Thin Ribbons Research Articles

Reimann Brake Ramp for planar flow casting processes and analysis of ribbon gluing

Planar flow casting is a rapid solidification process used to manufacture thin, metallic ribbons, and foil. Liquid metal is forced through a nozzle against a heat-sink wheel, and it rapidly solidifies into thin ribbons. A puddle of molten metal, held by surface tension, forms between the nozzle and wheel. This study examines a well-defined periodic surface defect called herringbone (HB), which is commonly produced when casting zirconium based alloys. The presence of this defect is related to processing conditions and puddle dynamics. Its formation has been correlated with the pinning of the liquid puddle at the nozzle edge. Here, the uniformity of thickness along a ribbon was successfully controlled (over a length of 50 m) using the Reimann Brake Ramp, which reduces the wheel speed at the start of the cast. For the alloy used in this study, the variation in the dimensionless thickness parameter, τ/G, with the Euler number (Eu=ΔP/ρU2) at assigned values of B/G followed an allometric scaling, with an exponent value close to the theoretical value of 1/3. Furthermore, the nozzle inclination was related to the ribbon thickness, τ, and the ribbon quality. Moreover, a newly developed automatized melt spinner permitted monitoring and controlling of the process parameters, elucidating the gluing phenomenon of the ribbon observed during the starting phase. The ribbon gluing was influenced by the puddle geometry, the recirculation in the puddle, and later, to the ribbon cooling rate. Within these results, high-quality ribbons with control thickness over a considerable length are achieved.

Magnetoelastic Ribbons as Vibration Sensors for Real-Time Health Monitoring of Rotating Metal Beams

In the current work, magnetoelastic material ribbons are used as vibration sensors to monitor, in real time and non-destructively, the mechanical health state of rotating beam blades. The magnetoelastic material has the form of a thin ribbon and is composed of Metglas alloy 2826 MB. The study was conducted in two stages. In the first stage, an experiment was performed to test the ability of the ribbon to detect and transmit the vibration behavior of four rotating blades, while the second stage was the same as the first but with minor damages introduced to the blades. As far as the first stage is concerned, the results show that the sensor can detect and transmit with great accuracy the vibratory behavior of the rotating blades, through which important information about the mechanical health state of the blade can be extracted. Specifically, the fast Fourier transform (FFT) spectrum of the recorded signal revealed five dominant peaks in the frequency range 0–3 kHz, corresponding to the first five bending modes of the blades. The identification process was accomplished using ANSYS modal analysis, and the comparison results showed deviation values of less than 1% between ANSYS and the experimental values. In the second stage, two types of damages were introduced to the rotating blades, an edge cut and a hole. The damages were scaled in number from one blade to another, with the first blade having only one side cut while the last blade had two side cuts and two holes. The results, as was expected, show a measurable shifting on the frequency values of the bending modes, thus proving the ability of the proposed magnetoelastic sensors to detect and transmit changes of the mechanical state of rotating blades in real time.

The effect of annealing temperatures on the phase constitutes, thermal properties and corrosion behaviors of Ti-Ni-Zr-Cu high entropy alloy thin ribbons

In the present study, the amorphous Ti-Ni-Zr-Cu thin ribbons were successfully prepared through rapid spinning technology. The crystallization temperature of Ti-Ni-Zr-Cu thin ribbon increased with the increasing of heating rate. The activation energy of crystallization for Ti-Ni-Zr-Cu thin ribbon is calculated to be 156 kJ/mol, which is remarkably lower than that of the reported Zr-Cu based metal glass due to the smaller negative enthalpy of mixing atomic pairs. The phase constituents of annealed Ti-Ni-Zr-Cu thin ribbons were largely related to the annealing temperatures. The phase constitutes of Ti-Ni-Zr-Cu thin films annealed at the temperatures lower than 850 °C is almost equal, but the lattice constant of various phases is gradually reduced with the increasing of annealing temperatures. In proportion, Ti-Ni-Zr-Cu thin ribbons annealed at the temperatures lower than 750 °C show the higher Vickers hardness, while a noteworthy reduction of Vickers hardness is observed in Ti-Ni-Zr-Cu thin ribbon annealed at 850 °C. Besides, the annealing temperature has a significant effect on the specific heat and corrosion properties, which can be attributed to the distinction of phase constituents.

