Reduction of Residual Stress in Low Alloy Steel with Magnetic Treatment in Different Directions

The behavior that different magnetic treatment directions induce various amounts of welding residual stress reductions in low alloy steel was studied. Reductions of 26%-28% in the longitudinal stress σ x were obtained when low frequency alternating magnetic treatment was applied perpendicularly to the welding bead, whereas reductions of 20%-21% in σ x were measured by using the same treatment parameters except that the field direction was applied parallel to the bead. It is proposed that different extent of stress reductions caused by the above two treatment directions is attributed primarily to the alteration of the energy absorbed by domains from the external magnetic field, which part of energy can arouse plastic deformation in microstructures by the motion of domain walls.

Magnetic Particle Imaging for Magnetic Hyperthermia Treatment: Visualization and Quantification of the Intratumoral Distribution and Temporal Change of Magnetic Nanoparticles in Vivo

Purpose: Magnetic hyperthermia treatment (MHT) is a strategy for cancer therapy using the tem-perature rise of magnetic nanoparticles (MNPs) under an alternating magnetic field (AMF). Re-cently, a new imaging method called magnetic particle imaging (MPI) has been introduced. MPI allows imaging of the spatial distribution of MNPs. The purpose of this study was to investigate the feasibility of visualizing and quantifying the intratumoral distribution and temporal change of MNPs and predicting the therapeutic effect of MHT using MPI. Materials and Methods: Colon-26 cells (1 × 106 cells) were implanted into the backs of eight-week-old male BALB/c mice. When the tumor volume reached approximately 100 mm3, mice were divided into untreated (n = 10) and treated groups (n = 27). The tumors in the treated group were directly injected with MNPs (Resovist?) with iron concentrations of 500 mM (A, n = 9), 400 mM (B, n = 8), and 250 mM (C, n = 10), respectively, and MHT was performed using an AMF with a frequency of 600 kHz and a peak amplitude of 3.5 kA/m. The mice in the treated group were scanned using our MPI scanner immediately before, immediately after, 7 days, and 14 days after MHT. We drew a region of interest (ROI) on the tumor in the MPI image and calculated the average, maximum, and total MPI values and the number of pixels by taking the threshold value for extracting the contour as 40% of the maximum MPI value (pixel value) within the ROI. These parameters in the untreated group were taken as zero. We also measured the relative tumor volume growth (RTVG) defined by (V-V0)/V0, where V0 and V are the tumor volumes immediately before and after MHT, respectively. Results: The average, maximum, and total MPI values decreased up to 7 days after MHT and remained almost constant thereafter in all groups, whereas the number of pixels tended to increase with time. The RTVG values in Groups A and B were significantly lower than those in the control group 3 days or more and 5 days or more after MHT, respectively. The above four parameters were significantly inversely correlated with the RTVG values 5, 7, and 14 days after MHT. Conclusion: MPI can visualize and quantify the intratumoral distribution and temporal change of MNPs before and after MHT. Our results suggest that MPI will be useful for predicting the therapeutic effect of MHT and for the treatment planning of MHT.

Influence of Magnetic Heat Treatment and Compressive Stress on Jump Effect of Magnetostriction of Tb_(0.3)Dy_(0.7)Fe_(1.95) Alloy

The 〈 110 〉 -oriented TTb0.3Dy0.7Fe1.95 polycrystalline alloy was magnetically annealed, and its influence on jump effect of magnetostriction was investigated. In the vacuum superconductive high magnetic field equipment, 〈 110 〉 -oriented Tb0.3Dy0.7Fe1.95 polycrystalline alloy of the directional solidification was annealed at 623 and 723 K for 5 min under the magnetic field vertical to specimen axis. It is found that magnetic annealing can enhance the jump effect under compressive stress, and increase the saturated magnetostriction coefficient λs, the λs of the magnetic annealing specimens at 623 K under 8.1 MPa is attained to 1950 × 10^-6, Magnetic annealing increases the maximum of dynamic magnetostriction coefficient, d33^max, as well as the magnetic field for d33^max under 8.1 MPa.

