Fe-Si Alloys Research Articles

Raman and XPS depth profiling technique to investigate the corrosion behavior of FeSiAl alloy in salt spray environment

Abstract As a promising material for electromagnetic microwave absorption, FeSiAl (FSA) alloy always suffers from inadequate corrosion resistance in the marine environment. Herein, the Raman and X-ray photoelectron spectroscopy (XPS) depth profiling techniques are adopted to investigate the basic corrosion behavior of FSA in salt spray environment. The Raman analysis contributes to the understanding of the composition change at various corrosive periods while the XPS depth profiling reveals the corrosion process of Fe0→Fe2+→Fe3+ in a sequence. The observed corrosion rates (CRs) of FSA immersed in 5 wt% NaCl solution for 1, 24 and 48 h are 2.99 × 10−12, 4.90 × 10−12 and 5.85 × 10−12 m/s, respectively. The increasing value of CRs as a function of time demonstrates the accelerated corrosion tendency. Moreover, to suppress the corrosive behavior of FSA alloy, carbon is decorated on its surface by catalytic chemical vapor deposition method using acetylene as the carbon source. The carbon coating restrains the corrosion process by impermeability and hydrophobicity of carbon materials in corrosive mediums. This study will help in the designing of microwave absorbers which can resist corrosion in harsh reaction conditions as well as available at commercial level to save the economy.

Simultaneous thermal and contraction / expansion curves analysis for solidification control of cast irons

The first part of the paper summarizes the performance of two mould devices, illustrating by representative shrinkage tendency results in ductile cast iron as affected by mould rigidity (green and furan resin sand moulds) and inoculant type (FeSi-based alloys). Less rigid green sand moulds encourage the formation of contraction defects, not only because of the high initial expansion values (εdi)max, but also because of the increased solidification undercooling. A high inoculation efficiency means not only lowering the carbides formation sensitivity and increasing the nodule count, but also a prolonged graphitization through to the end of the eutectic freezing, as observed by the high population of small late forming nodules, which leads to minimizing the tendency for shrinkage. The second part of the paper illustrates an application of this equipment to commercial foundry use. It conducts thermal analysis and volume change measurements in a single ceramic cup with cast iron quality as a variable. La-bearing FeSi inoculant appears to be more effective than RE (Rare Earth) -FeSi alloy in FeSiMgCa treated irons (no RE), in terms of reducing eutectic undercooling and (εdi)max, favourable for lower sensitivity to shrinkage formation. Experiments also compared solidification patterns for white [WI], grey [GI] and ductile [DI] irons, to correlate the most important events between the cooling curves and contraction curves, to evaluate the sensitivity to shrinkage formation. All of the irons have similar values for initial expansion up to the start of eutectic freezing, but, after that, the graphite formation promotes expansion (more than 5 times for nodular graphite), resulting in a difference in maximum expansion (2 times higher for DI). The graphitic expansion has two contrary effects. Increased graphitic expansion (force) leads to a higher shrinkage sensitivity during the first part of the eutectic reaction, but also to a decrease of shrinkage at the end of solidification, due to forcing the last liquid iron to occupy the previous formed cavities. Consequently, strong graphitization process promotion at the end of solidification favours the castings' soundness.

Production of Ferrosilicoaluminium from Aluminum Slag and Local Ore Via Carbothermic Reduction

This paper deals with the possibility of obtaining FeSiAl complex alloy by carbothermic reduction in a submerged arc furnace using aluminum dross, mill scale and feldspar.Bench scale experiments are carried out to clarify the effect of different variants such as reducing agent, basicity, and mill scale content of the charge on the metallic yield and chemical composition of the produced alloy.It was possible to get FeSiAl alloy containing 22% Si and 18% Al. the results reveal that to obtain such alloy less than 20% mill scale must be involved in the charge and the coke with amount 1 stoichiometric must be used.

Picosecond Acoustics Technique to Measure the Sound Velocities of Fe-Si Alloys and Si Single-Crystals at High Pressure

We describe here a time resolved pump-probe laser technique—picosecond interferometry—which has been combined with diamond anvil cells (DAC). This method enables the measurement of the longitudinal sound velocity up to Mbar pressure for any kind of material (solids, liquids, metals, insulators). We also provide a description of picosecond acoustics data analysis in order to determine the complete set of elastic constants for single crystals. To illustrate such capabilities, results are given on the pressure dependence of the acoustic properties for prototypical cases: polycrystal (hcp-Fe-5 wt% Si up to 115 GPa) and single-crystal (Si up to 10 GPa).

