Nonmagnetic Alloys Research Articles

EDDY CURRENT QUALITY CONTROL OF THIN-WALLED REFRACTORY ALLOY PIPES

The experience of non-destructive quality control of thin-walled pipes of small diameter from a refractory non-magnetic alloy based on eddy current and X-ray television methods is considered. An analysis of the signal of an eddy current differential transducer during scanning of defects of various types was performed. The possibility of detecting and classifying such pipe defects as cracks, pores, local wall thinning, and ferromagnetic inclusions is shown.

Eddy Current False Indications in Austenitic Steel and Titanium Alloys Heat Exchanger Tubes Activated by Stress

Eddy current non-destructive examination with the internal bobbin type probes is a mandatory test for heat exchanger tube manufacturing due to its high sensitivity to the different type discontinuities. In this paper, we want to highlight the problems related to the false indications in the nonmagnetic austenitic steel and titanium alloys due to magnetic inclusions. There are known origins for magnetic inclusions in stainless steel like chips or filings as a result of ferrous tool application, alloy depletion concerned with oxidation or corrosion, and magnetite deposits. The little-known origin of magnetic inclusions is concerned with stress induced martensitic transformation is shortly analyzed in this report as a possible mechanism for the creation of the magnetic inclusion in austenitic steel as in titanium alloy tubes. The phase transformation and as the result the presence of magnetic inclusions is generated by the activation of the spin magnetic moments of the free electrons under stress influence. These inclusions can radically influence the eddy current signal due to quite large difference in relative magnetic permeability but can be differentiated from real defects by re-inspection of the suspicious tubes at reduced operational frequency. During the eddy current examinations of stainless steel and titanium tubes by an internal probe, the false indications in tubes have been detected. The presence of these isolated indications is located always in the same length of the tested tube. The indications were detected in each tube and the signal amplitude was estimated in the range of 40-50% of the acceptance reference level. In stainless steels, the false indications generated are higher than in titanium alloys.

Multi-extreme conditions at the Second Target Station.

Three concepts for the application of multi-extreme conditions under in situ neutron scattering are described here. The first concept is a neutron diamond anvil cell made from a non-magnetic alloy. It is shrunk in size to fit existing magnets and future magnet designs and is designed for best pressure stability upon cooling. This will allow for maximum pressures above 10GPa to be applied simultaneously with (steady-state) high magnetic field and (ultra-)low temperature. Additionally, an implementation of miniature coils for neutron diamond cells is presented for pulsed-field applications. The second concept presents a set-up for laser-heating a neutron diamond cell using a defocused CO2 laser. Cell, anvil, and gasket stability will be achieved through stroboscopic measurements and maximum temperatures of 1500K are anticipated at pressures to the megabar. The third concept presents a hybrid levitator to enable measurements of solids and liquids at temperatures in excess of 4000K. This will be accomplished by a combination of bulk induction and surface laser heating and hyperbaric conditions to reduce evaporation rates. The potential for deployment of these multi-extreme environments within this first instrument suite of the Second Target Station is described with a special focus on VERDI, PIONEER, CENTAUR, and CHESS. Furthermore, considerations for deployment on future instruments, such as the one proposed as TITAN, are discussed. Overall, the development of these multi-extremes at the Second Target Station, but also beyond, will be highly advantageous for future experimentation and will give access to parameter space previously not possible for neutron scattering.

Three-wall piston-cylinder type pressure cell for muon-spin rotation/relaxation experiments

ABSTRACT A three-wall piston-cylinder type high pressure cell for muon-spin rotation/relaxation experiments was designed, manufactured, tested and commissioned. The outer cylinder of the cell body is made from MP35N and the middle and inner cylinders are made from NiCrAl nonmagnetic alloys. The mechanical design and performance of the pressure cell are evaluated and optimised using finite-element analysis. The outcomes of the experimental testing closely match the modelling results. The high pressure cell is shown to reach pressure of up to 3.3 GPa at ambient temperature, corresponding to 3.0 GPa at low temperatures, without irreversible damage.

