Structural Phase Transformation Research Articles

Physical vapor deposited coatings on high Ni content NMC811 Li-ion battery cathode powder

The storage capacity and reliability of Lithium-ion batteries has increased at an amazing rate in the past years. They are operated in millions of electrically powered devices, but still their components are subject to continuous optimization.In this paper we focus on the cathode material of the system, which is based on powders of Nickel-Manganese-Cobalt (NMC) mixed oxides. They store Lithium-ions by intercalation between their oxidic planes. A current trend in the development of these mixed oxides is to increase the Ni content. This would reduce the need for Co, an expensive material mined under hazardous conditions. However, a high Ni content has several drawbacks, like the irreversible occupation of Li sites by Ni, structural phase transformations upon Li removal or surface contaminations caused by the chemical reactivity of Ni.We address the last point by passivating the surface of the powder with a thin layer of inert oxide. Alumina (Al2O3) or Zirconia (ZrO2) with an approximate thickness of 0.2–1.6 nm were deposited by reactive magnetron sputtering on high Ni content NMC 811 powder with an average particle size of approx. 10 μm using a rotating and tumbling powder container. The average thickness and uniformity of the coating could be correlated to the electrical resistance of the powder, which was determined by a custom-built system for powder resistance measurement under variable compression force. These measurements were confirmed by imaging the coatings on selected powder particles using low voltage SEM. Generally, the coatings were found to be uniform on both, individual grains and large ensembles of powder particles. The impact of the coating on the release of Li-ions was checked by Li leaching experiments. The coating reduced the Li release rate by approximately 10 %, which could be tolerated in a battery.

Investigation of the process of bimetallic castings formation for crushing and grinding equipment

The analysis of the state of production of wear-resistant materials showed that one of the promising directions for improving their quality is the use of bimetallic castings, which have a complex of properties differentiated by the volume and surfaces of the products. However, the problem of obtaining a high-quality connection of the base and the working layer has not been solved until now. The article examines the influence of the chemical composition, temperature parameters, and mass ratio of alloys of bimetallic pairs on the process of bimetallic castings formation. The purpose of the study was to study the growth kinetics and structural-phase composition of the transition diffusion layers of bimetallic castings depending on the chemical composition, temperature parameters and the ratio of the masses of the alloys of the bimetallic pairs. As a research result, it was established that the formation of transition layers of bimetallic castings is determined by the processes of diffusion and structural-phase transformations in the interaction zone - "solid - liquid metal". The processes largely depends on the chemical composition of bimetallic pairs, temperature parameters, and the mass ratio of the layers. It was determined that in bimetallic castings obtained by pouring liquid metal onto a preheated solid billet, the transition layer is characterized by the presence of two zones - pearlitic, from the side of the base metal and without the carbide region of the matrix of the working layer. It has been established that the formation of transition layers in bimetallic castings obtained by successive pouring of melts into the mold through autonomous pouring systems is accompanied by the saturation of steel by carbon from cast iron to a depth of 600-800 microns and the formation of a zone with a lamellar pearlite structure along the border of the alloy junction, and the transition layer between cast iron and steel consists of pearlite in the form of a narrow strip and a zone of chromic ferrite from the side of cast iron. As a result of the study of the peculiarities of the formation of transitional layers of bimetallic castings when liquid metal is poured onto a solid billet, it was established that the degree of dissolution of the base metal in liquid cast iron increases with an increase of the billet preheating temperature and the temperature of the melt, as well as the ratio of the mass of liquid cast iron to a unit surface area of the metal base. At the same time, the rate of dissolution is proportional to the gradient between the temperatures of the contact surface and the cast iron solidus. It was established that the formation of a reliable diffusion bond for bimetallic pairs "carbon (low-alloy) steel - high-chromium cast iron" is ensured if the temperature of the contact surface exceeds the temperature of the eutectic transformation of cast iron. The mechanism is revealed of formation of the transition zone structure. The materials of the article can be used by scientists for further research and practitioners in the selection of materials for work in extreme conditions. Keywords: steel, cast iron, temperature, transitional layer, solidus, liquidus, melt, solidification.

