Properties Of Ferromagnetic Materials Research Articles

A measurement method for magnetic moment and magnetic declination of ferromagnetic samples based on rotating magnetic dipole

Abstract This paper presents a novel measurement method for detecting the magnetic properties of ferromagnetic materials. The proposed method uses a motor to rotate the ferromagnetic sample. At the same time, a triaxial magnetometer reads the magnetic field information, and the motor rotation frequency and the magnetometer sampling rate obtain the rotation angle information. A nonlinear optimization algorithm is applied to calculate the magnetic moment and magnetic declination angle of the sample. The effectiveness of the method is proved by numerical simulation and experimental measurement. Our results indicate that the proposed method offers several advantages, including its ease of deployment, simplicity of operation, high accuracy, and robustness. It provides a feasible solution for laboratory-based magnetic moment measurements and rapidly detecting magnetic moments in industrial settings.

Magnetic field dependent elastic moduli and internal frictions in nickel alloy revealed by a quantitative electromechanical impedance method

Accurately and quickly determining the moduli and damping properties of ferromagnetic materials with bias magnetic fields is very important for vibration control and instrument design. In this work, the magnetoelastic properties of a nickel alloy were investigated by using a quantitative electromechanical impedance (Q-EMI) method under bias magnetic fields from 0 to 1364 Oe. Measurement results demonstrate that both the Young’s modulus and shear modulus of the nickel increase steadily with the bias magnetic field, tending to saturate under high fields. The internal friction of nickel initially increases and subsequently decrease with the magnetic field, exhibiting a pronounced peak. Meanwhile, it is found that the torsional internal friction is always considerably larger than the longitudinal internal friction. The amplitude dependent internal friction (ADIF) of the nickel alloy under bias magnetic fields was further studied using a dog-bone shaped specimen and a strain-amplifier horn. Results show that the specimen under zero field shows the most significant ADIF when the strain amplitude exceeds 2 ⅹ 10−5. While under a large bias field over 1000 Oe, the ADIF cannot appear until the strain amplitude is over 1 ⅹ 10−4 strain, indicating that the ferromagnetic domains had been stabilized by the large bias field. This study demonstrates the superiority of the Q-EMI method in probing the magnetomechanical properties of ferromagnetic materials.

Magnetostrictive behavior of pure nickel core: A study on the effects of annealing and magnetization using VSM and optical microscopy techniques

This study investigates the impact of annealing and magnetization on the magnetostrictive behavior of pure nickel, which is used as the core of an ultrasonic transducer. Pure metals are not commonly used as magnetic materials due to their limited magnetic and non-magnetic properties. Analyzing the effects of alloying on different characteristics of pure elements is a complex process. Improving the efficiency of magnetostrictive transducers by enhancing their properties is an area of interest for researchers. Grain size, in particular, is a significant parameter that affects the properties of ferromagnetic materials. This study reveals that exposing pure nickel and magnetized samples to an electro-polishing solution with 10 % oxalic acid for 60 s results in the appearance of grain boundaries. Furthermore, the study finds that the 90° domain wall energy is higher than the 180° domain wall energy, impacting the radial magnetostrictive force more than the longitudinal magnetostrictive force. The results show that annealing reduces the maximum output magnetic hysteresis, while magnetization has little effect. Additionally, annealing significantly reduces the coercive field, increasing the magnetostriction effect. Therefore, annealed nickel is a promising candidate for use as the core of an ultrasonic transducer for removing residual chemicals from fruits and vegetables.

Development of dual-main excitation mechanism modes electromagnet EMAT for testing ferromagnetic materials

ABSTRACT In the ultrasonic testing of the mechanical properties of ferromagnetic materials, the main excitation mechanism modes of ultrasonic waves are Lorentz force mechanism ultrasonic and magnetostriction mechanism ultrasonic. Lorentz force mechanism ultrasonic mainly detects the conductive characteristics of materials, while magnetostriction mechanism ultrasonic mainly detects the hysteresis characteristics of materials. However, conventional electromagnetic acoustic transducers (EMATs) cannot simultaneously characterise these two characteristics of ferromagnetic materials. In this study, we conclude from the finite element simulation that a quantitative lift-off distance (i.e. the distance between EMAT and the specimen) can change the main mechanism mode of the excited ultrasonic wave. Based on this conclusion, an electromagnet electromagnetic acoustic transducer with dual main excitation modes (DM-E-EMAT) is designed, which can realise the dual mode switching of the main Lorentz force mechanism and main magnetostriction mechanism by adding or removing hollow square gasket. The ultrasonic testing of ferromagnetic materials based on the two main mechanisms of DM-E-EMAT can simultaneously characterise the conductivity and magnetostriction properties of ferromagnetic materials, which enables the characterisations of two types of characteristic parameters with one transducer, improves the efficiency of electromagnetic ultrasonic non-destructive testing of the mechanical properties and reduces the detection errors of ferromagnetic material.

