Maximum Magnetic Permeability Research Articles

Evaluation of the wear mechanism of ferromagnetic materials based on magnetic barkhausen noise

ABSTRACT As a typical form of damage, wear greatly affects the service properties of products, and non-destructive evaluation of the degree of wear is urgently needed. In this paper, the wear degree of AISI 1045 steel was evaluated by magnetic Barkhausen noise (MBN) testing. The root mean square (RMS) and full width at half maximum (FWHM) of MBN were extracted to establish the quantitative relationships between the tribological indicators and the stress state. The results indicate that the RMS decreases linearly and the FWHM increases quadratically with increasing tribological indicators, which can distinguish among different wear stages, including abrasive, adhesive and fatigue wear. However, the RMS shows a complicated nonlinear relation with the residual stress during the wear process. In addition, the MBN energy parameter is also calculated to reveal the features of the hysteresis loop at the wear scar. Both the coercivity H c and the maximum magnetic permeability μ max are linearly related to the tribological indicators and quadratically related to the stress, which reflects the effect of tribo-magnetisation on the MBN signals. The variation mechanism of MBN under different wear stages is attributed to the combined effect of plastic deformation and the stress state by microstructure observations.

Effect of elastic-plastic deformation by biaxial tension on the magnetic characteristics of the nickel

The studies were carried out in a test facility based on the original biaxial testing machine created at the IES UB RAS, designed to determine the physical properties of materials during elastic-plastic deformation independently along two axes. Finite element modeling of the stress-strain state of a cruciform nickel specimen has shown that, under symmetric biaxial tension, equivalent von Mises stresses are uniformly distributed in the central part. The results of microstructural studies indicate that dynamic recrystallization takes place in the material during biaxial deformation at room temperature. The results of studying the behavior of the hysteretic magnetic characteristics, magnetostriction, Barkhausen magnetic noise parameters, and electromagnetic parameters of nickel under biaxial symmetrical tension have been presented. A unique relationship between the coercive force and equivalent stresses in the region of plastic deformation has been revealed. It has been shown that such magnetic parameters as maximum magnetic permeability and the maximum in the field dependence of differential magnetic permeability, as well as the amplitude and frequency of the eddy current signal determined at a frequency of 10 kHz, vary monotonically with increasing equivalent stresses under both elastic and plastic deformations.

(Digital Presentation) Microstructure, Corrosion Resistance, and Magnetic Properties of Amorphous Alloy Co75Si15Fe5Cr4,5Al0,5 before and after Corrosion

Cobalt-based Amorphous Metal Alloys (AMA) can be used as soft magnetic materials in various magnetic devices due to the low value of the natural crystalline magnetic anisotropy. The addition of non-metallic components (Si, B) does not adversely affect the magnetic properties. On the contrary, AMA have high magnetic permeability at low values of coercive force and greater resistance to corrosion compared to crystalline ones.The required important parameters for corrosion description are: the concentration of chloride-ions, the microstructure (especially surface heterogeneity) and the composition of the oxide layer [1]. It was determined that the initial AMA Co75Si15Fe5Cr4.5Al0.5 possesses the low coercive force 0.38 A/m. The modification of the alloy surface with nanostructures by anodizing at different current densities (i) and times in the BmimBF4 ionic liquid (IL) does not affect the value of the coercive force, but its resistance to corrosion in a chloride solution increases. The coercive force increases after corrosion, which may be due to a change in surface morphology.The domain structures of the surface modified with nanostructures and initial alloys are different. After excerption at a constant (i) in IL, the domain structure of the surface consists of relatively large uniformly magnetized regions (Fig. 1a). The coercive force of the sample practically does not change compared to the initial sample.The surface domains after corrosion are broken into smaller ones, while the predominant orientation changes its direction (Fig.1 b). The change in the surface domain structure is accompanied by a significant increase in the coercive force (by a factor of 10), although the maximum magnetic permeability (the slope of the hysteresis loops) does not change.The EIS-tests (electrical impedance spectroscopy) were performed at -200 mV (Ag/AgCl) in the frequency range of 50,000 to 0.01 Hz and an oscillation amplitude of 20 mA in Ringer's solution (Fig.1 c, d) to compare the charge transfer kinetics for modified with nanostructures and initial samples. The simulated equivalent circuit included the values of the solution resistance Rs (22 Ω), the value of the constant phase element CPE associated with the double layer capacity, including the capacitance of the modified surface layer, and Rp is the charge transfer resistance across the interface. The capacity of the double layer is higher for the modified sample (4.28*10-5 Ohm-1*cN vs. 1.88*10-5 Ом-1*сN ) and the resistance value of the material has hardly changed (18000±13.5% Ohm for modified and 15500±3.5% Ohm for unmodified). The values of the phase angle (0.78 - modified and 0.88 - unmodified) indicate a greater heterogeneity of the charge distribution at the boundaries of the double layer for the modified surface of the alloy.So, surface modification affects the corrosion resistance, while it has little effect on the parameters of hysteresis loops, what is very important in practical applications. Nyby, C., Guo, X., Saal, J. E., Chien, S.-C., Gerard, A. Y., Ke, H., Frankel, G. S. (2021). Electrochemical metrics for corrosion resistant alloys. Scientific Data, 8(1).doi:10.1038/s41597-021-00840-y Figure 1