Microstructure and Texture Evolution during Severe Plastic Deformation at Cryogenic Temperatures in an Al-0.1Mg Alloy

The deformation structures formed in an Al-0.1Mg single-phase aluminium alloy have been studied during plane strain compression (PSC) down to liquid nitrogen temperature, following prior equal channel angular extrusion (ECAE) to a strain of ten. Under constant deformation conditions a steady state was approached irrespective of the temperature, where the rate of grain refinement stagnated and a minimum grain size was reached which could not be further reduced. A 98% reduction at 77 K (−196 °C) only transformed the ECAE processed submicron grain structure into a microstructure with thin ribbon grains, where a nanoscale high angle boundary (HAB) spacing was only approached in the sheet normal direction. It is shown that the minimum grain size achievable in severe deformation processing is controlled by a balance between the rate of compression of the HAB structure and dynamic recovery. The required boundary migration rate to maintain a constant boundary spacing is found far higher than can be justified from conventional diffusion-controlled grain growth and at low temperatures, a constant boundary spacing can only be maintained by invoking an athermal mechanism and is considered to be dominated by the operation of grain boundary dislocations.

Effect of aluminum alloying on the structure and properties of rapidly quenched TiNiCu alloy

The efficiency of shape memory alloys for the MEMS technology has been recently demonstrated. Quasibinary intermetallic TiNi-TiCu alloys produced by rapid quenching from liquid phase in the form of thin (about 40 um) ribbons are an attractive material for the fabrication of micro-actuators due to their narrow temperature hysteresis of the shape memory effect (SME) and relatively large recoverable strain. In order to broaden the functionality of SME microdevices, in this work we have alloyed TiNiCu containing 25 at.% copper with aluminum. The results have shown that alloying with 0.6 at.% Al increases the cast characteristics of the composition and favors its amorphization. Upon crystallization by isothermal annealing or electropulse treatment the resultant microstructure and SME properties of the Al containing alloy change but slightly in comparison with the original alloy however there is a significant shift (by more than 15°C) of the SME temperature range toward lower temperatures.

Effect of External Impacts on the Structure and Martensitic Transformation of Rapidly Quenched TiNiCu Alloys

TiNi-TiCu quasibinary system alloys with a high Cu content produced by rapid quenching from liquid state in the form of thin amorphous ribbons exhibit pronounced shape memory effect after crystallization and are promising materials for miniaturized and fast operating devices. There is currently no complete clarity of the mechanisms of structure formation during crystallization from the amorphous state that determine the structure-sensitive properties of these alloys. This work deals with the effect of the initial amorphous state structure and crystallization method of the alloys on their structure and phase transformations. To this end the alloy containing 30 at.% Cu was subjected to thermal and mechanical impact in the amorphous state and crystallized using isothermal or electropulse treatment. We show that after all types of treatment in the amorphous state the structure of the alloy remains almost completely amorphous but the characteristic temperatures and enthalpy of crystallization become slightly lower. Isothermal crystallization of alloy specimens produces a submicrocrystalline structure with an average grain size in the 0.4–1.0 μm range whereas electropulse crystallization generates a bimorphic structure consisting of large 4–6 μm grains and 2–3 μm high columnar crystals in the vicinity of the surface. The grains have nanosized plate-like and subgrain structures. The largest grains are observed in thermally activated samples, meanwhile, mechanical impact in the amorphous state leads to the formation of equiaxed finer grains with a less defective subgrain structure and to the shift of the temperature range of the martensitic transformation toward lower temperatures.

