Amount Of Ferrite Research Articles

Effect of prior austenite grain size on austenite reversion, bainite transformation and mechanical properties of Fe-2Mn-0.2C steel

To elucidate the response of austenite reversion and subsequent bainite transformation behavior to the prior austenite grain (PAG) size, the transformation kinetics and amount of reverted austenite in the intercritical region, the subsequent bainite transformation kinetics, and the tensile properties were investigated by dilatometers, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and the mechanical tests. The results show that, when annealed at 730 °C, fine-grained specimens exhibit faster reverted austenite transformation rate than coarse-grained specimens due to the presence of more PAG boundaries. As the intercritical temperature rises to 760 °C, more intragranular globular austenite forms in the coarse-grained specimen, which accelerates the reverted austenite transformation rate. Compared to fine-grained specimens, coarse-grained specimens exhibit faster bainite transformation and higher amount of bainitic ferrite. The microstructure after austempering consists of intercritical ferrite, bainitic ferrite, RA and fresh martensite. With increasing the austempering time, more bainitic ferrite is formed and the amount of RA and fresh martensite decreases. With increasing the austempering time, the increase in the amount of bainitic ferrite leads to an increase in the yield strength, while the decrease in the amount of RA leads to a decrease in the elongation. Moreover, compared with coarse-grained specimens, the finer microstructure in fine-grained specimens improves yield and tensile strengths, while higher amount of RA contributes to larger uniform and total elongations.

Development of parametric window and optimization of process parameters to predict bead profile in magnetically controlled gas tungsten arc welding

A novel methodology has been proposed to tame the arc shape by adopting an external magnetic field, resulting weld profile as required. The co-axial magnetic field developed by specially designed electromagnets is superimposed on the welding arc. It was found that 0-0-S-N configuration provided more penetration than conventional gas tungsten arc welding. A parametric window has been developed for the selected configuration to obtain the desired bead geometry. The experiments were performed using process parameters as suggested by the design matrix, developed using response surface method technique. Mathematical models were evolved from experimental data for penetration and bead width. The evolved model for penetration is adequate up to 99.72% confidence level and for bead width is 99.98% confidence level. The effects of process parameters have been presented in a graphical manner for better understanding. The penetration achieved with the magnetically controlled GTAW process is 3.92 mm, which is 30% more than that achieved with conventional GTAW. The bead width increases initially, up to a certain limit, and then reduces with an increase in excitation current. Further, the experiments have been conducted on the optimized parameters for the validation of models. The refined grains were obtained due to magnetic stirring of the molten pool, which is desirable for improvement in mechanical properties of welds. The average grain size was reduced from 42.55 to 31.03 µm. The improved microstructure containing more amount of acicular ferrite was obtained with magnetically controlled arc.

Exploring multifaceted properties of Polypyrrole-Cobalt ferrite nanocomposites: A comprehensive study

The remarkable properties of Polypyrrole (PY) hold immense potential for revolutionizing electronic device technologies. From flexible electronics to high-performance sensors, PY and its nanocomposites offer a plethora of opportunities to engineer advanced electronic components with enhanced functionalities. The properties of Polypyrrole (PY), Cobalt ferrite (CF) and their nanocomposites (PY1, PY2, PY3, PY4) have been explored with increasing amount of Cobalt ferrite. Their synthesis and nano size are confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. SEM confirmed the Walnut morphology of PY and it is maintained in nanocomposites but size of particles has been increased. Consequently, optical band gap (Eg) and thermal stability of samples observed from UV-Visible Spectroscopy and Thermogravimetric analysis get affected. A. C. Conductivity shows the dispersive nature and a significant increase can be seen from PY1 to PY4 i.e. ac conductivity increases with cobalt ferrite composition into the nanocomposites. Dielectric losses were explained using polarization effect and conductivity values of materials. Diamagnetic nature of PY changes into ferromagnetic in the nanocomposites. Electrodes of each sample were prepared using slurry method and their electrochemical analyses were done in 2 M KOH solution. By enhancing thermal stability, electrical conductivity, and capacitance while simultaneously reducing the optical band gap, the integration of Cobalt ferrite into the PY matrix unlocks new avenues for electronic device design. These advancements pave the way for the development of more efficient and sustainable electronic devices.