Magnetostriction reduction and magnetic permeability enhancement of Ti added Fe0.7Co0.3 alloy

The current work presents the study of three alloys, (1) the binary Fe0.7Co0.3 alloy (atomic fraction), (2) the addition of 3 at. % of Ti, and (3) the addition of 3 at. % of Ti and 1% of Nb. The interest is to increase the permeability of this binary alloy due to the additions of Ti and Nb, since Fe–Co alloys with Co content in the range of 27–35 at. % have much lower permeability than the commercial equiatomic alloy. The advantage of low Co Fe–Co alloys is the lower price compared to the equiatomic one. The alloys were produced by arc melting and were subsequently hot rolled and annealed in the final thickness at 1200 °C over 24 h. Microstructure characterization revealed single α-phased alloys with body centered cubic structures. Positive results were observed in the magnetic and electric properties of the (Fe0.70Co0.30)97Ti3 alloy compared to Fe0.7Co0.3, meaning the decreasing saturation magnetostriction λs, and the growth of the maximum relative permeability by 24% and of the resistivity by 63%, occurred without a change in the coercive field and in the maximum magnetic induction. The (Fe0.7Co0.3)97Ti3 alloy's maximum magnetic relative permeability is μrmax = 855 and occurs at a field of only 160 A/m, this field being more than two times lower compared to the one of the binary alloy. On the other hand, the addition of Ti + Nb has improved the deformation performance of the (Fe0.7Co0.3)97Ti3 alloy at high temperatures and did not change the magnetostriction, nor the resistivity. The quaternary alloy presents a maximum magnetic relative permeability of μrmax = 270 at 1960 A/m and a maximum magnetic induction reduced by 14% compared to the other two alloys.

Pressure effect on the structural, magnetic and thermophysical properties of X12Cr13 martensitic stainless steel prepared by powder metallurgy method

Low carbon (C: 0.03-0.15%) and high Cr contents (Cr: 11-15%) martensitic stainless steel (MSS) is widely used for industrial applications due to its good mechanical properties and corrosion resistance. In this study, we investigated the pressure effect on the structural, magnetic and thermophysical properties of X12Cr13 MSS which was compacted using powder metallurgy method under 400 and 600 MPa pressures and sintered at 1200 °C temperature for an hour under Ar atmosphere. Pressing and sintering processes resulted in increased density of microstructures from 5.84 g/cm 3 to 6.12 g/cm 3 , decreased porosity from 7.58% to 3.39%, increased hardness from 93.24 HB to 110.09 HB (N/ mm 2 ) and decreased carbide particles from 2.65% to 2.13 wt% in the structures. We observed α -Fe, γ -Fe and M 23 C 6 (M: Cr or Fe) phase formations in the structure due to the applied pressure and the sintering process. The magnetic properties of these steels have been investigated as a function of temperature between 300-400 K and applied magnetic field of ±4 T. We observed improved magnetic properties with increasing pressure, and ferromagnetic to paramagnetic phase transition occurred from 300 K to 400 K. While maximum saturation magnetization is found to be 70 emu/g at 300 K for 600 MPa sample, maximum magnetic susceptibility and permeability for 600 MPa sintered sample are recorded as 17.13 and 1.08 m 3 /kg, respectively. Also, the maximum specific heat capacity and enthalpy are recorded as 1.85 J/g °C and 536.05 J/g (at 579 °C temperature) on the sample compacted on the 600 MPa pressure, respectively. • X12Cr13 MSS samples were prepared by P/M method at 400 MPa and 600 MPa. • 600 MPa pressing and 1200 °C sintering enhanced physical and magnetic properties • MSS prepared at 600 MPa exhibits 110.09 HB hardness and 6.12 g/cm 3 density. • The maximum saturation magnetization found to be 70 emu/g at RT for 600 MPa sample. • The 600 MPa sample provided 536.0 J/g heat storage capacity at 579°C.