Numerical Investigation of the Stability and Spintronic Properties of Selected Quaternary Alloys

The use of electronic charge and spins (spintronics) has been proposed for much better data storage. This class of material is believed to have excellent capability for data integrity, low dynamic power consumption and high-density storage that showcases excellent protection against data loss. The spintronic and related properties have been investigated on four newly proposed quaternary alloys (NbRhGeCo, NbRhGeCr, NbRhGeFe and NbRhGeNi) through the first-principles calculation method of the Density Functional Theory (DFT). Specifically, the phonon frequencies, elastic stabilities, and the electronic structure were systematically studied in the full Heusler structure. The results predict that NbRhGeFe and NbRhGeCr are elastically and structurally stable. Both NbRhGeFe and NbRhGeCo are half-metals with ferromagnetic character, but NbRhGeCo is unfortunately elastically unstable. NbRhGeCr and NbRhGeNi are non-magnetic metallic alloys in their spin channels. All the results predict NbRhGeFe to be the only suitable among all the four alloys for spintronic application.

Planar Hall effect in c-axis textured films of Bi85Sb15 topological insulator

Measurements of the planar Hall effect (PHE) and anisotropic magnetoresistance (AMR) in polycrystalline films of topological insulator Bi85Sb15 are reported. The observation of PHE and AMR in these films of carrier density ≈2 × 1019 electrons/cm3 is like the behavior of in-plane field transport in thin films of metallic ferromagnets. However, the amplitudes of PHE (ΔρPHE) and AMR (Δρxx) are at variance. ΔρPHE and Δρxx also undergo a sign reversal near ≈160 K. We compare these results with the reported PHE of topological insulators and Weyl semimetals and discuss possible scenarios for anisotropic backscattering of charge carriers in this non-magnetic alloy.

Study of implants for intraoperative hyperthermia

At the present time hyperthermia is recognized as one of the most promising methods in the combined treatment of malignant tumors. Nevertheless, for the most of existing methods for heating of tumor tissues it is rather difficult to realize the exact localization of heat exposure. The aim of this study is to compare two types of implants for intraoperative local tumor bed hyperthermia carried out using induction heating in an alternating magnetic field of the sub-MHz range. Composite implants of the first type are created on the base of a self-curing plastic mass mixed with electrically conductive ferromagnetic particles. The second type of implant is a hollow object with thin walls that follows the shape of the tumor. Implants of this type are filled with a liquid metal non-magnetic alloy with melting point below room temperature. The model implants were heated in a self-designed inductor with a short cylindrical coil 35 cm in diameter. Biological tissues were modeled using an ultrasound gel. Experimental results show that both types of implants were heated in an external alternating magnetic field with a frequency of 90 kHz and an amplitude not exceeding 4 kA/m up to temperatures that allow both traditional hyperthermia (tissue heating to 41-45 °C) and thermal ablation therapy (tissue heating to temperatures above 50 °C). Good agreement between the experimental data and model numerical calculations was obtained.

Invariant plastic deformation mechanism in paramagnetic nickel–iron alloys

Significance Peculiar materials properties, such as Invar anomalies, including low thermal expansion and anomalous temperature dependence of modulus of elasticity, had substantial academic and technical impact. Today both invariant effects are associated with the interplay between temperature and magnetic order and thus they are considered to be specific to magnetically ordered alloys. In this work, an invariant phenomenon manifesting in temperature-independent stacking fault energy is discovered in magnetically disordered Ni–Fe alloys. Based on our understanding of the atomic-level mechanisms behind this Invar anomaly, a similar invariant phenomenon is identified in other systems including nonmagnetic alloys. These findings advance the design of high-temperature alloys with exceptional plastic stability.

Improvement in quality of bars made from vacuum melted nonmagnetic NMMts 38-2V alloy of monel type

The possibilities of improvement in quality of bars made from nonmagnetic alloy of monel type used in the production of electric vacuum microwave devices are analyzed.

Design and Performance Investigation of 3-Slot/2-Pole High Speed Permanent Magnet Machine

High-speed rotating mechanical machinery is a developed, mature and reliable technology for many engineering applications. In high-speed permanent magnet machines, the rotor's permanent magnet PM is not strong enough to withstand the centrifugal force resulting from excessive rotational speed; thus, the PM material must be protected by a non-magnetic alloy sleeve. This paper presents a novel high-speed PM machine with solid rotor PM covered by a titanium retaining sleeve. The rotor stress condition is simplified as a plane stress problem according to the strength measurement of solid PM rotors in the high-speed PM motors. The analytical formulas for rotor stress are presented based on the polar coordinate displacement method. The proposed model is compared with a conventional model having auxiliary slots in stator teeth. Using a finite element analysis environment, the performance analysis shows that the proposed design has reduced magnet eddy current loss, cogging torque, and iron losses. The initial design is also optimized using a deterministic optimization algorithm that increases output torque by 26% compared to the initial design.