Analysis of the melting process of carbon-bearing pellets in iron bath, slag bath and graphite crucible

Background With the increase in the amount of scrap steel in society, the proportion of electric furnace steelmaking is increasing year by year, especially in China. Due to the high Zn content, the electric furnace arc dust (EAFD) needs to be recovered by non-blast furnace process. Due to EAFD containing a large amount of zinc ferrite, it needs to be recovered by fire process. It is a promising process to melt the EAFD pellets to get the discount and zinc-rich secondary ash. Methods To clarify the melting behavior of pellets in the metallurgical process, the slag phase diagram and the effect of temperature and FeO on slag viscosity were calculated using FactSage, and the melting process of electric furnace arc dust (EAFD) pellets in a graphite crucible, iron bath, and slag bath were experimentally investigated. Results The experimental results show that the viscosity of the slag system decreases with increasing temperature and FeO content, and the effect of FeO on viscosity is greater. The viscosity decreased from 0.305 to 0.276 Pa·s when the FeO content in the slag was increased from 0 wt. % to 2 wt.% at 1773 K. The melting process of the EAFD pellets in an iron bath and graphite crucible was consistent, and after the formation of liquid-phase slag in the pellets, the liquid-phase slag was diffused to melt the pellets. Conclusions The iron bath improved the heat transfer conditions of the pellets, reducing the smelting time from 600 to 360 s. The slag bath promoted the slagging reaction of the contact part to change the pellet melting process and increase the pellet melting speed, and the EAFD pellets melted within 240 s in a slag bath.

Analysis of cracking failure of gast iron brake disc

To investigate the causes of crack initiation and propagation in brake discs, a comprehensive analysis of surface cracks was conducted using macroscopic observation, metallographic observation, scanning electron microscopy, and microhardness testing. The results revealed that the internal structure of the brake disc material consists mainly of pearlite and a small amount of ferrite. Near the friction surface, the internal structure undergoes grain refinement and the formation of a small amount of granular pearlite, with a microhardness range of 350 ∼ 410 HV. Based on metallographic observations, it is evident that there are loose defects within the brake disc. When the brake disc is subjected to external loads and thermal stress, stress concentration occurs around these defects, initiating cracks and their outward propagation, thereby accelerating the crack propagation rate. The crack growth exhibits a combination of transgranular and intergranular characteristics. Analysis of the crack width in the brake disc reveals that the width of the radial primary cracks is approximately three times that of the micro-cracks, and the depth of the micro-cracks is relatively shallow, with a maximum depth of 4 mm. In contrast, the primary crack extends to a depth of 9 mm. This implies that the failure of the brake disc is associated with the extension and deepening of cracks.

Formation condition of lacy ferrite during solidification and subsequent transformation in austenitic stainless steels solidified with primary ferrite

The formation conditions of lacy ferrite in austenitic stainless steels solidified with primary ferrite was clarified through crystallography in order to increase the amount of lacy ferrite which contributed to the improvement of properties. Lacy ferrite was formed when the misorientation between ferrite and austenite from the Kurdjumov–Sachs (K-S) relationship was ≤ 7° on the close-packed plane and ≤ 9° in the close-packed direction during solidification. In contrast, vermicular ferrite was formed if the misorientation exceeded these values. The temperature gradient during solidification was controlled unidirectionally by two-pass laser welding. Following the performance of two-pass welding with a highly unidirectional laser, it was confirmed that the formation ratio of lacy ferrite to total ferrite significantly increased in the second-pass weld metal by remelting the first-pass weld metal, in which the heat flow direction and preferential growth direction of ferrite and austenite were controlled to be almost parallel. The growth ratio while maintaining the K-S relationship established between ferrite and austenite in the first-pass weld metal, and/or the ferrite formation ratio that satisfies the K-S relationship, increased in the second-pass weld metal because the growth of both the primary ferrite and secondary austenite was crystallographically independent of each other during solidification.

