Ribbon Thickness Research Articles

Cooling wheel features and amorphous ribbon formation during planar flow melt spinning process

A numerical model incorporating actual production conditions of planar flow melt spinning process is presented. Knowledge of the process conditions at which an amorphous ribbon with uniform thickness can be obtained is important to reduce the manufacturing costs. Cooling wheel conditions play a significant role during rapid solidification of the melt. Hence a heat transfer analysis is performed to investigate the influence of cooling wheel temperature on ribbon formation. Nusselt's correlation is used for the first time for selecting a convective heat transfer coefficient between rotating wheel and surrounding air. This approach assists in predicting the conditions at which a continuous/broken/no ribbon formation is obtained during the process. The model could predict whether the ribbon to be obtained is amorphous or non-amorphous before the experiment is actually performed at a set of process conditions. Various internal and external conditions of the cooling wheel are tested, and they show little influence on the ribbon thickness up to 0.5s (10 rotations). Broken and nonamorphous ribbons are obtained for poor cooling conditions of the wheel with increase in time of cast from 0.5s to 1s (20 rotations). Amorphous ribbon with uniform thickness can be obtained for a wheel of 20mm wall thickness, when the inner and outer surfaces of the cooling wheel are maintained at a temperature of at least 300K.

Numerical and Analytical Modeling of Free-Jet Melt Spinning for Fe75−Si10−B15 (at. %) Metallic Glasses

Amorphous fiber, ribbon, or film is produced through melt spinning. In this manufacturing process, a continuous delivery of amorphous material is simultaneously dependent on the wheel spinning rate, metallic liquid viscosity, surface tension force, heat transfer inside the melt pool and along the substrate, and other parameters. An analysis of a free-jet melt spinning for fiber manufacture has been performed to relate the process control parameters with amorphous formation. We present a numerical simulation of transient impingement of a free melt jet with a rapidly rotating wheel, along with theoretical estimates of melt ribbon thickness, to investigate dynamical characteristics of the flow in melt pool. The nucleation temperature and the critical cooling rate are predicted in the paper for alloy Fe75–Si10–B15 (at. %). Thermal conduction is found to dominate undercooling in melt spinning by comparing the temperature and velocity measurements with our numerical simulation and the analytical solutions.

Ribbon thickness dependence of the Magnetic Alloy core characteristics in the accelerating frequency region of the J-PARC synchrotrons

We employ Magnetic Alloy (MA) core loaded RF cavities for the J-PARC synchrotrons to achieve a high field gradient. The MA core has a laminated structure of 18μm thick ribbon layers. We have been developing high shunt impedance MA cores to prepare for an increase of beam power. At low frequencies, it is well known that the eddy current loss in the ribbon is proportional to the square of the ribbon thickness. The MA core shunt impedance can be increased by using thinner ribbons. On the other hand, at high frequencies, the MA core magnetic characteristics are largely different from low frequencies. Using thinner ribbons might be effective to increase the MA core shunt impedance in the accelerating frequency region of the J-PARC synchrotrons. We reviewed the theoretical calculations of the ribbon thickness dependence of the MA core magnetic characteristics and we derived the ribbon thickness dependence from measured data. The measured data show that the MA core shunt impedance is inversely proportional to the ribbon thickness in the accelerating frequency region of the J-PARC synchrotrons, which is consistent with our calculations.

Preparation and Structural Characterization of Rapidly Solidified Al–Cu Alloys

Rapidly solidified Al100−x–Cux alloys (x = 5, 10, 15, 25, 35 wt%) were prepared and analyzed. High cooling rate increased the Cu solubility in α-Al matrix. The influence of the cooling rate on Cu solubility extension in Al was experimentally simulated. Thus the pouring was performed in metallic die and by melt spinning-low pressure (MS-LP) technique. Melt processing by liquid quenching was performed using a self-designed melt spinning set-up which combined the cooling technology of a melt jet on the spinning disc with the principle of the mold feeding from low pressure casting technology. The thickness of the melt-spun ribbons was in the range of 30–70 μm. The cooling rate provided by MS-LP was within 105–106 K/s after the device calibration. The obtained alloys were characterized from structural, thermal and mechanical point of view. Optical microscopy and scanning electron microscopy were employed for the microstructural characterization which was followed by X-ray analysis. The thermal properties were evaluated by dilatometric and differential scanning calorimetric measurements. Vickers microhardness measurements were performed in the study. In the case of the hypereutectic alloy with 35 wt% Cu obtained by MS-LP method, the microhardness value increased by 45% compared to the same alloy obtained by gravity casting method. This was due to the extended solubility of the alloying element in the α-Al solid solution.

