Amorphous Foils Research Articles

Development of New Amorphous and Nanocrystalline Magnetic Materials for Use in Energy-Efficient Devices

ABSTRACTFe-based amorphous and nanocrystalline soft magnetic alloys have been intensively researched for many applications, including high efficiency electrical distribution and power conditioning applications. New amorphous foils with a saturation magnetization of 1.63T and new nanocrystalline foils with saturation up to 1.9T have been developed. Often these new materials are not drop-in replacements for the conventional competing alloys and require significant changes in processing to be able to fabricate commercial devices.

Magnetic field sensors based on the foil of amorphous cobalt alloy and NiMnGa martensite single-crystals

The problem of creation of small size wideband sensitive sensors of magnetic field with a narrow directional diagram and a small coefficient of thermal drift is actual and requires searching for new magnetic materials. We present the results of the development of the flux-gate sensors with the 20μm magnetic core of amorphous foils of ММ-3Со and ММ-5Со cobalt alloys and magnetoelectric transducers with magnetic field sensitive element of NiMnGa martensite single-crystal. The peculiarities of our sensors are the usage of the parametric amplification and related to it the strong nonlinearity of the dependences of magnetic permeability of amorphous foil and NiMnGa single-crystal magnetostriction on the magnetic field amplitude.

Nondestructive Evaluation Using a High-<italic>T</italic>cSQUID Microscope

We report the application of a scanning high- $T_{{\rm{c}}}$ SQUID (superconducting quantum interference device) microscope with a ferromagnetic flux guide for the nondestructive evaluation of weld seams and wear tracks and scars on austenitic stainless steel plates as well as measurement of magnetic stray fields distribution above patterned by electron lithography 30-nm-thick cobalt films. A soft magnetic amorphous Vitrovac foil was used to guide the flux from the samples, which were held at room temperature, to the liquid-nitrogen-cooled SQUID-sensor and back. The flux guide passes through a hole in the $\text{1 mm}\times \text{2.5 mm}$ pick-up loop of the high- $T_{{\rm{c}}}$ SQUID sensor, thereby providing improved coupling of the magnetic flux from the object to the SQUID. In order to avoid the influence of the SQUID biasing the magnetic field on the object under investigation, a modulation and feedback coil was coupled to the pick-up loop of the SQUID directly and beyond the ferromagnetic flux guide. Such decoupling of feedback coil from soft magnetic flux antenna ensures that the high- $T_{{\rm{c}}}$ SQUID microscope does not disturb the sample magnetization during image recording. The SQUID microscope can be used to measure the spatial distribution of the z -component of the stray field above a specimen without mechanical contact to it.

Building metallic glass structures on crystalline metal substrates by laser-foil-printing additive manufacturing

In laser-foil-printing additive manufacturing, 3D metallic glass structures can be built by laser welding of amorphous foils, layer by layer, upon a crystalline metal substrate. In this paper, weldability studies for laser welding of Zr52.5Ti5Al10Ni14.6Cu17.9 amorphous foils onto a Ti-6Al-4V (Ti 6-4) or Zr 702 substrate are conducted. After laser welding, the weldments are analyzed using X-ray diffractometer, optical microscope, scanning electron microscope equipped with energy dispersive spectroscopy and micro-hardness tester. The results show that Zr 702 is a suitable substrate for Zr-based metallic glass structure since crack-free weld joints can be obtained owing to the formation of ductile α-Zr, while Ti 6-4 is not an appropriate substrate since it has high cracking susceptibility due to the formation of a large amount of hard and brittle intermetallics near the foil-substrate interface. It was found that the mixing between melted substrate and foil is not uniform but exhibits a distinct “swirl” pattern. The swirl structure is more pronounced in Ti 6-4 than in Zr 702 substrate which may contribute to its high cracking susceptibility. The aforementioned mixing leads to partial crystallization of the first amorphous layer; however, fully amorphous is achieved in the additional welding layers.

Induction Brazing of 304 Stainless Steel with a Metalloid-Free Ni-Zr-Ti-Al-Sn Amorphous Foil

Induction Brazing of 304 Stainless Steel with a Metalloid-Free Ni-Zr-Ti-Al-Sn Amorphous Foil

3D printing of large, complex metallic glass structures

Metallic glasses (MGs) or amorphous alloys although have superior mechanical properties their products are limited to simple geometries such as foils/plates or rods with thin section-thickness due to the requirement of high cooling rates. In this study, 3D, large dimensions of amorphous structures with complex geometry are manufactured by our newly developed Laser Foil Printing (LFP) technology. Zr-based (LM105, provided by Liquidmetal Technologies, Inc.) amorphous foils of 100μm thickness are used as feedstock, and they are laser welded, layer-by-layer, to become 3D amorphous structures. Test results by X-Ray diffraction (XRD), differential scanning calorimetry (DSC), and micro-hardness confirm that the printed structures at selected process parameters achieve the same or better degree of amorphization as the raw foils. A mathematical model was developed to calculate the heating and cooling rates during structure manufacturing which helps the selection of process parameters. This study expands MG products to 3D arbitrary geometries with large dimensions due to the inherited advantages of the LFP technology which would open many potential applications.

