Metallic Glass Wires Research Articles

Tensile plasticity with enhanced β-relaxation in high-energy metallic glass wires

Tensile plasticity with enhanced β-relaxation in high-energy metallic glass wires

Atomistic understanding of deformation-induced heterogeneities in wire drawing and their effects on the tensile ductility of metallic glass wires

Compared to crystalline metals, metallic glasses (MGs) show an exceptional feature of improved ductility after being mechanically processed by wire drawing. However, its underlying mechanisms have not yet been fully elucidated. In this study, with the aid of atomistic simulations, wire drawing and subsequent tensile loading were performed on MG nanowires to systematically investigate the deformation mechanisms of MGs in wire drawing, the deformation-induced heterogeneities and their influences on the tensile ductility. The results revealed that the deformation mechanisms of MGs in wire drawing are closely associated with the area reduction ratio (R): at a small R of 4.7%, the area reduction is realized via shear transformations of atoms near the surface, leaving the core intact; while at a large R of 9.3%, it relies on the formation of multiple spatially distributed shear bands that redistributes the plasticity throughout the sample. The deformation-induced heterogeneities were understood through the detailed analysis of the resultant residual strain and stresses, the gradient rejuvenated amorphous structures, the unique free volume distribution and spatially distributed shear bands. Moreover, the tensile simulations revealed improved ductility synchronized with decreased yield strength of the drawn samples. The improved ductility is attributed to the synergistic effects of three beneficial factors: 1) The surface compressive residual axial stress leads to a shift of the yield sites from the surface to the core, suppressing the rapid formation of shear bands; 2) The rejuvenated structures near the surface constrain and accommodate the plastic deformation in the core; 3) The spatially distributed shear bands, generated at large R, serve as heterogeneous nucleation sites for highly dispersed plastic shearing. The findings provide a comprehensive elucidation of the deformation-induced heterogeneities of MGs in wire drawing and establish a physical relationship between these heterogeneities and mechanical properties, which can serve to interpret the experimental results.

Micro-deposition of Cu-based metallic glass wire by direct laser melting process

In this study, the Cu66.5Zr33.5 (at%) metallic glass layers were deposited using laser melting additive manufacturing technique to investigate the effect of laser power on the deposition of CuZr metallic glass micro-wires. The Cu-based metallic glass micro-wires ∼150µm in diameter with circular cross section were produced by melt-extraction method. It was found that the mean width of deposited layer is expanded from 166µm to 356µm with increasing laser power attributed to a change in the wettability. The micro-hardness value of Cu-based metallic glass deposited layer was higher in low power deposition. The reliability for the optimization of processing parameters to control micrometer scale deposition by metallic glass wire is also evaluated.

Multi-stream Casting of Wire Directly from Melt

Wire is a versatile product that offer the highest strength in any material and has therefore been a product form that is highly valued in engineering alloys. The idea of direct casting wire directly from metallic alloy melt has been around for long but for many reasons has not progressed to large scale commercialization. The main problem had been the difficulty of maintaining a stable melt stream while melt jet can be quenched and continuously solidified into unbroken wire product. Here, we consider the factors responsible for stabilizing a liquid metallic melt jet and the optimization of these. Experimentation with Fe-Si-B-Cr melts for single and multi-strand is reported. It is demonstrated that high strength metallic glass wires were castable using up to five strands. The role of oxide forming elements in stabilizing and widening the range of process parameters is emphasized. X-ray photon electron spectroscopy (XPS) of direct cast wires showed that stable Cr/Si oxide were formed and the evaluation of experimental cast data suggest that a minimum concentration of oxide former is required to maintain continuity in wire products. Other significant process parameters to be optimized for continuous wire formation in multi-streaming wire casting were, nozzle spacing, nozzle-water clearance, and the cast temperature. The multi-streaming of the wire casting process was achieved using laser drilled nozzles and thus provided a credible path for increasing the throughput in a wire casting process.

Cooling rate-dependent yield behavior of metallic glass wires

The current work presents an exhaustively study on cooling rate-dependent yield behavior of Cu50Zr50 (at%) and Ni56Nb44metallic glass (MG) wires fabricated by a melt-extraction technique. After tension test, based on the measurement of the fracture angle, the yield behavior of the MG wires with different diameters is analyzed. Based on the Mohr-Columb criterion, the cohesion strength of the MG wires is evaluated. According to the free volume model, the cohesion strength of the MG wires is quantitatively predicted. The correlation between the yield behavior and the quantity of free volume in the glassy phase is elucidated.

