Metallic Glass Foils Research Articles

Antibacterial effect of surface-modified Zr50Cu50 metallic glass

Zr-based metallic glasses generally have an amorphous zirconium oxide film that strongly inhibits further oxidation. However, surface defects may deteriorate the glass stability of the amorphous oxide film, leading to the formation of a thick natural oxide layer. In this study, we demonstrated that the change in the oxidation behavior of a melt-spun Zr50Cu50 metallic glass foil caused by the surface casting defects on its wheel side can lead to a dramatic improvement in antibacterial properties. The superior antibacterial properties of the wheel side was attributed to the metallic Cu islands exposed on the surface.

Micro-mechanism for nanocrystallization of laminated Fe-based metallic glass foil side-milled

Although various achievements were made in past years to improve the mechanism of cystallization of metallic glass using annealing or deformation processes, the relationship between the micromechanisms of nanocrystalline formation in metallic glass while milling has not been thoroughly investigated. To elaborate on the connection between plastic deformation, stress, temperature, and nanocrystallization, the laminated Fe-based metallic glass foil (FMGF) was machined by side-milling with and without ultrasonic vibration. Plastic deformation can accelerate nucleation and therefore nanocrystallization with respect to phase separation in FMGF at high temperatures. The nanocrystal distributions in the FMGF milled with ultrasonic vibration is cyclical along the milling direction. The temperature of the nucleation and growth mechanism associated with phase separation is higher than that of the nucleation mechanism based on the linked-flus model. The results provide insights on the effects of plastic deformation and high temperature in the crystallization of FMGF.

Strength of 444 Stainless Steel Single-Lap Joints Brazed with Ni-Based Metallic Glass Foils for Corrosive Environments

Strength of 444 Stainless Steel Single-Lap Joints Brazed with Ni-Based Metallic Glass Foils for Corrosive Environments

Strength of 316L Stainless Steel Single-Lap Joints Brazed with Ni-Based Metallic Glass Foils for Corrosive Environments

In brazing, the choice of base metal, brazing filler metal (BFM), and braze process conditions involves complex tradeoffs among cost, mechanical strength, corrosion resistance, and others. In this work, the tradeoff between strength and corrosion resistance of 316L stainless steel joints brazed with a newer “very corrosion-resistant” Ni-Cr-P-Mo-Si BFM and a more established “corrosion-resistant” Ni-Cr-Si-B BFM is quantitatively analyzed. Corrosion tests and microstructural analyses were performed using common practices. Joint strength was evaluated by testing brazed single-lap joints (SLJs) in tension following standardized procedures. However, conventional interpretations were found to be inadequate for quantitative comparisons. Therefore, the SLJ stress state was analyzed in detail and a complete interpretation was developed. Joint strength is shown to be determined by the SLJ geometry, base metal properties, and braze microstructure. This analysis was used to explain the occurrence of different failure modes (fast fracture, peeling, and base metal failure) and to make suggestions for improved methods for conducting and analyzing brazed SLJ tensile tests. The newer BFM is shown to provide significantly better corrosion resistance for a moderate reduction in mechanical strength.

Влияние изохронных отжигов на поверхностные характеристики лент металлического стекла Ni-=SUB=-50-=/SUB=-Ti-=SUB=-50-=/SUB=-

In this paper we investigated the crystallization of NiTi metallic glass foils of equiatomic composition by XRD and AFM. The initial foil surface which was obtained by the melt spinning method contained only cristalline phases of impurities. Ten-minute annealing at 500°C leads to phase transition in the form of devitrification of Ni50Ti50 phase. The analisys of foil surface geometry included calculation of direct inhomogeneities characteristics, roughness and fractal dimension, as well as the parameters of multifractal fromalism. It was showen that after ten-minute heat treatment at 500°C all above mentioned characteristics have local extrema. In particular there is a minimum of the widths of the singularities spectra which indicates the monofractalization of the system.

Influence of tool coating condition on side milling of amorphous laminated composite block

Iron-based amorphous metallic glass foil has a growing demand for the energy-efficient electric parts due to the excellent magnetic performances. The extreme mechanical properties in terms of high ultimate strength and high hardness make it to be a typical difficult-to-cut material. In addition, the form of ribbon foil formed by melt spinning technique can effectively reduce the eddy loss but also makes the conventional milling to be hardly performed. Amorphous laminated composite block consisted of metallic glass foils bonded by adhesive material provides an alternative structure. In this work, the investigations on machineability and tool wear were conducted using amorphous composite block consisted with iron-based metallic glass foil and acrylic adhesive bonding to advance the understanding of cutting performance. TiAlN and diamond coatings were used to reveal the wear mechanisms. Infrared camera was used to capture the cutting temperature of tool and produced chip as well as wear types were identified by SEM/EDS analysis. As a result, good surface quality of machined surface was obtained, associated with burrs generated on the margin along laminating direction. TiAlN coating exhibited a superior cutting performance and wear resistance compared with diamond-coating, which on the other hand showed a better chip removal process but was suffered from the thermo-chemical wear significantly.

