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Highlights • The high magnetic field increases the number density of carbides by twice. • Denser carbides increase the dislocation density by larger critical unpinning stress. • Hardness remains unchanged because the increase in offset the reduction in hardness. Abstract The influence of a 12 Tesla magnetic field on the microstructure of high Chromium-containing steel during tempering was investigated. The experimental results revealed that an external magnetic field significantly increases the number density of carbide (Fe, Cr) 3 C and the dislocation density. The external magnetic field decreases the Gibbs free energy of (Fe, Cr) 3 C and then decreases the nucleation barrier; hence, the number density of (Fe, Cr) 3 C increases by approximately 2.42 times. The higher number density of carbides doubles the dislocation density, corresponding to the larger critical unpinning stress τ c , which results in a dislocation pile-up in front of the carbides. The hardness change is negligible with an external 12 T magnetic field because the increment of hardness due to the denser carbides (Fe, Cr) 3 C and dislocations that originate from the 12 T magnetic field offsets the decrement of hardness that results from the decrease in the solid solution strengthening from the carbon atoms. The investigation of the impact of an external high magnetic field on the behavior of carbides and dislocations can provide a better understanding for the precipitation strengthening mechanism of nuclear fusion steels. [ABSTRACT FROM AUTHOR]

Highlights • Low field magnetic permeability up to Curie point reported for ferrite-pearlite steels. • FE microstructure model to predict permeability-temperature relationship developed. • Excellent agreement between modelled and measured data for ferrite-pearlite steels. • Model can predict permeability-temperature data for ferrite-austenite microstructures. Abstract The magnetic properties of steels are sensitive to temperature and currently the only way to determine them is by experimental measurement. In this work a cylindrical shaped ceramic cored EM sensor has been used to measure the low magnetic field inductance of pure iron and C-Mn steels with ferrite + pearlite microstructures during heat treatment up to 800 °C in a furnace. The low field relative permeability values have been determined by fitting the sensor readings to a finite element sensor model generated in COMSOL, where the model has been validated for room temperature measurements using samples of known low field relative permeability. The low field relative permeability values with temperature follow the expected trend of increasing values with temperature, particularly close to the Curie temperature. The measured low field relative permeability values for the mixed ferrite + pearlite microstructures have been compared to predicted values from an FE microstructure-permeability model using the single phase (ferrite or pearlite) low field relative permeability values as input. The model predictions agree well with the experimentally measured values allowing any two-phase ferrite + pearlite microstructure low field relative permeability with temperature relationship to be determined. The model has also been used to determine the low field relative permeability of ferrite + austenite microstructures with temperature. [ABSTRACT FROM AUTHOR]

Highlights • The magnetic properties of electrical steel sheet are measured by two specimens. • The effect of temperature and pressure on magnetic properties is revealed. • The difference in results is related to environmental factors, shape and size. Abstract Motor made of electrical steel sheet is sometimes used in extreme environments, for example, submersible motors are operated at temperatures and pressures coupling environment. However, most related reports only consider the effect of single environmental factor (temperature or stress) on the magnetic properties of electrical steel sheets. Therefore, in order to accurately design a motor that can operate at temperatures and pressures coupling environment, the magnetic properties of electrical steel sheets used in the motor should be clarified firstly. In the paper, two kinds of specimens (ring specimen and rolled specimen) are used to measure the magnetic properties under temperature and pressure coupling environment. It not only reveals the influence of temperature and pressure coupling environment on the magnetic properties, but also analyzes the difference between the measurement results obtained by two kinds of measurement samples. The measurement results show that the effect of pressure on magnetic properties decreases with increasing temperature under the conditions of temperature and pressure coupling. According to the domain theory, a reasonable explanation for the influence of temperature and pressure coupling environment on electrical steel sheet is given. Meanwhile, combining the shape and size of the two measurement samples, the possible causes of the differences in the measurement results of the two measurement samples were analyzed in detail. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Coercivity of the α′-martensite is characterized by strong magnetic shape anisotropy. • α′ → γ transformation is split into two stages during continuous annealing. • Magnetic properties present an annealing time-dependence between 500 and 600 °C. • Formation of γ-nanograins in the early stages of reversion induces strong magnetic shape anisotropy. • Athermal α′-formation within the prior athermal ε-phase is observed for temperatures lower than 100 °C. Abstract Strain-induced martensite (SIM) formation was evaluated upon cold-rolling of a 17.6 wt.%Mn-TRIP steel by means of magnetic measurements, X-ray diffraction, and high-resolution electron backscatter diffraction (EBSD). α′-martensite formation was observed to be dependent on the presence of prior ε-martensite. Upon deformation, the coercivity of the ferromagnetic α′-martensite is characterized by strong magnetic shape anisotropy. Austenite (γ) reversion was evaluated by means of in situ magnetic measurements during continuous annealing. The experimental results were compared to thermodynamic simulations. It turned out that γ-reversion was not completed in the regime where a γ-single phase field is expected, which suggests the splitting of α′ → γ transformation into two stages. The Curie temperature of remaining α′-martensite was determined as being ∼620 °C. Magnetic properties presented an annealing time-dependence within the temperature range of 500–600 °C, suggesting long-range diffusional α′ → γ transformation. With the aid of electron channeling contrast image technique (ECCI), we noticed that the formation of γ-nanograins in the early stages of reversion is sufficient to induce strong magnetic shape anisotropy in this steel. After full austenitization at 800 °C, further in situ magnetic measurements were also used to track the magnetic response of the material upon controlled cooling. Athermal formation of α′-martensite within the prior athermal ε-phase was clearly observed for temperatures lower than 100 °C. Using thermodynamic modeling we also calculated the start temperature for ε-formation (M s ε). Results showed that ε-martensite is indeed expected to form before α′, which was confirmed in all cases by means of EBSD. [ABSTRACT FROM AUTHOR]