The effects of rapid solidification on microstructure and hydrogen sorption properties of binary BCC Ti–V alloys

Abstract The main purpose of the present work was to study the effect of rapid solidification (RS) on the microstructure and hydrogen storage properties of body centred cubic (BCC) Ti rich Ti–V alloys (Ti1−xVx, x = 0.1–0.3). Ribbons were prepared by melt spinning at spinner rotation velocities of 1000–3000 rpm. Ribbon morphology and microstructure were found to depend on the vanadium content and spinner velocity. For Ti0.8V0.2, the relation between the ribbon thickness and velocity can be expressed as a power law function, indicating that, during solidification of the Ti–V ribbons, heat transfer at the interface between spinner and ribbon controls the heat extraction. Temperature desorption spectroscopy (TDS) and in situ synchrotron (SR-XRD) studies of the RS alloys showed that hydrogen desorption from the RS alloy hydrides occurred at lower temperatures than from the as cast alloys. RS caused a microscale chemical element separation in the alloys, which depends on the vanadium content and the spinner velocity. In addition, ribbon recalescence was observed to cause nanoscale chemical redistribution trough spinodal decomposition. These two last features were proposed to be the reasons for the observed thermal destabilisation.

Full-scale magnetic, microstructural, and physical properties of bilayered CoSiB/FeSiB ribbons

The paper is devoted to the detailed analysis of microstructural and magnetic properties of the as-quenched bilayered Co72.5Si12.5B15/Fe77.5Si7.5B15 ribbons prepared by the planar flow casting (PFC) method with single crucible. The interface between both amorphous Co- and Fe-based layers is not uniform and its thickness ranges from 0.5 to 6μm over the whole ribbon length. Dependences of mechanical characteristics on the ribbon thickness show increase in Young’s modulus from 140 to 170GPa and decrease in microhardness from 18 to 13GPa, when measured from the wheel (Co) to air (Fe) side. By fixing the coiled ribbon on the planar sample holder a uniaxial magnetic anisotropy with the out-of-plane and the in-plane easy axis is induced on the air and wheel side, respectively. Bulk magnetic properties confirm that perpendicular anisotropy observed on the air side becomes stronger as getting deeper under the surface and overlaps the in-plane anisotropy from the wheel side. This is in good agreement with Mössbauer measurements. Magnetic characteristics (surface hysteresis loops and domains, bulk hysteresis loops and thermomagnetic curves) of the bilayered samples were further compared with the single-layered CoSiB and FeSiB alloys.

Changes of Structure and Magnetic Properties of Fe<sub>66</sub>Co<sub>24</sub>Si<sub>3</sub>B<sub>7</sub> Amorphous Alloy under Heat Treatment

In this paper features of structure at the atomic level, magnetic properties, and mechanisms of structural relaxation during thermal annealing of melt-spun ribbon Fe66Co24Si3B7(ribbon thickness is 28 microns) will be discussed. By means of differential scanning calorimetry and X-ray diffraction analysis of melt-spun alloy it has been shown that structural relaxation processes have complex multi-step nature, primarily related with instability of alloy. Using this data it has been shown that magnetic structure-sensitive properties, such as coercivity and magnetic moment, can be considered as structural relaxation indicators in amorphous alloys. The original amorphous material when heated to crystallization temperature partially passes to the crystalline state, causing the increase in residual magnetic moment and coercivity.

Dipping Paint Curing Amorphous U-Core Used as Reactor

Non-oriented silicon steel (35W310) and amorphous ribbon (Fe78Si9 B13 amorphous alloy) reactor U-cores are made by welding and dipping paint curing, respectively. Amorphous U-core used to make reactor cut sharply eddy current loss due to high electrical resistivity characteristic, thickness of thin ribbon and insulation of dipping paint. The amorphous alloy has high and constant magnetic permeability, and is more suitable for reactor design power to filter high order harmonic component. Keeping off high magnetostriction district with magnetic flux density of 50—100 mT can weaken influence on inductance of inductor due to elongation of magnetostriction. Amorphous alloy has a lower temperature rise using the software Infolytica 7. 2 simulation.