Electronic fitness function, effective mass and thermoelectric properties of Rh-based (-ScTe; -TiSb; -VSn) alloys for thermoelectric generator applications

The electronic fitness function, effective mass, and other thermoelectric properties of novel Rh(ScTe; TiSb; VSn) half-Heusler-like alloys are predicted from first-principles calculations in conjunction with Boltzmann’s Transport Theory. The calculated power factor, Seebeck coefficient, electrical conductivity, and thermal conductivity were obtained via the constant relaxation time approach implemented in the BolzTraP code. Six doping levels (3 each for electrons and holes) were used to determine the transport properties in the present work. The present results revealed that RhScTe is a non-magnetic semiconductor alloy with a narrow bandgap of 0.40 eV. Whereas, RhTiSb and RhVSn are semi-metals with no bandgaps. Besides, corresponding excess holes per unit cell at all doping levels were observed, which implies that RhScTe and RhTiSb are p-type semiconductors. In Particular, for RhScTe, we observed an increasing power factor with temperature; at 800K, the power factor is slightly above 60μWcm−1K−2s−1. At room temperature, the compound exhibits a power factor of 24μWcm−1K−2s−1 at a carrier concentration of 1×1022cm−3 which is similar to a reference p-type FeNbSb compound.

INFLUENCE OF WINDING ENDS ON THE PARAMETERS OF PULSE INDUCTOR WITH U-SHAPED CORE

It is known from the scientific literature that magnetic pulse processing of electrically conductive non-magnetic sheet materials helps to reduce residual stresses, especially in welded joints. This is due to magnetoplastic and electroplastic effects. To create such effects in non-magnetic electrically conductive materials with welded joints, an inductor with pulsed magnetic field, U-shaped magnetic circuit and hollow conductor for possibility of active cooling of the winding is proposed. Such inductor allows inducing high-density pulsed currents in electrically conductive non-magnetic sheet materials with welded joints. It studies the parameters of the inductor - active resistance and inductance in the frequency-domain mode. The parameters calculated in two-dimensional and three-dimensional models are compared. The electromagnetic field is calculated using Maxwell equations and finite element method. Parameters of an ends of winding are determined by the difference in the parameters of the three-dimensional and two-dimensional models of the induction system. Resistance is calculated separately in the groove`s part of the winding, the outer part and on the frontal parts. The parameters of the induction system with a ferromagnetic core and non-magnetic thin-sheet alloy AMg6 are calculated for various values of complex amplitude of current in winding. Additionally, the parameters are calculated both without the magnetic core and without the non-magnetic metal. The quantitative comparison of the parameters of the three-dimensional model with the two-dimensional one is performed. The active resistance and inductance of end parts of the inductor are investigated by well-known analytical expressions from handbooks of electric machines. References 11, figures 3, tables 6.

Large spin Hall angle in nonmagnetic PtSn alloy films at room temperature

High efficient nonmagnetic materials for generating and detecting spin currents are extremely sought after for prospective spintronic devices. We investigate the spin pumping and inverse spin Hall effects (ISHE) in Y3Fe5O12 (YIG)/ Pt1-xSnx (x = 0.06, 0.11, 0.17, 0.23, 0.28) bilayer using a coplanar waveguide based broadband ferromagnetic resonance setup. We find that the measured effective spin mixing conductance geff↑↓ and spin Hall angle θSH strongly correlate with the Sn content. A large spin Hall angle θSH = 0.089 ± 0.001 is obtained in a Pt0.77Sn0.23 alloy film while θSH = 0.055 ± 0.001 in pure Pt thin film under the same conditions. This enhancement of spin Hall angle is due to skew scattering from the Sn impurities resulting from spin-orbit interaction. Meanwhile, the spin Hall (SH) resistivity of the spin current induced by Sn impurities in Pt has been revealed. The SH resistivity of Pt1-xSnx remain pretty low values (0.17–1.1 × 10−9 Ω⋅m), which are promising for construct high-speed spintronic devices exploiting the spin Hall effect.

