Amorphous Foils Research Articles

Preparation and Properties of a Custom-Designed Nickel-Based Amorphous Brazing Foil

The custom-designed amorphous brazing filler metals in foil form has been developed for application in brazing stainless steel 0Cr18Ni9. The new alloys contains 10.5wt% chromium, 5.4wt% silicon, 1.5wt% boron, 3wt% cobalt and nickel as the balance. The melting range is within 971°C1070°C. The alloy exhibits good melting characteristics and wetting behavior. With a 25μm thick foil, the joint is free of brittle central eutectic phases inside the joint via diffusion of the alloying elements into adjoining base metal and results on a high mechanical joint strength.

Induction brazing of cermets to steel

The paper considers the induction brazing of TiC based cermets with Ni-Mo and Fe-Ni binder phase and Cr3C2 based cermets with Ni binder to structural and stainless steels under vacuum and air conditions. Commercially available traditional filler metals and experimental amorphous filler foils were tested. Possibility of mechanical metallizing of cermet surfaces with rotating Ti brushes prior to the brazing process was studied. Increase in the surface roughness after mechanical metallizing and non-uniform distribution of Ti on the treated surfaces were observed. Positive influence of electrochemically deposited Ag and Ni coatings on the shear strength of joints was found when optimal filler metals were used. Maximum shear strength up to 200-250 MPa was achieved with Ti- and Ni-based amorphous filler foils. Brazing in air by optimal fluxes and Ag- and Cu-based conventional brazing fillers can be used for brazing of cermets. Shear strength up to 150-190 MPa was achieved. The shear strength of vacuum brazed joints increases with the increase of the metal binder content in the cermet. Diffusion of the filler metal to base metal and to joint interface was studied by EPMA and SEM. It was found that cermets are successfully brazed with amorphous filler metals and the strength of the joints was not affected by the rapid heating during the induction process and relatively low vacuum.

Interaction of low energy protons, deuterons, H 2 + and D 2 + with carbon foils: energy-angle distributions and velocity dependence of the energy loss

We have performed measurements of energy-angle distributions for low energy (E ≲ 10 keV) hydrogen ions transmitted through thin amorphous carbon foils. The applicability of standard potentials for the description of the multiple scattering is tested by making comparisons of the experimental results with theoretical calculations using the model of Sigmund and Winterbon on a broad angular scale. The angular dependence of the energy loss for protons and deuterons is analyzed using the three-components model of Fama et al., that separately considers the contribution of elastic and inelastic mechanisms and the roughness effect. Additionally, the velocity dependence of the stopping power and the possible existence of isotopic and molecular effects in the energy loss is investigated by measurements with H+, D+, \hbox{${\rm H}_2^+$}H2+ and \hbox{${\rm D}_2^+$}D2+ beams of velocities between 0.15 and 0.6 a.u.

Correlation between thermal induced structural and magnetic transformations in Si-rich Fe73Cu1Si16B7Nb3 metal alloy

Properties of amorphous Fe73Cu1Si16B7Nb3 foil, the Si rich metal alloy, and the foils partly crystallised after annealing, were analysed structurally and magnetically in the temperature range from 4 to 1000K. The Fe (Si) and Fe (B) structures were identified and characterised with the crystallisation temperatures: 750 and 893K, activation energies 460 and 580kJ/mol. The Curie temperatures for amorphous structure: 613K and for crystalline structures: 820, 875, 920 and 980K were determined. It was found and analysed a delay of the sample magnetisation, determined by thermomagnetometry, with respect to structural crystallisation, determined by scanning calorimetry, which was correlated with magnetic hyperfine field, determined by transmission Mössbauer spectroscopy.

Mechanical properties of AISI 316L stainless steels joined with a commercial Ni based amorphous foil

AbstractNi based braze filler metals containing B and Si elements, prepared either by rapid solidification or powder metallurgy have relatively low melting temperatures, which make them liable to join. This work presents the mechanical resistance of stainless steels 316L joints, bonded with an amorphous Metglas© MBF‐15® foil at 1105°C and 1170°C joined for 5, 10, 15, 20 and 40 minutes, under a nitrogen atmosphere into an electric resistance furnace. Intermixed precipitate particles at the joining zone were formed and an improvement on the bonding samples for conditions of 1105°C for 10 minutes were observed, since the number of unjoined islands were reduced and no interfase crack was detected. The average shear‐tensile mechanical resistance of the joints ranged from about 54 MPa to 70 MPa, and from 47 MPa to 79 MPa, for samples joined at 1105°C and 1170°C, respectively.

