Fe Cr Si Research Articles

Improvement in power inductor performance at 3 MHz by mixing carbonyl iron powder with Fe–Si–Cr crystalline alloy

Improvement in power inductor performance at 3 MHz by mixing carbonyl iron powder with Fe–Si–Cr crystalline alloy

Effect of Si on Desulfurization in Fe–Si–S, Fe–Si–Cr–S and Fe–Si–Ni–S Melts

Effect of Si on Desulfurization in Fe–Si–S, Fe–Si–Cr–S and Fe–Si–Ni–S Melts

Quasicrystal-related mosaics with periodic lattices interlaid with aperiodic tiles.

Quasicrystals, which have long-range orientational order without translational symmetry, are incompatible with the theory of conventional crystals, which are characterized by periodic lattices and uniformly repeated unit cells. Reported here is a novel quasicrystal-related solid state observed in two Al-Cr-Fe-Si alloys, which can be described as a mosaic of aperiodically distributed unit tiles in translationally periodic structural blocks. This new type of material possesses the opposing features of both conventional crystals and quasicrystals, which might trigger wide interest in theory, experiments and the potential applications of this type of material.

Effects of Etching on Amorphous Alloys

Features of surface etching are investigated along with the decoration of shear bands of Co–Fe–Cr–Si–B amorphous alloys obtained via melt quenching. The nature of the observed etching effects is discussed on the basis of data from Auger spectroscopy and predicted coefficients of diffusion.

Amorphous-Alloy-Based Composites Prepared by High-Pressure Torsion

Abstract—Deformation-induced composites consisting of alternating layers of amorphous Fe–Ni–B and Co–Fe–Cr–Si–B alloys are prepared by consolidation via high-pressure torsion in a Bridgman chamber. The sequence of changing structural states of the composites and their individual components upon severe plastic deformation and variations of the Vickers hardness and magnetic characteristics are studied in accordance with the degree of deformation. It is found that the use of high-pressure torsion at a high strain efficiently favors the transition of the materials from an amorphous into a nanocrystalline state, increases their microhardness, and retains soft magnetic properties.

Corrosion behavior of Fe–Cr–Si alloys in simulated PWR primary water environment

Fe–Cr–Si alloys are potential candidates as accident tolerant fuel (ATF) cladding, which could offer similar benefits as Fe–Cr–Al alloys. The corrosion and oxidation behaviors of three Fe–Cr–2Si alloys with various chromium content (12 wt. %, 16 wt. %, 20 wt. %) in simulated primary water chemistry of a pressurized water reactor (PWR) were investigated. Post-test characterization included weight change, scanning electron microscopy (SEM), and X-ray Photoelectron Spectroscopy (XPS). The results showed that Fe12Cr2Si had the worst corrosion/oxidation resistance among the three alloys, while Fe16Cr2Si and Fe20Cr2Si showed excellent oxidation resistance due to their thin, continuous, dense oxide layers grown in simulated PWR conditions. These results bring insight into the corrosion behavior of Fe–Cr–Si alloys with varying chromium content exposed to the primary water environment during normal operating conditions found in PWRs.

Magnetic Spectra of Soft Magnetic Composites Based on Fe-Si-Cr-B Amorphous and Carbonyl-Iron Powders

Fe–Si–Cr–B amorphous and carbonyl-iron powders insulated with phosphoric acid solution were used to prepare soft magnetic composites. The mass ratios of phosphoric acid insulation solution and the carbonyl-iron powder dependences of the magnetic spectrum, the density, and the resistivity were studied. Both the real part and the imaginary part of the core’s complex permeability increased after an initial decrease with the acid mass ratio increasing. This is similar to the variation tendency of the core’s density and opposite to the variation tendency of the core’s resistivity. The amount of the air gap, reflected by the density, was proposed to be the most important factor that has a great influence on the composite’s magnetic properties. The increase of the air gap reduced the effective demagnetizing field and the resistivity. This improved the permeability and the hysteresis loss and deteriorated the eddy-current loss. Carbonyl-iron powder addition was found to improve the moldability and the permeability of the composite based on the Fe-Si-Cr-B amorphous powder, although its loss was higher than that of the amorphous powder. All these findings can be referenced when designing an amorphous-based soft magnetic composite (SMC) core with balanced permeability, loss, and cost for high-frequency inductor within a MHz band.