A Study on Welding Characteristics of Laser Beam Coatings by Fe-Based Bulk Metallic Glass

In this study, the mechanical properties and microstructure of a surface hardenings coating layers formed by laser cladding using bulk metallic glass (BMG) wire as a filler, have been evaluated. The fabricated powder shape as a filler metal was observed as sphericalness, which is suitable for laser welding. X-ray diffraction analysis observed that the powder was fully amorphous. The mechanical properties were measured by tensile strength tests and micro-hardness tests, whereas the microstructure and grain structure were analyzed by using a field emission scanning electron microscope and transmission electron microscope. Surface coating was carried out by laser cladding and gas tungsten arc welding (GTAW) processes. The tensile strengths of the laser-clad and GTAW coatings were determined to be 2.0 and 1.7 GPa, respectively. The tensile strength and microhardness of the laser-clad coating were about 15% and 14.3% higher, respectively, than those of the GTAW coating. Additionally, the laser-clad coating showed finer grains and fewer dendrites due to reduced dendrite distribution. The BMG layer was composed of a mixture of α-Fe and amorphous phases.

On the Stability of the Melt Jet Stream during Casting of Metallic Glass Wires

The factors that affect the stability of the melt stream during the casting of wire directly from the melt have been investigated. It is shown that the criticality of process parameters centres mostly on the forces imposed on the melt stream at confluence with the cooling water. The analysis of these forces indicated that the shear component of the disturbance is dependent on the ratio of the velocity of the melt stream (vm) to that of the cooling water (vw) in accord with results obtained from previous experiments. The role of oxide-forming elements in widening the process parameters range is attributed to the increased stability of the melt stream due to the additional shear force resistance offered by the solid oxide layer. The roles of Cr and Si oxides in stabilising the melt stream are confirmed by X-ray photoelectron spectroscopy (XPS) of wire indicating the presence of these oxides on fresh as-cast wires. Melt superheat and nozzle clearance distance are not strictly stream stability factors, but rather their role in glass formation prescribes optimal limits for fully amorphous wire.

Log-normal diameter distribution of Pd-based metallic glass droplet and wire.

We have studied the formation of Pd42.5Cu30Ni7.5P20 metallic glass droplets and wires in the gas atomization process. We demonstrate that the sizes of droplets and wires can be distinguished by the Ohnesorge number (Oh), which is the proportion of the spinnability to the capillary instability, and the diameter distributions follow a log-normal distribution function, implying cascade fragmentation. For droplets, the number significantly increases at Oh < 1 but the diameter gradually decreases. For wires, the number greatly increases at Oh > 1 while the diameter steadies below 400 nm. Further, the wire diameter is quadrupled at Oh = 16 due to the high viscosity which suppresses both capillary breakup and ligament elongation.

Functional localization of kinesin/microtubule-based motility system along metallic glass microwires

We report an approach using metallic glass microwires for functional organization of kinesin/microtubule-based molecular motility systems along a quasi-one-dimensional track. The molecular motility system assembled along a metallic glass microwire exhibits the typical kinesin-powered gliding motion of microtubules, while the variance of the gliding direction depends on the wire diameter. As a result of the geometrical boundary condition given by the wire tracks, the angle within which the orientations of gliding microtubules fall becomes narrower for smaller wire diameter. Such behavior supports the feasibility of using microwires as a simple and flexible means of spatial regulation of the molecule-based in-vitro motion. Furthermore, the metallic glass wires interact with microtubules, the negatively charged polyelectrolyte, by creating electric fields. We experimentally demonstrate how the electric field-induced forces act as an additional control parameter in the wire-based manipulation of the molecular motility system.

Ultrahigh-strength submicron-sized metallic glass wires

In situ deformation experiments were performed in a transmission electron microscope to investigate the mechanical properties of submicron-sized Pd40Cu30Ni10P20 metallic glass (MG) wires. Results show that the submicron-sized MG wires exhibit intrinsic ultrahigh tensile strength of ∼2.8 GPa, which is nearly twice as high as that in their bulk counterpart, and ∼5% elastic strain approaching the elastic limits. The tensile strength, engineering strain at failure and deformation mode of the submicron-sized MG wires depend on the diameter of the wires.