Magnetoelectric effect in crystallographically textured BaTiO3 films deposited on ferromagnetic metallic glass foils

We demonstrate a significant control of the polarization response under an applied magnetic field for a magnetoelectric (ME) heterostructure. This structure was comprised of a 2 μm thick ferroelectric BaTiO3 (BTO) film deposited on flexible ferromagnetic metallic glass foil (25 μm thick). Au was used as a buffer layer to control BTO growth orientation, and to protect the metallic glass from oxidation. x-ray diffraction and scanning electron microscopy demonstrated the successful growth of well-crystallized BTO films with a high degree of (111) orientation on the amorphous metallic glass foils. Well-defined polarization (P-E) and magnetization (M-H) hysteresis loops confirmed the coexistence of ferroelectric and ferromagnetic properties. A ME voltage coefficient of about ∼60 mV/cm Oe was measured.

Plasma modification of PET foils with different crystallinity

Polymers are commonly used in industry for packaging applications and as protective coatings but are sometimes unsuitable to use due to their low surface energies. For these latter applications, surface modification is usually necessary to improve wettability, printability and adhesive properties. In the past decades, plasma surface treatment of polymers has been extensively studied and different treatment conditions have been investigated. However, the influence of polymer crystallinity on plasma treatment effects is not well-known and therefore this study focuses on plasma treatment of PET foils with different degrees of crystallinity. The different PET foils are treated with a DBD discharge operating in air at medium pressure and the effect of polymer crystallinity on the treatment efficiency is studied in detail using contact angle measurements and atomic force microscopy (AFM). Also the ageing behavior of the different types of plasma-treated samples is investigated in this work. Results clearly show that the crystallinity of the PET foil influences both the plasma treatment effect as well as the ageing process of the samples. AFM analysis indicated that the DBD plasma homogeneously etches the surface of the amorphous PET foil resulting in smoother surfaces after plasma treatment, while for the more crystalline PET foil the etching effect is more randomly leading to rougher surfaces. As a result, amorphous polymer regions are most likely more prone to plasma etching than crystalline regions.

Microstructure and electrochemical properties of the bonding zone of AISI 316L steel joined with a Fe-based amorphous foil

The effect of temperature and holding time on the microstructure and corrosion resistance of the junction zone of AISI 316L stainless steel (SS) bonded to itself with Fe 75Cr 8P 10B 7 filler alloy was investigated. The brazing alloy was prepared in the laboratory in the form of amorphous ribbons and its melting temperature was determined by differential thermal analysis (DTA) to be 1571 K. The joining process was carried out in a chamber with controlled Ar atmosphere at two temperatures: 1173 and 1273 K for different holding times not exceeding 40 min. Joining took place by the mechanism of diffusion bonding. The joints produced at 1273 K for 40 min exhibited no porosity in the reaction zones and presented the best quality. Scanning electron microscopy (SEM) characterization of the bonding zone revealed an improvement in the quality of the joints brazed at 1173 K for 20 min and longer. These samples had continuous base metal–filler alloy interfaces with minimum porosity. At 1273 K the bonding interfaces diffused and for the samples held for 40 min completely vanished and porosity disappeared. Even the presence of particle precipitates the bonding zone showed acceptable resistance to localised corrosion in non-aggressive electrolytes. SEM study revealed that irregularly precipitated particles and other phases of about 10 μm in size formed in the interlayer during the joining process. The presence of σ-phase in samples bonded at 1273 K promoted preferential dissolution in the bonding zone in NaCl solution.

Resonant Bending Fatigue Tests on Thin Films

The fatigue properties of thin-fi lm materials are extremely important in the design of durable and reliable micro-electromechanical systems (MEMS). However, it is rather diffi cult to apply the conventional fatigue testing method for bulk materials to thin fi lms as the specimen size is extremely small. Therefore, a fatigue testing method suitable for thin-fi lm materials is required. We have developed a fatigue testing method that uses the resonance of a cantilever-type specimen prepared from thin fi lms. Cantilever beam specimens with dimensions of 3(L) × 1(W) × 0.01(t) mm3 were prepared from Ni-P amorphous alloy thin fi lms and gold foils. In addition, cantilever beam specimens with dimensions of 3(L) × 0.3(W) × 0.005(t) mm3 were prepared from single-crystal silicon thin fi lms. These specimens were fi xed to a holder that was connected to an audio speaker (actuator) and were resonated in the bending mode. The Young’s moduli measured from the resonant frequencies of Ni-P and gold foil were 116 and 72 GPa, respectively. These values were comparable to those measured by other techniques, indicating that the specimens resonated in a theoretically predictable manner and that our method is valid. Resonant fatigue tests were carried out for these specimens by changing the amplitude range of resonance, and S-N curves were successfully obtained for Ni-P amorphous alloy thin fi lms, gold foils, and single-crystal silicon thin fi lms.