DEPENDENCE OF ELECTROMAGNETIC PARAMETERS OF PRODUCTS FROM STEEL 09G2S ON THEIR MECHANICAL PROPERTIES

"This work presents a method for a non-destructive method for determining the tensile strength, yield strength and relative elongation of steel products by identifying the relationship between mechanical and electromagnetic properties. Coercive force, maximum magnetic permeability and residual magnetic induction were chosen as electromagnetic properties, as the most structurally sensitive parameters to the composition and heat treatment of products. The difference of the work carried out is the use of several physical characteristics simultaneously as control parameters, since multi-parameter control methods provide higher information content and reliability of assessing the state of materials. The result of the research is a method for determining the relationship between mechanical and electromagnetic parameters. At the same time, the deviation of the values ​​obtained by this method and the actual values ​​during the tensile test does not exceed 5 %. The proposed method for determining the values ​​of mechanical properties can be used for any steel product and its grade, having previously established, for the corresponding composition of the material, the relationship between mechanical and electromagnetic properties. Keywords: coercive force, tensile strength, non-destructive testing, mathematical model, mechanical properties of steel."

The evolution of microstructure, micromechanical and magnetic properties of FeCoNiSi alloys solidified under high pressure

A comprehensive study has been conducted on the effects of high-pressure solidification (HPS) on the evolution of microstructures, micromechanical properties, and magnetic properties of FeCoNiSi alloys. As solidification pressure increases(up to 7GPa), FeCoNiSi alloy's columnar grain changes into an equiaxed grain, and the grain size and Ni-rich precipitates are significantly refined. Furthermore, HPS facilitates the conversion of in-coherent matrix/precipitates interface of alloy solidified under atmospheric pressure into semi-coherent, which reduces the pinning effect of phase boundaries on the motion of the magnetic domains and enhances the exchange coupling between matrix and precipitates. As FeCoNiSi alloy solidifying under 7GPa, the maximum magnetic permeability (μ m ) is significantly increased (from 52,600 to 113,000), the inherent coercivity is decreased by 29.5%, and the saturation magnetic polarization( Js ) is increased by 21%. In addition, the high temperature magnetic properties of FeCoNiSi alloys are improved by HPS. Furthermore, HPS produces compressive stress in both the precipitates and matrix, which significantly improved the modulus of precipitates and matrix (i.e. from 171GPa to 215 GPa in matrix),as well as microhardness (i.e. from 5.46 GPa to 10.65 GPa in matrix). Based on the results of these studies, HPS is capable to improve the comprehensive properties of magnetic alloys significantly. • The J s and μ max (H MC ) of FeCoNiSi alloy are increased (decreased) by 21% and 114% (29.5%) after solidified under 7GPa. • HPS produces compressive stress in the precipitates and matrix and significantly improved the modulus and microhardness. • HPS refine the microstructure of FeCoNSi alloy and result in the semi-coherent interface. • The semi-coherent interface enhances the exchange coupling effect between precipitates and matrix.

Estimation of residual stresses in plastically deformed eutectoid steel with different perlite morphology via magnetic parameters

Measurements of magnetic properties, as well as microscopic and X-ray diffraction investigations, of eutectoid steels with the structure of spheroidized and of coarse lamellar pearlite after cold plastic deformation by tension have been carried out. The steel with the coarse lamellar pearlite was unexpectedly found to have a lower coercivity than the steel with the spheroidized pearlite. With growing elongation, the coercivity of the steels with various pearlite morphologies grows, whereas the remanence and maximal magnetic permeability decrease. At an elongation more than 0.7%, the remanence and maximum magnetic permeability become almost equal. The difference in the coercivity of eutectoid steel with various pearlite morphology raises with elongation growth. The main changes in magnetic properties occur prior to elongations of 2–4%. The magnetoelastic fields Hσ were calculated from the field dependences of the magnetic incremental permeability and the residual compressive stresses, estimated. It is found that the average residual stresses are −222 MPa for steel with the spheroidized pearlite and −349 MPa for steel with the lamellar pearlite. According to the results of X-ray diffraction analysis, the values of residual stresses are −251 MPa and –342 MPa for steels with the spheroidized and lamellar pearlite, respectively.