The effect of bonding time on the microstructure and mechanical properties of transient liquid phase bonding between SAF 2507 and AISI 304

The aim of this study was to evaluate the effect of the bonding time on the transient liquid phase (TLP) bonding of SAF 2507 super duplex stainless steel to AISI 304 austenitic stainless steel. The bonding process was carried out at 1050°C for different bonding times of 5, 10, 30 and 45min to achieve a joint free of the inter-metallic compounds. For this purpose, an amorphous foil of Ni–7Cr–4.5Si–3.2B–3Fe alloy (AWS BNi-2) was used as the interlayer. Microstructure analyses were performed using optical microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Microhardness examinations and shear tests were performed to assess the effect of holding time on the mechanical behavior of dissimilar TLP bonded joints. The results indicated that the width of the athermally solidified zone was decreased with the increase of holding time at a constant temperature. The appearance of hardness peak values in the athermally solidified zone was due to the formation of eutectic compounds. Also, the shear strength was improved by increasing the bonding time. The TLP bonded joint fabricated at the bonding time of 45min exhibited the best mechanical behavior due to the completion of isothermal solidification. Fractographic studies revealed that the fracture mode was completely ductile in the case of the joint made at the bonding time of 45min.

Microstructure Evolution and Mechanical Properties of TLP Bonded Joint of IN-738LC Superalloy using MBF-20 Amorphous Foil

Microstructure Evolution and Mechanical Properties of TLP Bonded Joint of IN-738LC Superalloy using MBF-20 Amorphous Foil

Investigation of tungsten/steel brazing using Ta and Cu interlayer

The brazing processes, using Ta and Cu interlayer respectively, were carried out to study the joining of W and steel with Ni–based amorphous foil filler. The W/Ta/steel and W/Cu/steel joints were conducted in vacuum at 1050°C for 1h. The interfacial microstructure and mechanical properties of joints were investigated by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and tensile strength measurement. The results show that a reliable bonding between W and steel could be obtained by using both Ta and Cu interlayer. The fracture sources of W/steel brazing joints were predominantly in the tungsten substrate near the brazing seam, which agrees reasonable well with the calculation result of finite element method (FEM). The average tensile strength of W/Ta/steel and W/Cu/steel joints were 257.8MPa and 276.7MPa respectively. Comparing with hard interlayer Ta, soft interlayer Cu could reduce residual tress in W substrate and improve the mechanical property more effectively.

Microstructural evolution mechanisms of Ti600 and Ni-25%Si joint brazed with Ti-Zr-Ni-Cu amorphous filler foil

A commercial Ti-Zr-Ni-Cu amorphous filler foil was applied to braze the high-temperature Ti600 and Ni-25at%Si, resulting in the good joint between both of alloys. The interfacial microstructure of Ti600/Ti-Zr-Ni-Cu/Ni-25at%Si brazed joint at 1213K for 10min is mainly comprised of the continuous Ti2Ni phase. Most of Ti-rich phases such as α-Ti, β-Ti, Ti3Al, Ti2Ni, (Ti,Zr)2(Ni,Cu) and (Ti,Zr)2Si formed in the vicinity of the Ti600 substrate except that Ti5Si3 precipitates near the Ni-25at%Si region, resulting in the formation of six distinct layers. The corresponding formation mechanism were clarified. The Ti5Si3 and Ni31Si12 were firstly formed during the initial stage followed by diffusion reactions at Ni-25at%Si side. The continuous Ti2Ni phase formed through the reaction of Ti(L)+Ni(L)→Ti2Ni. α-Ti, Ti3Al, (Ti,Zr)2(Ni,Cu) and (Ti,Zr)2Si in the brazing joint precipitated through a solid-solid phase transformation.