The role of surface oxide composition on the fatigue strength of metallic glass wire

The application of cyclic bending has been the most practical way in evaluating the fatigue behaviour of thin sub-millimetre wires. For metallic glass wires, the fatigue behaviour is typically expressed in the form of strain–cycle relationship because conversions of applied bend strain to stress require the accurate measure of the modulus of elasticity (E). Here, we have applied the use of ultra-nano indentation testing (UNHT) to determine modulus of elasticity of metallic glass wire of compositions Fe77.5−x CrXSi7.5B15 (x=0, 4, 8). It is found that the modulus of elasticity averaged 187±5GPa and do not show any marked dependence on the Cr substitution for Fe. The value of E so measured was used to represent fatigue data in stress–cycle configuration. It is shown that fatigue limits were both composition and atmosphere dependent. The ternary Fe77.5 Si7.5B15 alloy wire had fatigue limit dependent on humidity ranging from 1GPa in ambient (60–70% RH) to 1.86GPa at reduced humidity (10% RH) and no limit in aqueous environment. It is also evident that Cr substitution of Fe in the ternary alloy wire, improved the fatigue behaviour, reaching a fatigue strength of 2.32GPa for alloy wire with 8at.% Cr. The effects of composition and atmosphere on fatigue limits are related to the role played by the composition of oxide film on the wire surface. XPS studies indicated that Cr containing wires had established Cr/Si oxides that were responsible for protection against an environmentally induced fatigue failure. The drop in fatigue strength for Cr containing wire in the aqueous medium is due to the reduced protection as a result of the deterioration of the high temperature oxide that is not reformed at room temperature because of low Si chemical activity.

Preparation of Ti-Based and Zr-Based Bio-Metallic Wires by Arc-Melting Type Melt-Extraction Method

New Ti-based and Zr-based metallic wires for the future application as biomaterials were developed by arc-melting type melt-extraction method. Zr-based metallic glass wire, -Ti type Ti-Zr binary wire and -Ti type Ti-Nb-Ta-Zr (TNTZ) wire show high tensile strength and good vending ductility. Zr-based metallic glass wire shows extremely high tensile strength over 1GPa and large elastic strain limit reached approximately 2%. Ti-Zr binary alloy shows high wire-shape forming tendency during melt-extraction, and high Ti concentration Ti90Zr10 alloy wire was obtained. TNTZ wire shows superior bending ductility and full ductility is achieved.

Tensile properties of glassy MgZnCa wires and reliability analysis using Weibull statistics

Mg-based metallic glass wires were produced via the melt-extraction technique. Their mechanical properties were evaluated by carrying out tensile tests on electrochemically polished dogbone-shaped wire samples, and their reliability was estimated using Weibull analysis. The wires exhibit a tensile strength of 675–894 MPa with a characteristic strength of 817 MPa and a Weibull modulus of 20.6. The high Weibull modulus is explained by the plastic behavior and necking of the tensile samples. The tensile tests also reveal an extended amount of homogeneous plastic deformation, which can be assigned to the circular geometry and flawless surface quality of the specimens.

Preparation of Zr-Based Metallic Glass Wires for Biomaterials by Arc-Melting Type Melt-Extraction Method

New Zr-based metallic glass wires with and without bio-toxic elements of Ni and Al for the application to biomaterials were prepared by arc-melting type melt-extraction method and their characteristics were tested. The continuous metallic glass wires with a good white luster and smooth surface were obtained in various alloys such as conventional Zr-Al-Ni-Cu, Ni-free Zr-Al-Co-Cu, and Ni and Al free Zr-Ti-Co alloys. The Zr-based metallic glass wires exhibit high tensile strength reaching 1 GPa. Furthermore, the metallic glass wires showed good bending ductility and could be bent through 180 degrees without fracture. The Zr-based metallic glass wires achieve simultaneously high tensile strength, good bending ductility and high thermal stability. [doi:10.2320/matertrans.MRA2008006]

Preparation of Zr-based Metallic Glass Wire for Biomedical Application

AbstractNew Zr based metallic glass wires without bio-toxic elements of Ni, Al and Be were devel-oped for the further application as biomaterials by arc-melting type melt-extraction method. The continuous metallic glass wires with a good white luster and smooth surface were obtained in Zr-Ti-Al-Co, Zr-Al-Co-Cu, Zr-Al-Co and Zr-Ti-Co alloys. The Zr-based metallic glass wires show high tensile strength reaching 1000MPa. Furthermore, the wires exhibit good bending duc-tility and can be bent through 180 degrees without fracture. The Zr-based metallic glass wires achieve simultaneously high tensile strength, good bending ductility and high thermal stability.