Non-destructive method for determining the mechanical properties of rolled steel

This article describes the developed methodology for the prompt and reliable determination the mechanical properties quantitative indicators of the heat-treated steel products by a non-destructive method. For these cases, the non-destructive method of testing steel products is the most optimal option, due to the fact that it does not require destruction of the controlled sample and provides for the possibility of the product further operation. The use of non-destructive testing methods also contributes to significant savings in material and time resources. The essence of the method described in this work lies in the initial study of steel samples, measuring their coercive force, maximum magnetic permeability and residual magnetic induction for subsequent statistical analysis to determine the relationship between mechanical and electromagnetic properties. As a result of finding this correlation and checking its reliability, it becomes possible to determine the ultimate strength, yield strength and relative elongation on finished products, which are normalized indicators of the steel structural products strength properties. The proposed non-destructive method for determining the mechanical properties will allow its use in the production flow, while having the reliability of determining the quality indicators above 96 %.

Predicting hardness profile of steel specimens subjected to Jominy test using an artificial neural network and electromagnetic nondestructive techniques

ABSTRACT Based on relationships between electromagnetic properties and microstructural changes in steel, the current paper describes the development of an electromagnetic technique to determine steel hardenability, non-destructively. Performing Jominy end-quench test, magnetic hysteresis loop and eddy current methods have been applied to SAE 4140 standard steel samples to explore applicability of the non-destructive techniques for determining hardenability. Different hysteresis loop parameters (maximum magnetic flux density, coercivity, hysteresis loss and maximum differential permeability) as well as eddy current outputs (induced voltage, normalised impedance and phase angle) as a function of distance from the end-quenched surface were investigated and the results show a clear agreement with data obtained by traditional hardness testing. In addition, taking advantage of a generalised regression neural network, magnetic data obtained from hysteresis loop and eddy current methods could be used to accurately estimate results in the hardness profile of a given sample, using a few training data points. This paper shows that coupling the proposed non-destructive methods to Jominy end-quench test facilitates accurate non-destructive hardenability determination of steel samples while reducing time and cost of the test process.

Effect of Chemically Active Medium on Magnetic Characteristics of Soft Magnetic Co-Based Amorphous Alloy

The interaction of the ribbon surface with acetone and its effect on the magnetic characteristics of ribbon are studied in this work using the example of soft magnetic Co-based AMAG-172 (Co–Ni–Fe–Cr–Mn–Si–B) amorphous alloy. The studies show the different effect of acetone treatment of ribbon on the magnetization distribution and magnetic permeability of material in states differing in the sign of saturation magnetostriction. The treatment of the ribbon in the state with λs > 0 favors the increase in both the volume of domains with the orthogonal magnetization and the magnetic texture sharpness in the ribbon plane; in the state with λs < 0, the treatment favors the decrease in both the volume of domains with the orthogonal magnetization and magnetic texture sharpness and an increase in the maximum magnetic permeability. This can result from the predominantly planar anisotropic compressive stresses induced in the ribbon by catalytic oxidation and hydrogenation of acetone.

COMPARISON STUDY BEWTWEEN THE RECOVERY BEHAVIOR OF DEFORMED QUENCHED, PRE-ANNEALED AND PULSED LASER DAMAGED Fe50Ni50 ALLOY BY MAGNETIC MEASUREMENTS

Through the magnetic measurements, isochronal annealing experiments in the temperature 25950 ºC of deformed, quenched, pre-annealed and pulsed laser damage samples Fe50Ni50 alloy revealed the existence of three annealing stages I, II and III in the annealing spectrum of heavily cold-worked by observing the associated changes in maximum magnetic permeability (µmax) on the magnetic field(H) for different annealing temperature. The first annealing stage I appeared in the temperature range from125-500 ºC and it was activated by energy 1.05 eV. It was attributed to the short range order caused by the long range migration of vacancies. The second annealing stage II appeared in the temperature range from 550-750 ºC and it was activated by 1.82 eV, it is associated with an increase in µmax due to the dissociation of vacancy clusters formed during stage I. The third annealing stage III appeared in the temperature range from 750-825 ºC and it was activated by 3.04 eV, it was related to the climb motion of dislocation during the recrystallization process.