MAGNETIC TREATMENT TECHNOLOGY APPLIED TO OILFIELD PRACTICE

Petroleum exploration is a strategic task for our country in its economic development.At present,petroleum production in most of east China’s oilfields is in the waning period after reaching a peak.To raise the oil recovery rate is a key measure for their production increase.Because of this,a major provision was included in the third cooperative protocol signed in 1986 by the

Effect of Quench Treatment on Fe/Mo Order and Magnetic Properties of Double Perovskite Sr_2FeMoO_6

A quench-treatment technique is used to prepare a high-quality polycrystalline sample of double perovskite Sr2FeMo06 （SFMO）. X-ray powder diffraction analysis reveals that the sample has a single phase and exhibits I4/m symmetry. The cation order η of the sample increases to 98.9（2）% from 94.2（3）%, which is prepared by the traditional sol-gel method. The initial magnetization isotherm of the sample is detected at 300 K. Unit-cell magnetization for the current sample is 1.332 #s at 300 K, and the one for the traditional sol-gel method sample is 0.946#9. Unit-cell magnetization is enhanced to 40.80% by the quench-treatment technique. Quench treatment is an effective method of enhancing the Fe/Mo order and magnetic properties of double perovskite SFMO.

Interface strengthening for thermal sprayed WC-10Co4Cr coating subjected to pulsed magnetic treatment

The reliability of the coated industry components demands ideal fatigue properties of the coating,and it is mainly determined by the performance of the interfaces.In this study,pulsed magnetic treatment(PMT)was applied to the thermal sprayed WC-10Co4Cr coating,and the fatigue lifetime of the coated bolt increased by 219.82%under an imitation of the operating mode condition.Scratch tests further proved that both the adhesion and cohesion strength were improved after PMT,and they benefit from the interface strengthening effects.The formation of coherent WC/Co interfaces was characterized by in-situ transmission electron microscopy(TEM),and the molecular dynamic simulations indicate that the work of separation of these interfaces is much higher than the original disordered ones.Residual stress was relaxed and distributed more homogeneously after PMT,and it mainly contributes to the coating/substrate strengthening.This work provides a new post-treatment method focusing on the interfaces in the WC-based coating and gives insight into its mechanism so that it is hopeful to be applied to other kinds of coatings.

Mechanism and application of mechanical property improvements in engineering materials by pulsed magnetic treatment:A review

Pulsed magnetic treatment(PMT)has been adopted as an effective strengthening method for engineering materials and components in recent years,and the development of its application depends on the comprehensive understanding of the nature of PMT.The deep mechanism was thought initially to be the magnetostrictive effect,while further investigation found that the magnetic field could lead to the change of the defect states in the crystal,which is called the magnetoplastic effect.Due to the complexity of the engineering materials,manifestations of the magnetoplastic effect become more diverse,and they were reviewed in the form of microstructure homogenization and interfacial stabilization.Further,the mechanism of the magnetoplastic effect was discussed,focusing on the changes in the spin states under the external magnetic field.Microstructure modifications could also alter material performances,especially the residual stress,plasticity,and fatigue properties.Therefore,PMT with specific parameters can be utilized to obtain an ideal combination of microstructure,residual stress,and mechanical properties for better service performance of different mechanical parts,and its applications on machining tools and bearings are perfect examples.This work reviews the effect of PMT on the microstructure and properties of different materials and the mechanism,and it also summarizes the fundamental applications of PMT on essential mechanical parts.

Behavior of leaching and precipitation of weathering crust ion-absorbed type by magnetic field

With weathering crust Ion-Absorbed Type Rare Earth （IATRE） ores in southern Jiangxi as an example, rare earth percolation leaching and leaching solution precipitation process research were carried out under conditions of magnetic field. The effect on the rare earth leaching process such as magnetic field strength, magnetization time, magnetization manner, and other factors were discussed. The effect on the mother rare earth liquor sedimentation rate, purity, and crystallization behavior such as magnetic field strength, magnetization time, and magnetization manner were investigated. Leaching and precipitation mechanism of magnetization on IATRE were analyzed. The results showed that the magnetic treatment can improve leaching rate of weathering crust IATRE and the sedimentation rate, and reduce consumption of reagents.