Spin-orbit torque in chemically disordered and L11 -ordered Cu100−xPtx

The binary alloys with heavy elements have been considered promising candidates for spin-orbit torque application due to the tunable spin Hall effect. In light of previous studies, the effect of crystalline structure on spin Hall effect in nonmagnetic alloys has not been thoroughly studied. Here, we present a systematic investigation of the spin-orbit torques in chemically disordered $\mathrm{C}{\mathrm{u}}_{100\text{\ensuremath{-}}x}\mathrm{P}{\mathrm{t}}_{x}$ and $\mathrm{L}{1}_{1}\text{\ensuremath{-}}\mathrm{C}{\mathrm{u}}_{50}\mathrm{P}{\mathrm{t}}_{50}$ by the spin torque ferromagnetic resonance technique. The results indicate that both the atomic concentration and the degree of the chemical ordering substantially influence the spin-orbit torque efficiency of the CuPt alloys. In chemically disordered $\mathrm{C}{\mathrm{u}}_{100\text{\ensuremath{-}}x}\mathrm{P}{\mathrm{t}}_{x}$, the primary mechanism of spin Hall effect changes from extrinsic to intrinsic when the Pt concentration is increased to larger than $80%$. In $\mathrm{L}{1}_{1}\text{\ensuremath{-}}\mathrm{C}{\mathrm{u}}_{50}\mathrm{P}{\mathrm{t}}_{50}$ with weak chemical ordering, the side-jump and intrinsic mechanisms dominate, whereas the skew scattering mechanism dominates for strong chemical ordering. This work provides a perspective to control the spin-orbit torques in alloys.

Ab initio theory of the spin-dependent conductivity tensor and the spin Hall effect in random alloys

We present an extension of the relativistic electron transport theory for the standard (charge) conductivity tensor of random alloys within the tight-binding linear muffin-tin orbital method to the so-called spin-dependent conductivity tensor, which describes the Kubo linear response of spin currents to external electric fields. The approach is based on effective charge- and spin-current operators, that correspond to intersite electron transport and that are nonrandom, which simplifies the configuration averaging by means of the coherent potential approximation. Special attention is paid to the Fermi sea term of the spin-dependent conductivity tensor, which contains a nonzero incoherent part, in contrast to the standard conductivity tensor. The developed formalism is applied to the spin Hall effect in binary random nonmagnetic alloys, both on a model level and for Pt-based alloys with an fcc structure. We show that the spin Hall conductivity consists of three contributions (one intrinsic and two extrinsic) which exhibit different concentration dependences in the dilute limit of an alloy. Results for selected Pt alloys (Pt-Re, Pt-Ta) lead to the spin Hall angles around 0.2; these sizable values are obtained for compositions that belong to thermodynamically equilibrium phases. These alloys can thus be considered as an alternative to other systems for efficient charge to spin conversion, which are often metastable crystalline or amorphous alloys.

Polarized beam option for the time-of-flight spectrometer NEAT

We present the basic design of the incoming neutron beam polarizer system recently installed at the TOF spectrometer NEAT at HZB and the first experimental test results. The recent upgrade of the instrument resulted in beam flux on the sample, which is one of the highest worldwide for this class of instruments. The substantial intensity gain obtained in the upgrade provides good conditions for polarized neutron experiments, considering the inherent cuts of neutron intensity by polarizing the beam. The neutron beam polarizer is placed inside a 3.8 m long evacuated neutron “guide changer”, which allows us to move into the beam delivery guide one of 3 alternative straight neutron guide sections mounted in parallel on a linear translation stage. The new transmission polarizer takes up the inside volume of a 1.33 m long, 60 mm x 125 mm cross section straight guide portion. The focusing of the beam after the polarizer to the 30 mm x 50 mm sample area happens over a total length of 3.5 m, of which 2.92 cm is a converging guide assembly with m=4 supermirror coating and parabolic end. This guide section leaves 58 cm space between guide exit and sample axis for sample environment equipment, in particular for high field cryomagnets. The transmission polarizer contains 8 “V cavity” channels with non-polarizing supermirror coated, opaque side walls and neutron-transparent Si cavity plates, coated by m=3 polarizing supermirror on both sides. The nominal operational wavelength band width of the polarizer is 2.5 – 8 Å, with measured polarization efficiency between 92 and 96 % for well collimated beam. The beam transmission efficiency for the preferred neutron spin state is about 65 %. The first 110 cm of the neutron spin guide field after the exit of the polarizer is provided by the stray fields of the magnet around the polarizer and of a permanent guide field magnet acting in the same direction. This section contains a wavelength tunable single coil Mezei flipper with flipping efficiency > 99 %. The rest of the guide field magnets are solenoids around the glass neutron beam guide. The supermirror coating in the polarized neutron section of the beam guide has been manufactured using a non-magnetic Ni alloy, the guide exchanger housing and its mechanical parts are made of non-magnetic alloys, primarily stainless steel. The polarized beam delivery system is by now operational and it is available for polarized neutron beam experiments on samples in a magnetic field. A 14 T vertical field cryomagnet is on hand at the HZB Sample Environment Group for use on NEAT. The NEAT sample chamber has been designed and built with non-magnetic or weakly magnetic materials in order to allow both for polarized neutron beam experiments and for polarization analysis work.