Ferromagnetic Order in Rapidly Cooled Nd-Fe-Co-Al Alloy Ribbons

We have studied the magnetic properties of Nd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">45</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> alloy ribbons with various thicknesses of about 120 (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ) and 50 μm (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) prepared by melt-spinning. Structural analyses based on an X-ray diffractometer and a high-resolution transmission electron microscope revealed an existence of nanocrystals with sizes of 10 ~ 20 nm surrounded by an amorphous host matrix. With decreasing ribbon thickness and nanocrystalline size, magnetic studies upon a vibrating sample magnetometer indicated the decrease of the Curie temperature (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> ), coercive force (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ), and magnetic entropy change (ΔS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ). In the ferromagnetic region, however, magnetization values determined for N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> are greater than those determined for N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> . These results are related to the differences in the critical exponents of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> (β=0.418 and γ=1.173), and N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (β=0.512 and γ=1.077), which are characteristic for the ferromagnetic nature existing in the alloy ribbons with different thicknesses.

Observation of melt puddle behavior in planar flow casting in air

Abstract Planar Flow Casting (PFC) is well known as an industrial technique for rapid quenching to produce amorphous ribbon used mainly as soft magnetic materials. However, formation mechanism of amorphous ribbon in PFC is not clear still now. On the other hand, in Chill Block Melt Spinning (CBMS) which is developed before PFC, it is clear that behavior of melt puddle, formed on the surface of quickly rotating wheel when the molten alloy stream impinges on it, determines the thickness of amorphous ribbon. Observation of the melt puddle in PFC is unfortunately limited in casting in vacuum. So, formation mechanism of amorphous ribbon does not appear to have been extensively studied. In the present work, new photographing technique has been investigated to observe the melt puddle. As the result, more clear photographs have been obtained in casting in air. Furthermore, we have tried to make clear the difference between in casting in vacuum and in air. Ni78Si8B14 alloy is used in this work. The alloy melted by induction heating in quartz crucible is impinged on Cu–1%Cr roll of 300 mm diameter by argon gas pressure through rectangular nozzle of 0.6 × 20 mm.

Microstructures and Electrochemical Properties of Si–xTiNi Alloys for Lithium Secondary Batteries

The rapidly solidified Si-xTiNi (x = 0.2-0.45) alloy ribbons were fabricated via melt spinning process. The thickness of the melt-spun ribbons was about 12.5 microm, and the sound section was selected for the experiment. The microstructures of the ribbons were analyzed using XRD, FE-SEM, and HR-TEM: The primary silicon particles of 30 nm-100 n min diameter were finely dispersed in the inactive buffering matrix of Si7Ni4Ti4 phase. The charge/discharge energy capacity and electrochemical properties were significantly influenced by the relative ratio of NiTi to silicon. With increasing the total amount of Ni and Ti content up to 45 at%, the amount of Si7Ni4Ti4 phase increased and the cycle performance was improved. The Si7Ni4Ti4 phase acted as a buffer for the volume expansion/contraction of Si occurring during the alloying and dealloying, and it could prevent a significant deterioration in cycle performance of the battery.

Investigation of magnetostrictive/piezoelectric multilayer composite with a giant zero-biased magnetoelectric effect

In this paper, we investigate the resonance magnetoelectric (ME) effect in the middle supported multilayer composites consisting of high-permeability Fe-based nanocrystalline soft magnetic alloy Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB), Nickel (Ni), and piezoelectric Pb(Zr1−x Ti x )O3 (PZT). The coupling effect between positive magnetostrictive FeCuNbSiB and negative magnetostrictive Ni results in the build-in magnetic bias due to their different magnetic permeability and coercivity. As a result, a giant resonance ME voltage coefficient (α ME,r ) at zero DC magnetic bias field (H dc) and multi-peaks of α ME,r for FeCuNbSiB/Ni/PZT/Ni/FeCuNbSiB composite are observed. The experimental results show that the giant zero-biased α ME,r strongly depends on the thickness of FeCuNbSiB ribbon. The maximum zero-biased α ME,r is up to 86 V/cm Oe for FeCuNbSiB/Ni/PZT/Ni/FeCuNbSiB with four-layer FeCuNbSiB ribbons, which is ∼500 times higher than that of the previously reported NKNLS-NZF/Ni/NKNLS-NZF trilayer composite. Compared with the peak α ME,r and the optimum H dc of Ni/PZT/Ni composite, the largest peak α ME,r of FeCuNbSiB/Ni/PZT/Ni/FeCuNbSiB composite with four-layer FeCuNbSiB ribbons increases ∼185 %, and the optimum H dc decreases ∼300 Oe, respectively. Based on the nonlinear magnetostrictive constitutive relation and the magnetoelectric equivalent circuit, a theoretical model of α ME,r versus H dc is built under free boundary conditions. Calculated zero-biased α ME,r and α ME,r versus H dc are in good agreement with the experimental data. This laminate composite shows promising applications for high-sensitivity power-free magnetic field sensors, zero-biased ME transducers and small-size energy harvesters.