Novel micro-flat springs using the superior elastic properties of metallic glass foils

A thin metallic glass foil of 100mg mass forming a sinusoidal arc behaves as non-conventional flat micro-spring withstanding loads 105 times higher than its load. Upon a normal load applied on the top of the arc, the foil deforms elastically leading to sinusoidal wavy patterns of higher order. The lifespan of the novel spring is higher than conventional low cycle springs and can potentially be further improved by eliminating surface and edge preparation induced defects. This unique behavior of metallic glass foils has the potential to revolutionize the field of springs and can be exploited for numerous applications.

Crystallisation behaviour during tensile loading of laser treated Fe–Si–B metallic glass

Effect of tensile loading on crystallisation behaviour of as-cast and laser thermal treated Fe–Si–B metallic glass foils was investigated. Tensile loading lacked any marked influence on the crystallisation behaviour of as-cast and structurally relaxed laser-treated metallic glass foils. Furthermore, the average crystallite/grain size in partially crystallised laser-treated metallic glass foil was nearly equal to the average crystallite/grain size in the region away from the fracture of the same partially crystallised laser-treated metallic glass foil after tensile loading. However, a significant crystallite/grain growth/coarsening of the order of two and half times was observed in the fractured region compared to the region around it for the laser-treated partially crystallised metallic glass foils. The simultaneous effects of stress generation and temperature rise during tensile loading were considered to play a key role in crystallite/grain growth/coarsening.

Optimization of laser thermal treatment of Fe–Si–B metallic glass

Fe–Si–B metallic glass foils were laser treated using a continuous wave Nd:YAG laser. Electrical resistivity and ultimate tensile strength of the laser treated foils were evaluated using four point probe method and Instron universal testing machine respectively in order to realize the structural changes during laser treatment. Electrical resistivity increased with laser fluence till the laser fluence of 0.42J/mm2 and then steadily reduced. Ultimate tensile strength remained stable in the laser fluence range of 0.39–0.52J/mm2 and then substantially reduced. The analysis of variance (ANOVA) based statistical analysis for optimization helped to identify the laser processing condition that contributed the most to maximize ultimate tensile strength and minimize the electrical resistivity.

Dynamic crystallization during non-isothermal laser treatment of Fe–Si–B metallic glass

Fe–Si–B metallic glass foils were subjected to non-isothermal laser treatment to induce crystallization, and the effect of laser fluence on crystallite size was investigated. Temperature, and corresponding heating and cooling rates generated during laser processing of metallic glass were estimated using multiphysics computational models. Estimation of the onset and arrest temperatures of crystallization was based on the results obtained using the thermal model. Crystallite size was measured with the aid of x-ray diffraction and transmission electron microscopy. The fraction of crystallization was estimated with a differential scanning calorimetry. Crystallite size increased with laser fluence in the initial stages and saturated later within the laser fluence range (0.6–0.9 J mm−2) explored in the current efforts. The fraction of crystallization steadily increased with the increase in laser fluence. Unlike conventional processes, in the present situation the dynamic effects during laser processing dominated the crystallization and growth process. Rapid heating rates during laser processing led to a shift in the onset of crystallization temperature to a higher level. Faster cooling rates prematurely arrested the crystallite growth yielding much finer crystallite sizes.

Mechanically induced waves in metallic glass foils

The response of vitrified metallic arc foils under normal load is studied. Application of normal load on an initial arc shaped vitrified metallic foil is followed by multiplication of the initial arc. A sinusoidal mathematical expression can be used for the description of the produced harmonic undulations. The number of the formed waves increases as the displacement increases. Therefore, this undulatory behavior of the vitrified foils can be exploited as a flat spring with multiple spring constants. For comparison crystalline foils were tested. The enormous elastic region of vitrified alloys allows this undulatory response to occur extensively while plastic deformation is unavoidable when crystalline foils are used. Exploiting the metallic glass characteristics, the predefined extrema positions of the formed undulations and the mechanical characteristics of the vitrified foils a new type of electromechanical switch is suggested.

Tensile behavior of laser treated Fe-Si-B metallic glass

Fe-Si-B metallic glass foils were treated with a linear laser track using a continuous wave Nd-YAG laser and its effect on the overall tensile behavior was investigated. Microstructure and phase evolutions were evaluated using X-ray diffraction, resistivity measurements, and transmission electron microscopy. Crystallization fraction was estimated via the differential scanning calorimetry technique. Metallic glass foils treated with the lower laser fluences (<0.49 J/mm2) experienced structural relaxation, whereas higher laser fluences led to crystallization within the laser treated region. The overall tensile behavior was least impacted by structural relaxation, whereas crystallization severely reduced the ultimate tensile strength of the laser treated metallic glass foils.