Specimens of austenitic stainless steel were compressively deformed or irradiated with Xe ions at room temperature. The characterization of the magnetic properties and microstructural variations were done by vibrating sample magnetometer, grazing incidence X-ray diffraction and TEM. The results indicated that higher deformation or irradiation damage causes more significant magnetization phenomenon. The amount of ferromagnetic phase can be deduced from M s and increases with deformation and irradiation. The stress relief after deformation or irradiation may be responsible for the ferromagnetic phase formation. H c increases first and then decreases continuously with a turning point at deformed to 40% or irradiated to 2dpa. The different contributions of dislocation density and ferromagnetic precipitates on H c can explain this variation. [ABSTRACT FROM AUTHOR]

This study has been done by separately measuring Magnetic Barkhausen noise (MBN) under different structure characteristics, namely the carbon content, hardness, roughness, and elastic modulus in commercial steels. The result of the experiments shows a strong dependence of MBN parameters (peak height, Root mean square (RMS), and average value) on structure characteristics. These effects, according to this study, can be explained by two kinds of source mechanisms of the MBN, domain wall nucleation and wall propagation. The discovery obtained in this paper can provide basic knowledge to understand the existing surface condition problem of Magnetic Barkhausen noise as a non-destructive evaluation technique and bring MBN into wider application. [ABSTRACT FROM AUTHOR]

Stainless steel containers are widely used in the pharmaceutical and biopharmaceutical industry for the storage of buffers, process intermediates, and purified drug substance. They are generally held to be corrosion resistant, biocompatible, and nonreactive, although it is well established that trace amounts of metal ions can leach from stainless steel equipment into biopharmaceutical products. We report here that the use of stainless steel containers in conjunction with magnetic stirring bars leads to significantly aggravated metal contamination, consisting of both metal particles and significantly elevated metal ions in solution, the degree of which is several orders of magnitude higher than described for static conditions. Metal particles are analyzed by scanning electron microscopy with electron-dispersive X-ray spectroscopy, and metal content in solution is quantitated at different time points by inductively coupled plasma-mass spectrometry. The concentration of iron, chromium, nickel, and manganese increases with increasing stirring time and speed. We describe the impact of buffer components on the extent of metal particles and ions in solution and illustrate the effect on model proteins. [ABSTRACT FROM AUTHOR]

The primary goal of this research is to investigate the effect of loading speed on the stress-induced magnetic behavior of a ferromagnetic steel. Uniaxial tension tests on Q235 steel were carried out with various stress levels under different loading speeds. The variation of the magnetic signals surrounding the tested specimen was detected by a fluxgate magnetometer. The results indicated that the magnetic signal variations depended not only on the tensile load level but on the loading speed during the test. The magnetic field amplitude seemed to decrease gradually with the increase in loading speed at the same tensile load level. Furthermore, the evolution of the magnetic reversals is also related to the loading speed. Accordingly, the loading speed should be considered as one of the influencing variables in the Jies-Atherton model theory of the magnetomechanical effect. [ABSTRACT FROM AUTHOR]