Tuning superconductivity and charge density wave order in TaSe2 through Pt intercalation

Tantalum diselenide ($\mathrm{Ta}{\mathrm{Se}}_{2}$) has emerged as a promising platform to investigate the interplay between two intriguing quantum electronic states in materials: the charge density wave order (CDW) and superconductivity. In this work, we report the ability to tune these quantum electronic states by intercalating Pt into $2H\ensuremath{-}\mathrm{Ta}{\mathrm{Se}}_{2}$. By introducing 20% of Pt into $2H\ensuremath{-}\mathrm{Ta}{\mathrm{Se}}_{2}$, we demonstrate that the structural phase changes from the $2H$ to the $4{H}_{b}$ phase of $\mathrm{Ta}{\mathrm{Se}}_{2}$ with Pt atoms intercalated within the van der Waals spacing. According to the Fermi surface of the $4{H}_{b}$ phase, a Lifshitz transition occurred, destroying the Fermi-surface nesting found in the $2H$ phase. This can be attributed to the structural phase transformation and the influence of donated electrons from Pt, thus tuning the Van Hove singularities into the Fermi-level vicinity, suppressing the CDW state, and enhancing the superconducting temperature $({T}_{c})$ to $\ensuremath{\sim}2.7$ K. The resulting superconducting properties of the $4{H}_{b}\ensuremath{-}\mathrm{P}{\mathrm{t}}_{0.2}\mathrm{Ta}{\mathrm{Se}}_{2}$ are consistent with those of a BCS type-II superconductor, with a superconducting gap of 3.0 meV. Our results provide insights into the role of electron doping and structural phase changes in fine-tuning quantum electronic-state phenomena in materials. These findings could have significant implications in designing superconducting materials with tailored properties for practical applications.

Effects of structural phase changes on the luminescence of Eu-doped (1-x)BaTiO3-xCaZrO3

We investigated the structural and luminescent properties of Eu3+-doped (1-x)BaTiO3-xCaZrO3 (BCTZ:Eu). The changes in the structural symmetry of BCTZ:Eu with CaZrO3 substitution and Eu3+ doping was determined using Rietveld refinement of the X-ray diffraction patterns. Under ultraviolet photoexcitation, the specimens exhibited typical red-orange emission peaks resulting from the f–f transitions from Eu3+ ions. The intensities and asymmetry ratios of the emission intensities, as well as Stark splitting of the emission bands from Eu3+ were found to be strongly dependent on the structural phase transformation of BCTZ from tetragonal to rhombohedral. These findings suggest that BCTZ:Eu possesses a great potential for multifunctional devices that have both ferroelectric and luminous properties.

Enhanced Energy Storage Properties of (1-x) Ba0.96Li0.04TiO3−xBiYO3 Ceramics

The lead-free perovskite ceramics of (1-x) Ba0.96Li0.04TiO3-xBiYO3 (BLT-xBY) (x = 0.02 ∼ 0.10) were synthesized using traditional solid reaction sintering at 1250 °C. XRD and Raman spectra analysis showed that the phase structure transformation occurred at 0.06 < x < 0.08. When x is in the range of 0.02 ∼ 0.06, the orthorhombic and tetragonal phases coexist in the sample. When x ≥ 0.08, the tetragonal phase disappears, and the orthorhombic phase and the cubic phase coexist. All the samples displayed almost pore-free microstructures with relative densities above 91%. As x increases, the maximum permittivity decreases and moves towards low temperature. The dielectric constant at different frequencies shows dispersion phenomenon. When x = 0.08, the remnant polarization (Pr) and the maximum polarization (Pmax) of the composition were 1.047 μC cm−2 and 11.643 μC cm−2, respectively. Meanwhile, the recoverable energy storage density (Wrec) is increased to 0.319 J cm−3 with a high dielectric breakdown strength (BDS) of 69.2 kV cm−1 at x = 0.08.

Study of regularities of structural-phase transformations during thermocyclic treatment of tool steels

Movement of carbon atoms to dislocations reduces the specific volume of the martensite phase, which, in turn, affects the general level of volumetric changes that occur as a result of phase transformations during quenching. The measurements carried out on samples of steel ShX15 showed that the minimum increase in geometric dimensions is observed. Intermediate tempering and re-quenching do not change this pattern. At the same temperature, for this steel grade, the minimum degree of martensite tetragonality was recorded. This study has shown that to obtain a high level of final properties of tool steel, the most optimal is to obtain a substructure with a high level of defectiveness of the crystal structure of steel. It was found that the use of thermal cycling treatment contributes to an increase in the level of defectiveness of the crystal structure. It was also found that the use of aqueous solutions of polymers as a quenching medium makes it possible to obtain a cooling rate less than in oil quenching, which helps to reduce the level of quenching stresses.