The Einstein-de Haas effect in an Fe15 cluster

Classical models of spin-lattice coupling are at present unable to accurately reproduce results for numerous properties of ferromagnetic materials, such as heat transport coefficients or the sudden collapse of the magnetic moment in hcp-Fe under pressure. This inability has been attributed to the absence of a proper treatment of effects that are inherently quantum mechanical in nature, notably spin–orbit coupling (SOC). This paper introduces a time-dependent, non-collinear tight binding model, complete with SOC and vector Stoner exchange terms, that is capable of simulating the Einstein-de Haas (EdH) effect in a ferromagnetic Fe15 cluster. The tight binding model is used to investigate the adiabaticity timescales that determine the response of the orbital and spin angular momenta to a rotating, externally applied B field, and we show that the qualitative behaviors of our simulations can be extrapolated to realistic timescales by use of the adiabatic theorem. An analysis of the trends in the torque contributions with respect to the field strength demonstrates that SOC is necessary to observe a transfer of angular momentum from the electrons to the nuclei at experimentally realistic B fields. The simulations presented in this paper demonstrate the EdH effect from first principles using a Fe cluster.

Theoretical model of magnetoacoustic emission considering the microstructure of ferromagnetic material

Magnetoacoustic emission (MAE) holds great promise for evaluating the mechanical properties of ferromagnetic materials. To refine the problems of the current theoretical and numerical models of MAE, a theoretical MAE model that considers the microscopic dependence of the hysteresis properties is proposed in this paper. The microstructure (dislocation density and grain size) and the correlation of MAE jumps are considered and incorporated into the model. Then, the influences of magnetization parameters and microstructure parameters on the envelope of the MAE signal are analyzed by the proposed theoretical model. The proposed theoretical model is then fully evaluated by simulations and experiments. The MAE experiments are conducted on ferromagnetic specimens with different hardnesses, and the MAE signals with different hardnesses are simulated by inverting the basic parameters of the MAE model with the genetic algorithm. Further, the crucial hysteresis parameters of the specimens are calculated using the results of microscopic measurements and the calculated parameters agree well with inversion results from experimental signals. The results demonstrate that the proposed theoretical model is valid for the MAE signal simulation. The trends of different hardnesses can be predicted by the MAE simulation signals. Moreover, the model can be used for theoretical analysis of the microscopic dependence of the MAE signal.

Using the Magnetic Anisotropy Method to Determine Hydrogenated Sections of a Steel Pipeline

The paper deals with a non-destructive method of detecting hydrogenated sections of pipelines, which is based on variations of the level of mechanical stresses generated in the surface layers of the steel pipe material during its hydrogenation. The use of a magnetoanisotropic method based on the phenomenon of metal magnetoelastic anisotropy development, which consists in the variation of the magnetic properties of ferromagnetic materials in direction and magnitude under the influence of mechanical stresses, is proposed as a way to register that variation. Based on the results of tensile testing of carbon steel plates with measurement of the difference in principal mechanical stresses (DPMS) occurring in metal, as well as experiments on electrolytic hydrogenation of specimens with measurement of the DPMS signal, it was confirmed that when steel structures are saturated with hydrogen, tensile stresses are generated in the surface layers, the magnitude of which increases as the concentration of hydrogen increases in the metal. In this case, it is assumed that the indicated dependence between the hydrogen concentration in the metal and the stresses arising as a result of hydrogenation is linear. For the example of lamellar specimens made of pipe low-carbon steel, the possibility of using the magnetoanisotropic method for registering sections of underground pipelines with a high content of hydrogen is substantiated, which can become the basis for a method of diagnosing sections of pipelines with broken insulation for the possibility of their further operation. The scientific novelty of this article is the establishment of a relationship between the hydrogen content in the metal, the stresses that arise in this case, and the change in the magnetic properties of ferromagnetic materials, characterized by the magnitude of the DPMS signal. This study contributes to the understanding of the process of hydrogenation of metals, and may be useful in detecting and preventing damage to gas and oil pipelines caused by hydrogen embrittlement as a cause of stress corrosion.