The purpose of this work was to study the influence of different kinds of rolling on the magnetic properties of NOG steel, an electric steel widely used in electrical motors. These properties are highly correlated with the crystallographic texture of the material, which can be changed by rolling. Three kinds of rolling were examined: conventional rolling, cross-rolling and asymmetrical rolling. The crystallographic texture was determined by X-ray diffraction and the magnetic properties were calculated from a theoretical model that related the magnetic induction to crystallographic texture through the anisotropy energy. The results show that cross-rolling yields higher values of magnetic induction than the other processes. [ABSTRACT FROM AUTHOR]

In this paper, a new portable magnetic perturbation probe using a Giant Magneto-Resistance (GMR) sensor to detect and characterize surface cracks in ferromagnetic steels is presented. Measurements from one tangential component of the magnetic flux density are obtained during a single scan over a crack, and two parameters are defined from the output voltage of the GMR sensor: the distance between the peaks, DX, and their voltage difference, DV. The correlations between DX and DV and crack features such as depth, width, and orientation angle are determined. Sensitivity analyses are performed based on the studied features. The probe permits the user to obtain the crack׳s orientation angle using only one measured tangential component of the magnetic flux density. A simple procedure to estimate the crack׳s features is proposed based on the presented analysis. [ABSTRACT FROM AUTHOR]

The precipitation behavior of M 23 C 6 carbides and its influence on the tensile properties were investigated in a novel 0.3C–20Cr–11Mn–1Mo–0.35N austenitic stainless steel isothermally aged at 900 °C. It was found that typical M 23 C 6 carbides retaining a cube-on-cube crystallographic relation with austenite matrix precipitated on grain boundaries, twin boundaries and dislocations. With increasing aging time, the intergranular M 23 C 6 carbides grew along the grain boundaries and into the adjacent austenite grain to form a film-shaped morphology. The precipitation of cellular M 23 C 6 carbides on grain boundaries was a discontinuous reaction involving both the diffusion of C and Cr. And the formation of lamellar M 23 C 6 carbides on incoherent twin boundaries associated with the gliding of partial dislocations and the formation of stacking faults. Meanwhile, the intragranular M 23 C 6 carbides in rectangular or rhombic shapes initially nucleated on dislocations, and finally arranged in stringers corner-to-corner or face-to-face. The strength of the material was modestly improved by the precipitation of M 23 C 6 carbides, although the strengthening effect was weakened by the dominant precipitation of cellular M 23 C 6 after long-term aging duration. However, the ductility was significantly deteriorated by the intergranular and cellular M 23 C 6 . [ABSTRACT FROM AUTHOR]

There has been increased interest in using graphene oxide (GO) in various industrial applications such as working fluids, lubricants, oil and gas fields, heavy metal removal from water, anticorrosion paints and coatings etc. We studied electrochemical properties of steel in the presence of suspended GO in saline media. GO suspension has been characterized using Transmission electron microscopy (TEM) and X-ray diffractometer (XRD). We measured the effect of the GO concentration (0–15 ppm) on electrochemical properties of steel using different techniques: open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and potentiodynamic (PD) methods. Results indicate that the suppression of corrosion is directly proportional to increasing GO concentrations in saline environments. Surface morphology of corroded samples was examined using Scanning Electron Microscopy (SEM). Identification of the elements at accumulated layer was estimated from peaks of energy dispersive x-ray spectroscopy (EDX) and XRD. Increased protection abilities with increasing GO concentration have been attributed to the domination of salt layer presence at the surface of steel which occurs via precipitation of sodium chloride. Surface analysis confirm that there is no direct effect of GO on the protection behavior of steel. The presence of GO in the solution can enhance the precipitation of NaCl due to the decreased solubility NaCl which further slows down the corrosion. The pourbaix diagram shows that GO forms an anionic compound with sodium which may enhance the precipitation at working electrode. [ABSTRACT FROM AUTHOR]