Polymer coating and magnetic characteristics of amorphous cobalt-based soft magnetic alloy

The polymer coating influence which used in the magnetic screens manufacture, and the conditions of its formation on the magnetization distribution and magnetic properties of the ribbon from a soft cobalt-based alloy with close to zero saturation magnetostriction was studied. The coating was applied in the temperature range 90–130 °C on the ribbon after heat treatment in air, which formed a state with different signs of magnetostriction saturation. It was shown that the flat compressive stresses induced by the coating contribute to a certain decrease in the maximum magnetic permeability due to an increase in the level of internal stresses, however, for 1–2 years there is no decrease in μmax in the ribbon with coating, which were formed in the temperature range 110–130 °C. The existence of a temperature range in which the coating formation changes the saturation magnetostriction sign was found. This is due to the change in the structural-phase state of the ribbon because diffusion processes by repeated heat treatment during of the polymer coating formation. Diffusion processes that occur at room temperature over time also contribute to changes in the structural-phase state of the ribbon and the λs sign in this state.

Temperature of the Formation of a Protective Polymer Coating and the Magnetic Properties of Cobalt-Based Amorphous Alloys

The influence of the polymer coating used in the manufacture of magnetic shields and of the conditions of its formation on the distribution of the magnetization and on the magnetic properties of shields has been studied. Samples of a ribbon of the Co-based soft-magnetic amorphous alloy AMAG-172 (Co–Ni–Fe–Cr–Mn–Si–B) with a saturation magnetostriction close to zero were used in the study. The coating was deposited in the temperature range of 90–130°C on the ribbon subjected to heat treatments in air that form a state with a negative saturation magnetostriction. The change of magnetic characteristics was investigated over a two year period. It has been shown that there is a temperature range in which a change in the sign of the saturation magnetostriction occurs upon the formation of the coating. This change is due to a change in the structural-phase state of the ribbon because of the diffusion processes that occur upon heating. The formation of the coating leads to a reduction in the maximum magnetic permeability; nevertheless, over a two year period, no decrease in μmax is observed in the ribbon with a coating formed in the 110–130°C temperature range.

Comparison of Magnetic Parameters of Quenched Pipe Steels with X-Ray–Evaluated Residual Macro- and Microstresses

Residual micro- and macrostresses have been determined by X-ray diffraction analysis in 22KhG2A, 30KhMA, and 32G2 grade steels quenched and tempered from various temperatures. It is demonstrated that not only residual macrostresses need to be determined, as prescribed by existing regulatory documents, but also microstresses, which characterize the extreme values of residual stresses. The possibility of using magnetic parameters for evaluating residual micro- and macrostresses has been investigated. It has been established that coercive force, maximum magnetic permeability, and Barkhausen magnetic noise characteristics can be used as informative parameters in the evaluation of microstresses.

Influence of tensile stress on hysteresis loop of Reduced Activation Ferrite & Martensitic steel

The influence of tensile stress on hysteresis loop of Reduced Activation Ferrite & Martensitic steel (RAFM steel) in elastic region was quantitatively evaluated through experiments in this paper. In view of in vessel structures of the RAFM steel in the Tokamak devices, the variation of magnetic material properties caused by forces or mechanical deformation may lead to unexpected influences on their dynamical behaviors, even safety problem. In this paper, tensile experiments of a RAFM steel were conducted under magnetic field up to 60 kA/m to measure its hysteresis loops under different tensile stress. Tensile specimens of a RAFM steel developed in China (CLAM steel) were fabricated and measured with a multi-field coupling experimental system. The maximum relative permeability under different experimental conditions was extracted from the measured hysteresis loops. Experimental results show that a clear variation of the maximum magnetic permeability was observed when the external tensile stress was enlarged. In addition, based on a linear theory of magneto-solid coupling mechanics, a model of constitutive relation between tensile stress and maximum magnetic permeability was put forward and validated based on the experimental results.