SU‐F‐T‐127: Charged Particle Transport in Condensed Media

Purpose:Provide quality interaction cross sections for charged particle Monte Carlo (MC) track structure codes and evaluate low energy electron transport in condensed media.Methods:MC methods and codes are often used to model or simulate charged particle radiation transport in matter. Detailed (or event‐by‐event) track structure simulations are of special interest for the modeling of the physical and chemical stages of radiation action with matter and the initial radiation damage to biological systems. They require reliable interaction cross sections of all radiation qualities considered (e.g., electrons, protons, alpha particles, light and heavy ions) with the target material under consideration, mainly in the condensed phase, including liquids and solids. Interaction cross sections are calculated using the dielectric formalism, a mixture of first principles, theoretical modeling and experimental information for bulk and surface transport and implemented into MC track structure codes. Secondary electron emission yields from amorphous solid water (ASW) and thin metal foils (copper and gold) after fast proton impact are simulated and measured experimentally.Results:After considering different transport models for bulk and surface transport and a careful modeling of the experimental geometry, simulated secondary electron emission yields follow the trends of experimental data well. Furthermore, yields for electron emissions below 50 eV are sensitive to differential elastic scattering cross sections.Conclusion:Low‐energy electron transport in condensed media is still a challenge for detailed track structure simulation codes. Interaction cross‐sections, transport models, and target geometry need to be considered adequately.The research was funded in part by NSF Major Research Instrumentation Program 2009, Award Number: 0923270 and by NIH/NCI R01 CA93351.

Tailoring the Magnetoelectric Properties of Pb(Zr,Ti)O3 Film Deposited on Amorphous Metglas Foil by Laser Annealing

This study demonstrates the modulation of off‐resonance magnetoelectric (ME) response of the Pb(Zr,Ti)O3 (PZT)/ Metglas (FeBSi) bilayered composite by laser annealing. A continuous‐wave 532 nm Nd:YAG laser with varying fluences (210–390 J/mm2) was utilized to anneal the 2 μm thick PZT film deposited using granule spray in vacuum (GSV) technique on magnetostrictive amorphous Metglas foil. It was found that the dielectric and ferroelectric properties of the PZT film are strongly affected by the exposure to laser fluence. The ME voltage coefficient of PZT/Metglas increased with the fluence up to 345 J/mm2, reaching a high value of 880 mV/cm·Oe. The electrical and ME properties were correlated with the changes observed in crystallinity and grain size of the PZT film as well as with the alterations in microstructure and magnetic behavior of Metglas. Our results demonstrate that enhanced ME coupling can be realized in PZT/Metglas film composites by controlling the laser fluence.

Centimeter-order view for magnetic domain imaging with local magnetization direction by longitudinal Kerr effect

An observation system of centimeter-order of view of magnetic domain with local magnetization direction was developed by designing a telecentric optical system of finite design through the extension of microscope technology. The field of view realized in the developed system was 1.40 × 1.05 cm as suppressing defocus and distortion. Detection of the local magnetization direction has become possible by longitudinal Kerr observation from the orthogonal two directions. This system can be applied to the domain observation of rough surface samples and time resolved analysis for soft magnetic materials such as amorphous foil strips and soft magnetic thin films.

Brazing of ZrB2–SiC ceramic with amorphous CuTiNiZr filler

In the present work, amorphous CuTiZrNi foils with low melting point of 1133K were synthesized using a melt-spinning method in argon atmosphere. A ZrB2–SiC ultra high temperature ceramic was brazed at 1153–1253K for 900s. The wetting and spreading characteristics of amorphous alloy filler on the ceramic were studied with the sessile drop method. The reaction products between the ZrB2–SiC ceramic and the CuTiZrNi filler were systematic studied by X-ray diffraction and scanning electron microscopy. Also, the formation process of interfacial product of joint was discussed. A maximum room temperature three-point bending strength of 210MPa of the joint was obtained by reasonable processing. The high temperature strength of the joint was also studied, and the joint was found to exhibit a stable strength (240MPa) at a high temperature of 873K. The presence of refractory Ti5Si3 compound was believed to be contributed to the stable high temperature strength.

Ultrastable gold substrates: Properties of a support for high-resolution electron cryomicroscopy of biological specimens.

Electron cryomicroscopy (cryo-EM) allows structure determination of a wide range of biological molecules and specimens. All-gold supports improve cryo-EM images by reducing radiation-induced motion and image blurring. Here we compare the mechanical and electrical properties of all-gold supports to amorphous carbon foils. Gold supports are more conductive, and have suspended foils that are not compressed by differential contraction when cooled to liquid nitrogen temperatures. These measurements show how the choice of support material and geometry can reduce specimen movement by more than an order of magnitude during low-dose imaging. We provide methods for fabrication of all-gold supports and preparation of vitrified specimens. We also analyse illumination geometry for optimal collection of high resolution, low-dose data. Together, the support structures and methods herein can improve the resolution and quality of images from any electron cryomicroscope.