High velocity solid particle erosion may cause severe damage and high wear rates in materials used for wear protection. An experimental work on the behavior of wear resistant steels, including three high-strength martensitic alloys and a carbide-reinforced metal matrix composite, was performed in high rate single impact conditions. Characterization of the mechanical behavior of the materials at high strain rates was conducted using the Hopkinson Split Bar technique to identify the effects of strain rate on strain hardening and the prevailing failure mechanisms. The high velocity impact experiments using spherical projectiles were carried out at various impact angles and projectile velocities. The effects of impact energy and impact angle were studied and discussed. Wear was analyzed as volume loss from the surface, but it was also presented in a more precise way by taking into account the actual energy spent on the plastic deformation and wear. In-situ high speed photography and post impact characterization of the impact craters were used to reveal the prevailing failure and wear mechanisms. Depending on the impact angle and impact energy, different wear mechanisms of plastic deformation, cutting, shear banding and fracture were identified. The martensitic steels exhibited adiabatic shear banding in the microstructure at high strain rates and impact velocities, which may accelerate the wear. The carbide reinforced steel was found susceptible to catastrophic fracturing especially at high impact angles. [ABSTRACT FROM AUTHOR]

Abstract: An investigation was carried out to analyze and quantify the mechanical property changing mechanism of high speed steel by pulsed magnetic treatment. Specifically, a pulsed magnetic treatment system was designed and applied to the tool material treatment. The micro-hardness and red hardness were measured to quantitatively investigate the influence of magnetic treatment on the mechanical properties. Results showed that high speed steel material possessed better mechanical properties using the proposed pulsed magnetic treatment, of which the maximum increase of micro-hardness was 50HV. Also, the red hardness with low temperature could be improved. Moreover, the influence of magnetic treatment conditions on the micro-hardness change rate was investigated. It was shown that the micro-hardness change rate first increases and then stabilizes with the increase of magnetic field intensity, and it decreases with the increase of magnetization time. Ultimately, the dislocation densities were calculated by XRD data analysis according to the Williamson–Hall method and the interaction between magnetic field and dislocation was discussed in detail. Results revealed that the dislocation density of high speed steel material increased by 24% after pulsed magnetic treatment. The dislocation multiplication and motion induced by magnetic field led to the increase of dislocation density, which was the main reason of the increase in micro-hardness. The dislocation pile-up mechanism was responsible for the treatment effects of different magnetic treatment conditions. The dislocation configuration determined from TEM micrographs was in good agreement with the X-ray results and the discussion of dislocation mechanisms. [Copyright &y& Elsevier]

Abstract: The stress-associated and the stress-induced changes in the magnetic properties of ferromagnetic materials have been identified and studied for more than a century. The results typically show multiple patterns which vary depending on the specimen under study and the mechanism by which the stress is applied. The measurements presented in the literature for iron, nickel, and steels show two unique magnetic features; the stress crossover and the bulging of the magnetization loop. The existence of these features in the magnetization measurements of different sets of high strength steel is studied. A statistical interpretation of the Preisach diagram is utilized to explain and model their existence. The modified DOK Preisach model effectively simulated the two features. [Copyright &y& Elsevier]

Abstract: Since reactor pressure vessel steels are ferromagnetic, provide a convenient means to monitor changes in the mechanical properties of the material upon irradiation with high energy particles, by measuring their magnetic properties. Here, we discuss the correlation between mechanical and magnetic properties and microstructure, by studying the flux effect on the nuclear pressure vessel steel used in reactors currently under construction in Argentina. Charpy-V notched specimens of this steel were irradiated in the RA1 experimental reactor at 275°C with two lead factors (LFs), 93 and 183. The magnetic properties were studied by means of DC magnetometry and ferromagnetic resonance. The results show that the coercive field and magnetic anisotropy spatial distribution are sensitive to the LF and can be explained by taking into account the evolution of the microstructure with this parameter. The saturation magnetization shows a dominant dependence on the accumulated damage. Consequently, the mentioned techniques are suitable to estimate the degradation of the reactor vessel steel. [Copyright &y& Elsevier]

Highlights: [•] We model electro-chemical magnetic abrasive machining process for simulation. [•] Finite element method is used to model complex magnetic abrasive machining process. [•] Electrochemical dissolution and synergistic effects are also considered. [•] Simulation of material removal and R a are validated using experimental results. [ABSTRACT FROM AUTHOR]