Process development of metallic glass wires by a groove quenching technique for production of coil springs

We have developed a continuous production process of metallic glassy alloy wires directly from melt. In the groove quenching process, Zr–Al–Cu–Ni alloy melt was injected to semi-circular groove located on upside surface of Cu-rotating disk. In an optimum operation condition, long glassy alloy wires with diameters ranging from 1 to 2 mm were produced. The cross-sectional geometry of the wires was nearly circular. The resultant wires exhibited almost the same thermal stability as that for the ribbon produced by a single roller melt spinning technique. The change in diameter was measured at an interval of each 10 mm. In addition, coil springs with a mean diameter of 7.2 mm could be formed using a viscous flow process. In this paper, the performance and properties of Zr-based glassy alloy wire are discussed.

Effects of process variables on the multi-strand casting of high strength sub-millimetre metallic glass wire

The casting of amorphous iron-based wires of sub-millimetre diameters have been studied in a multiple jet casting condition. The effects of process parameters; melt jet to water velocity ratio (vr), melt super heat, nozzle diameter, nozzle clearance distance, and alloy composition on the stability of the melt jet and consequently on the quality of the wire has been studied. In order to increase the output rate, a multiple-nozzle crucible was designed for the casting process. Three nozzle designs were considered. It was found that when other cast variables were optimised, the nozzle types affected the flow and coherency of the jet. The best multi-nozzle crucible was made by using laser-drilled quartz platelets. The nozzle spacing did not affect the rapid cooling of the melt jet and thus the amorphous structures in the wires were retained for the closest spacing of 1mm. It is demonstrated that the use of a multiple-nozzle crucible can effectively be used to increase by many folds the casting rate in the rotating water bath wire casting process.

Wireless Magnetoelastic Resonance Sensors: A Critical Review

This paper presents a comprehensive review of magnetoelastic environmental sensor technology; topics include operating physics, sensor design, and illustrative applications. Magnetoelastic sensors are made of amorphous metallic glass ribbons or wires, with a characteristic resonant frequency inversely proportional to length. The remotely detected resonant frequency of a magnetoelastic sensor shifts in response to different physical parameters including stress, pressure, temperature, flow velocity, liquid viscosity, magnetic field, and mass loading. Coating the magnetoelastic sensor with a mass changing, chemically responsive layer enables realization of chemical sensors. Magnetoelastic sensors can be remotely interrogated by magnetic, acoustic, or optical means. The sensors can be characterized in the time domain, where the resonant frequency is determined through analysis of the sensor transient response, or in the frequency domain where the resonant frequency is determined from the frequency-amplitude spectrum of the sensor.

Fatigue fracture morphologies of some Fe-based amorphous alloy wires

This work presents the fatigue fracture morphology of some Fe-based metallic glass wires obtained from a novel fatigue testing machine that imparts compressive to tensile bending stresses. The results show three different types of fracture surface, one from 80% to 100% ductile, i.e., rough for high amplitude stress range, other is from 50% to 80% rough for medium amplitude stress range and the third is from 15% to 50% rough for low stress range; in all cases, the rest of the fractures were brittle. The first type of fracture morphology is because both sides of the wire are exposed to extremely high tensile stresses; subsequently, as the amplitude stress was decreased, the fraction of ductile fracture diminished.

Fatigue behaviour of Fe–Cr–Si–B metallic glass wires

Cyclic compressive/tensile bending has been carried out on Fe–Cr–Si–B metallic glass wires using a controlled strain double pulley testing machine. The fatigue performance of two series of glassy alloy wires Fe 78−xCr xSi 10B 12 and Fe 77.5−xCr xSi 7.5B 15 have been compared with those of HT steel wires. Because of differences in modulus, the ranking of the materials studied changes according to whether the results are reported in terms of stress or strain. In terms of stress, the HT steel wire had a superior fatigue performance to the glassy wires; however, in terms of strain, the Fe 69.5Cr 8Si 7.5B 15 glassy wire, under higher cycle conditions, had a superior fatigue performance, to HT steel wire. The fatigue performance of the glassy wires improved with the partial substitution of Fe by Cr. The short fatigue life of the glassy wires containing zero or low Cr contents in the present study was at least partly due to the necked morphology along their lengths. Fractography revealed that corrosion pits nucleated on the surface of the wires and resulted in crack initiation at these points.