Ferrite Content Research Articles

Effect of CoFe2O4 on Dielectric and Conduction Behavior Pb0.75La0.25TiO3 Based Composites

(1-x) (Pb0.75La0.25TiO3)-x (Co2FeO4) where x = 0.50 & 0.60 Ceramic Composites have been successfully synthesized via mechanical mixing method. The substitution of CoFe2O4 with La3+ modified Lead Titanate (Pb0.75La0.25TiO3) in above mentioned stoichiometric proportions on has been explored for temperature dependent electrical properties. The both real and imaginary parts of dielectric permittivity decreases with increasing both temperature as well as ferrite content. The real part of impedance decreases with increasing temperature as well as Co2FeO4 content whereas maxima in imaginary part reveals the presence of temperature dependent dielectric relaxation. Both conductivity as well as dielectric loss increases with increase in Co2FeO4 content in stoichiometric proportion.

Effect of CoFe2O4 on Dielectric and Conduction Behavior Pb0.75La0.25TiO3 Based Composites

(1-x) (Pb0.75La0.25TiO3)-x (Co2FeO4) where x = 0.50 & 0.60 Ceramic Composites have been successfully synthesized via mechanical mixing method. The substitution of CoFe2O4 with La3+ modified Lead Titanate (Pb0.75La0.25TiO3) in above mentioned stoichiometric proportions on has been explored for temperature dependent electrical properties. The both real and imaginary parts of dielectric permittivity decreases with increasing both temperature as well as ferrite content. The real part of impedance decreases with increasing temperature as well as Co2FeO4 content whereas maxima in imaginary part reveals the presence of temperature dependent dielectric relaxation. Both conductivity as well as dielectric loss increases with increase in Co2FeO4 content in stoichiometric proportion.

Effects of EPS, Mn–Zn Ferrite, and Layers on the Electromagnetic Absorption Performance of Magnesium Phosphate Cement

In view of the excellent bonding capacity, rapid hardening, and high early strength, magnesium phosphate cement (MPC) functionalized with impedance matching agent of expanded polystyrene (EPS) and absorber of Mn–Zn ferrite that exhibits excellent electromagnetic wave absorption performance (EWAP) is fabricated to shield the construction of buildings against the ever-increasing electromagnetic radiation hazards. Influences of EPS and Mn–Zn ferrite contents and layers of specimens on the reflection loss (RL) of MPC in the frequency range of 1–18 GHz are systematically investigated. Test results demonstrate that EPS and Mn–Zn ferrite significantly enhance the EWAP of MPC due to the porous structure effect by EPS and multiple magnetic loss effects by Mn–Zn ferrite. MPC with double-layer structure shows an optimal EWAP as featured by a peak RL value of −23.2 dB and a bandwidth of 17 GHz below −10 dB. The electromagnetic energy absorbing mechanisms of MPC are further analyzed with scanning electron microscopy/energy disperse spectroscopy (SEM/EDS) and X-ray diffraction (XRD) results. In view of structural strengths, the modified MPC is able to repair damaged concrete of prefractured specimens, which ensures the reliability and rapidity of electromagnetic radiation protection.

Influence of SiO2 Embedding on the Structure, Morphology, Thermal, and Magnetic Properties of Co0.4Zn0.4Ni0.2Fe2O4 Particles.

(Co0.4Zn0.4Ni0.2Fe2O4)α(SiO2)(100-α) samples obtained by embedding Co0.4Zn0.4Ni0.2Fe2O4 nanoparticles in SiO2 in various proportions were synthesized by sol-gel process and characterized using thermal analysis, Fourier-transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, inductively coupled plasma optical emission spectrometry, and magnetic measurements. Poorly crystalline Co-Zn-Ni ferrite at low annealing temperatures (500 °C) and highly crystalline Co-Zn-Ni ferrite together with traces of crystalline Fe2SiO4 (800 °C) and SiO2 (tridymite and cristobalite) (1200 °C) were obtained. At 1200 °C, large spherical particles with size increasing with the ferrite content (36-120 nm) were obtained. Specific surface area increased with the SiO2 content and decreased with the annealing temperature above 500 °C. Magnetic properties were enhanced with the increase in ferrite content and annealing temperature.