Origin of the magnetic ground state developed upon Si, Ge, and Sb-substitution at Sn site in Fe2TiSn

A nonmagnetic full Heusler alloy, Fe2TiSn, was substituted with Si, Ge, and Sb at the Sn site with a primary aim of investigating the physical properties of these compositions that are much anticipated to result in a high thermoelectric power factor and generate a half-metallic ground state. The X-ray diffraction (XRD) study carried out using the synchrotron source confirms the solubility limit of substituent atoms to be a mere 5% for Si and Ge and 60% for Sb that results in a pure L21 Heusler phase. Rietveld refinement of the XRD profiles yields the lattice parameters. Despite the fact that chemical substitution should lead to atomic disorder and an increase in the scattering of charge carriers, resistivity measurements show a significant decrease in the magnitude with as little as 5% substitution of Sn by Si or Ge. The weak localization present in Fe2TiSn seems to drastically reduce in the substituted compositions, and the long range magnetic order seems to affect the transport of the charge carriers. The origin of magnetic interactions is investigated using extended X-ray absorption fine structure spectroscopy. The changes in the local crystal structure in terms of the Fe–Fe bond distance are determined. The inference drawn from the experimental study is further complemented with exchange coupling parameter, Jij, and orbital projected density of states calculations, thus presenting an overall understanding of the origin of magnetic interactions in these technologically relevant compositions.

Transparent and p-type conductive NixO:V thin films obtained by reactive DC sputtering at room temperature

A non-magnetic alloy consisting of Ni(92%):V(8%) was used to obtain NixO:V thin films by reactive DC magnetron sputtering on unheated glass substrates. The oxygen content and the nickel oxidation state were modified by the oxygen partial pressure (Opp) applied for sputtering, while the film thickness (t) was changed through the deposition time. The structural, optical and electrical properties of the samples have been analyzed by x-ray diffraction, Raman spectroscopy, spectrophotometry and Hall-effect measurements. Visible transmittance and sheet resistance have been used to evaluate the quality of the films as transparent electrodes, which is found maximum for the layers prepared at 24% Opp with t ≤ 100 nm. These samples show maximum p-type conductivity σ = 0.78 S cm−1 and optical absorption α = 1.4 × 105 cm−1 at 0.55 μm wavelength, both independent of the layer thickness.

Electrodeposition of Ternary Fe–W–H Alloys

Electrochemical deposition, structure, and properties of Fe–W alloys are studied. The alloys formed at a low current density are crystalline supersaturated solid solutions which are magnetic. At higher current densities, amorphous nonmagnetic alloys of the same composition are formed. As a result of treatment at 500–600°С, both amorphous and crystalline transform into a more equilibrium binary system, containing W solid solution in Fe and an intermetallic compound. The concentration of the remaining W in the solid solution was much higher than the equilibrium solubility. A considerable amount of hydrogen incorporates into the deposits. The deposits may be qualified as ternary Fe–W–H alloys. The incorporated hydrogen plays a crucial role in the transition from a crystalline state typical for specimens produced at low current densities to the amorphous or nanocrystalline deposits formed at higher current densities.

Study on a biodegradable antibacterial Fe-Mn-C-Cu alloy as urinary implant material

Biodegradable Fe based alloys have been investigated for fracture fixation and cardiovascular support to overcome complications of permanent implants. This study was focused on the development of a new Fe-Mn-C-Cu alloy with antibacterial and anti-encrustation properties as a urinary implant material. The microstructure and mechanical properties of the alloy were studied. The degradation behavior, antibacterial and anti-encrustation properties were evaluated by immersion test, antibacterial test and encrustation test, respectively. The results showed that Fe-Mn-C-Cu alloy was a non-magnetic, biodegradable, anti-bacterial and anti-encrustation alloy that could inhibit the biofilm and stone formations on its surface through the dual effects of degradation and Cu ions release. The study revealed the preliminary mechanisms of anti-infection and anti-encrustation for Fe-Mn-C-Cu alloy due to the continuous release of Cu2+ ions, which provides a new idea for application of biodegradable Fe-based material and the treatment of urinary tract infections and stones in the urinary system.