Abstract: Numerous machine components are constantly subject to different magnetic fields mainly due to the environments they are in, and they show some wear process throughout their life time. To understand this wear process better, the effect of magnetic field on the tribological properties of AISI 4140 steel has been investigated by applying different magnetic field intensities. One of the important factors affecting the wear and friction properties of a tribological system is wear debris and their properties like chemical structure and movement between mating bodies. For this respect, magnetic field was applied on a ferromagnetic material both before and during wear tests. Then, tribological properties of the samples magnetized before the wear tests were compared with the samples to which magnetic field was applied during the tests. It was observed that samples subjected to the magnetic field during tests showed better wear resistance and lower friction coefficient values than the others as the magnetized wear debris produced during test could be removed between mating bodies by means of magnetic effect while oxidized debris were held at the rubbing interface and lowered the debris production. [Copyright &y& Elsevier]

Abstract: We have re-examined the Steinmetz law for unsymmetrical flux-density(B)–field(H) loops in an arbitrary magnetized state for cold rolled steels from the viewpoint of magnetization mechanism. Under the criterion of B–H loops with 1.1T, a relation between the hysteresis loss and flux density change was found to fall almost the same curve as that for symmetrical loops obtained conventionally. In the intermediate B regime, the relation follows the usual Steinmetz law with a power-law exponent of 1.6, whose coefficient increases with defect density. These observations demonstrate that the hysteresis loss is only the function of the flux density change and the Steinmetz law always holds true in an arbitrary magnetized state if the pinning mechanism of irreversible Bloch wall motion prevails. [Copyright &y& Elsevier]

Abstract: We report results of minor B–H loop measurements on a highly neutron-irradiated A533B-type reactor pressure vessel steel. A minor-loop coefficient, which is a sensitive indicator of internal stress, changes with neutron fluence, but depends on relative orientation to the rolling direction in the low fluence regime. At a higher fluence of ∼10×1023 m−2, on the other hand, an anomalous increase of the coefficient was detected irrespective of the orientation. The results were interpreted as due to competing irradiation mechanisms of the formation of Cu-rich precipitates, recovery process, and the formation of late-blooming Mn–Ni–Si-rich clusters. [Copyright &y& Elsevier]

Abstract: Scaling laws in dynamical magnetic minor hysteresis loops have been investigated in the magnetizing frequency range of 0.05–300Hz for various steels including Cr–Mo–V steel subjected to creep, cold rolled steels, and plastically deformed Ni. Although scaling laws in the medium magnetization range found previously fail in the high magnetization frequency regime owing to a significant contribution of eddy currents, a scaling power law of the relation between remanence and remanence work of minor loops, associated with a constant exponent of approximately 1.9, holds true in a very low magnetization regime, irrespective of magnetization frequency and investigated materials. The coefficient of the law is proportionally related to Vickers hardness over the wide frequency range. These observations demonstrate that the scaling analysis of dynamical minor loops enables us to evaluate materials degradation in a short measurement time with low measurement field and high sensitivity to defect density. [Copyright &y& Elsevier]

Abstract: The austenite–ferrite superduplex stainless steel (SDSS) is essentially an Fe–Cr–Ni alloy to which additional elements (e.g. Mo, Mn, Si, Cu, C, P, S) were added so as to confer additional advantageous characteristics such as higher mechanical strength and resistance to corrosion. Many of its applications require the process of rolling which, due to the two-phase character, induces a marked texturing, elongation of grains, and directional ordering in each of the constituent phases. This, in turn, imprints a strong anisotropic features in the mechanical, magnetic, and other properties. Using various experimental techniques, such as magnetization and ac susceptibility, this work investigated the induced magnetic anisotropy. An easy axis (parallel to the rolling direction) anisotropy was observed. The nature of the magnetic anisotropy, manifested during low and high applied magnetic fields, will be discussed in terms of the combined influences of two main anisotropies, namely shape anisotropy (arising from demagnetizing forces) and texture anisotropy (arising from the induced preferred orientation). [Copyright &y& Elsevier]