Conditions for the Formation of a Polymeric Coating and the Magnetic Properties of Cobalt-Based Amorphous Alloys

This paper presents the results of an investigation of the influence of the polymeric coating used in the course of the production of magnetic shields and conditions necessary for its formation on the distribution of magnetization and magnetic properties of amorphous soft magnetic ribbons made from AMAG-172 alloy (Co‒Ni–Fe–Cr–Mn–Si–B). Study was performed on samples with a nearly zero saturation magnetostriction. The coating was applied onto the ribbon in the 90–130°C temperature range after heat treatments in air, which formed a state with a positive saturation magnetostriction. This study has shown that the formation of a polymeric coating at temperatures of 110–130°C leads to a reduction in the volume of domains with the orthogonal magnetization because of the change in the sign of the saturation magnetostriction. The maximum magnetic permeability in the ribbon with a coating is decreased upon its formation in the entire temperature range; however, a certain increase is observed over time.

Effect of temper rolling and subsequent annealing on texture development and magnetic permeability of semi-processed electrical steel with 2.3 wt.% Si

Abstract The effect of temper rolling and subsequent annealing on texture development and magnetic properties of semi-processed non grain oriented electrical steel has been investigated. The result shows that 5% temper rolling and final annealing at 850°C resulted in strong α-fiber component. The etch-pit technique shows that strain induced boundary migration is responsible for new texture component augmentation. Vibrating sample magnetometery reveals that maximum and minimum magnetic permeability are related to rolling and transverse directions, respectively. Average magnetic permeability is improved to some extent as a result of temper rolling and subsequent annealing.

Nanomodified composite magnetic materials and their molding technologies

Advanced electro-magnetic machines and systems require new materials with improved properties. Heterogeneous 3D nanomodified soft magnetic materials could be efficiently applied. Multistage technology of iron particle surface nanomodification by sequential oxidation and Si-organic coatings will be reported. The thickness of layers is 0.5-5 nm. Compaction and annealing are the final steps of magnetic parts and components shaping. The soft magnetic composite material shows the features: resistivity is controlled by insulating coating thickness and equals up to ρ =10-4 Ω⋅m for metallic state and ρ =104 Ω⋅m for insulator state, maximum magnetic permeability is μm = 2500 and μm = 300 respectively, induction is up to Bm=2.1 T. These properties of composite soft magnetic material allow applying for transformers, throttles, stator-rotor of high-efficient and powerful electric machines in 10 kHz–1MGz frequency range. For microsystems and microcomponents application, good opportunity to improve their reliability is the use of nanocomposite materials. Electroplating technology of nanocomposite magnetic materials into the ultra-thick micromolds will be presented. Co-deposition of the soft magnetic alloys with inert hard nanoparticles allows obtaining materials with magnetic permeability up to μm=104, magnetic induction of Bs=(0.62–1.3) T. Such LIGA-like technology will be applied in MEMS to produce high reliable devices with advanced physical properties.

Relationship between the structure and physical-mechanical properties of U8A steel subjected to cold plastic deformation by hydrostatic extrusion

The structure and physical-mechanical properties of U8A high-carbon steel subjected to cold plastic deformation by hydrostatic extrusion have been investigated in a wide range of strain extents. Cold plastic deformation by hydrostatic extrusion has been shown to lead to the dispersion of the structure of U8A high-carbon steel. As the degree of true deformation increases, the ultimate strength and conventional yield limit of U8A steel monotonically grow by 2 and 3.6 times, respectively. Such parameters as coercive force, the number of jumps in magnetic Barkhausen noises, maximum magnetic permeability, residual induction, and the speed of elastic waves are more sensitive to changes in the dislocation density than in the dispersion of the grain and subgrain structure of extruded U8A steel. It has been established that at least two informative testing parameters are needed for nondestructive evaluation of the level of strength properties in extruded U8A steel. Those are coercive force (or maximum magnetic permeability, residual induction, the number of Barkhausen jumps, the speed of elastic waves) for a true deformation of up to 1.62 and the root-mean-square voltage of magnetic Barkhausen noises for true deformations above 1.62.