AgCrO2 formation mechanism during silver inner electrode and Fe–Si–Cr alloy powder co-firing in metal multilayer chip power inductors

Multilayer Fe–Si–Cr alloy chip power inductors have the benefits of a smaller, thinner profile, lower DC resistance and higher rated current. During metal multilayer power inductor co-firing, Fe–Si–Cr alloy powders react with the inner electrode, silver, to form a large amount of hexagonal flaky AgCrO2. The p-type semiconductor, AgCrO2, will cause co-fired Fe–Si–Cr alloy multilayer chip power inductor insulation degradation, hence reducing the power conversion efficiency due to the increase in eddy current loss. The AgCrO2 forming mechanism is investigated in this study. It was observed that silver reacts with the Fe–Si–Cr thermal grown oxide layer, Cr2O3, and subsequently leads to the formation of Ag2CrO4 when the temperature is lower than 650 °C. The formed Ag2CrO4 with low melting temperature then volatilizes at higher temperatures through the pore channels to react with the volatilized Cr2O3 to form the AgCrO2. AgCrO2 will cause Fe–Si–Cr alloy multilayer chip inductor resistivity and breakdown voltage degradation.

Study on Fe–Si–Cr Soft magnetic composite coated with silicon dioxide

The purpose of this experiment is to explore the effect of SiO2 coating on the properties of Fe–Si–Cr materials. The suitable surface modifier (CTAB) for this experiment was selected by sol-gel method. And the SiO2 insulating layer was coated on the surface of Fe–Si–Cr powder by controlling the addition of TEOS and CTAB. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), powder particle size analyzer and scanning electron microscope (SEM) were used to characterize the microstructure, composition and dispersibility of the powder. Soft magnetic AC testing system and soft magnetic DC testing system were used to test the magnetic properties of magnetic ring. The results showed that the surface of Fe–Si–Cr powder was modified by CTAB and then when the ethyl orthosilicate was added, the surface of Fe–Si–Cr powder can be coated with a layer of flocculent amorphous SiO2; with the increase of ethyl orthosilicate and surface modifier, the SiO2 coating amount also increased. The magnetic flux density (BM) varies from 0.020 T to 0.025 T, and the coercivity (HC) remains basically unchanged. When 10 ml ethyl orthosilicate and 3 g CTAB were added, the coating effect and performance were the best, with magnetic loss of 4.666 kW m−3, magnetic flux density of 0.0248 T and coercive force of 13.87 A m−1.

Relationship Between the Microstructure and Magnetic Properties of Fe–Si–Cr Powder Cores

Magnetic components prepared using Fe–Si–Cr alloy powders have been widely used in high-current power inductors due to their high initial permeability, high-saturation magnetization, and excellent dc-bias characteristics. Fe–Si–Cr alloy bodies were prepared in this paper using a uniaxial molding press at different compaction pressures. Samples were then annealed at different temperatures to form a chromium-rich oxide insulating layer on the powder surface to reduce the core loss. The compaction pressure and the annealing temperature effects on the microstructure, internal strain, and insulating layer thickness and the electromagnetic properties for Fe–Si–Cr alloy powder compacts were investigated. The results showed that the relative density gradually increased with increasing compaction pressure, leading to increased saturation magnetization, thereby improving the initial permeability from 29 to 37. After annealing, the internal strain was reduced, which resulted in the initial permeability increasing substantially. Moreover, the electric resistivity and dc-superposition characteristics also increased with increasing heat treatment temperature. However, excessively thick insulating layer formed on the Fe–Si–Cr alloy powder surface resulting from annealing at too high temperature leading to initial permeability and saturation magnetization degradation.

Laser deposition technology assisted by friction stir processing for preparation of nanostructured Fe–Cr–Si alloy layer

Although laser deposition has found its widespread applications in materials manufacture, this technology has been significantly limited by the associated metallurgical defects, such as pores, brittle phase precipitation along grain boundary during the laser melting/solidification process. In this paper, we used a novel laser deposition technology assisted by friction stir processing (FSP) to eliminate these common metallurgical defects. A Fe–Cr–Si alloy was selected as a representative material. Severe plastic deformation caused by FSP has refined the coarse solidification microstructure into ultrafine grained or even nano-grained microstructure on the top surface of the Fe-Cr-Si samples. Meanwhile, the large and interconnected Fe-Cr intermetallics precipitates were broken down to nanoparticles. The refinement of both primary grains and intermetallic particles results in an increase of microhardness from 640 HV to above 700 HV and a decrease of wear rate from 4.8 × 10−14 to 3.2 × 10−14 mm3/m.

Effect of external actions on the magnetic properties and corrosion resistance of Co70.5Fe0.5Cr4Si7B18 amorphous alloy

Variations in the magnetic characteristics (specific saturation magnetization and coercive force) of Co–Fe–Cr–Si–B amorphous alloy (AA) are studied after high-pressure torsion (HPT) and heat treatment. The behavior of AA magnetic properties is analyzed with respect to structural transformations caused by external actions. The corrosion resistance of AA upon transitioning from an amorphous to a crystalline state is investigated. The established optimum annealing and HPT conditions yield a satisfactory combination of the magnetic properties and corrosion resistance of the investigated alloy.