Experimental and numerical investigation of thermomechanical cycling of notched NiTi shape memory ribbon using SMA model accounting for plastic deformation

Shape memory alloys (SMAs) are being increasingly applied as thermally driven actuators. The commercially available SMA elements, however, frequently contain stress risers, either due to internal or surface defects or due to the required component shape. Stress risers represent a potential danger for the preliminary fatigue failure of such actuators but its actual mechanism is not very clear. This paper presents a combined experimental (2D DIC analysis of surface strains) and numerical analysis (SMA model with plastic deformation) of the stress, strain and phase fraction fields evolving in a thin NiTi shape memory ribbon with an artificial notch subjected to cyclic cooling-heating through transformation range under constant external force. It appeared that, even if only very low tensile stress is externally applied upon thermal cycling, local tensile stress at the notch tip sharply increases during the first cooling due to the forward martensitic transformation (MT) proceeding heterogeneously in space. This heterogeneity gives rise to plastic deformation at the notch-tip, which gradually accumulates upon thermal cycling and shields the notch tip from tensile overloading. Hence, fatigue performance of thermal NiTi actuator with stress riser depends very much on the plastic deformability of the alloy.

Aeroelastic Vibrations of a Thin Ribbon in a Laminar Air Flow

Aeroelastic Vibrations of a Thin Ribbon in a Laminar Air Flow

Production and Mechanical Properties of Cu-Al-Ni-Be Shape Memory Alloy Thin Ribbons Using a Cold Co-Rolled Process

The use of shape memory alloys for micro-actuators constitutes a field of application in which copper–aluminum-based alloys find their usefulness because they can reach higher activation temperatures and are easier to produce than titanium-based alloys, particularly by the method proposed in this work. SMA tapes are a two-dimensional structure that offers many design options such as stamping, punching, and deep drawing, but they are also suitable for laser cutting, engraving, stamping, and EDM machining. This work has been made to study the manufacture of copper-based shape memory alloys (SMAs) using the cold co-rolling process also called the cold-roll bonding (CRB) process. In this process, a thin metal sandwich can be produced with a rolling machine. This sandwich consists of layers of CuNiBe master alloy and Al. During the rolling phase, the sandwich has no shape memory effect (SME) or superelastic effect (SE), so thin strips can be easily produced. After the rolling phase, the sandwich is subjected to a complex heat treatment to gain the SME. To validate this process to produce Cu-based SMAs, several alloys with different CuAlNiBe compositions have been tested. The SMAs obtained were characterized by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The martensitic transformation was studied by Differential Scanning Calorimetry (DSC) and SME and SE were studied by three-point bending tests. This work shows that the CRB is a good process for making a wide variety of Cu-based SMA ribbons.

MMP20-generated amelogenin cleavage products prevent formation of fan-shaped enamel malformations

Dental enamel forms extracellularly as thin ribbons of amorphous calcium phosphate (ACP) that initiate on dentin mineral in close proximity to the ameloblast distal membrane. Secreted proteins are critical for this process. Enam−/− and Ambn−/− mice fail to form enamel. We characterize enamel ribbon formation in wild-type (WT), Amelx−/− and Mmp20−/− mouse mandibular incisors using focused ion beam scanning electron microscopy (FIB-SEM) in inverted backscatter mode. In Amelx−/− mice, initial enamel mineral ribbons extending from dentin are similar in form to those of WT mice. As early enamel development progresses, the Amelx−/− mineral ribbons develop multiple branches, resembling the staves of a Japanese fan. These striking fan-shaped structures cease growing after attaining ~ 20 µm of enamel thickness (WT is ~ 120 µm). The initial enamel mineral ribbons in Mmp20−/− mice, like those of the Amelx−/− and WT, extend from the dentin surface to the ameloblast membrane, but appear to be fewer in number and coated on their sides with organic material. Remarkably, Mmp20−/− mineral ribbons also form fan-like structures that extend to ~ 20 µm from the dentin surface. However, these fans are subsequently capped with a hard, disorganized outer mineral layer. Amelogenin cleavage products are the only matrix components absent in both Amelx−/− and Mmp20−/− mice. We conclude that MMP20 and amelogenin are not critical for enamel mineral ribbon initiation, orientation, or initial shape. The pathological fan-like plates in these mice may form from the lack of amelogenin cleavage products, which appear necessary to form ordered hydroxyapatite.