Correlated transformation of the microrelief of the stressed surface of an amorphous alloy

Samples of Fe70Cr15B15 and Fe77Ni1Si9B13 amorphous alloy foils are loaded at tensile stresses of 0.2–1.2 GPa under constant strain or constant stress conditions. The submicroscopic profiles of the surface are recorded on a scanning tunneling profilometer. The “instantaneous” or extended (in time) transformation of the surface relief is statistically described by calculating the autocorrelation functions of the change in the relief height along two-dimensional scanning paths parallel to the loading axis. The autocorrelation functions thus constructed allow one to estimate the correlation radii of the surface profile, i.e., typical scales of relief components (holes, protuberances, flat regions). The performed analysis has revealed a considerable spatial correlation (∼2 × 103 nm) between the relief components in both initial (unloaded) foils. The application of the tensile load leads to an immediate increase in the roughness of the relief and a sharp decrease in the correlation radius. Subsequently, the relief does not remain stable and changes as a result of competing processes, such as microcrack growth, leveling of bends, and nucleation of kink bands. The behavior of the autocorrelation functions adequately reflects the transformation of the surface profile.

Microstructural characterization of explosively welded rapidly solidified foil and stainless steel plate through the acceleration employing underwater shock wave

Rapidly solidified amorphous and metallic glass thin foils clad on a stainless steel base plate was fabricated by employing underwater shock wave generated by the detonation of an explosive, and the microstructure of the welded interface was characterized. The rapidly solidified thin foils were successfully welded indicating waves without the formation of interfacial zone in most of the area. However, some interfacial zones caused due to the trapped metal jet were occasionally found. It is expected that the quality of welding would not be significantly affected by the presence of interfacial zones. The interfacial microstructure was characterized through optical, scanning electron and transmission electron microscopes as well as using micro-focus X-ray diffraction and EDX analyses.

Brazing of Si 3N 4 with amorphous Ti 40Zr 25Ni 15Cu 20 filler

Amorphous active brazing filler foils having a composition of Ti 40Zr 25Ni 15Cu 20 was synthesized using a melt-spinning method in a roll forging machine in argon atmosphere. Si 3N 4 ceramic was brazed with synthesized Ti 40Zr 25Ni 15Cu 20 amorphous foil. The effects of brazing temperature and time on joint strength and interfacial microstructure were investigated. The structure, composition and property of the brazing alloys as well as interfacial microstructure were characterized by X-ray diffraction, differential thermal analysis, scanning electro-microscopy and energy dispersive X-ray spectroscope. The results showed that joint strength first increased then decreased with the increasing brazing time and brazing temperature, which was significantly affected by reaction layer thickness. Under the same brazing conditions, the strength of joint brazed with amorphous Ti 40Zr 25Ni 15Cu 20 filler alloy was much larger than that bonded with Ti 40Zr 25Cu 20Ni 15 crystalline filler due to improved wettabilty.

Magnetostrictive effect type force (strain) sensor using mutual induction of planar coils

AbstractA new structure is proposed for the magnetostrictive effect type force sensors using a pickup head layered with magnetostrictive foil and pair of planar coils. Mutual coupling between two planar coils is used as a measure of force applied to the magnetostrictive foil. In this type of force sensor, the output voltage is zero when force is zero, and the planar coils with electric wires can be put on and taken off easily because the magnetostrictive foil does not need a current contact. Basic characteristics of the force sensors are examined using Metglas2605SC amorphous foil glued to the side of an aluminun square bar of 15 mm×15 mm cross‐sectional area and a pair of 16‐turn planar coils. Sensitivity was 38.4 mV/Nm [1.57 mV/μϵ (ϵ = δ l/l)] at the coil excitation condition of 1 MHz, 60 mA. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 1–7, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20740

The nucleation stage in electron beam induced deposition

With electron beam induced deposition structures as small as 1 nm can be deposited. The nucleation stage of the growth of such deposits is studied in dependence of the substrate material and substrate temperature. On amorphous carbon foils larger deposit sizes are obtained at higher substrate temperatures during growth. On SiN membranes unusually high growth rates are observed which seem to relate to charging effects.

