25 mV//spl mu/T with a linearity error of 1.5% full scale, which is suitable for detecting Earth's magnetic field (/spl plusmn/60 /spl mu/T full-scale) in an electronic compass.     

ΔE effect and magnetomechanical coupling factor in Fe80B20and Fe78Si10B12glassy ribbons

Field annealing experiments on amorphous Fe80B20ribbon (Metglas 2605) and amorphous Fe78Si10B12ribbon (Tsuya, Tohoku University) are reported. The maximum magnetomechanical coupling constant,k, and change in Young's modulus, ΔE/E0found in Fe80B20were 0.64 and 0.87, respectively, for an anneal of 376° for 6 min in a field of 2.0T. The maximumkfor Fe78Si10B12was found to be 0.82, following a similar anneal at 373°C. This is higher than 0.75 reported by Tsuya and Arai for Fe78Si10B12, previously the highest known for any material.     

The use of metallic glass scroll as an acoustic transducer element

A study was made of the piezomagnetic and elastic properties of scrolls of Metglas 2605 SC, used as an acoustic transducer element. This study involved quasi-DC magnetic induction measurements and ultrasonic complex plane analysis of scrolls of various annealing histories. An optimum effective magnetomechanical coupling coefficient. K(eff), of 0.75, was found. The best magnetomechanical response in air obtained for metallic glass scroll during the study was for the unconsolidated case. However, preliminary experiments have shown that structural weakness and corrosion problems are significant when using the unconsolidated scrolls in water.     

非晶合金应用现状

非晶合金经过几十年的研究,已经到了研发性能卓越、质量稳定,可大批量生产的新产品的阶段.通过简介非晶合金发展历史中3个商业化比较成功的公司非晶体金属公司、安泰科技股份有限公司和液体金属科技股份公司研发新产品的艰难历程,以及非晶合金国内外当前的应用研究状况,说明非晶合金在作为软磁功能材料和薄、轻、小的3C产品结构材料方面具有很大发展潜力.     

Enhanced Resonance Magnetoelectric Coupling in (1‐1) Connectivity Composites

Bulk‐magnetoelectric (ME) composites consisting of various piezoelectric and piezomagnetic materials with (3‐0), (3‐1), (2‐2), and (2‐1) connectivity are proposed in a bid to realize strong ME coupling for next‐generation electronic‐device applications. Here, 1D (1‐1) connectivity ME composites consisting of a [011]‐oriented Pb(Mg,Nb)O₃‐PbTiO₃ (PMN‐PT) single‐crystal fiber laminated with laser‐treated amorphous FeBSi alloy (Metglas) and operating in L‐T mode (longitudinally magnetized and transversely poled) are reported, which exhibit an enhanced resonant ME coupling coefficient of ≈7000 V cm^?1 Oe^?1, which is nearly seven times higher than the best result published previously, and also a superhigh magnetic sensitivity of 1.35 × 10^?13 T (directly detected) at resonance at room temperature, representing a significant advance in bulk magnetoelectric materials. The theoretical analyses based on magnetic‐circuit and equivalent‐circuit methods show that the enhancement in ME coupling can be attributed to the reduction in resonance loss of laser‐treated Metglas alloy due to nanocrystallization and the strong magnetic‐flux‐concentration effect in (1‐1) configuration composites.     

New extensometers using amorphous magnetostrictive ribbon wound cores

New reliable and accurate extensometers are presented using a single amorphous core multivibrator with a dc output. These extensometers can detect strains as large as 40 percent for tensile test samples without any destruction due to the outstanding elasticity of the Metglas 2605A amorphous ribbon-wound cores. High linearity (0.18 percent full scale (FS)) is realized by annealing and applying 1000 times alternating stresses to the cote. Hysteresis against alternating strains is removed to less than 0.48 percent FS by the effect of a compensation spring. The amorphous core extensometer has advantageous points regarding reliability, temperature stability, and maximum operating temperature over conventional extensometers using semiconductor strain gauges.     

Surface crystallization behaviour of Metglas 2605-SC and 2826-MB

The crystallization behaviour of two quaternary amorphous alloys, Metglas 2605-SC and Maglas 2826-MB, were investigated by reflection electron diffraction observations ofin situ heat treatment. The surface crystallization phenomena of these materials were compared to those of the bulk, in particular with respect to the structures of the initial metastable crystallization products. Anisotropic crystallization of the surfaces was observed on both of these ribbons, indicated by oriented arc patterns of the initial crystallites. This effect was determined to be a result of local elemental depletion of the surface layers.     

Some tensile properties of metal-metallic glass laminates

The tensile properties of brass (Cu-30% Zn)-nickel base metallic glass (MBF-35 Metglas) laminates have been investigated. Laminates were prepared by soldering these constituents together with a Pb−Sn alloy. The metallic glass exhibited an enhanced tensile ductility in the metal matrix environments, and such enhanced ductility depended on the metal matrix strength and elongation. Multiple shear bands have been observed in the metallic glass ribbon with enhanced tensile ductility. The failure modes of the laminates have been analysed based on stress-strain concentration concepts, following failure of the glass. The results were consistent with the experimental observations.     

Kinetics of two-stage crystallization in Metglas 2826A

Crystallization kinetics of MSI and MSII stages in Metglas 2826A has been investigated by quantitative transmission electron microscopy. The volume fraction of crystallization against time curve has been found to show a plateau in the lower temperature region of annealing. It has been found that the glass transition temperature, T _g, has no effect on the sequence reversal of the crystallization reaction. It has been shown that the sequence reversal of transformation stages occurs due to the large difference in the activation energy of crystallization of MSI and MSII. In addition, the change in the morphology of the crystals obtained by annealing the amorphous alloy below and above the glass transition temperature, T _g, is reported.     

High speed scanning calorimetry for amorphous alloys

A high speed scanning calorimeter has been developed for simultaneous measurements of heat capacity and electrical resistivity of thin strips. The system was designed for amorphous alloys but can be used for other materials as well. The specimen is heated by an electrical current at rates ranging from 250 to 40,000 K·s^–1, and the temperature is sensed by an IR pyrometer ranging down to room temperature. The maximum data acquisition rate is 50 kHz. Operational characteristics of the system are given, and various phenomena that affect design and operation are discussed. Data are taken for some Metglas alloys. Glass transition and crystallization temperatures as well as rough viscosity data are evaluated. At high heating rates the glass transition is spread over a wide temperature range. The formation of metastable crystalline phases can be bypassed so that stable phases form directly from the amorphous state.     

Crystallization behaviour of Metglas 2826 MB (Fe40Ni38Mo4B18)

Differential scanning calorimetry, x-ray diffraction and transmission electron microscopy have been employed to determine the thermal stability and identify the crystalline phases on devitrification of Metglas 2826 MB. The glass crystallizes intoγ-FeNiMo and fcc (FeNi)₂₃B₆ with activation energies of 270 and 375 kJ mol⁻¹ respectively. The reactions are primary and polymorphic in nature. The influence of Mo towards crystallization of Fe₄₀Ni₄₀B₂₀ has been to enhance the formation of the fcc (FeNi)₂₃B₆ phase in preference to orthorhombic (FeNi)₃B phase and to raise the thermal stability of the amorphous state.