A thickness reduction testing method for ferromagnetic materials based on variable intensity DC magnetization

The assessments of internal thickness reduction of ferromagnetic components are extremely important. Traditional nondestructive testing (NDT) methods are usually non-linear and sometimes the electromagnetic parameters of components are required. In this paper, a thickness reduction testing method based on variable intensity DC magnetization (VIDC-MAG) is proposed. Both theoretical modeling analysis and simulation modeling analysis show that a pole point of magnetic permeability μm appears with the increase of DC magnetization intensity, which corresponds to an inflection point magnetizing current im. The im decreases with the increase of the defect depth of the wall thickness reduction and shows a linear relationship. The experimental results show that the method performs well for the inner wall thickness thinning and the relative error of the measurement results is small. Additionally, the measurement results are related to the width of the thickness reduction, the probe excitation frequency, the magnetic properties of ferromagnetic material and the lift-off distance of the magnetizer. The method is applicable to the thickness variation of the cover layer and does not need to know the electromagnetic parameters of the components in advance, which has greater practical application value.

Influence of Hydrogen Reduction Stage Conditions on the Microwave Properties of Fine Iron Powders Obtained via a Spray-Pyrolysis Technique

The relationship between the chemical purity of one-size particles and microwave properties in ferromagnetic materials is not clearly studied. Ferromagnetic nanostructured iron powders were synthesized from iron nitrate solution using ultrasonic spray-pyrolysis and then reduced in H2 flow at 350, 400, 450, and 500 °C. A rise in the concentration of solutions of a precursor from 10 to 20 wt. % led to an increase in mean particle size. The interrelationship was studied between chemical composition and the microwave dispersion of the powders obtained. An increase in the temperature of reduction changes the chemical composition and increases the amplitude of complex microwave permeability, which was studied using solid-state physics methods (XRD, STA, SEM, and VNA). It was found that annealing at 400 °C is the optimal treatment that allows the production of iron powders, consisting of about 90% of α-Fe phase, possessing a particle surface with low roughness and porosity, and demonstrating intense microwave absorption. Annealing at a higher temperature (500 °C) causes an even higher increase in permeability but leads to the destruction of nanostructured spheres into smaller particles due to grain growth. This destruction causes an abrupt increase in permittivity and therefore significantly reduces potential applications of the product. The insight into chemical–magnetic relationships of these materials enhances the data for design applications in magnetic field sensing.

Coercive Force of Low-Carbon Steel Specimens Subjected to Cyclic Loading and Impulse Current

The change in the coercive force of the 10kp5 steel specimens subjected to cyclic loading and impulse current has been studied. The choice of processing methods, including their combination in a certain sequence, was shown to provide the best plastic or strength properties of metal materials. The feasibility and good perspectives of express assessment of the effectiveness of the chosen method or methods of processing metal materials by magnetic properties, e.g., coercive force, without resorting to mechanical tests with the destruction of specimens, are noted. The highest changes towards increase in strength and coercive force in the 10kp5 low-carbon steel have been found after cyclic loading and in a combined mode with cyclic loading at the final stage. The optimal combination of cyclic loading and pulse current can make it possible to control the strength and magnetic properties of ferromagnetic materials.