Effect Mechanism of α-Ferrite Sustained Precipitation on High-Temperature Properties in Continuous Casting for Peritectic Steel

Exploring the mechanism of the α-ferrite precipitation process on high-temperature properties plays an important guiding role in avoiding slab cracks and effectively regulating quality. In this work, in situ observation of the α-ferrite sustained precipitation behavior for peritectic steel during the austenitic phase transition process has been investigated using high-temperature confocal scanning laser microscopy. Meanwhile, the high-temperature evolution of the phase fractions during the phase transition process was quantitatively analyzed based on the high-temperature expansion experiment using the peak separation method. Furthermore, the high-temperature properties variations of the casting slab during the α-ferrite sustained precipitation process were investigated with the Gleeble thermomechanical simulator. The results show that the film-like ferrite precipitated along the austenite grain boundaries at the initial stage of phase transition, then needle-like ferrite initiates rapid precipitation on film-like ferrite when the average thickness reaches 15~20 μm. Hot ductility reached a minimum at the ferrite phase fraction fα = 10~15%, while high-temperature properties returned to a higher level after fα > 40~45%. The appearance of a considerable amount of needle-like ferrite and grain refinement effectively improves the high-temperature properties with the α-ferrite precipitation process advances.

Взаимосвязь микроструктуры с ударной вязкостью металлов сварного шва трубных высокопрочных низколегированных сталей (обзор исследований)

Introduction. The modern pipeline industry requires the development of materials of high strength and toughness for the production of steels for oil and gas pipelines. Changes in steel production and rolling technologies have become a challenge for welding consumables and joining technologies. This is more critical for strength levels above 830 MPa, where there are no specific regulations for the approval of welding consumables. Research methods. The failure of stainless steel pipeline welds is becoming a serious problem in the pipeline industry. Multiphase microstructures containing acicular ferrite or an acicular ferrite-dominated phase exhibit good complex properties in HSLA steels. This paper focuses on the results obtained using modern methods of scanning electron microscopy for microstructural analysis, backscattered electrons (BSE) for electron channel contrast imaging (ECCI) and orientation microscopy based on electron backscatter diffraction (ORM), as well as characteristic X-rays for compositional analysis using energy-dispersive X-ray spectroscopy (XEDS) and secondary electrons (SE) for observing surface morphology. Results and discussion. This paper analyzes the characteristics of the microstructure of the weld and its relationship with impact toughness. It is shown that predicting impact toughness based on the microstructural characteristics of steel weld metals is complicated due to the large number of parameters involved. This requires an optimal microstructure of the steel. Satisfactory microstructure depends on several factors, such as chemical composition, hot work processing, and accelerated cooling. Alloying elements have a complex effect on the properties of steel, and alloying additives commonly added to the steel composition include Mn, Mo, Ti, Nb and V. From a metallurgical point of view, the choice of alloying elements and the metallurgical process can greatly influence the resulting microstructure. A longer cooling time tend to improve the toughness and reduce the mechanical strength of weld deposits on high-strength steels. Welding thermal cycles cause significant changes in the mechanical properties of the base material. The analysis showed that impact toughness strongly depends on the microstructure of the multi-pass weld of the material under study, which contains several sources of heterogeneity, such as interdendritic segregation, and the effective grain size can also be a significant factor explaining large deviations in local impact toughness values. Acicular ferrite nucleated in intragranular inclusions has been shown to produce a fine-grained interlocking arrangement of ferrite plates providing high tensile strength and excellent toughness, and is therefore a desirable microstructural constituent in C-Mn steel weld metals. At the same time, discussion regarding the relationship between acicular ferrite and toughness is very complex and still open at present. Relating impact toughness to acicular ferrite, taking into account the top bead, is not a reliable procedure, even for single-pass deposit welding. Impact strength depends on several factors, and the strong effect of acicular ferrite is generally recognized due to its fine-grained interlocking structure, which prevents the propagation of brittle cracks by cleavage. The large-angle boundaries and high dislocation density of acicular ferrite provide high strength and toughness. However, for the same amount of acicular ferrite, different viscosity values may be observed depending on the content of microalloying elements in the steel. An analysis of the results of various studies showed that other factors also affect the impact strength. For example, microphases present along the Charpy-V notch are critical for the toughness of weld metals. The combination of OM, SEM and EBSD techniques provides an interesting method for metallographic investigation of the refined metal microstructure of stainless steel pipeline welds. Conclusion. This review reports the most representative study regarding the microstructural factor in the weld of pipe steels. It includes a summary of the most important process variables, material properties, regulatory guidelines, and microstructure characteristics and mechanical properties of the joints. This review is intended to benefit readers from a variety of backgrounds, from non-welding or materials scientists to various industrial application specialists and researchers.