Formation mechanism of ternary NiAl-Mo eutectic alloy under quenching condition

The rapid solidification of ternary NiAl-Mo eutectic alloy is investigated by using melt-spinning technique, and the conventional casting is also carried out for a comparison study. The phase constitutions of the alloy samples obtained from different experiments each include both B2-NiAl intermetallic and bcc-Mo solid solution, which are both presented in the 〈110〉priority growth direction. The growth orientation relationship of the coupled two eutectic phases are obtained to be (110)NiAl//(110)Mo. The cast alloy is composed mainly of two regular eutectic phases in structure and exhibits daisy-like eutectic cells. However, the melt-spinning ribbons show the microstructures of the columnar grain near the roller surface zone and the equiaxed grain near the air zone. With the wheel speed increasing from 10 m/s to 50 m/s, the cooling rate of the alloy ribbons increases from 1.01×107 K/s to 2.46×107 K/s, while the thickness of alloy ribbons decreases from 49.4 μm to 22 μm. Meanwhile, the volume fraction of columnar grain zone increases gradually, and the grains are refined obviously. The cooling rate in the melt-spinning experiment for alloy ribbon is obviously higher than that in the conventional casting test, which leads to a significant difference in solidification microstructure between two techniques.

Magnetostriction Behavior of Pseudobulk CoFeBSiNb(Ga) Systems

Co-based ferromagnetic amorphous systems prepared by rapid quenching are parts of a very interesting group of materials from the perspective of new magnetic application possibilities. Practical applications of amorphous metallic glasses are in some cases limited by the thickness of the ribbon. In the present contribution as-cast and after annealing Co–Fe–B–Si–Nb ribbons (monolayer), pseudobulk (bilayer, trilayer) materials with increased thickness in comparison with ribbons (monolayer) and Co–Fe–B–Si–Nb-Ga ribbon were investigated by measurements of magnetostriction λs. These materials were prepared by planar flow casting method (PFC) and modified PFC method with a single crucible which has two or three nozzles for preparation of pseudobulk samples, respectively. The field dependence of the parallel [λpar(H)] and perpendicular [λperp(H)] magnetostrictions in the sample plane was measured at room temperature. These dependencies were used to calculate the values of saturation magnetostriction λs. Microstructure of the as-cast samples as well as annealed samples was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM).

Metallic glass formation in the binary Cu–Hf system

Glass formation, structure and thermal properties of alloys in the binary Cu100−x Hf x alloy system, where x = 25–50 at.%, are reported and discussed. This work also presents a comparison between copper casting techniques, from thick melt-spun ribbons to suction cast cylindrical rods, and the prediction of critical diameter, d c, based on maximum ribbon thickness, x c. Ribbons of Cu60Hf40 and Cu65Hf35 exhibited a fully glassy phase up to a thickness of 170 μm. Suction casting lead to an increase in the largest diameter over which both alloys could be cast, in comparison to melt-spun ribbons, and remain amorphous, with Cu65Hf35 showing a large critical diameter of 1 mm. This result is rationalised by a lower liquidus temperature, T l, which maximises the reduced glass transition temperature, T rg, and also correlates closely with the eutectic point. Finally, there were remarkable similarities between the Miedema model and the efficient packing model for predicting the range for metallic glass formation in this binary system.

Thermal-capillary analysis of the horizontal ribbon growth of silicon crystals

A thermal-capillary, finite-element model is developed for the Horizontal Ribbon Growth (HRG) system to study the characteristics of the process and to assess its feasibility to grow silicon sheets. The mathematical model formulation rigorously accounts for mass, energy, and momentum conservation while simultaneously representing capillary physics of the menisci, tracking of the solidification front, and self-consistent determination of ribbon thickness. Model results show the potential, with suitable heat transfer design, for the HRG process to achieve the formation of an extended, wedge-shaped interface with latent heat dissipation primarily in a direction perpendicular to the pulling direction. These attributes allow the HRG system to achieve higher pull rates under lower thermal gradients than vertical ribbon growth systems. Crystal thickness is predicted to decrease with increasing pull rate; however, contrary to prior analyses, pull rate limits are identified as limit-point bifurcations to quasi-steady solutions. Multiple solution branches correspond to stable and unstable operating states, exhibiting dramatically different interfacial shapes that identify possible failure mechanisms.