Transparent, Compliant 3D Mesostructures for Precise Evaluation of Mechanical Characteristics of Organoids.

Recently developed methods for transforming 2D patterns of thin-film materials into 3D mesostructures create many interesting opportunities in microsystems design. A growing area of interest is in multifunctional thermal, electrical, chemical, and optical interfaces to biological tissues, particularly 3D multicellular, millimeter-scale constructs, such as spheroids, assembloids, and organoids. Herein, examples of 3D mechanical interfaces are presented, in which thin ribbons of parylene-C form the basis of transparent, highly compliant frameworks that can be reversibly opened and closed to capture, envelop, and mechanically restrain fragile 3D tissues in a gentle, nondestructive manner, for precise measurements of viscoelastic properties using techniques in nanoindentation. Finite element analysis serves as a design tool to guide selection of geometries and material parameters for shape-matching 3D architectures tailored to organoids of interest. These computational approaches also quantitate all aspects of deformations during the processes of opening and closing the structures and of forces imparted by them onto the surfaces of enclosed soft tissues. Studies of cerebral organoids by nanoindentation show effective Young's moduli in the range from 1.5 to 2.5 kPa depending on the age of the organoid. This collection of results suggests broad utility of compliant 3D mesostructures in noninvasive mechanical measurements of millimeter-scale, soft biological tissues.

Mechanics of nonbuckling interconnects with prestrain for stretchable electronics

The performance of the flexibility and stretchability of flexible electronics depends on the mechanical structure design, for which a great progress has been made in past years. The use of prestrain in the substrate, causing the compression of the transferred interconnects, can provide high elastic stretchability. Recently, the nonbuckling interconnects have been designed, where thick bar replaces thin ribbon layout to yield scissor-like in-plane deformation instead of in- or out-of-plane buckling modes. The nonbuckling interconnect design achieves significantly enhanced stretchability. However, combined use of prestrain and nonbuckling interconnects has not been explored. This paper aims to study the mechanical behavior of nonbuckling interconnects bonded to the prestrained substrate analytically and numerically. It is found that larger prestrain, longer straight segment, and smaller arc radius yield smaller strain in the interconnects. On the other hand, larger prestrain can also cause larger strain in the interconnects after releasing the prestrain. Therefore, the optimization of the prestrain needs to be found to achieve favorable stretchability.

Thermal buckling and symmetry breaking in thin ribbons under compression

Understanding thin sheets, ranging from the macro to the nanoscale, can allow control of mechanical properties such as deformability. Out-of-plane buckling due to in-plane compression can be a key feature in designing new materials. While thin-plate theory can predict critical buckling thresholds for thin frames and nanoribbons at very low temperatures, a unifying framework to describe the effects of thermal fluctuations on buckling at more elevated temperatures presents subtle difficulties. We develop and test a theoretical approach that includes both an in-plane compression and an out-of-plane perturbing field to describe the mechanics of thermalised ribbons above and below the buckling transition. We show that, once the elastic constants are renormalised to take into account the ribbon’s width (in units of the thermal length scale), we can map the physics onto a mean-field treatment of buckling, provided the length is short compared to a ribbon persistence length. Our theoretical predictions are checked by extensive molecular dynamics simulations of thin thermalised ribbons under axial compression.

Shape Memory Behavior of Rapidly Quenched High-copper TiNiCu Alloys

Rapidly quenched quasibinary TiNi–TiCu system alloys with high copper contents (above 20 at.%) exhibit excellent shape memory effect and have considerably narrower hysteresis as compared with the TiNi binary alloy, this advantage being of special importance for cyclic load applications, e.g. for microelectromechanics (MEMS). The aim of this work is to study the effect of annealing parameters and copper content on the shape memory effect in TiNiCu alloys. Thin amorphous ribbons of TiNi-TiCu alloys with copper contents of 25 to 40 at.% were produced by planar flow casting at a melt cooling rate of about 106 K/s. The alloys were crystallized by isothermal annealing with variable duration and by exposing specimens to a short (10 ms) electric pulse. Increasing the copper content to above 30 at.% considerably reduces the plasticity and shape memory effect of the alloys. However, significant reduction of annealing duration greatly improves the shape memory performance due to prevention of the formation of brittle Ti-Cu phases in the alloys structure.