Effects of Silicon Content on the Properties of Gas-Atomized Fe–Si–Cr Powders

Fe-7%, 8%, 9%, and 11%Si–Cr powders were gas atomized and then annealed at 25 °C–750 °C to investigate the effects of Si content, DO3 phase, and B2 phase on the high-frequency permeability of the powders. The formation of the B2 phase could not be suppressed during the atomization process of all the powders. The evolution temperatures of the DO3 phase in the Fe-7%, 8%, and 9%Si–Cr powders as measured by X-ray diffractometer were 550 °C, 550 °C, and 450 °C, respectively. As the annealing temperature was increased, the DO3 phase grew rapidly, and the lattice parameters of the powders were decreased except for those of the Fe-11%Si–Cr powder. The coercivity of all powders decreased with increasing temperature; however, the coercivity of the Fe-8%, 9%Si–Cr powders increased sharply after annealing at 450 °C. Permeability decreased rapidly with increasing temperature except for the Fe-11%Si–Cr powder; thus, the highest real permeability was obtained for the as-atomized Fe-8%Si–Cr powder. The changes in the coercivity and permeability of the powders with annealing temperature could be attributed to the evolution of the DO3 phase, Si segregation, and changes in electrical resistivity.

Effects of Ordering on the Magnetic Properties of Gas-Atomized Fe–Si–Cr Powders

Fe–9%Si–2%Cr powder was gas-atomized and then annealed in order to investigate the effects of DO3 and B2 ordered phases on high-frequency permeability of the powder. The B2 phase is formed during the atomization process. The DO3 phase began to form at 450 °C and grew rapidly when annealed at higher temperature as confirmed by X-ray diffractometer, whereas the existence of the DO3 phase in the as-atomized powder could be confirmed by electron transmission microscope. With the increase in the temperature, the average lattice parameter and the coercivity decreased. There was an abrupt increment of the coercivity in the powder annealed at 450 °C. Highest permeability could be obtained in the powder annealed at a relative low temperature of 150 °C and then the permeability real decreased with the temperature. The behavior of the coercivity and the permeability with the temperature could be successfully explained by the formation of the DO3 ordered phase and the change of the electrical resistivity.

The Effects of Iron, Silicon, Chromium, and Aluminum Additions on the Physical and Mechanical Properties of Recycled 3D Printing Filaments

AbstractWith the increasing use of 3D printers especially the fused filament fabrication type in the industries and general public, there is indeed a need to consider the after‐use treatment for the products. The use of recycled filaments as the feedstock for 3D printers is a feasible alternative, but its application is limited to rather poor product quality. This study, thus, evaluates the effects of adding iron (Fe), silicon (Si), chromium (Cr), and aluminum (Al) nano‐crystalline powders into the recycled polypropylene/high‐density polyethylene plastics feedstock for filament extrusion. Physical and mechanical analysis tests revealed that the addition of 1% Fe–Si–Cr or Fe–Si–Al resulted in better thermal stability, and up to 37% and 17% improvement, respectively, in yield strength and Young modulus compared with the original recycled filaments, possibly due to the enhancement of interfacial adhesion between the nano‐metal powders and the polymer, leading to reduced crack formation.

Influence of heat treatment on the structure and magnetic properties of amorphous Co–Ni–Fe–Cr–Si–B alloy and its thermal stability

The causes of changes in the magnetic properties of an amorphous Co–Ni–Fe–Cr–Si–B alloy obtained by melt spinning in the form of a thin ribbon subjected to heat treatment and subsequent action of temperatures corresponding to various conditions of its exploitation have been analyzed. We have established the regimes of heat treatment that provide for the highest values of the maximum magnetic permeability of the alloy and the shielding factor of a magnetic shield made from the alloy. We have analyzed changes in the magnetic properties, shielding properties, and total magnetization distribution in an alloy ribbon at a temperature well below the crystallization temperature. We have found the temperature ranges that determine the practical application of this alloy.

DEVELOPMENT OF WEAR RESISTANT COATINGS FORMED BY PLASMA SPRAYING OF ALLOY Ni–Fe–Cr–Si–B–C SYSTEM REINFORCED WITH CERAMICS Al2O3