Characterisation of melt spun Ni-Ti shape memory Ribbons’ microstructure

NiTi alloys are the most technologically important medical Shape Memory Alloys in a wide range of applications used in Orthopaedics, Neurology, Cardiology and interventional Radiology as guide-wires, self-expandable stents, stent grafts, inferior vena cava filters and clinical instruments. This paper discusses the use of rapid solidification by the melt spinning method for the preparation of thin NiTi ribbons for medical uses. Generally, the application of rapid solidification via melt-spinning can change the microstructure drastically, which improves ductility and shape memory characteristics and leads to samples with small dimensions. As the increase in the wheel speed led to a reduced ribbon thickness, the cooling rate increased and, therefore, the martensitic substructure became finer. Furthermore, no transition from the crystalline phase to the amorphous phase was obtained by increasing the cooling rate, even at a wheel speed of 30 m/s. Specimens for our metallographic investigation were cut from the longitudinal cross sections of melt-spun ribbons. Conventional TEM studies were carried out with an acceleration voltage of 120 kV. Additionally, the chemical composition of the samples was examined with a TEM equipped with an EDX analyser. The crystallographic structure was determined using Bragg-Brentano x-ray diffraction with Cu-Kα radiation at room temperature.

Indication of Intrinsic Macroscopic Forces Affecting Magnetic Properties of Fe-Nb/Mo-Cu-B-Si Ribbons

Si-rich (at.% <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm Si}&gt;12$</tex></formula> ) Fe-Nb/Mo-Cu-B-Si nanocrystalline ribbons are already successfully used in industry. Still the impact of intrinsic macroscopic stresses on magnetic anisotropy is not known in enough detail. Domain structure, hysteresis loops and surface chemistry have been studied in the as-annealed (nanocrystalline) state as well as the response to surface removal by etching. Creep-induced anisotropy established during annealing was found to be the essential source of the observed anisotropy. Apparently smooth gradient of transversal to longitudinal creep-induced anisotropy was identified from air-side center across the ribbon width as well as across the ribbon thickness. The relative rise of transversal anisotropy due to surface removal points to different surface etching efficiency. Raman spectroscopy confirmed the presence of ferrous oxides on both the ribbon surfaces. The existence of a defined oxide layer generating the macroscopic stress was not indicated.

Correlation of soft magnetic properties with free volume and medium range ordering in metallic glasses probed by fluctuation microscopy and positron annihilation technique

Amorphous ribbons of different thicknesses of Co64.5Fe3.5Si16B14Ni2 alloy were synthesized using the melt spinning technique by varying wheel speed. The effect of cooling rate on the ribbon thickness and their soft magnetic properties have been studied. The amorphous structure has been characterized in terms of structural free volume and medium range order (MRO) by positron annihilation spectroscopy and fluctuation electron microscopy techniques. Positron lifetime spectra of amorphous samples showed two lifetime components. The first component was found to be correlated with MRO whereas, the second lifetime component was found to be associated with nanovoid type of defects, and the second component was strongly dependent on processing conditions. It could be established that the coercivity of the amorphous samples produced by the rapid solidification technique mainly depends on the defects formed during processing rather than change induced in MRO.

Effect of Processing Parameters on Thickness of Columnar Structured Silicon Wafers Directly Grown from Silicon Melts

In order to obtain optimum growth conditions for desired thickness and more effective silicon feedstock usage, effects of processing parameters such as preheated substrate temperatures, time intervals, moving velocity of substrates, and Ar gas blowing rates on silicon ribbon thickness were investigated in the horizontal growth process. Most of the parameters strongly affected in the control of ribbon thickness with columnar grain structure depended on the solidification rate. The thickness of the silicon ribbon decreased with an increasing substrate temperature, decreasing time interval, and increasing moving velocity of the substrate. However, the blowing of Ar gas onto a liquid layer existing on the surface of solidified ribbon contributed to achieving smooth surface roughness but did not closely affect the change of ribbon thickness in the case of a blowing rate of <svg style="vertical-align:-1.29163pt;width:42.525002px;" id="M1" height="12.4875" version="1.1" viewBox="0 0 42.525002 12.4875" width="42.525002" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(1.25,0,0,-1.25,0,12.4875)"> <g transform="translate(72,-62.01)"> <text transform="matrix(1,0,0,-1,-71.95,63.35)"> <tspan style="font-size: 12.50px; " x="0" y="0">≥</tspan> <tspan style="font-size: 12.50px; " x="12.027886" y="0">0</tspan> <tspan style="font-size: 12.50px; " x="18.279387" y="0">.</tspan> <tspan style="font-size: 12.50px; " x="21.405136" y="0">6</tspan> <tspan style="font-size: 12.50px; " x="27.656635" y="0">5</tspan> </text> </g> </g> </svg>&#x2009;Nm<sup >3</sup>/h because the thickness of the solidified layer was already determined by the exit height of the reservoir.