On the ferrite-controlled iron coupling for enhanced soft magnetic hybrid composites via first-order reversal curves

The substitution of conventional non-magnetic binder in soft magnetic iron composites by insulating spinel ferrite has been proven as a powerful avenue for enhancing the interparticle coupling while suppressing eddy currents. The inherent shortcomings of macroscopic characterization, hindering the phase- and magnetization process-resolved reconstruction, are overcome by generalized application of the first-order reversal curves analysis for the first time. The mechanism of involving ferrite coating as a true matrix, evolving from the beneficial coupling effect at low concentrations towards the reappearing demagnetizing interactions that trigger a partial decoupling at higher fractions, is evidenced in the computed diagrams encompassing the microscopic switching. This substantial improvement is related to a thin and uniform layer of submicron ferrite grains, occupying less than 5 vol% of bulk composite, which compensates the free magnetic poles at the surface of iron particles and restrains the action of local anisotropic demagnetizing field. A significant constriction of switching and interaction field distributions in ferrite-coated iron composites with respect to a ferrite-free system is modeled and the conditions for having amplified interphase coupling are defined. We further demonstrate that heterogeneous switching of core particles and their shell provides an efficient way of manipulating the domain walls activity with increasing prevalence of spin rotations with excessive content of ferrite.

Structural and magnetic investigations of (1-x) (Bi0.5Na0.5TiO3)0.94-(BaTiO3)0.06 + (x) SrYFe11O19

This paper describes the manufacturing, structural characteristics, and magnetic properties of a ferroelectric (Na0.5 Bi0.5TiO3-BaTiO3; BNBT) and ferromagnetic (SrYFe11O19; SRYFO) composite system. The polycrystalline composite system (1-x) (Bi0.5Na0.5TiO3)0.94-(BaTiO3)0.06 + (x) SrYFe11O19 (x = 0.00, 0.25, 0.50, 0.75 and 1) was synthesized via solid state reaction followed by modified Sol-gel auto-combustion method. Rietveld refinement of the XRD pattern confirms the presence of dual phase symmetry consisting of BNBT (P4bm) and SRYFO (P63/mmc) phases without any external impurity phase. The calculated value of c/a, cell volume, and grain size confirms the lattice distortion. FE-SEM (Field emission scanning electron microscope) was used to study the morphology formation of prepared composites, which revealed that composites are dense ferroelectric grains well distributed in the ferrite matrix, and the grain size of the nanoparticles ranged from 166 to 240 nm. The magnetic characterization was carried out by VSM (Vibrating Sample Magnetometer) with the applied field in the range of −15 kOe to + 15kOe at room temperature. The M−H loop reveals the ferromagnetic nature of composites. The calculated saturation (MS), remnant (Mr), and coercivity (HC) values are increased with ferrite content. The obtained MS/Mr values are found lesser than 0.49, proving the presence of a solitary, non-interacting realm with a single axial anisotropy. These samples can be used to make permanent magnets and perpendicular recording media.

Flash butt welding on microstructures and mechanical properties of joints for high strength acid resistant steel

In this research, the 600 MPa acid resistant steel was used as flash butt welding base material, to study the effect of different upset allowance on the microstructure and mechanical properties of the joints. The results can be obtained as follows: with the increase of the upset allowance, it has a significant effect on the elongation, the ferrite content in the heat affected zone increases, and the joint strength first increases and then slowly decreases. When the upset allowance is bigger than 4mm, there are wide and large bainitic ferrites in the coarse grained zone, the joint strength deteriorates sharply. When the upset allowance is 3-4mm, the mechanical properties of the welded sample are the best, the tensile strength is 686-708MPa, the yield strength is 610-636MPa, the elongation is higher than 13.77%. The steel matrix can be strengthened effectively by forming grain refinement and dispersed granular bainite with proper upset allowance. The different hardness distributions of welded joints to display the difference of microstructure in different regions.