Effect of Magnetic Field on Enzyme Activities in Main Soils of Northeast China

Soil enzyme activities as affected by applied magnetic field were studied with three main soils (brown soil, black soil and albic soil) collected from Northeast China. Appropriate intensities of magnetic field could obviously enhance the activities of hydrogen peroxidases, invertases, amylases and phosphatases in the three soils, although the effect varied with types and water regimes of the soils. Increasing times of magnetic treatment could multiple its good effect on the activities of hydrogen peroxidases in soils.

Cost-effective integrated strategy for the fabrication of hard-magnet barium hexaferrite powders from low-grade barite ore

Ultrafine barium hexaferrite（BaFe12O19） powders were synthesized from the metallurgical extracts of low-grade Egyptian barite ore via a co-precipitation route. Hydrometallurgical treatment of barite ore was systematically studied to achieve the maximum dissolution efficiency of Fe（～99.7%） under the optimum conditions. The hexaferrite precursors were obtained by the co-precipitation of BaS produced by the reduction of barite ore with carbon at 1273 K and then dissolved in diluted HCl and FeCl3 solution at pH 10 using NaOH as a base; the product was then annealed at 1273 K in an open atmosphere. The effect of Fe^3＋/Ba^2＋ molar ratio and the addition of hydrogen peroxide（H2O2） on the phase structure, crystallite size, morphology, and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. Single-phase BaFe（12）O（19） powder was obtained at an Fe^3＋/Ba^2＋ molar ratio of 8.00. The formed powders exhibited a hexagonal platelet-like structure. Good maximum magnetization（48.3 A×m^2×kg^–1） was achieved in the material prepared at an Fe^3＋/Ba^2＋ molar ratio of 8.0 in the presence of 5% H2O2 as an oxidizer and at 1273 K because of the formation of a uniform, hexagonal-shaped structure.

EFFECT OF TEMPERING IN PULSE MAGNETIC FIELD ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HIGH SPEED STEEL

Using a self-made pulse magnetic field heat treatment equipment with low or medium intensi- ty,the tempering process of high speed steel W6Mo5Cr4V2 was investigated.It was found that the secondary hardening process and the transformation of retained austenite for the steel were accelerated by the pulse magnetic field,and the tempering period could be reduced to half of the original.It was shown by the analyses of X-ray and eletron microscopy that the precipitation of carbides becomes more homogeneous and dispersive,and the tetragonality of martensite increases obviousely,which causes the improvement of hardness and red-hardness for the steel.It was confirmed that the service life of tools as centre bits,screw taps and punches for nuts could be increased by 0.4 to 1.4 times by the tempering in magnetic field.

Spontaneous Cervical Epidural Hematomas in Mild Cervical Spondylotic Myelopathy Patients：An Analysis of 8 Cases

Spontaneous cervical epidural hematoms（SCEH） complicated with mild cervical spondylotic myelopathy（CSM） is a rare but emerging condition.Early diagnosis and treatment are important for good outcomes.This study aimed to investigate the clinical characteristics of this condition and to discuss the optimal treatment.The clinical data from 8 patients with SCEH plus CSM who were divided into two groups by treatment methods were retrospectively analyzed.The neurological function of the patients was assessed by Japanese Orthopedic Association（JOA） score before and after the surgical operations.Other factors were reviewed with medical records.Among them,4 out of the 8 patients underwent emergency surgery,and the rest 3 patients experienced an initial conservative treatment and ultimately received a laminectomy.We found that the Frankel Scale scores in most of the surgical patients were increased after surgery（6/7,85.7%）.However,the JOA scores at the 6th month after onset were even lower than those before onset in 3 of the operative cases,and those in the patients who were given conservative treatment showed no significant change.It was concluded that some patients with SCEH and CSM treated with a timely operation may obtain relief from their previous CSM symptoms.However,the final neurological deficits of these patients were closely related to the progressive interval which refers to the hours between the initial onset and the occurrence of new neurological deficits or mild CSM deterioration,no matter whether they accept the operation.We found the crucial progressive interval may be in 9 h.Early MRI and prompt neurosurgical intervention are also important to improve the neurological deficits.