Surface Irregularities and Magnetism in Amorphous Metal Foils on Fe Basis

This paper presents the study results of morphology contact and free surface at amorphous metal foils (Fe7Co71Ni12(SiB)10, Fe70Ni10(SiB)10, Fe60Co30(SiB)10) and their analysis of the elemental composition. Using spectral methods of research was allowed to make a comparative analysis size and anisotropy of distribution topological inhomogeneities. A parallel study of spinning foils by Mossbauer spectroscopy and Vibrating sample magnetometer (VSM) possible to determine the magnetic state of the samples.

Transient liquid phase bonding of CLAM/CLAM steels with Ni-based amorphous foil as the interlayer

Transient liquid phase bonding is employed to join China low activation martensitic (CLAM) steels, with Ni-based amorphous foil as interlayer. The effects of the Ni-based amorphous foil on the microstructure and mechanical performance of the joint are investigated. During bonding, as the temperature reaches to the start temperature of austenite transformation, boron, a melting point depressant in amorphous foil, can diffuse along austenite boundaries, resulting into compounds containing boron and the fine-grain zones adjacent to the interlayer. Owing to the melting of interlayer and the dissolution of substrate material, the final width of the interlayer is increased. Moreover, at the interlayer close to the joint interface, small voids can be observed, associated with the difference between Fe and Ni in diffusion rates. It should also be noted that the bonded CLAM/CLAM steels always fracture at the interlayer.

Energy loss and straggling of 1–50 keV H, He, C, N, and O ions passing through few layer graphene

Graphene could be an alternative to amorphous carbon foils, in particular in space plasma instrumentation. The interaction of ions or neutral atoms with these foils results in different effects: electron emission, charge exchange, angular scattering, and energy straggling. We showed in previous studies that (1) the charge exchange properties are similar for graphene and regular carbon foils, and (2) the scattering at low energies (few keVs) is less for graphene than for one of our thinnest practical carbon foils. In this study, we report measurements of the energy loss and straggling of ∼1–50keV H, He, C, N, and O ions in graphene. We compare graphene and a carbon foil for hydrogen. We provide simple power law fits to the average energy loss, energy straggling, and skewness of the energy distributions. We find the energy loss for ions transiting through graphene to be reduced compared to thin carbon foils but the energy straggling to be larger, which we attribute to the non-uniformity of the graphene foils used in this study.

Enhanced off-resonance magnetoelectric response in laser annealed PZT thick film grown on magnetostrictive amorphous metal substrate

A highly dense, 4 μm-thick Pb(Zr,Ti)O3 (PZT) film is deposited on amorphous magnetostrictive Metglas foil (FeBSi) by granule spray in vacuum process at room temperature, followed by its localized annealing with a continuous-wave 560 nm ytterbium fiber laser radiation. This longer-wavelength laser radiation is able to anneal the whole of thick PZT film layer without any deteriorative effects, such as chemical reaction and/or atomic diffusion, at the interface and crystallization of amorphous Metglas substrate. Greatly enhanced dielectric and ferroelectric properties of the annealed PZT are attributed to its better crystallinity and grain growth induced by laser irradiation. As a result, a colossal off-resonance magnetoelectric (ME) voltage coefficient that is two orders of magnitude larger than previously reported output from PZT/Metglas film-composites is achieved. The present work addresses the problems involved in the fabrication of PZT/Metglas film-composites and opens up emerging possibilities in employing piezoelectric materials with low thermal budget substrates (suitable for integrated electronics) and designing laminate composites for ME based devices.

Low-temperature joining of Fe-based amorphous foil with aluminum by ultrasonic-assisted soldering with Sn-based fillers

Abstract Low temperature joining of amorphous alloys has big challenges to prevent them from crystallization. An ultrasonic-assisted soldering method was proposed to join the Fe-based amorphous alloys with the aluminum plates in air by using Sn-based solders. No obvious defects were observed and the joining ratio was more than 90%. At the interface of solder/aluminum, scallop α-Al solid solutions were formed and large fretting (pits) with a size of 50 μm on the aluminum plates was found due to ultrasonic vibrations. At the interface of solder/amorphous, Fe–Zn intermetallic compound (FeZn 13 ) was probably formed. Its formation activation energy was approximately 30.9 kJ/mol between the amorphous iron and the Sn–9Zn during the solid state diffusion, which was much lower compared with crystallized couples. The enhanced diffusion/reaction and the much low activation energy in this work are probably attributed to the amorphous state of the Fe-based foils. Adding nickel in the Sn–Zn solder can improve the hardness of the joints by formation of NiAl 3 intermetallic particles and depress the corrosion on the aluminum. Both the initially interfacial wetting and the microstructure refinement during solidification of the filler solder were improved by ultrasonic vibrations.