Temperature-induced transformation between layered herringbone polymorphs in molecular bilayer organic semiconductors

Herein we investigated the temperature-induced transformation between distinct layered herringbone (LHB) polymorphs in model organic semiconductors (OSCs) of a series of $2\text{\ensuremath{-}}\mathrm{mono}\text{\ensuremath{-}}\mathrm{alkylated}\text{\ensuremath{-}}\mathrm{benzothieno}[3,2\text{\ensuremath{-}}b][1]\mathrm{benzothiophenes} (mono\text{\ensuremath{-}}{\mathrm{C}}_{n}\text{\ensuremath{-}}\mathrm{BTBTs})$. The component molecules are composed of a one-sided linkage between the BTBT core and alkyl chains of various lengths. We propose that the polymorphism originates from a unique feature of LHB structures in which two types of $T$-shaped contacts are possible for BTBT cores that exhibit relatively low symmetry. Based on polarized UV-visible absorption spectra and powder x-ray diffraction analyses, we show that four long-alkylated $mono\text{\ensuremath{-}}{\mathrm{C}}_{n}\text{\ensuremath{-}}\mathrm{BTBTs}$ ($n=8$, 9, 10, and 11) undergo mostly irreversible structural phase transformations into short-chain-type polymorphs at elevated temperatures of approximately $85\ensuremath{-}100{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. These transformations allowed the investigation of the stability of each polymorph in terms of thermal analysis. Based on the chain-length dependent transition entropies, we demonstrate that the polymorphic transformations are triggered by the partial entropy gain of alkyl chains, followed by the total entropy gain at solid--liquid transitions observed at higher temperatures of approximately $110{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. We also analyzed the structure and intermolecular interactions of the four compounds. The results confirm that each molecular packing consists of a balance between the core--core and chain--chain interactions and also that the unique odd--even parity alkyl-chain-length effect of the transitions emerges as a result of the variation in interlayer stacking arrangements. We highlight the critical role of alkyl chains in terms of their large structural degrees of freedom in solution-processable and highly layered crystalline OSCs. These findings lead to a better understanding of molecular packing toward a more rational design of OSCs for efficient carrier transport.

A comparative study on structural, magnetic and optical properties of rare earth ions substituted Bi1−x R x FeO3 (R: Ce3+, Sm3+ and Dy3+) nanoparticles

Abstract A comparative study on the manifestation of rare earth ions substitution induced alteration in structure, magnetic and optical properties of BiFeO3 nanoparticles was done. Sol-gel technique was employed to synthesize Bi1−x R x FeO3 (x = 0.05 and 0.10; R: Ce3+, Sm3+ and Dy3+) nanoparticles. X-ray diffraction patterns and Raman spectra analysis confirmed substitution driven structural phase transformation from distorted rhombohedral structure to orthorhombic structure for x = 0.10 samples. The enhanced magnetic properties with weak ferromagnetic behaviour were observed with increasing concentration of rare earth ions in BiFeO3 nanoparticles. The improved magnetic characteristics are attributed to many factors such as the uncompensated surface spins in nanoparticles, breaking of spin cycloid with R 3+ ions substitution and super exchange interaction between R 3+ and Fe3+ ions. The maximum magnetization values of 1.77 emu g−1, 1.87 emu g−1 and 5.5 emu g−1 were observed for x = 0.10 samples with Ce3+, Sm3+ and Dy3+ substitution, respectively. The magnetization increased with increasing difference in ionic radii of host Bi3+ (1.17 Å) ion and dopant Ce3+ (1.14 Å), Sm3+ (1.08 Å) and Dy3+ (1.03 Å) ions. UV–Visible diffuse reflectance spectra showed a sharp absorption in visible region and energy band gap values variation in the range 2.2 eV–2.33 eV.

Quasi-One-Dimensional Transition-Metal Chalcogenide Semiconductor (Nb4Se15I2)I2.