Abstract: From practical point of view, determining the decarburizing depth is important in quality control of steel parts as it has undesirable effects on the mechanical properties such as hardness, wear and fatigue resistance. Traditional destructive methods of determining the depth of decarburized layer include metallographic and hardness test which are time-consuming and costly. Since response to eddy current is sensitive to chemical composition as well as microstructure of the material under consideration, the non-destructive method can be used in determining the depth of the decarburized layer in steel parts. It is mainly due to the difference in the microstructures, and as a result, in the magnetic properties of the decarburized layer with other parts of the specimen. In the present study at the first step, the magnetic properties of decarburized carbon steel bars (0.45wt.% C) were evaluated using an electromagnetic sensor and correlated with the microstructure changes from surface to the core of the sample. At the second step the steel bars were held in 900°C for different period of times and the depth of decarburizing layers were measured using hardness testing. Finally, the non-destructive eddy current technique was used and the response of test samples to the induction current including primary and secondary voltages, normalized impedance, phase angle and harmonic analysis parameters were investigated. Results show an acceptable accuracy in comparison to the destructive method. [Copyright &y& Elsevier]

Abstract: The magnetic behaviour and martensitic transformation at cryogenic temperatures (down to 4K) of the austenite phase of the duplex stainless steel (DSS), 7MoPLUS, were studied. As regards the prediction of Neel temperature, the empirical expressions for austenitic stainless steels are not applicable to the austenite phase of 7MoPLUS, although the composition of the austenite phase falls within the composition ranges within which the expressions were developed. Regarding the prediction of martensitic point Ms, the applicability of ‘old’ and recently developed expressions has been examined. The recently developed expressions, which take into account more alloying elements and their interactions, are not suitable for the austenite phase of 7MoPLUS. But for the ‘old’, simpler expressions, they seem to be valid in the sense that they all predict high stability of the austenite phase. Results obtained from 7MoPLUS were qualitatively the same as those obtained from another DSS, designated as 2205. Reasons for the applicability and inapplicability of these empirical expressions are suggested. [Copyright &y& Elsevier]

Abstract: 5Cr–0.5Mo steel having initial bainitic microstructure has been aged at 600°C for 5000h and subjected to creep at 600°C/60MPa. At different lengths of time the tests were interrupted for magnetic measurement using magnetic Barkhausen emissions (MBE) and magnetic hysteresis loop (MHL) techniques. Composition, morphology and distribution of carbides were studied using scanning electron microscopy (SEM). Magnetic softness was observed in the material up to 1600h of ageing due to the decrease in pinning density for the coarsening of carbides by accumulation of large number of finer carbides. At higher ageing periods the demagnetizing field offered by the large massive carbides causes magnetic hardening. During creep test since the material has been normalized at 50h of creep test also the structural change in creep test is accelerated, the magnetic softening for the interstitial carbon migration to the grain boundary and stress relaxation has removed in such early periods of ageing. When the carbides started coarsening the number density of the carbides decreased and inter-carbide distance increased which enhances the magnetic softening in the material in the secondary stage of creep. Formation of massive carbides and micro voids at the late tertiary stage of creep offers demagnetizing field causes magnetic hardening before failure of the material. [Copyright &y& Elsevier]

Abstract: For investigating the magnetic abnormality influenced by stress in ferromagnetic materials, static tension tests on a case-hardened steel were carried out. Different loads, which covered tensile elastic loads up to plastic deformation and break, were applied. Meanwhile, the normal component of magnetic flux leakage, H p(y), was measured by metal magnetic memory testing. The results indicate that H p(y) values change with the tensile loads and positions. There exists a relationship between k, which is the inclination of the linear amplitude-locus magnetic flux leakage curve, and static tension load. A simple model is derived. Additionally, the mechanism of the magnetic memory effect can be explained by the theory of the interaction between dislocations and domains. The research provides the potential possibility of quantitative inspection for metal magnetic memory testing. [Copyright &y& Elsevier]

Abstract: Case depth measurements of surface-hardened steel parts are important for quality control. Here, the magnetic properties of two sets of carefully characterized 25-mm-diameter case-hardened steel rods were studied with the aim of developing new methods to evaluate the case depth nondestructively. Induction-hardened 4140 steel and carburized 8620 steel rods were studied. Each set contained control samples (heat-treated but not surface-hardened) and samples hardened to three different nominal depths. After fabrication, the microhardness profiles of the rods were measured and the data analyzed to obtain the mid-hardness depth in each case. These measurements were compared with optical micrographs that reveal the microstructure of the samples as a function of depth below the surface. By the analysis of measured magnetization curves and hysteresis loops, the differential permeability and saturation magnetization of the rods were extracted. It was found that differential permeability increases with increasing case depth at a certain strength of the applied field (1350–1450A/m) for both hardening mechanisms, but only significantly for induction-hardened rods. Saturation magnetization was evaluated using the ‘law of approach’ and was observed to decrease as the depth of case hardening increases, for both induction-hardened and carburized steel rods. The observed behavior is described adequately by a simple model in which for the rod is represented as a volume-weighted sum of saturation magnetization values in the core and in the surface layer. [Copyright &y& Elsevier]