Effect of melt cooling rate on glass transition kinetics and structural relaxation of Vit1 metallic glass

The thin ribbons and the bulk cylindrical rods with diameters of 2 mm and 10 mm of the Vit1 metallic glass (MG) were prepared by the single roller melt spinning method and the copper mold injection casting method, respectively. The cooling rates of the samples during melt solidification were evaluated. The glass transition behaviors of three groups of MG samples with different solidification cooling rates were studied by differential scanning calorimetry (DSC) at different heating rates. The effects of melt cooling rate on the glass transition kinetic parameters such as apparent activation energy (E) and fragility parameter (m) of the Vit1 MG were studied using the Kissinger and the Vogel-Fulcher-Tammann (VFT) equations. Additionally, the structural relaxation enthalpy (ΔHrel) of three groups of MG samples was quantitatively analyzed by DSC through multi-step temperature rise and fall measurements. Results show that the melt cooling rate (R) has a significant effect on the glass transition kinetics and the structural relaxation of the Vit1 MG. As R decreases in the order of magnitude, the glass transition temperature (Tg), E, m, and ΔHrel of the Vit1 MG gradually decreases. Furthermore, in the range of the experimental cooling rates, E, m, and ΔHrel all have an approximately linear relationship with lgR.

From magneto-elastic impedance model to accurate magneto-mechanical coefficient measurements.

The measurement of the magneto-elastic impedance enables the magneto-mechanical coefficient of amorphous tapes, for example, to be accurately estimated. We first propose an analytical model describing the principle of a resonator based on magnetostrictive ribbons. We show how, from the impedance described by a circle in the complex plane, the characteristics of a magnetostrictive resonator can be established and estimated from the evolution of the impedance as a function of frequency. This method, which is entirely implemented with an amorphous metal ribbon (Metglas™ 2826), is perfectly adapted to estimate the magneto-mechanical coupling coefficient k33 and thus establish the magnetostriction curves λ(H) of amorphous ribbons. However, application to thick nickel foil shows that the current method is restricted to magnetic materials in a thin ribbon form (<∼100 µm). It should also be noted that this technique has serious advantages over those commonly used: it is non-destructive, inexpensive, and very easy to use.

Numerical analysis of NiTi actuators with stress risers: The role of bias load and actuation temperature

NiTi wires and thin ribbons are used in shape memory actuators as active elements undergoing repeated thermal cycles. The NiTi actuators operate either under constant force (CF loading constraint) or they act against a variable force (VF loading constraint) from an elastic bias spring. Any stress riser represents a danger for potential actuator failure upon cycling. Although NiTi actuators always include stress risers either inherently in their design or as material flaws, their effect on actuation performance has, however, not been studied thoroughly yet. This issue is addressed in the present paper through numerical analysis of the effects of actuation load type (CF or VF loading constraint), maximum temperature, and stiffness of the bias springs (in VF loading constraint) on the local evolution of martensitic transformation (MT) and mechanical fields around the notch upon the cyclic thermomechanical loading of a thin NiTi shape memory notched ribbon. The analyses clearly show a strong amplification effect of the transformation strain on the stress concentration factor. The results reveal that the evolution of the forward MT upon cooling causes a sharp stress peak around the notch-tip the magnitude of which depends on the bias spring stiffness while upon heating, the stress at the notch-tip area relaxes due to the reverse MT of the surrounding bulk. Moreover, the simulations indicate that any overheating during the actuation is harmful to the notch-tip as the complete reverse MT at the notch-tip has stress rising effect while incomplete MT at the notch-tip has stress relaxing effect.