The discovery of new low-dimensional transition-metal chalcogenides is contributing to the already prosperous family of these materials. In this study, needle-shaped single crystals of a quasi-one-dimensional (1D) material, (Nb4Se15I2)I2, were grown by chemical vapor transport, and the structure was solved by single-crystal X-ray diffraction (XRD). The structure has 1D (Nb4Se15I2)n chains along the [101] direction, with two I- ions per formula unit directly bonded to Nb5+. The other two I- ions are loosely coordinated and intercalated between the chains. Individual chains are chiral and stack along the b axis in opposing directions, giving space group P21/c. The phase purity and crystal structure were verified by powder XRD. Density functional theory calculations show (Nb4Se15I2)I2 to be a semiconductor with a direct band gap of around 0.6 eV. Resistivity measurements of bulk crystals and micropatterned devices demonstrate that (Nb4Se15I2)I2 has an activation energy of around 0.1 eV, and no anomaly or transition was seen upon cooling. Low-temperature XRD shows that (Nb4Se15I2)I2 does not undergo a structural phase transformation from room temperature to 8.2 K, unlike related compounds (NbSe4)nI (n = 2, 3, or 3.33), which all exhibit charge-density waves. This compound represents a well-characterized and valence-precise member of a diverse family of anisotropic transition-metal chalcogenides.

Role of oxygen vacancies in the structural phase transformations of granular TiO2 thin films

Tailoring the structural phases of titanium dioxide (TiO2) is nowadays highly attracting for diverse applications, ranging from optical coatings, where rutile outperforms anatase, to photocatalysis, where a mix of the two is preferred. In this framework, the very high temperature transformation of anatase to rutile constitutes a big drawback. Here, we investigate the structural transformations of granular TiO2 thin films subjected to thermal treatments in different gaseous environments, such as air, oxygen, and vacuum, with the latter expected to enhance the formation of oxygen vacancies. To this aim, we used a combined approach of X-ray diffraction (XRD), Raman Spectroscopy (RS), Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM), and we demonstrate that the achievement of a crystallization temperature as low as 150 °C for the anatase and 250 °C for the rutile is possible. By using a Gibbs free energy minimization approach, the combination of granular morphology and oxygen vacancies is proposed to tune both the amorphous to anatase transition and the anatase to rutile transformation. Finally, we explore the possibility of a low-dimensional growth of anatase-TiO2 by studying phonon confinement-like effect and crystallization kinetics thanks to time-dependent RS experiments.

Investigation of VxOy thin films using Raman Spectroscopy: Role of oxygen vacancies and structural phase transformation on thermochromic properties

Vanadium Oxide is a well-known transition metal oxide showing metal–insulator transition and is important for thermochromic and smart window applications. We have grown amorphous vanadium oxide thin films on barium borosilicate 7059 glass using cathodic arc- deposition methods. Especially, here we present a detailed investigation of these films using Raman spectroscopy performed at different temperatures and laser powers and correlate these results with XRD measurements. We demonstrate the static and dynamic structural phase transformations induced by laser and explain these results due to oxygen content changes.

Phase separation and gelation of chemically reactive macromolecules.

Phase transitions are ubiquitous in inanimate systems, and recent discoveries have shown that they also play a key role in living cells. Many membrane-less, liquid-like organelles (“biomolecular condensates”) have been shown to form via liquid-liquid phase separation (LLPS). Intriguingly, several such condensates display irreversible aging behavior akin to gelation. In this work, we first construct a theoretical framework to investigate the phase behavior of multi-component macromolecular systems in which chemical reactions, phase separation and gelation are present concurrently. We then formulate a thermodynamically consistent phase-field model to study coupled compositional and structural phase transformation phenomena in chemically reactive, multi-component biomolecular systems undergoing LLPS. The mesoscale nature of phase-field models enables the study of spatially extended systems over macroscopic timescales. Results such as phase diagrams that capture LLPS and gelation, size distribution of droplets and morphology of gel-state condensates will be presented.