Formation Mechanism of Dislocation Walls during Cyclic Deformation in an Fe–Si Alloy

Formation Mechanism of Dislocation Walls during Cyclic Deformation in an Fe–Si Alloy

Bifunctional carbon-encapsulated FeSiAl hybrid flakes for enhanced microwave absorption properties and analysis of corrosion resistance

Designing of materials which can resist aging and corrosion in harsh reaction conditions is required to mitigate the omnipresent issue of electromagnetic interference pollution. Particularly, FeSiAl alloy is a relevant composite material, however, it always suffers aging and corrosion when exposed to crude saline environment. Herein, Carbon-encapsulated FeSiAl (FeSiAl@C) hybrid flakes are developed by catalytic chemical vapor deposition (CCVD) technique through the reaction of FeSiAl precursor with acetylene (C2H2) gas at 300 °C for 5 min. The carbon coating efficiently improves the impedance matching characteristics of FeSiAl powder leading to enhance microwave absorption. Not only that, the carbon capsule also plays an effective shielding function to prevent the alloy from corroding. Specifically, the FeSiAl@C-300 °C delivers increased complex permeability and permittivity in the frequency range of 7–14 GHz, as well as improved impedance matching. In addition, the corrosion resistance is measured using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in 5 wt% NaCl solution. The results indicate that the synthesized hybrid exhibits excellent corrosion resistance capability. So, the composite synthesis is a worthy approach to design hybrid materials for effective microwave absorption and corrosion resistance properties for practical applications.

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.

Impact of the magnitude of the magnetization on the induced anisotropy in transverse field annealed nanocrystalline cores

We study the relation between the induced anisotropy obtained on nanocrystalline Fe73.0Cu1.1Nb3.1Si15.7B7.1 toroidal cores crystallized under transverse field at 570 °C, and the polarization Jc of nanograins. To do this, an original disposition is used, mixing treated cores with cores made of electrotechnical SiFe alloy, featuring same geometry, using the interfacial magnetic charges to increase the field in treated cores. The field supplied by the coil being μ0Ha=33mT, playing on the proportion between treated and SiFe cores, effective field ranging between 33mT and 230mT were obtained inside treated cores. As a result, the induced anisotropy at the scale of the alloys at the end of crystallization range from Ku=12J/m3 to Ku=20J/m3.To simulate the evolution of Jc during the crystallization process, the configuration of treated and SiFe cores in the sample holder was implemented in Altair FluxT FEM simulation environment with the dedicated polarization laws. Dealing with treated cores, the law Jcor(H) at the scale of the core reflects the law JcH featured by nanograins during the crystallization process. JcH was modelized as a function of the crystallized fraction fc.The relation between the simulated Jc and the experimental final values of Ku/fc (i.e. the anisotropy in nanograins) was then studied. This was done considering the polarization 〈Jc〉 averaged on the entire crystallization process, wondering about a possible memory effect.

溶湯浸透法によるSiC反応焼結体の機械的性質と電気抵抗率に及ぼすFe-Si 合金組成の影響

溶湯浸透法によるSiC反応焼結体の機械的性質と電気抵抗率に及ぼすFe-Si 合金組成の影響

Axial Compressibility and Thermal Equation of State of Hcp Fe–5wt% Ni–5wt% Si

Knowledge of the elastic properties and equations of state of iron and iron alloys are of fundamental interest in Earth and planetary sciences as they are the main constituents of telluric planetary cores. Here, we present results of X-ray diffraction measurements on a ternary Fe–Ni–Si alloy with 5 wt% Ni and 5 wt% Si, quasi-hydrostatically compressed at ambient temperature up to 56 GPa, and under simultaneous high pressure and high temperature conditions, up to 74 GPa and 1750 K. The established pressure dependence of the c/a axial ratio at ambient temperature and the pressure–volume–temperature (P–V–T) equation of state are compared with previous work and literature studies. Our results show that Ni addition does not affect the compressibility and axial compressibility of Fe–Si alloys at ambient temperature, but we suggest that ternary Fe–Ni–Si alloys might have a reduced thermal expansion in respect to pure Fe and binary Fe–Si alloys. In particular, once the thermal equations of state are considered together with velocity measurements, we conclude that elements other than Si and Ni have to be present in the Earth’s inner core to account for both density and seismic velocities.

The Degree‐of‐Order Dependent Electronic Structures and Magnetic Properties of Fe3Si Alloys

The effect of ordering degree on the electronic structures and magnetism of Fe3Si alloys are investigated scientifically using first‐principles calculations based on plane‐wave pseudopotential theory. The studied results of the heat of formation and cohesive energy for D03 and B2 structures of Fe3Si reveal that the order of structural stability from high to low is B2‐9, B2‐8, B2‐7, B2‐6, D03/B2‐1, B2‐2, B2‐3, B2‐4, and B2‐5. Both D03 and B2 structures of Fe3Si exhibit the metallic feature. A wider breadth of the pseudogap with occupation of Si sites by more Fe[B] atoms except B2‐5 implies that the hybridization and covalent bond are intensified. Meanwhile, with substitution of Fe[B] atoms by more Si atoms, the stability of the system improves because the Fermi level is nearer to the bottom of the pseudogap. The origin of ferromagnetism for ordered Fe3Si except B2‐9 is mainly from the Fe 3d spin polarization. Compared with D03 structure of Fe3Si, an increment in the concentration of Fe atoms with occupation of Si sites by more Fe[B] atoms causes the change of interaction between Fe and Si atoms and the total magnetic moment increases. On the contrary, the total magnetic moment decreases with gradual substitution of Fe[B] atoms by Si atoms.