Abstract: In geomagnetic field, a series of tensile experiments on the low-carbon steel sticks were carried out. A special homemade detector was used to measure the magnetic gradient on the material surface. The results showed that the relationship between the magnetic gradient and the stress varied with different conditions of measurement. There was no obvious correlation between the magnetic gradient and the tensile stress if the sample remained on the material test machine. If the sample was taken off from the machine, the measured magnetic gradient was linear with the prior maximum stress. In Nanjing, PR China, a place of 32°N latitude, the slope of the linear relationship was about 67(uT/m)/MPa. This offered a new method of non-destructive stress testing by measuring the magnetic gradient on the ferromagnetic component surface. The prior maximum applied stress of the sample could be tested by measuring the present surface magnetic gradient. Actually this phenomenon was the metal magnetic memory (MMM). The magnetic gradient near the stress concentration zone of the sample, the necking point, was much larger than other area. Thus, the hidden damage in the ferromagnetic component could be detected early by measuring the magnetic gradient distribution on its surface. In addition, the magnetic memory signal gradually weakened as the sample was taken off and laid aside. Therefore, it was effective for a given period of time to detect the stress or stress concentration based on the MMM testing. [Copyright &y& Elsevier]

Abstract: The magnetic response of AISI 304L and AISI 316L obtained through powder metallurgy and sintered in nitrogen were studied. AISI 304L sintered in nitrogen showed a ferromagnetic behaviour in as-sintered state while AISI 316L was paramagnetic. After solution annealing both were paramagnetic. Magnetic behaviour was analysed by using a vibrating sample magnetometer, a magnetic ferritscope and magnetic etching. A microstructural characterization was performed by means of optical metallography, X-ray diffraction, scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDS). Some samples when needed were submitted to aged heat treatments at 675 and 875°C for 90min, 4, 6, 8 or 48h. The main microstructural feature found was the presence of a lamellar constituent formed by nitride precipitates and an interlamellar matrix of austenite and/or ferrite. The abnormal magnetic response was explained based on this. [Copyright &y& Elsevier]

Abstract: Three series of samples of low-carbon steel were investigated by the method of magnetic adaptive testing (MAT). The samples were plastically deformed by cold rolling to five consecutive stages of deformation. Samples in one series were magnetically closed, those in the other two series were magnetically open. The presented results of MAT – typical by its low required magnetization of the samples – show highly sensitive and reliable correlation with plastic deformation and as a consequence also with mechanical embrittlement of the investigated material, regardless of the sample shape. [Copyright &y& Elsevier]

Abstract: Magnetoelastic properties of materials are strongly influenced by changes of the dislocation structure that take place during the process of plastic deformation. Such changes can be used as a basis for a method of nondestructive evaluation (NDE) of the deformation level. So far, various methods, based on magnetic hysteresis loop properties as well as on the Barkhausen effect (BE), have been proposed. In the paper, the results obtained with the help of the abovementioned methods are compared with the results of the magnetoacoustic emission (MAE) signal measurements. The MAE signal is relatively easy to implement as a nondestructive method and unlike the BE effect signal gives information about the whole magnetized volume. [Copyright &y& Elsevier]

Abstract: The magnetic properties of ten types of ferritic and martensitic stainless steels have been measured at room temperature and at 77K. The steel samples studied were in the annealed state as received from the manufacturer. Our room temperature measurements indicate significantly harder magnetic properties than those quoted in the ASM International Handbook, which studied fully annealed stainless steel samples. Despite having harder magnetic properties than fully annealed steels some of the as-received steels still display soft magnetic properties adequate for magnetic applications. The carbon content of the steels was found to affect the permeability and coercive force, with lower-carbon steels displaying significantly higher permeability and lower coercive force. The decrease in coercive force with reduced carbon content is attributed to fewer carbide inclusions which inhibit domain wall motion. Cooling to 77K resulted in harder magnetic properties. Averaged over the ten steels tested the maximum permeability decreased by 8%, the coercive force increased by 14%, and the residual and saturation flux densities increased by 4% and 3%, respectively. The change in coercive force when cooled is comparable to the theoretical prediction for iron, based on a model of domain wall motion inhibited by inclusions. The modest changes of the magnetic properties indicate that the stainless steels can still be used in magnetic applications at very low temperatures. [Copyright &y& Elsevier]