Synthesis and thermal stability of ferrites added polymers nanocomposites

Nanocomposites of ferrite and polymer constituents with the ordered combination (x) wt% Ni0.48Cu0.12Zn0.4Fe2O4 + (1-x) wt% polyaniline, (0 ≤ x ≤ 1) and (x) wt% (NCZ-PANI), Ni0.48Cu0.12Zn0.4Fe2O4 + (1-x) wt% paraformaldehyde, (0 ≤ x ≤ 1) (NCZ-PFD) were prepared by mechanical alloying method. A microwave digestion system was used to prepare nanopowders of Ni0.48Cu0.12Zn0.4Fe2O4 (NCZ) by microwave hydrothermal method. Infrared Fourier Transform Spectroscopy (FTIR) was used to characterise the samples. Spinel and polymer phases were confirmed by the characterisation tests in the composite samples. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study the thermal properties of nanocomposites. It reveals that thermal stability is increased with ferrite content for the nanocomposites. The DC conductivity increased with polymer content.

Study of a nearly Ni-free V-containing lean duplex stainless steel and the deformation mechanism

A novel nearly Ni-free V-containing lean duplex stainless steel with the composition of Fe-0.1C-20Cr-5Mn-0.2Ni-0.2N-0.18V (V-LDSS) was developed, with a low content of the precious element Ni and good mechanical properties. In the present study, the microstructures, mechanical properties, precipitate behaviors, and the evolution of the microstructural features under different logarithmic strains of the V-LDSS at different annealing temperatures were investigated. The results indicated that the annealing temperature had significant influences on the precipitation behavior, the volume fraction of the austenite phase, and the grain size of the V-LDSS. The tensile curves changed from discontinuous yielding to continuous yielding, under the control of the precipitate behavior and the phase content of ferrite. The deformation mechanism revealed the synergistic deformation behavior of the transformation-induced plasticity (TRIP) effect in the austenite and the rapid growth of dislocations in the coarse ferrite, resulting in excellent plasticity of the current V-LDSS. After annealing at 1125 °C for 5 min, the annealed samples showed a good combination of the ultimate strength and elongation.

Effect of Direct Rolling of Without-Heating on the Differentiation of Mechanical Properties of Rebar

This paper focuses on the mechanical property differentiation and phase content differentiation of HRB400 rebars under the direct rolling of without-heating (DROW) process. The results showed that the temperature distribution from the head region to the tail region of the billet before rolling under the DROW process was different compared to the traditional hot rolling (THR) process, which resulting in the difference of each phase volume fractions and the grain size of the rebar. Compared with the THR process, the phase distribution of the rebars under the DROW process is not uniform, showing the characteristics of low ferrite content in the head region, followed by the tail region, and the highest in the middle region. It was demonstrated that the DROW process could improve the mechanical properties of the rebar, but the difference in phase content and grain size distribution leads to a large variability in the enhancement of the mechanical properties of rebar rolled in different areas of the billet.

Microstructural Characterization of Spheroidal Graphite Irons: A Study of the Effect of Preconditioning Treatment