Evolutions of microstructure and mechanical property of 308L stainless steel repaired by the local dry underwater wire arc additive manufacturing

Local dry underwater wire arc additive manufacturing process (LDU-WAAM) was innovatively proposed to repair the damaged large underwater structures. A thorough investigation was performed to explore the microstructure and mechanical properties of 308L stainless steel multi-layer components prepared by LDU-WAAM technique. The results demonstrate that the microstructure of all components was composed of a significant amount of austenite and a minor amount of ferrite. Subjected to the repeated action of local arc heating and rapid water cooling, the multi-layer components were deposited into a stratified structure, each layer was mainly composed plenty of directional columnar crystals, and the adjacent layers were separated by a small number of equiaxed crystals. With the increase of deposited layer counts, the heat transfer paths from deposited metal to the substrate were gradually lengthened, which increased average grain size, LAGBs proportion, dislocation density, and austenite deformed twinning content of the multi-layer sample, also decreased its ferrite content. Hence, the microstructure of LDU-WAAM multi-layer component varied significantly from the bottom to the top, which led to the deteriorated mechanical properties along the building direction. In the 3-layer component, the ultimate tensile strengths of the first, second, and third layers were 554 MPa, 532 MPa, and 519 MPa, respectively. And the elongations of that were 25.3%, 23.2%, and 19.5%, respectively. The research results verify the feasibility of local dry underwater wire arc additive manufacturing process and provide a new process method for underwater on-site repair.

Обзор современных требований к сварке трубных высокопрочных низколегированных сталей

For many years, proven arc welding processes have been used to weld large pipes of oil and gas pipelines, the scope of which extends from manual arc welding with stick electrodes to the use of metal orbital welding machines. Introduction reflects that the creation of new steel compositions for oil and gas pipelines is an urgent task to ensure its high reliability. Research Methods. Low-carbon steels with ferrite-perlite structure are usually used in pipe production, but these steels are unable to meet the increased market demands. New grades of steel with bainitic structure are appearing. Results. The failure of welded joints of pipelines made of high-quality steel is becoming a serious problem for the pipeline industry. Discussion. This paper analyzes the characteristics of weld microstructure and its relationship with impact toughness. The prediction of impact toughness based on the microstructural characteristics of weld-seam metals is complicated due to a large number of parameters involved. The common practice linking this property to the microstructure of the last roll of a multi-pass weld turned out to be unsatisfactory because the amount of needle ferrite, the most desirable component, may not always be the main factor affecting the impact toughness. The present review reports on the most representative study regarding the microstructural factor in the welded seam of pipe steels. It includes a summary of the most important process variables, material properties, normative rule, as well as microstructure characteristics and mechanical properties of the joints. Conclusion. It is intended that this review will help readers with different backgrounds, from non-specialist welders or material scientists to specialists in various industrial applications and researchers.

Investigation of ER308L and ER309L filler wires on dissimilar metals between carbon steel and 3CR12 ferritic stainless steel by GTAW through boiler fabrication in a sugar factory

Dissimilar metal welding is a popular process in very large coal and gold, power generation, and pulp and paper factories. It has mainly been applied to produce large boilers in sugar factories. The aim of the present study was to examine the characteristics of dissimilar metal welded joints made from carbon steel and 3CR12 ferritic stainless steel. The welding specimen was made from filler wires of ER308L and ER309L, and a gas tungsten arc welding process was employed for the V-shaped butt weld joints. The effects of the process parameters, such as the microstructural characteristics and mechanical properties, were investigated. The results from the welding parameters with filler wire of ER308L applied at 70A of welding current showed the microstructure of delta ferrite and austenite. In comparison, 100A of welding current presents delta ferrite, austenite, and martensite. Furthermore, carbide formation was not observed in the fusion zones of any of the experiments. When the ER308L filler wire was used, the amount of delta ferrite was higher than that of the ER309L filler wire, and the amount of delta ferrite increased with increasing hardness. In addition, the results of the filler wire of ER308L could replace the ER309L filler wire, which effectively reduces the material cost.