Abstract: The magnetic properties of nonoriented electrical steels are influenced by the grain size and crystallographic texture. The technologies used to control the grain size in nonoriented electrical steels are approaching their limits. However, there is still some room for improvement of the magnetic properties through texture control. Hot-band annealing is known to be one of the most effective processing stages for texture modification. In this study, two types of initial grain sizes prior to cold rolling are obtained by different hot-band annealing. The effect of initial grain size on texture evolution and magnetic properties in nonoriented electrical steels containing 2% Si is examined. The specimens having different initial grain sizes have significantly different textures in the cold-rolled state and the annealed state. During the recrystallization stage, new grains formed in the coarse-grained specimens have stronger Goss but weaker γ-fibre texture than those in the fine-grained specimens. During the grain growth after complete recrystallization, the coarse-grained specimens still have weaker γ-fibre texture than the fine-grained specimens. The magnetic induction of the coarse-grained specimens is always higher at the same temperature than that of the fine-grained specimens. The core loss of the coarse-grained specimens is lower at the same temperature than that of fine-grained specimens. However, the improvement of the core loss becomes less pronounced as the annealing temperature increases. [Copyright &y& Elsevier]

Abstract: The austenitic stainless steel 316 Low Vacuum Melting is a material that is widely used in biomedical applications, particularly for bone substitution or repair. Sandblasting is commonly used as surface modification for biomaterials to obtain better mechanical fixation of the prosthesis. However the microstructural changes beneath the surface associated with this modification as well as other physical properties are not well known. In this work, the results for microstructural, magnetic and mechanical features of the sandblasted austenitic steels 316LVM subsurface are analyzed for the first time. [Copyright &y& Elsevier]

Abstract: An experimental investigation was carried out to study the effect of stresses that approach and exceed the yield point, on the magnetic properties of ground samples of medium carbon steel upon surface grinding. The observed magnetic behaviour included magnetic Barkhausen emission measurements, characteristics changes in the shape of hysteresis loop and magnetic properties derived from hysteresis loop. Relation between Barkhausen Noise (BN) parameters and other magnetic properties with stress have been discussed in term of degree of plastic deformation. It was observed that peak of BN signal, saturation magnetization and permeability derived from hysteresis loop depend to some extent on residual stress and degree of plastic deformation while other magnetic properties obtained from BN profile and hysteresis loop are stress insensitive. X-ray diffraction (XRD), metallographic study and microhardness measurement of ground samples have been undertaken to confirm the results obtained by analysis of magnetic parameters. [Copyright &y& Elsevier]

Abstract: The effect of magnetic field with different intensities on fatigue life of AISI 4140 steel has been investigated. For this purpose, unnotched and notched specimens were prepared from AISI 4140 steel. It was obtained that when the magnetic field especially was applied to the specimens at the stage of fatigue crack initiation, the fatigue life improved by reason of delaying formation time of slip bands due to regular direction and distribution of magnetic domains. And, it was observed that magnetic field was applied from the beginning of fatigue test up to occur the fatigue fracture, it was detrimental on the fatigue life because of over heating of the specimens. [Copyright &y& Elsevier]

Measurements of the bulk magnetic properties for two non-oriented electrical steels after a rapid heating are reported. A deterioration of the magnetic properties was observed for the fully processed non-oriented grade and an improvement for the semi-processed non-oriented grade. This publication emphasizes the effects due to the competition between the increase of the grain size and the appearance of thermal stresses during the rapid heating on the magnetic properties of the steels. [Copyright &y& Elsevier]

A model of magnetic loss separation based on the distribution of relaxation times is suggested. If the magnetic flux excitation is sinusoidal and the magnetization process by planar 180° domain wall movement is dominant, then it is possible to separate the hysteretic and dynamic part of total losses analytically. The experimental verification of proposed model is performed on a set of grain-oriented laminations cut at various angles with respect to the rolling direction. [Copyright &y& Elsevier]