Manufacturing of Surface Nanostructured Fibers Featuring an Antibacterial Effect by Magnetic Field Transportation of Magnetite@Silver Core-Shell Nanoparticles

Magnetic core-shell nanoparticles of type Fe3O4@Ag were synthesized in gram scale following a combined co-precipitation phase-transfer method and afterwards, processed to nanoparticle polymer (polypropylene and polyamide) composites. These composites were used as sheath material for the fabrication of core-sheath fibers. During the melt spinning process, a magnetic field was applied around the roving, whereby the particles move in the still liquid sheath polymer towards the surface. The produced fiber materials were investigated by AFM showing a nanostructuring of the surface, which was indirectly confirmed by determination of a slight surface tension lowering. Nanoparticle movement was shown by cross-section SEM and EDX measurements. The antibacterial activity of the spun fibers was proven by contacting them with Escherichia coli. A long-term stability of this effect was observable by carrying out a standard washability test. In contrast to previous works this new approach uses no deposition technique to introduce surface changes. It rather applies a magnetic force to move appropriately equipped nanoparticles from the inside of the fiber to the surface. This leads in only one step to a strong superficial anchoring of the particles resulting in a unique combination of long-term stable antibacterial and improved anti-soiling effects.

Enhanced magnetic properties of Ce_(17)Fe_(76.5)Co_1Zr_(0.5)B_6 alloys by magnetic field heat treatment

In the present work,Ce_(17)Fe_(76.5)Co_1Zr_(0.5)B_6 ribbons were prepared by a direct melt spinning method.The effects of chamber pressure and magnetic field annealing temperature on the magnetic properties and microstructures of the alloys were investigated.The grain size and content of Ce_(2)Fe_(14)B phase can be changed by adjusting the chamber pressure,and the optimal magnetic performance is obtained at0.04 MPa.The magnetic properties can be influenced under magnetic field heat treatment.When the annealing temperature is lower than the Curie temperature,the refinement and a uniform distribution of the grains is obtained.The irreversible magnetic susceptibility curve reveals that magnetic field heat treatment enhances the exchange coupling interaction between grains of the Ce_(2)Fe_(14)B phase.When the magnetic field annealing temperature is 438 K,the alloy displays the optimal magnetic properties.Compared with the as-spun sample,the values of intrinsic coercivity(H_(ci)),remanence(B_r) and maximum energy product((BH)max) increase by 3.4%,9.8% and 18.7%,respectively.This work provides an effective approach by which to enhance the magnetic properties of Ce-Fe-B alloys.

Empirical study of magnetohydrodynamic effect on fluid flow in clayey porous media

Enhancing oil recovery from clayey reservoirs is a significant challenge in petroleum industry due to complex interactions between fluids and rock surfaces,particularly clay swelling.This study presents the first empirical analysis of magnetic fields'impact on fluid flow in clayey porous media.Our core findings indicate that magnetic treatment of water increases oil recovery by an average of 15–30%in clayey media,with limited effectiveness in pure quartz media.Detailed experiments unraveled that improved recovery factor by magnetic treatment stem from both mitigated swelling and altered magnetic properties at clay surface;introducing 30%clay to porous medium decreased the recovery by 32%compared to pure quartz sand.Heating the clay to around 1000°C to reduce its swelling property improved the recovery by only 16%,suggesting magnetic treatment is not solely attributed to clay swelling mitigation.Treating ferromagnetic films at clay surface with HCl to produce non-magnetic FeCl_(3) resulted in a high recovery factor,similar to the clay-free medium.Moreover,it was determined that a magnetic field intensity of 43760–51740 A/m is optimal for fluid displacement in clayey media.Notably,the intensity of 47760 A/m increased recovery to 84.5%in a 30%clay medium,compared to 49.7%without treatment.Interestingly,it was observed that the maximum flow rate was associated with zero potential difference across the medium,providing a faster method to determine the optimum magnetic field intensity.Lastly,the concept of‘Magnetic memory’was investigated,referring to the persistence of magnetic field's influence after its removal.Our findings indicated that pressure build-up time stability lasted 10 days post-treatment,after which water behavior reverts,and clay swelling resumes.This insight into the temporal dynamics of magnetic field application provides a deeper understanding of its long-term impacts on fluid flow in clayey reservoirs.