Effects of Base Metal Preheating on the Microstructure, Mechanical Properties, and Corrosion Resistance of UNS S32750 SDSS Pulsed Nd:YAG Laser Welding

Super duplex stainless steel has a microstructure consisting of equal proportions of austenite and ferrite. However, welding with Nd:YAG pulsed laser results in an imbalanced microstructure that compromises the steel’s properties. This paper studied the effects of preheating the base metal on pulsed Nd:YAG laser welding. Four conditions were evaluated (no preheating and heating at 100 °C, 200 °C, and 300 °C). The analysis included studying the microstructure, microhardness, and corrosion resistance. Preheating the base metals was found to be an effective method for increasing the volume fractions of austenite. The preheated samples showed an improvement in corrosion resistance compared to the untreated sample. The microhardness varied, with the ferrite amount being higher in the untreated sample.

A comparative study on the microstructure, mechanical properties, wear and corrosion behaviors of SS 316 austenitic stainless steels manufactured by casting and WAAM technologies

Replacing the traditional casting method with wire arc additive manufacturing (WAAM) to produce complex shaped parts will lead to using cost-effective technology even for challenging engineering applications depending on their geometry and number of the parts to be produced. This work performed a comparative study on the stainless steel 316 parts manufactured by WAAM and sand casting to reveal the microstructural, mechanical, wear, and corrosion behaviors. The WAAM components were manufactured using three different cooling dwell times and compared in terms of microstructures with the as-cast and heat-treated cast parts to reveal the properties of the WAAM parts. It was concluded that WAAM is a viable engineering alternative to the casting technology. Results showed that the WAAM and cast parts revealed similar microstructures, including delta ferrite and austenite phases, but the cast parts had a coarser grain and lower amount of delta ferrite due to slower cooling during the solidification. The yield and tensile strength of WAAM parts showed an increasing trend with the increase in dwell time, and on average, their yield strength was ∼1.5 times higher than in cast parts due to the smaller grains and more elevated δ-ferrite content resulting from rapid cooling. Furthermore, the greatest wear resistance was obtained in the cast parts after solution annealing heat treatment followed by water quenching. In contrast the highest corrosion resistance was obtained from WAAM parts produced using a dwell time of 120 sec. In conclusion, WAAM technology can be an excellent alternative to casting technology for producing stainless-steel parts with optimized process parameters.

Microstructure, thermophysical properties and neutron shielding properties of Gd/316 L composites for spent nuclear fuel transportation and storage

In this paper, (0.5–5.0 wt%)Gd/316 L composites were prepared by vacuum arc melting, and the microstructure, thermophysical properties, and neutron shielding properties were analyzed deeply. The results showed that the Gd/316 L composites started solidification in primary ferrite mode and terminated solidification by a peritectic-type reaction forming (Fe, Ni, Cr)3Gd that is rich in Ni and Gd. In the peritectic-type reaction, local convection in the Ni-rich and Gd-rich peritectic liquid phase leads to the formation of multiple variants of (Fe, Ni, Cr)3Gd. The higher the Gd content, the greater the amount of (Fe, Ni, Cr)3Gd and ferrite, and the harder it is to keep the austenitic matrix of 316 L stainless steel. The solidification temperature range of Gd/316 L composites is 1074–1460 °C, which severely limits the ability to further process it by high-temperature deformation techniques such as hot rolling or hot forging. (Fe, Ni, Cr)3Gd preferentially nucleates and grows in the triangular region of austenite grain boundaries at 1074 °C. At 50–500 °C, with increasing Gd content, thermal expansion and thermal diffusion coefficients become decrease, and thermal conductivity and specific heat capacity increase. The trend of thermophysical property changes is favorable for SNF transportation and storage applications. The thermal neutron shielding properties of 1.0 wt%Gd/316 L composite is comparable to that of 4.45 wt% B content boron steel and 15 wt%B4C/Al composite. The Gd content in Gd/316 L composites material should not exceed 2.5 wt%. If the Gd content continues to increase, it is of little significance to improving shielding properties and material thinning. A shielding thickness of 3 mm is more appropriate for Gd/316 L composites. Too thin would not provide sufficient mechanical properties and increase processing and manufacturing costs.