The effect of preconditioning treatments on the control and improvement of spheroidal graphite iron (SGI) microstructure was evaluated. In the melt, 0.15% of Zr-(Ca, Al) FeSi preconditioner was added into different conditions. Four samples were produced for this investigation: (1) in the first melt, there was no addition of a preconditioner for comparative purposes; (2) in the second melt, the preconditioner was added at the cold charge; (3) in the third melt, the preconditioner was added before the last cold charge; and (4) in the fourth melt, the preconditioner was added at tapping from the furnace. Microstructural characterization was conducted to understand the effect of the treatment on the SGI. Optical microscopy results show that preconditioning treatment increases graphite’s nodule density, ferrite content, and nodularity. Scanning electron microscopy (SEM), energy dispersive energy (EDS), and electron backscatter diffraction (EBSD) analysis were used to identify the types of microparticles present in the graphite nodules. Some complex microparticles were identified as AlMg2.5Si2.5N6, MgS, and CaS. The microstructural characteristics of the matrix, such as grain size, crystallographic orientation, and misorientation, were also evaluated by the EBSD. The addition of the preconditioning at tapping results in a higher ferrite fraction, smaller grain size, misorientation, and hardness values. This work suggests that the different preconditioning practice has a crucial effect on the microstructural characteristics of the SGI. This knowledge is vital, allowing the microstructure tailoring to enhance the mechanical properties of SGI to obtain the best performance of these materials.

Microstructure, mechanical and electrochemical properties of wire-arc additively manufactured duplex stainless steel

Wire-arc additively manufactured (WAAM) super duplex stainless steels (DSS) 2594 walls were fabricated to investigate the microstructure of different regions, including top, body and root as well as the influence of microstructure on mechanical and electrochemical properties. The microstructure was composed of ferrite and austenite with a few nitride precipitates. The ferrite content decreased from top to root. The average hardness increased slightly from top to root. The ultimate tensile strength of different regions varied slightly, comparable to that of the hot-rolled plate. Compared with those in vertical direction, samples in the horizontal direction had higher strength and lower elongation. The corrosion resistance ranked as root ≈ body > hot-rolled > top.

Machine learning (deep learning) and visualization assisted ferrite content prediction in austenitic stainless steel

The ferrite content of 202 austenitic stainless-steel welds was predicted based on Machine Learning (ML), and the data set was analysed by manifold learning, feature engineering, and other methods. Multiple ML methods such as K-Nearest Neighbors (KNN), Support Vector Regression (SVR), Ensemble Learning (EL)、Multiple model Merging (MM), and Artificial Neural Network (ANN) performed algorithm model building and model tuning on the data set and evaluated the prediction performance of the model. The ML visualization and ML interpretation tools are used to demonstrate in detail the comparison of the prediction performance of ferrite number (FN) of various ML models and the effect of welding parameters on FN prediction. SVR, Gradient Boost, Xgboost, Catboost, Voting, Stacking, and MLP regression models demonstrate precision prediction and generalization. The coefficient of determination ( R 2 ) of the MLP model was 0.956 on the test set, which showed generalization and robustness. The visual data analysis and ML sample tracking methods are used to optimize the model. An ANN model with high prediction accuracy was proposed, and the R 2 of the test set was 0.972. This paper reveals the comprehensive application of ML-assisted material design and data sample visual tracking in the field of materials. • PyTorch deep learning framework to improve prediction accuracy. • Welding parameters are used to analyse welding parameters’ effect on ferrite content in welds. • 13 kinds of algorithms are selected for modelling and training. • Visualization tools explain the model prediction and feature importance. • The determination coefficient of the neural network model is 0.972.

On the correlation among ultra-fast quenching, retained ferrite content and strengthening mechanism in PC steel bars

Prestressed Concrete (PC) steel bars made of 30MnSi are widely used in various prestressed components. This paper compared the hot-rolled, cold-drawn, quenched and tempered samples of PC steel bars, observed the microstructure evolution and hardness changes of steel bars in various processes, and studied the austenitizing process and mechanical properties at different quenching temperatures. The results show that there is a small amount of residual ribbon ferrite in the tempered microstructure, and the hardness of the quenched and tempered microstructure fluctuates locally, which may be related to the inhibition of ferrite recrystallization by rapid heating and the heterogeneity of carbon during austenitizing. With the increase of quenching temperature, the residual ferrite content decreases, and the tensile strength, hardness and yield ratio increase, while the plasticity decreases.