Mechanism of Residual Stress Reduction in Low Alloy Steel by a Low Frequency Alternating Magnetic Treatment

Residual stress reduction in low alloy steel by a low frequency alternating magnetic treatment and its mechanism were investigated. Experimental results revealed that average stress reductions of 20%-24% were obtained in the welded samples. Moreover, compared with the zones with lower initial stress levels, more remarkable stress reductions were obtained in the stress concentration zones. The microstructures and magnetic domains were observed by scanning electron microscopy （SEM） and atomic force microscopy （AFM）. Based on the analysis of the microstructure and magnetic domain changes, the mechanism of stress reduction by the magnetic treatment has been concluded： （1） the magneto-plastic deformations mainly due to the more uniform redistribution of dislocations are the fundamental cause of stress relaxation; and （2） surface topography is also proved to affect the magnetic treatment results to some degree by influencing magnetic domains.

The Impact of magnetic water treatment on salt distribution in a large unsaturated soil column

The use of saline water for crop production leads to soil salinization.Magnetically-treated water(MTW)has been used for many years and has shown promise in leaching some ions from soil.At the same time,results have been inconsistent and somewhat controversial.In this study,we used large unsaturated columns(diameter 15 cm and length 90 cm)to determine:1)salt distributions at depths of up to 90 cm after adding magnetically-treated,saline water to soil;2)whether MTW could reduce the rate of accumulation of salts(measured by EC)in soil,and;3)whether MTW could increase the leaching effect of soluble salts below root zones compared to control.The soil tested had a lower salt content compared to the water,a real-world scenario often faced when farmers elect to switch from higher-cost municipal water sources to ground water sources that have a higher saline content.Results indicated that the rate of salt accumulation was greater in the control group at the 30–60 cm depth.At the same time,the salt content at the 90 cm depth was greater in the MTW column.The results have shown that MTW changes the distribution of salts between soil layers reducing their content in the upper layers which are more important for agriculture.

Tribological Performance Improvement of Bearing Steel GCr15 by an Alternating Magnetic Treatment

This paper discusses the tribological performance of the bearing steel GCr15 treated by an alternating magnetic field. The wear test results showed that the average of wear mass losses decreased by nearly 80% after the magnetic treatment, compared to those before the magnetic treatment. The micro-hardness and microstructures（i.e., grain size,carbide morphology and dislocation distribution） before and after the magnetic treatment were experimentally investigated,and the mechanism of the tribological performance improvement of the bearing steel GCr15 due to the magnetic treatment was then revealed based on the above results.

Microstructure improvement related coercivity enhancement for sintered NdFeB magnets after optimized additional heat treatment

The micro structure, especially the Nd-rich phase and the grain boundary, in sintered NdFeB magnets plays an important role in magnetic reversal and coercivity mechanism. To better understand the effects of the microstructure on the coercivity, we investigated the microstructure and properties improvements of a commercial sintered NdFeB magnet after optimized additional heat treatment. The coercivity is enhanced from 1399 to 1560 kA/m. This enhancement has been explained in terms of the evolution of the grain boundary structure, and the formation of continuous thin layers of Nd-rich phase is important for high coercivity. The micromagnetic simulation together with the numerical analysis based on the nucleation model suggest that the reversed magnetic domains nucleate mainly at the interface of multijunctions of Nd_2 Fe_（14）B grains with high stray fields during the demagnetization process. Both improved anisotropy fields at grain boundaries and reduced stray fields at multi-junction Nd-rich phases contribute to the coercivity enhancement. This work has importance in understanding the crucial micro structure parameters and enhancing the obtainable properties for sintered NdFeB magnets.

MAGNETIC RESONANCE IMAGING AND MICROSURGICAL TREATMENT OF INTRAMEDULLARY HEMANGIOBLASTOMA OF THE SPINAL CORD

Thirteen cases of intramedullary hemangioblastoma of the spinal cord were studied radiologically, especially with magnetic resonance imaging (MRI). Microsurgery was used to remove the tumors in all cases. Signs and symptoms were improved in 84.6% of the cases after operation. The diagnosis and microsurgical techniques for excision of intramedullary hemangioblastoma of the spinal cord are discussed. This dis-ease should be differentiated from hydromyelia, intramedullary ependymoma, and vascular malformation of the spinal cord. Total removal of the tumor is recommened.