Processing and characterization of Ni63Cr12Fe4Si8B13 amorphous alloy for the manufacturing of electrical resistances

Amorphous alloys exhibit random atomic arrangements in solid state form, and the phenomena of segregation and grains boundaries are absent. These alloys are obtained by rapid quenching techniques of the melt, with cooling rates of 105 … 106 ℃/s. As a result of the requirement of an extremely high cooling rate, their delivery forms are usually limited to thin films, thin ribbons and, powders. The resistivity of amorphous metals does not depend on temperature as in the case of crystalline ones, exemplified in a situation in which a Pd76Si20Cr4 alloy was heated to a temperature of 4000 K and it was observed that the resistivity in the case of the amorphous alloy increased 3 times higher than in the case of the crystalline alloy. The chemical composition of the processed alloy, in which Si and B are added to stabilize the amorphous phase, leads to an electrical resistivity of 1.72 × 10−6 Ωm and an electrical resistance of 2.9 Ω, which is 3 times higher than that of the Ni-based crystalline alloy, from which the electrical resistances are manufactured.

New data on sulphosalts from the hydrothermal siderite-type veins in the Spišsko-gemerské rudohorie Mts. (eastern Slovakia): 2. Jaskólskiite and associated sulphosalts from the Aurélia II vein near Rožňava

New samples of jaskólskiite were recently collected at the Aurélia II siderite-type hydrothermal vein with sulphides near Rožňava, Spišsko-gemerské rudohorie Mts., Rožňava Co., Košice Region, Slovakia. It forms lead-gray, irregular aggregates up to 1.5 × 1 cm in size, which are enclosed in quartz-siderite gangue. Aggregates of jaskólskiite are consisting of individual, subhedral acicular crystals to 2 mm long, strongly replaced by younger bournonite and associated with Bi-rich jamesonite, tetrahedrite-(Fe), tintinaite, native bismuth and ullmannite. Significant variation of Cu (from 0.04 to 0.23 apfu) and Bi contents (from 0.32 to 0.77 apfu) was observed in studied sample. The average (n = 69 analyses) empirical formula of jaskólskiite from Rožňava-Aurélia vein based on Pb+Bi+Sb = 4 apfu is corresponding to Pb2.11Cu0.13(Sb1.42Bi0.47)1.89S5.14. Bi-rich jamesonite is the most common sulphosalt at the studied locality and it forms prismatic crystals up to 2 cm or irregular aggregates to 3 cm in size. The Bi content in jamesonite is ranging between 0.49 to 1.69 apfu. Bournonite is also common and two compositional types were distinguished. The first, dominant type is represented by Bi-rich bournonite (containing up to 0.14 apfu Bi). The second type of bournonite, represented by thin ribbons shows significant enrichment in As (reaching up to 0.49 apfu), but has only minor content of Bi (up to 0.08 apfu). Tintinaite is rare and its average (n = 9) empirical formula based on sum of all atoms = 63 apfu is corresponding to (Pb9.67Ag0.06)9.73(Cu2.55Fe0.40Zn0.07)3.02(Sb10.19Bi5.37)15.56S34.59Cl0.10.

Contactless Detection of Natural Bending Frequencies using Embedded Metallic-Glass Ribbons inside Plastic Beams made of 3-D Printing

In the current work, to identify the bending mode harmonics, 30 microns thin magnetoelastic ribbons made of metallic glass are embedded inside 6 mm thick PLA plastic cantilever beams made by 3-D printing. This is possible because the ribbons are of magnetoelastic nature and thus change their mechanical state inducing a corresponding change in their magnetic state. The ribbons are placed at four different depths, starting with zero depth at the beam’s external surface all the way inside to the beam’s mid-plane. This technique is capable of detecting seven harmonics, and remarkably, these frequencies remain the same within a marginal error of 1% for all the depths. The amplitude of the modes drops with the increase in depth but is still strong enough, except at the midplane, to be used as a sensing signal. The harmonics spectrum is the unique signature of the structure’s state; this is a proof of concept that in a contactless fashion, the embedded ribbons provide useful information about the mechanical health of a structure.