Study on magnetic properties of ferromagnetic materials in cryogenic conditions

Cryogenic motors are the main actuators in submerged pumps used in liquefied natural gas (LNG) transportation industry. When cryogenic motors are submerged and operating in an LNG environment with a temperature lower than 110 K, the motor performances will be affected by changes in magnetic conductivity and loss properties of ferromagnetic materials used. However, there still exist obvious confusions in iron loss calculations of cryogenic motors in existing studies. Some studies claimed that the calculated iron loss increased greatly at cryogenic temperatures, whereas some other studies insisted that iron loss would maintain unchanged from room temperatures to cryogenic ones. In most studies, loss characteristics were studied, while the magnetic conducting performances were neglected. In this paper, based on summarizing related prior studies, cryogenic characteristic measurements were designed and conducted aiming at three types of silicon steel sheets materials that can be used in cryogenic motors, including 35W300, 50W600, and 2AT1500, according to Chinese national standard GB/T 2521-2008. Tested data and errors were compared and analyzed. According to the results, it can be concluded that the general losses increase an average of 20 % at cryogenic temperatures, which corresponding to the 20–30 % increase of electrical conductivity values ranges at cryogenic temperatures. Besides, the magnetic performances at cryogenic temperatures are enhanced, including the values of saturation magnetic density, remanence, and coercivity, etc.

Study on the inherent magnetism and its relationship with mechanical properties of structural round steel

Inherent magnetism is an important properties of ferromagnetic materials. In this study, the internal magnetic field intensity (IMFI) and internal magneto-mechanical effect (IMME) of Q390B in a structural field were investigated to detect and verify the inherent magnetism in structural settings. In the IMFI test, the magnetic flux was used to detect the change in magnetic field to verify the existence of magnetism. In the IMME test, a novel instrument was implemented to measure the magnetic variation in the Q390B specimen without magnetic flux. Based on the low frequency cyclic (LFC) tensile loading tests, the inherent magnetism was fully described. Experimental results indicate that IMME shows great potential and more efficiency in inherent magnetism studies and can be promoted in the near future.

Study of Acoustic Attenuation Trends in Permendur 49 Magnetostrictive Material

The mechanical properties of ferromagnetic materials change when the magnetization level of these materials changes. This phenomenon occurs due to magnetostriction. The change in direction of the magnetic domains is the reason for magnetostriction. In this paper, we hypothesize that the amount of acoustic attenuation in ferromagnetic materials depends on their magnetization level. To prove this hypothesis, a numerical approach is employed and the results compared to previous results in the literature. Permendur, an iron-cobalt alloy that exhibits a large magnetostriction effect, is used for the simulation. The results of the numerical study show that ultrasonic reflection and transmission coefficients in Permendur change in response to changes in the external magnetic field. A comparison between these numerical results and experimental results in the literature allows us to determine the changes in acoustic attenuation due to the magnetic field. The results show that there is an increasing trend at first, and then a decreasing trend, between acoustic absorption attenuation and increasing external magnetic field. This approach would be useful in ultrasonic testing of ferromagnetic materials when the reflected echoes are not detectable due to attenuation.

Study of Acoustic Attenuation Trends in Permendur 49 Magnetostrictive Material

The mechanical properties of ferromagnetic materials change when the magnetization level of these materials changes. This phenomenon occurs due to magnetostriction. The change in direction of the magnetic domains is the reason for magnetostriction. In this paper, we hypothesize that the amount of acoustic attenuation in ferromagnetic materials depends on their magnetization level. To prove this hypothesis, a numerical approach is employed and the results compared to previous results in the literature. Permendur, an iron-cobalt alloy that exhibits a large magnetostriction effect, is used for the simulation. The results of the numerical study show that ultrasonic reflection and transmission coefficients in Permendur change in response to changes in the external magnetic field. A comparison between these numerical results and experimental results in the literature allows us to determine the changes in acoustic attenuation due to the magnetic field. The results show that there is an increasing trend at first, and then a decreasing trend, between acoustic absorption attenuation and increasing external magnetic field. This approach would be useful in ultrasonic testing of ferromagnetic materials when the reflected echoes are not detectable due to attenuation.The mechanical properties of ferromagnetic materials change when the magnetization level of these materials changes. This phenomenon occurs due to magnetostriction. The change in direction of the magnetic domains is the reason for magnetostriction. In this paper, we hypothesize that the amount of acoustic attenuation in ferromagnetic materials depends on their magnetization level. To prove this hypothesis, a numerical approach is employed and the results compared to previous results in the literature. Permendur, an iron-cobalt alloy that exhibits a large magnetostriction effect, is used for the simulation. The results of the numerical study show that ultrasonic reflection and transmission coefficients in Permendur change in response to changes in the external magnetic field. A comparison between these numerical results and experimental results in the literature allows us to determine the changes in acoustic attenuation due to the magnetic field. The results show that there is an increasing trend at first, and then a decreasing trend, between acoustic absorption attenuation and increasing external magnetic field. This approach would be useful in ultrasonic testing of ferromagnetic materials when the reflected echoes are not detectable due to attenuation.