. Creating a functionally oriented, including nanostructured, anti-friction materials and coatings with qualitatively new complex of service properties is an important scientific and practical problem. In particular, for the cable industry it is urgent task of ensuring the high performance properties of fast deteriorating stretching and supporting rollers. Working surfaces of these parts operate under practically dry friction conditions with constantly updated material of stretching wire. Plasma spraying is one of the widely used methods of surface engineering to create wear resistant coatings and which is characterized with process flexibility and the ability to create coatings using various materials and alloys including composite ones. The installation UPU-3D with the PP-25 plasma torch was used for plasma spraying. The thickness of the sprayed layer was 0.8–1.1 mm. As a material for the deposition of composite coatings a powder mixture of self-fluxing nickel alloy PG-HN80SR4 (system Ni–Fe–Cr–Si–B–C) and a neutral oxide ceramics Al 2 O 3 was used. The amount of ceramics varied from 15 to 33 %. This ceramic oxide was selected due to the desire to reduce coatings’ costs while providing high durability. Carried out phase and microstructural studies have shown when ceramics was added in an amount more than 20 % a formation of conglomerates formed by not melted alumina particles often was observed. These conglomerates serve as crack formation centers in the coating. The phase composition of the coatings practically does not depend on the content of ceramics compounds. Tribological tests have shown that the best results were obtained when the content of the oxide ceramic in the coating was in the range from 15 to 20 %.

Studies on Magnetic Properties and Ball-Milling Process of Fe–Si–Cr Powders

Flake-shaped Fe–Si–Cr alloy powders were prepared by crushing alloy ingots and the ball milling method. Magnetic properties of Fe–Si–Cr alloy powders with the nominal compositions of Fe81.4+ x Si17– x Cr1.6 ( $x=0,2,4$ , and 6) and the different values of milling time (0 to 120 h) were investigated. A scanning electron microscope, X-ray diffraction, and a vibrating samples magnetometer were used to characterize Fe–Si–Cr alloy powders. It is observed that, with the increase of parameter $x$ , the permeability of Fe81.4+ x Si17– x Cr1.6 ( $x=0$ , 2, 4, and 6) powders first increases and then decreases in 0.5–2 GHz, meanwhile the peaks of the imaginary part of the magnetic permeability ( $\mu ''$ ) transfer to the lower frequency in 0.5–6 GHz. The saturation magnetic ( $M_{S})$ and the coercivity ( $H_{C})$ were also investigated. The value of $M_{S}$ increases from 110 emu/g ( $x=0$ ) to 148 emu/g ( $x=6$ ), while the value of $H_{C}$ changes in the opposite trend from 30.7 Oe ( $x=0$ ) to 25.5 Oe ( $x=6$ ). For Fe85.4Si13Cr1.6 alloy powders with the increase of milling time, the peaks of $\mu ''$ transfer to the higher frequency, while the values of $\mu ''$ first increase and then decrease in 0.5–10 GHz. We attributed this to the change of the aspect ratio. A large aspect ratio increases planar anisotropy, which can enhance the magnetic permeability of the material. It is observed that the imaginary part of the magnetic permeability is 3.91 with $x=4$ and milling time $= 48$ h at 1.1 GHz.

Approximants of Al–Cr–Fe–Si decagonal quasicrystals described by single structural block

The orthorhombic (3/2, 2/1) approximant with a = 3.06 nm, b = 1.23 nm, c = 2.24 nm, and the coexisting (2/1, 3/2) approximant of decagonal quasicrystals with a = 1.90 nm, c = 3.64 nm, and β ≅ 90° are found in Al–Cr–Fe–Si alloys by aberration-corrected transmission electron microscope. The structural relationships of these two approximants are analyzed and discussed based on the high-angle annular dark-field scanning transmission electron microscopy images at atomic resolution. We find that both of their structural tiling along the [010] direction can be described by one shield-like tile, with the superiority over the previous HBS tiling model due to the clarity. Combining the shield-like tile and HBS tiling model, the domains of approximants are clearly demonstrated.

Passivation layer for the magnetic property enhancement of Fe72.8Si11.2B10.8Cr2.3C2.9 amorphous powder

This paper reports the preparation of insulated soft magnetic powders by HNO3 passivation process with SWAP Fe72.8Si11.2B10.8Cr2.3C2.9 amorphous powder. The toroid-shaped cores were fabricated by pressing the mixture of the insulated magnetic powder and silicone resin under a pressure of 1.31GPa (density=5.15g/cm3). The results showed that amorphous magnetic powder produced by 8vol.% nitric acid insulating process had good frequency characteristics and high quality factor at higher frequency (1MHz). The value of initial permeability (μi) was 29.03, and the value of quality factor (Q) was 68.2. The value of saturation magnetization (Ms) was 0.93T, and the coercive force (Hc) was 89.6A/m. Furthermore, the amorphous powder was mixed with the Fe–Si–Cr alloy powder by the powder metallurgy process and formed into toroid-shaped cores. The maximum permeability of the toroid-shaped cores with 10wt.% alloy powder annealed for 10min at 773K increased by about 69.8%. The cores were annealed to improve the soft magnetic properties and decrease the stress. The mixed powders also indicated excellent soft magnetic properties; the Ms increased from 0.93T to 0.97T, and the Hc decreased from 89.6A/m to 68.6A/m.