Study on the role of solution treatment on corrosion behavior of duplex lightweight steel in different environments

Diverse microstructure and complex application environments increases the uncertainty of the corrosion resistance of lightweight steels. The effect of solution treatment on the corrosion behavior of Fe–16Mn–10Al–1.5C–0.1Ti lightweight steel in Cl−, HSO3− and Cl−–HSO3− environments was investigated using electrochemical measurement, scanning electron microscope (SEM) and X–ray photoelectron spectroscopy (XPS). The lightweight steels are dominated by austenite and contain a small amount of ferrite. The increase in solution treatment temperature leads to more ferrite formation, but it has less effect on grain size. The decrease in austenite content results in more corrosion microcells and a porous oxide film; therefore, the corrosion resistance of the steel deteriorates with increasing temperature. In addition, in the Cl−–HSO3− environment, the synergistic effect of Cl− and HSO3− leads to the formation of a weak protective oxide film, resulting in a significant increase in corrosion rate compared to the Cl−and HSO3− environment.

Features of formation of austenite grains in 12 % Cr heat-resistant ferritic-martensitic steels

Ferritic-martensitic heat-resistant high-chromium steels (FMHS) with chromium content of 11 – 12 % are quenched to martensite from temperatures of 1050 – 1100 °С. Possible undesirable consequences of heating to such high temperatures are an increase in the size of austenite grains, increase in the amount of delta ferrite in the final structure, and a decrease in mechanical characteristics. In this work, the change of all these factors during heating of FHMS to quenching temperatures in the range of 950 – 1250 °С was studied. Ratios of the contents of martensite (its amount was identified with the proportion of austenite before quenching) and high-temperature delta ferrite on metallographic sections were analyzed. It was found that behavior of structure of the studied FHMS upon heating to temperatures of 1150 °С and above depends on the steels structural class. In steels whose structure at room temperature consists of martensite and delta ferrite, or in which delta ferrite begins to form at heating temperatures of 1200 °С and higher, size of austenite grain decreases with increasing temperature in the range of 1200 – 1250 °С, and the amount of delta ferrite – increases. Such structural transformations can be associated with features of the phase equilibrium diagrams of steels of this class. Such structural transformations can be associated with a change in the position and (or) inclination of boundaries of the high-temperature region of coexistence of austenite and delta-ferrite in the phase equilibrium diagrams of FHMS at a change in heating temperature in this range. Compression tests at 20 °С of 15Cr12Mn3SiMoW2VB steel samples after heat treatment with heating to temperatures for hardening 1000 – 1250 °С showed that formation of an additional amount of delta ferrite at temperatures above 1200 °С is a stronger factor than the refinement of austenite grains. This causes a decrease in yield strength of the samples quenched from these temperatures followed by high tempering.

Structural and dielectric properties of lead free BiFeO3/NiFe2O4 multiferroic heterostructures

Multiferroic nanocrystalline ceramics of Bismuth ferrite (BiFeO3) and nickel ferrite (NiFe2O4) were synthesised via sol- gel auto combustion technique using organometallic precursors. An equimolar amount of bismuth ferrite (BFO) and nickel ferrite (NFO) were pressurised in bi-layer (BFO-NFO) and tri-layer (BFO-NFO-BFO) by giving a pressure of about 100 kg/cm2 using a hydraulic pellet press. X-ray Diffractometer (XRD) was employed to analyse the structural properties in relation to the resulting heterostructures. Scanning Electron Microscopy (SEM) was used to examine the cross-sectional micrograph of the heterostructures. The dielectric properties were measured using LCR meter and corresponding dielectric constant data was fitted with Cole-Cole equation to decipher the nature of dielectric relaxation. Impedance analysis was carried out at elevated temperature in the frequency range of 100 Hz–1 MHz and fitted with equivalent circuit model. We could observe slight enhancement in the electrical properties in tri-layer heterostructure as compared to the bilayer structure.