Investigation of Structural and Magnetic Properties of Co, Ni and CoNi Alloy Thin Films by Fabricated with Electrodeposition

The production of nanoparticles as thin film coating performed with electrodeposition method is easier and cheaper than other methods. Because, thin film production can be controlled with the change of ingredients in the bath composition. In this study, Co, Ni, and CoNi alloy thin films were fabricated with electrodeposition method through the bath composition that consists of cobalt sulphate (CoSO4.7H2O), nickel sulphate (NiSO4.6H2O), nickel (II) chloride (NiCl2 6H2O) and boric acid (H3BO3). Crystal structure (XRD), morphological (SEM), elemental composition (ICP) and magnetic properties (VSM) of the fabricated thin films were investigated. Chemical properties of coating bath (CV) was examined as well. Magnetization measurements of the thin films were performed by applying magnetic fields between + 75000 Oe and -75000 Oe and then hysteresis loops were obtained. The Co, Ni, and CoNi films showed ferromagnetic material properties. Coercivity (Hc), permanent magnetization (Mr), saturation magnetization (Ms) values of these alloys were significantly affected by the amount of the cobalt, magneto crystal anisotropy and grain size. It was understood that some materials having hard and soft magnetic properties can be fabricated by controlling the bath composition.

Method of measuring the stress of ferromagnetic materials based on EMAT and magnetic Barkhausen noise characteristic parameters

The magnetostrictive properties of ferromagnetic materials are related to their microstructure which varies between different stress states. This paper proposes a new method of stress detection based on EMAT (electromagnetic ultrasonic transducer) to better identify the early defect and stress state of materials. For experimental verification, an experimental platform consisting of cantilever beam, strain gauge and EMAT detection system was constructed. Compared with the traditional method of magnetostrictive effect detection, the transmitter and the receiver were deployed in 7 different ways to explore the relationship between electromagnetic ultrasonic signal and stress. According to the amplitude of EMAT signal and the intensity of magnetic field as obtained under different stress states, the relationship curves between them were drawn, with ten representative EMAT characteristic parameters selected. In addition, BP (back propagation) neural network was applied to establish the mapping relationship between the electromagnetic ultrasonic characteristic parameters and the stress state of the specimen, and the material stress was predicted with the maximum error of 8.10%. Moreover, BP neural network was adopted to combine EMAT characteristic parameters with Barkhausen characteristic parameters for establishing the mapping relationship between the characteristic parameters and stress state of specimen. The research results show that the accuracy of quantitative prediction was improved for material stress, with the maximum error reaching 6.27%.

Method of measuring the mechanical properties of ferromagnetic materials based on magnetostriction EMAT and sound velocity

• A NDT method to measure the mechanical properties of ferromagnetic materials based on the magnetostriction EMAT and sound velocity . • Extract reliable pattern parameters (including five magnetostrictive parameters and sound velocity parameter) from the EMAT signal. • Parameter estimation of mechanical properties based on generalized regression neural network. The measurement of mechanical properties parameters has been found as the standard process to predict the quality of ferromagnetic materials, which is a critical step in the production of ferromagnetic materials. The conventional testing methods of mechanical properties are dependent on Destructive tests. In this study, a non-destructive method was proposed based on magnetostriction EMAT and sound velocity to measure the mechanical properties of ferromagnetic materials imprinted by the materials’ microstructure since the microstructure can have an effect on the pattern of the magnetostrictive effect and sound velocity of ferromagnetic materials. For experimental verification, the ultrasonic propagation time was calculated by filtering the orthogonal demodulation of the electromagnetic ultrasonic signal. Based on BP (back propagation) neural network, the Mean Impact Value (MIV) of each characteristic value was investigated to predict the effect arising from sound velocity on the network output. Moreover, with GRNN (general regression neural network), this study established the mapping relationship between magnetostrictive parameters (with or without combined sound velocity) and mechanical properties of the material, and the mechanical properties of the materials were non-destructively measured. The testing samples of cold-rolled steel specimens synthesized by Bao-steel Inc. were verified. As indicated by the results, the method combined with sound velocity achieved higher prediction accuracy, and the passing rate of relative error less than 10% could reach 95%.