Features of the combined technology based on laser metal deposition with layered laser heat treatment

The results of combined using of laser metal deposition technology with layer-by-layer laser heat treatment technology are presented and the experimental setup is described to unite the laser metal deposition technology with layer-by-layer laser remelting and/or laser surface hardening implementation. The layers formed at the stages of laser metal deposition and additional layer-by-layer laser heat treatment alternate in the material. The ratio between the thicknesses of the layers obtained during crystallization at the laser metal deposition stage and at the laser remelting stage is shown to vary widely depending on the technological parameters. The surface temperature of the irradiated layer is maintained in laser surface hardening mode in the range of 1100 °C – 1400 °C with present laser power function. It is proposed to use this mode for local structural-phase transformation of the material.

Electric field-induced irreversible phase transformations in Pb(Zr, Ti)O3-based piezoceramics

La-modified Pb(Zr,Ti)O3 (PLZT) (d33 ∼ 650 pC/N) and unmodified Pb(Zr1-x, Tix)O3 in the composition range (0.35 = x ≤ 0.51) were electrically poled through a novel powder poling technique. The mechanisms of large piezoelectric response in morphotropic phase boundary (MPB) and non-MPB-based compositions were discussed. Structural analysis suggests MPB-based compositions undergo irreversible structural phase transformation and lattice distortion after poling, and non-MPB undergo irreversible structural phase transformation. In the framework of theories, it has been argued that the MPB compositions satisfy the polarization rotation cum structural distortion phenomenon and non-MPB-based compositions follow the polarization rotation model.

Composition-dependent shuffle-shear coupling and shuffle-regulated strain glass transition in compositionally modulated Ti-Nb alloys

Athermal pure shuffle O′ nanodomains have been reported as a common structural state in metastable β-Ti alloys. In this study, by integrating thermodynamic databases, first-principles calculations, phase field simulations, and experiments, we reveal the coupling between the shuffle (O′) and shear (α″, orthorhombic martensite) nanodomains as a function of Nb concentration in Ti-Nb alloys. In particular, our first-principles calculations suggest a change in the phase transformation path from β → α″ to β → O′ as the Nb concentration increases, and our CALPHAD calculations based on the available thermodynamic database show a large metastable miscibility gap in Ti-Nb. Informed by these findings, our phase field simulations demonstrate how the O′ and α″ nanodomains form and evolve upon cooling in compositionally modulated Ti-Nb alloys produced by spinodal decomposition and the corresponding transformation behavior. Finally, our experimental characterization shows a continuous change of the shuffle component across the O′/α″ nanodomain boundaries. The novel microstructural states and their unique phase transformation path lead to an unprecedented continuous transformation behavior accompanied by superelasticity with almost zero hysteresis and small residual strain over a wide temperature range, all of which have been observed in the experiments. This unique transformation behavior upon cooling can be well characterized as a shuffle-regulated strain glass transition. This study could provide new insight in alloy design by utilizing composition-dependent shuffle-shear coupling during a structural phase transformation.

Structural Phase Transformations Induced by Guest Molecules in a Nickel-Based 2D Square Lattice Coordination Network.

Herein, we report the crystal structure and guest binding properties of a new two-dimensional (2D) square lattice (sql) topology coordination network, sql-(azpy)(pdia)-Ni, which is comprised of two linker ligands with diazene (azo) moieties, (E)-1,2-di(pyridin-4-yl)diazene(azpy) and (E)-5-(phenyldiazenyl)isophthallate(pdia). sql-(azpy)(pdia)-Ni underwent guest-induced switching between a closed (nonporous) β phase and several open (porous) α phases, but unlike the clay-like layer expansion to distinct phases previously reported in switching sql networks, a continuum of phases was formed. In effect, sql-(azpy)(pdia)-Ni exhibited elastic-like properties induced by adaptive guest binding. Single-crystal X-ray diffraction (SCXRD) studies of the α phases revealed that the structural transformations were enabled by the pendant phenyldiazenyl moiety on the pdia2- ligand. This moiety functioned as a type of hinge to enable parallel slippage of layers and interlayer expansion for the following guests: N,N-dimethylformamide, water, dichloromethane, para-xylene, and ethylbenzene. The slippage angle (interplanar distances) ranged from 54.133° (4.442 Å) in the β phase to 69.497° (5.492 Å) in the ethylbenzene-included phase. Insight into the accompanying phase transformations was also gained from variable temperature powder XRD studies. Dynamic water vapor sorption studies revealed a stepped isotherm with little hysteresis that was reversible for at least 100 cycles. The isotherm step occurred at ca. 50% relative humidity (RH), the optimal RH value for humidity control.