Dissimilar material welding of rapidly solidified foil and stainless steel plate using underwater explosive welding technique

Rapidly solidified amorphous and metallic glass thin foils clad on a stainless steel base plate is attempted by employing underwater shock wave assembly. The conditions of the explosive welding are numerically analyzed and discussed based on the earlier welding limits. The thin foils successfully welded along the length of 50 mm show clear waves typically found in explosively welded interface. The interfacial microstructure characterized through optical and scanning electron microscopes shows evidence of excessive melting generated due to the trapping of metal jet in limited area.

Multilayer carbon foils for cyclotron beam extraction

The TRIUMF Applied Technology Group operates high-power industrial cyclotrons for commercial radioisotope production. Two of these cyclotrons, TR30-1 and TR30-2, are capable of accelerating H − ions to an energy of 30 MeV and beam currents in excess of 1000 μA. For many years, amorphous carbon foils of approximately 2.0 μm thickness have been utilized to extract proton beams from these accelerators. Novel multilayer foils consisting of layers of amorphous and diamond-like carbon (DLC) of 2.0±0.2 μm thickness were manufactured in-house by carbon arc and pulsed laser deposition, respectively. In the TR30 cyclotrons, the new composite foils with 25% DLC content show a three times longer lifetime than the purely amorphous foils, while maintaining their excellent physical and mechanical characteristics during irradiation.

Neutron spin turners with a rotating magnetic field: first experiments

Spin turners are the key elements of a neutron spin-echo spectrometer with rotating magnetic fields. Here we describe the results of experiments with thin-film spin turners made of 25 µm amorphous ferromagnetic foils, whose in-plane magnetization is rotated by a weak external rotating field. The behaviour of the polarization vector of a 0.2 nm neutron beam is analysed in 3D after transmission through such a foil and, apart from a non-negligible depolarization, the results show that they are in good accordance with simulations. This observed depolarization is due to a domain structure with a net magnetization.

Resonant Fatigue Testing of Cantilever Specimens Prepared from Thin Films

AbstractFatigue properties of thin film materials are extremely important to design durable and reliable microelectromechanical systems (MEMS) devices. However, it is rather difficult to apply conventional fatigue testing method of bulk materials to thin films. Therefore, a fatigue testing method fitted to thin film materials is required. In this investigation, we have developed a fatigue testing method that uses a resonance of cantilever type specimen prepared from thin films. Cantilever beam specimens with dimensions of 1(W) × 3(L) × 0.01(t) mm3 were prepared from Ni-P amorphous alloy thin films and gold foils. In addition, cantilever beam specimens with dimension of 3(L) × 0.3(W) × 0.005(t) mm3 were also prepared from single crystalline silicon thin films. These specimens were fixed to a holder that is connected to an golddio speaker used as an actuator, and were resonated in bending mode. In order to check the validity of this testing method, Young's moduli of these specimens were measured from resonant frequencies. The average Young's modulus of Ni-P was 108 GPa and that of gold foil specimen was 63 GPa, and these values were comparable with those measured by other techniques. This indicates that the resonance occurred theoretically-predicted manner and this testing method is valid for measuring the fatigue properties of thin films. Resonant fatigue tests were carried out for these specimens by changing amplitude range of resonance, and S-N curves were successfully obtained.

Nanosecond x-Ray diffraction from polycrystalline and amorphous materials in a pinhole camera geometry suitable for laser shock compression experiments

Nanosecond pulses of quasimonochromatic x-rays emitted from the K shell of ions within a laser-produced plasma are of sufficient spectral brightness to allow single-shot recording of powder diffraction patterns from thin foils of order millimeter diameter. Strong diffraction signals have been observed in a cylindrical pinhole camera arrangement from both polycrystalline and amorphous foils, and the experimental arrangement and foil dimensions are such that they allow for laser shocking or quasi-isentropic loading of the foil during the diffraction process.

Temperature dependence of deformation mechanism in bonding zone of TLP joint of nickel base single crystal superalloy after tensile test

A nickel base single crystal superalloy was transient liquid phase (TLP) bonded using Ni–Cr–B amorphous foil at 1230°C for 4 h. Tensile tests of the TLP joint were carried out at different temperatures under constant strain rate. The microstructures and the deformation substructures in the bonding zone of the joint were investigated. The results show that the deformation mechanism of bonding zone depends on test temperature greatly. At low temperatures, the deformation is dominated by γ′ shearing; at high temperatures, the deformation occurs by means of γ′ bypass; at intermediate temperatures, the deformation exhibits a transitional behaviour. The deformation mechanism of different parts of TLP joint is identical.