Experimental evaluation and theoretical analysis of the mechanical properties of ferromagnetic materials using the magnetic hysteresis properties

The magnetic hysteresis properties of ferromagnetic materials have been investigated by experimental measurement and theoretical analysis for mechanical property evaluation. A modified Jiles-Atherton (JA) model is proposed considering both the frequency and microscopic dependence of the hysteresis properties. Dynamic hysteresis experiments of ferromagnetic specimens with different hardness values were performed to measure the hysteresis loops. Microscopic measurements of the specimens were performed to obtain the grain size and dislocation density, which were introduced into the dynamic JA model to calculate the theoretical hysteresis loops. The genetic algorithm was used to inverse the basic parameters of the JA model by matching the theoretical hysteresis loops with the experimentally measured hysteresis loops. Two magnetic parameters (the coercivity and power-law coefficient) were extracted from the hysteresis loops for mechanical property evaluation of ferromagnetic materials. It was found that the proposed JA model can be used for theoretical analysis of the influence of the microstructure on the magnetic hysteresis properties, and the coercivity and power-law coefficient can be used for mechanical property evaluation of ferromagnetic specimens. The research reveals the influence of microstructure on the mechanical properties (hardness) and magnetic characteristic parameters of ferromagnetic materials.

Mechanical and magnetic properties of TRIP690 steel strengthened by strain-induced martensite

The sensitivity of the induced magnetic signals to microstructures makes it possible to characterize nondestructively the mechanical properties of ferromagnetic materials. In this study, utilizing the hysteresis loop measurement and the magnetic Barkhausen noise measurement, the correlation between the mechanical and the magnetic properties of low-alloy multiphase transformation-induced plasticity (TRIP) steel after plastic deformation was investigated, then the strength of the TRIP steel after plastic deformation was characterized. The results showed that, as the strain level increased from 0 to 0.2, the martensite volume fraction of TRIP690 steel increased from 0.78% to 3.64% which contributed to the enhancement of mechanical properties and the change of magnetic properties, and in particular, hardness and tensile strength had linearly increased by approximately 42% and 20%, respectively. Meanwhile, the peak value of the magnetic Barkhausen noise signal (MBNS) increased linearly with the increasing strain levels, the coercivity increased rapidly and then slowly, while the susceptibility decreased exponentially. By theoretically deriving the effects of the ferromagnetic phase volume fraction, dislocation density and residual stress of the TRIP690 steel on susceptibility and coercivity, the variation of the MBNSs under the influence of phase transformation, dislocation and residual stress was analyzed. The above non-destructive magnetic technique makes it possible to evaluate the mechanical response of the TRIP steel after plastic deformation, which allows it to be further applied to the quality evaluation of steel parts in stamping, such as body-in-white for the automotive industry.

Effects of Heat Treatment and Cr Content on the Microstructures, Magnetostriction, and Energy Harvesting Performance of Cr‐Doped Fe–Co Alloys

The magnetostrictive effect is one of the most useful properties of ferromagnetic materials. Vibrations in dynamic structures and machines represent a nontraditional alternative energy source, and ferromagnetic materials could potentially convert the kinetic energy of these vibrations into electrical energy using the inverse magnetostrictive effect. Herein, Fe–Co–Cr alloys are fabricated and these materials are applied to vibrational energy harvesting. Specifically, (x = 0, 0.5, 1.0, or 3.0 at%) alloys are made by arc melting in an argon atmosphere and then heat treated at temperatures that promoted magnetostrictive characteristics. The structural properties of these materials are subsequently investigated using energy‐dispersive X‐ray spectroscopy, while their magnetic properties are assessed with a vibrating sample magnetometer (VSM) and their magnetostrictive characteristics are evaluated with a strain gauge method. Vibrational energy harvesting experiments are conducted and the relationship between the output power and the magnetic/magnetostrictive characteristics of these alloys is examined. The data shows that magnetic permeability is an important factor determining the output power of these Fe–Co alloys, in addition to their magnetostrictive properties. The results provide a basis for the systematic development of magnetostrictive material variants and for new alloys required to meet the needs of future designs.