Phase-structural transformation of erbium trihydride studied by thermal desorption spectroscopy

Thermal desorption behaviours of erbium trihydride (ErH3) powders were studied using simultaneous thermogravimetry and thermal desorption spectroscopy (TG-TDS) method. The crystal structures and chemical compositions of the samples were investigated by X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Two-peak structures were observed in the hydrogen desorption spectra and the corresponding activation energies were determined to be 160.7 and 212.3 kJ/mol, respectively. The phase transformation sequences during thermal desorption process were established by combining the changing trends in the temperature/hydrogen content with the Er–H phase diagram. It was established that the low-temperature and high-temperature peaks were related to the β + γ → β and α + β → α phase transformation steps, respectively. The origins of the observed TDS peaks and shoulders were attributed to the equilibrium hydrogen pressures of the phase regions that the decomposition reaction passed through.

Structural-phase transformations during nitro oxidation of steels and surface properties

Structural and phase changes in the surface diffusion layer during gas nitriding of steel were studied, with the formation of a crystallographic structure of the nitride layer for subsequent oxidation in water vapor. The conditions for forming carbides and nitrocarbides with simultaneous diffusion of nitrogen and decarburization of the steel matrix are determined depending on the nitrogen potential of the saturating medium. The structural-phase states of the surface diffusion layer with a stepwise change in the nitrogen potential during nitriding at the first stage and followed by oxidation at the second stage, the formation of a surface oxide layer, as well as the conditions for participation in mutual diffusion processes of carbon in the nitride layer, decarburized from the steel matrix with the formation compositions of modified nitride phases. The nitride-oxide layer’s corrosion properties and gradient properties in various structural-phase states of nitride phase compositions have been studied.

Structural phase transformation of quantum spin liquid herbertsmithite via pressure induced enhancement of the cooperative Jahn-Teller effect and antisite disorder.

Herbertsmithite, Cu3Zn(OH)6Cl2, serves as one of the most promising candidates for quantum spin liquids with a perfect quantum kagome Heisenberg antiferromagnetic system. It can comprise an ideal model system for studying the compression response of the unique structure as well as exotic properties of kagome quantum spin liquid materials, which is of fundamental importance from both scientific and technological viewpoints. In this work, the structural evolution of herbertsmithite was investigated via in situ X-ray diffraction and Raman scattering techniques up to 30 GPa. The trigonal herbertsmithite structure transformed into a monoclinic clinoatacamite-like structure at 12.6 GPa. High pressure seems to act in a reverse way as Zn-doping for herbertsmithite, with the distortion degree of the system changing continuously. The occurrence of the displacive and reversible phase transition between the polymorphs is a consequence of the interplay between the external pressure and cooperative Jahn-Teller (JT) effect, aided by the presence of antisite mutual substitution of magnetic Cu2+ ions and nonmagnetic Zn2+ ions between the kagome layer and interlayer sites.

Study of the corrosion properties of structural steels using magnetic characteristics

Heterogeneities of the crystal structure and chemical composition, as well as the impurity elements forming inclusions cause deviations of the properties of test object from the required physical and mechanical parameters which significantly affects the reliability and service life of the product. We present the results of studying the susceptibility of structural steels to corrosion in aggressive environment using their magnetic characteristics. Structural-phase transformations occurred in steels under the effect of heat treatment change their properties, including magnetic and corrosion ones. Heat-treated 09G2S, St3, 15XSND steel samples were studied. In addition to the main magnetic parameter — coercive force, we also used spectral characteristics of the samples obtained using a remagnetization curve, magnetic hysteresis loop. The multi-parameter approach with harmonic components was used to identify the corrosion rate and coercive force correlation. Determination of the corrosion rate in this case can be reduced to classical problems of technical diagnostics. It is shown that a complex parameter based on harmonic components obtained using a magnetic hysteresis loop and the corrosion rate exhibit a pronounced correlation which provide developing a non-destructive method for predicting the corrosion resistance of structural steels. The results obtained can be used to improve the rapid method for determining the corrosion-hazardous zones of steels using the magnetic parameters.