Study on Behavior of CO2 Gas Shielded Welding Joint of Ultrafine Grain Steel

This research paper mainly studied the microstructure and hardness of the weld bead and welding heat affected zone of ultrafine grain steel after CO2 gas-shielded welding. After normalizing and quenching heat treatment, the changes in microstructure and hardness of welded joints were studied. These experimental results showed that the microstructure of the weld bead of the welded joint was dendritic. The microstructure of weld bead was a mixed structure of proeutectoid ferrite, side plate ferrite, bainite, and pearlite. The microstructure of the overheated zone of HAZ under the as-welded condition was ferrite and pearlite with coarse grains, and the normalized zone was pearlite and ferrite with smaller grains than that of base metal. The microstructure of the normalized + quenched welded joint was a mixture of low carbon martensite, pearlite and ferrite, and the ferrite content was less. The hardness change of these welded joints was that the welded joint hardness after normalizing + quenching was significantly higher than that of welded joints before heat treatment.

Prediction model for crack sensitive temperature region and phase fractions of slab under continuous casting cooling rates based on finite number of experiments

Accurate prediction of the crack sensitive temperature region and phase fractions variation of slabs during continuous cooling is an important guide to avoid cracks and effectively control the quality. Based on finite number of measurements, at different cooling rates of the continuous casting process, a prediction model for characteristic temperatures of austenite decomposition, the variation of phase fractions with temperature, the crack sensitive temperature regions, and the final microstructural compositions of casting slabs at different cooling rates has been established and evaluated the accuracy. The results show that austenite decomposition temperature range moves toward the low temperature region as cooling rate increases, and the independent peak of ferrite transition become weaker. The characteristic temperatures of austenite decomposition can be quantitatively calculated by TC(CR) = A−exp(B + C/CR) at different cooling rates, which the maximum relative error for experimental steels is −2.2%. The ferrite and pearlite phase fractions increases with decreasing temperature during continuous casting cooling, which means that the ability of the billet to resist deformation and external force changes. Meanwhile, the final ferrite content of slabs for Steel B and Steel C at different cooling rates are 83.24620−exp(2.59364–13.72283/CR) and 85.07143−exp(1.71320–15.82244/CR), respectively. The crack sensitive temperature region Ae3 ∼ Tα40%(CR) calculated by the prediction model is in good agreement with the low ductility zone measured by experiment. Moreover, the critical temperatures Tα40%(CR) of the crack sensitive temperature regions are 890.35731−exp(2.99719–20.67781/CR), 745.87462−exp(4.83056–44.18511/CR) and 729.46168−exp(2.96621–12.21949/CR) for three experimental steels under different cooling rates.

Effect of Permanent Magnet Stirring on Solidification of High‐Sulfur Micro‐Alloyed Steel under Different Magnetic Flux Densities

The effects of permanent magnet stirring (PMS) with different center magnetic flux densities (0, 850, 1450, and 1800 Gs) on the solidification process of high‐sulfur micro‐alloyed 49MnVS3 steel are investigated by analyzing the MnS precipitation, microstructure, and tensile properties. The results indicate that with an increase in the magnetic flux density, an enhanced turbulent flow is introduced to the melt, and the MnS precipitates are not limited by grain boundary and distributed randomly and uniformly in the steel. When the magnetic flux density of PMS increases from 0 to 1800 Gs, the mean length of MnS decreases from 6.8 to 2.9 μm, and the number density of MnS increases from 1562 to 2293 n mm−2. Meanwhile, the content of the intragranular ferrite (IGF) increases from 0.4% to 3.1%, and the ratio of IGF in the total ferrite increases significantly from 4.2% to 30.1%, due to the growing precipitation of finer MnS‐ (Nb, V, Ti) (C, N) complex inclusions after PMS that induces the formation of IGF. In addition, both the tensile strength and toughness of the steel are improved under PMS with enhanced magnetic flux densities, which is attributed to the increased small‐sized MnS precipitates and promotes the formation of IGF.