FeSiCr soft magnetic composites with significant improvement of high-frequency magnetic properties by compositing nano-YIG ferrite insulating layer

FeSiCr soft magnetic composites (SMCs) with yttrium iron garnet (YIG) coating layer were studied in this work. The YIG with nano size was synthesized by reverse co-precipitation method, which was coated on FeSiCr powders with different YIG contents. The effect of the annealing temperature on the FeSiCr/YIG SMCs was also investigated. It was found that a moderate amount of YIG ferrite could form a thin and uniform layer, resulting in significant optimizations in core loss, permeability, and DC bias characteristics. The results show that the FeSiCr/YIG SMCs with 0.75 wt% YIG exhibit the best magnetic performance (Pcv = 131.34 mW/cm3, μe = 44.5 at 10 mT and 500 kHz). In addition, it was demonstrated that the FeSiCr/YIG SMCs with 0.75 wt% YIG presented the lowest core loss and largest permeability at the optimal annealing temperature of 500 °C. This study provides a new kind of FeSiCr/YIG SMCs which have good prospects to be used in high-frequency fields.

Effects of annealing temperature and V addition on microstructure and mechanical properties of Fe-Mn-Al-C austenitic low-density steel

This study investigated the effect of annealing temperature (Ta=800–1000 ℃) on the microstructure and mechanical properties of Fe-25Mn-10Al-1.1 C-(0,0.48)V (wt%) austenitic low-density steels. The results show that Ta has significant influence on the microstructures of the two tested steels. Considerable amount of ferrites and κ-carbides appeared on grain boundaries due to precipitation reaction (γ→α + κ) when annealed at a lower temperature of 800 ℃, and the V addition would promote the precipitation reaction and cause an increase of ferrite content when annealed at no more than 900 ℃. The content of VC reached a maximum at Ta= 900 ℃, which also significantly inhibited the formation of κ-carbide and delayed the recrystallization besides grain refinement for the V-added steel. Moreover, VC also inhibited the development of the Σ3n (n = 1,2,3) boundaries at Ta of no more than 900 ℃. Ultra-high yield strength of 1120 MPa was obtained when the V-added steel was annealed at 900 ℃ mainly due to the drastic VC precipitation. The present work provides a promising strategy to enhance the yield strength of austenitic low-density steel via tailoring Ta and the addition of V.

Strengthening the ferroelectric properties in the three-component multiferroic ceramic composites

The paper proposes a new solution for obtaining multiferroic ceramic composites by connecting two ferroelectric ceramic materials of the PbZrTiO3-based (P) and BaTiO3 (B) (in an equal amount, i.e., 50/50) and the zinc-nickel ferrite (F) material. The main purpose of the experiment is to improve the ferroelectric performance of the multiferroic composites using the free sintering method (pressureless). Three multiferroic composite materials (BPF) with the content of ferroelectric/magnetic 95/05, 90/10, and 85/15 were obtained. The crystal structure, electrical behaviours, as well as the dielectric, ferroelectric, and magnetic characteristics of the multiferroic ceramic composites were investigated in detail. The research has proven that using two ferroelectric materials improves the ferroelectric properties of multiferroic composites (spontaneous polarization is in the range of 5.10–7.80 µC/cm2, whereas remnant polarization in the range of 2.37–4.05 µC/cm2). The ferroelectric hysteresis loops exhibited high saturation, while the electrical breakdown strength of the composite samples is very high. Also, the entire set of physical parameters of the multiferroic composite remains high. The permittivity at room temperature is in the range (800–1230), the tangent loss value in the range (0.016–0.022), and the spontaneous magnetization in the range (1.5–0.04 emu/g). The magnetic properties of the composite samples depend on the amount of ferrite in the composition, and are the highest for the composition with the highest amount of ferrite.