Characterization, shear strength and corrosion resistance of self joining AISI 304 using a Ni Fe–Cr–Si metallic glass foil

This work studied the microstructure of the interlayer formed after self joining of AISI 304 stainless steel, using a commercial metallic glass foil as the joining element and its effect on the shear and corrosion resistances at the interface zone. Different joining times and temperatures were used varying from 25 to 90min, and 800°C, 900°C and 1000°C, respectively. The joining process induced an inter-diffusion of alloy elements from the steel to the amorphous foil, conveying to the formation of intermetallics and second phases at the joining interphase, as was observed by SEM. The residual porosity at the joining zone was reduced as both, the bonding time and temperature increased. The mechanical behavior of the bonded samples was evaluated by shear tests presenting a maximum value of 108MPa for joints produced at 900°C for 60min, however the shear test presented values higher that 75MPa for the temperature vary from 850°C to 1000°C and time of 45min. Fractures occurred on the interlayer, indicating a strong relationship between the microstructure of the interface and the mechanical strength of the joints. Electrochemical tests in 3.5wt.% NaCl solution presented pitting corrosion at room temperature under conditions of open circuit potential in the form of preferential dissolution.

Rapid thermoplastic formation of Fe-based metallic glass foil achieved by electropulsing

In this study Fe78B13Si9 metallic glass ribbons were bent into a U-shape between a pair of copper electrodes and subjected to electropulsing for 30s. The ribbons were permanently deformed after electropulsing and remained amorphous. The temperature of the ribbon did not have to exceed the glass transition temperature for deformation under electropulsing. By varying the electrode separation, current and pulsing frequency, the extent of permanent bending could be controlled. It was concluded that momentum transfer by electron led to enhancement of free volume motion in the sample. This is more effective than softening by conventional heating. This work revealed a faster and easier novel way of shaping metallic glasses of limited plasticity, while evading embrittlement and crystallization.

Laser welding of Ni-based metallic glass foil

Metallic glass is an amorphous alloy that shows the glass transition phenomenon and maintains its amorphous condition even when cooled at 1–100 K/s, a rate at which the usual solidification process...

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.

Homogenization of plastic deformation in metallic glass foils less than one micrometer thick

Metallic glasses do not possess crystalline structures with slip systems that provide for plastic deformation via dislocation glide. As such, when put under applied stress, they show a wide reversible elastic deformation ${\ensuremath{\epsilon}}_{\text{el}}\ensuremath{\approx}2\mathrm{%}$ before plastic flow occurs heterogeneously by localization in shear bands only tens of nanometers in thickness. Very recently, there have been reports that in microscopic (submicron thickness) pillars, such shear bands no longer form and deformation occurs homogeneously. Here we report on plastic deformation of submicron thickness foils of metallic glasses. When such foils are compressed or notched, a similar transition occurs from the usual heterogeneous plastic deformation mode via shear banding to more homogeneous deformation without formation of shear bands. Some shape instabilities in the form of vortices observed at interfaces between plastic zones and nondeformed regions are consistent with sharp deformation-induced density, velocity, and viscosity gradients. The onset of homogeneous deformation in the microscopic regime is discussed in relation to shear-band formation energy and thickness.

Metallic glass coating on metals plate by adjusted explosive welding technique

Using an adjusted explosive welding technique, an aluminum plate has been coated by a Fe-based metallic glass foil in this work. Scanning electronic micrographs reveal a defect-free metallurgical bonding between the Fe-based metallic glass foil and the aluminum plate. Experimental evidence indicates that the Fe-based metallic glass foil almost retains its amorphous state and mechanical properties after the explosive welding process. Additionally, the detailed explosive welding process has been simulated by a self-developed hydro-code and the bonding mechanism has been investigated by numerical analysis. The successful welding between the Fe-based metallic glass foil and the aluminum plate provides a new way to obtain amorphous coating on general metal substrates.

Ni基金属ガラス箔のレーザ溶接

Ni基金属ガラス箔のレーザ溶接

Ultrasonic bonding of Zr 55Cu 30Ni 5Al 10 metallic glass

The present study estimates the feasibility of ultrasonic bonding technique to bond Zr 55Cu 30Ni 5Al 10 metallic glass to each other. Bonding without external heat has been challenged, as well as that with assisting external heat. The results indicate that the metallic glass foils can be bonded even under the condition without external heat. Although the strength of the bonds is low due to the insufficient fraction of adhered area, the bonds are successfully formed retaining the glassy structure. The adhered area can be increased by employing the bonding condition with an external heat up to 423 K, which is still lower than the glass transition temperature of the Zr 55Cu 30Ni 5Al 10 metallic glass alloy.