Rietveld refined crystal structure, magnetic, dielectric, and electric properties of Li- substituted Ni–Cu–Zn ferrite and Sm, Dy co-doped BaTiO3 multiferroic composites

The conventional solid-state reaction technique is used to fabricate the multiferroic xLi0.1Ni0.3Cu0.1Zn0.4Fe2.1O4(LNCZFO)+(1-x)Ba0.95Sm0.05Ti0.95Dy0.05O3(BSTDO) composites. To determine the ferrite and ferroelectric phases, the Rietveld refinement analysis is used. The excellent fit of experimental diffraction data is confirmed by the low values of reliability factors and the goodness of fit index, and so the crystal structure is perfect. Increasing the LNCZFO phase in the composites causes the formation of more ferrite grains and enhancement of magnetization values. The anisotropy field varies due to compressive stress created by a lattice mismatch between the BSTDO and LNCZFO phases. The dielectric peak shifts to higher temperatures as the ferrite phase increases, indicating that magnetoelectric interaction between the constituent phases exists in composites. At 100 kHz, the diffuseness exponent ranged from 1.01 to 1.79, indicating that a diffuse phase transition (DPT) occurred for some composites. As the ferrite content increases, the DPT effect decreases, resulting a narrower dielectric peak. The small polaron hopping mechanism is responsible for electrical conduction, which followed Jonscher's power law. The magnitude of the angular frequency exponent factor increases with frequency, indicating an increase in charge carrier mobility from long to short range.

Effect of Heat Input on Hydrogen Embrittlement of TIG Welded 304 Austenitic Stainless Steel

Welds made with 304 austenitic stainless steel play an important role in high-pressure hydrogen storage systems. However, there are few investigations of the effect of heat input on the hydrogen embrittlement (HE) of tungsten inert gas (TIG) welded 304 austenitic stainless steel. In this study, the effect of heat input on the HE of TIG welded 304 austenitic stainless steel is investigated. It was found that with the increase in TIG welding heat input, the ferrite content in the weld shows a tendency to first increase and then decrease. From the perspective of morphology, it first changes from lathy ferrite and strip ferrite to dendritic ferrite, and then becomes reticular ferrite and lathy ferrite. Slow strain rate tensile (SSRT) testing shows that with the increase in heat input from TIG welding, the susceptibility of the weld to HE first increases and then decreases. Our study shows that TIG welds of 304 austenitic stainless steel exhibit the best HE resistance when the welding heat input is 0.778 kJ/mm, the relative elongation (RE) is 0.884, and the relative reduction of area (RRA) is 0.721. This work can provide a reference for the optimization of the 304 stainless steel TIG welding process.

Achieving ultra-high yield strength in austenitic low-density steel via drastic VC precipitation

In this study, the precipitation behavior of V in austenitic low-density steel (LDS) and its influence on microstructure and mechanical properties were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscope, electron backscatter diffraction, physicochemical phase analysis and tensile testing in an attempt of enhancing the yield strength. Forging samples of novel Fe–25Mn–10Al-1.1C-(0,0.5)V (wt.%) austenitic LDSs were annealed at 900 °C followed by water quenching. Results showed that a drastic VC precipitation could be achieved in the austenitic matrix, which is mainly attributed to the decreased solid solubility products of VC and the reduction of the nucleation barrier due to the 10 wt% Al addition as well as the high C content. Thus, an extremely high yield strength of 1120 MPa, an increase of 260 MPa compared with that of the V-free steel, was obtained due to the precipitation strengthening and dislocation strengthening effect. Moreover, the addition of V inhibited the precipitation of κ-carbide and increased the ferrite content. Dispersedly distributed VC precipitates enhanced the initial work hardening rate and delayed the recrystallization of the V-containing steel. The V-containing steel exhibited primary planar slip but deformation twins were also observed in some austenite grains due to its decreased stacking fault energy. This study thus offers a potential strategy to significantly improve the yield strength of low-density steels through a suitable addition of V and corresponding simple annealing treatment.