Plastically deformed La–Fe–Si: Microstructural evolution, magnetocaloric effect and anisotropic thermal conductivity

La(Fe,Si)13-based alloys are considered to be one of the most promising magnetocaloric materials for solid state cooling. However, the intrinsic brittleness of NaZn13-type functional phase (1:13 phase) obstructs the shaping of La–Fe–Si alloys into desired geometries for the applications in magnetic cooling devices. Here, by exploiting the excellent deformability of α-Fe phase, we propose a near-net shaping method of open die-forging to prepare La–Fe–Si thin plates. This novel approach is demonstrated for the first time to exhibit several advantages including producing full-dense materials, facilitating the phase formation, and maintaining large magnetocaloric effect. The microstructural and texture evolution have been systematically investigated for the pre-deformed and annealed La–Fe–Si alloys. Large magnetic entropy change of 14 J/kg K at 2 T is obtained in the annealed sample and 11 J/kg K for the hydrogenated sample without hydrogen-induced cracking. Furthermore, a unique dual-phase structure consisting of aligned α-Fe phase and non-equiaxial 1:13 grains brings about the significant anisotropic thermal conductivity in cross-plane and in-plane directions for the plastically-deformed plates. This new insight would greatly benefit the design of high efficient magnetic refrigerator with one-way enhanced thermal conduction.

Geochemical constraints on core-mantle differentiation in Mercury and the aubrite parent body

Differentiation of Mercury and the aubrite parent body (AuPB) at extremely reducing conditions is implied from the low FeO and high S contents of their mantles. Here, the mantle abundances of these elements as derived from remote sensing (in the case of Mercury) and aubrite meteorite analysis are used in conjunction with new experimentally determined metal-silicate partition coefficients at reducing conditions presented in Steenstra et al. (2020a) to quantify the geochemical consequences of core formation in highly reduced planetary bodies. Plausible core compositions of Mercury and the AuPB are assessed, and the distribution of Si and other elements during core formation are quantified.Combining the new results with previous remote sensing observations of the surface of Mercury it is found that its core is likely to be Si-rich (>4.5–21 wt%). The estimated core Si contents depend mostly on the assumption of C saturation in Mercury's mantle and the type of bulk composition considered. Calculations for C-free conditions also yield significant quantities of Si in the AuPB core (>6–20 wt%, depending on bulk composition and redox state). The amount of Si in the AuPB core is greatly decreased if C-saturation is assumed.The new experimental data and related thermodynamic parameterization for predicting the C contents at graphite saturation of FeSi alloys (CCGS) shows that Mercury's mantle was likely C-saturated following formation of a Si-rich core, allowing for the separation of a graphitic flotation crust. Due to the lower Si contents calculated for the AuPB core under C-saturated conditions, a graphitic flotation crust is unlikely to form in smaller-sized reduced asteroids such as the AuPB.The Si-rich nature of the AuPB core for C-undersaturated scenarios is expected to have resulted in preferential partitioning of the majority of the volatile siderophile elements (VSE) into the AuPB core. However, depletions for the most volatile VSE cannot be reconciled with core formation depletion only. Their depletions in aubrites require additional depletion from (I) segregating sulfide liquids during AuPB differentiation and/or (II) compatible behavior during mineral-melt fractionation and/or (III) loss of these elements in a vapor phase during and/or after AuPB differentiation.

Electrochemical performance enhancement of porous Si lithium-ion battery anode by integrating with optimized carbonaceous materials

Silicon (Si) is regarded as a promising negative material for Li-ion batteries (LIBs), but the poor cyclic performance limits its practical applications. Herein, we used several different carbonaceous materials as carbon sources to form Si/C composites, which was formed by etched Fe–Si alloys followed by mechanical ball mill mixing with carbon. It is found that the artificial graphite as the carbonaceous material can form a well-distributed mixture during the ball milling, and then uniformly coated with amorphous carbon pyrolyzed by the phenolic resin. The pore structure of Si particles can provide rapid diffusion for lithium ions, resulting in improving the electrochemical properties. The well-coated carbon layer promotes the formation of stable SEI layer on the composites surface, which is advantageous for the long cycle performance. The carbonaceous materials (artificial graphite, flake graphite and soft carbon) have remarkable influence on the electrochemical performance of Si/C composites. The silicon/graphite-artificial graphite (Si/C-AG) exhibits the best performance among these three Si/C composites. It delivers a specific capacity of 445 mAh g-1 at 0.5 A g−1 with a retention of 94% after 200 cycles. This work would be helpful with choosing suitable carbonaceous materials for the Si/C composites.

Recent Developments in Non-Oriented Electrical Steels

This paper gives an overview of developments in the field of non-oriented electrical steels that are widely used in motor cores in recent years, focusing mainly on texture control. ND//<100> texture is recognized as the ideal texture for application to motor cores. To obtain a suitable texture, precise control is required during each manufacturing process. This involves adjusting the chemical components during the steel making, fine temperature and reduction control during hot rolling, temperature control during hot-band annealing, temperature and reduction control during cold rolling and heating rate and temperature control during final annealing. High silicon Fe-Si alloy containing 6.5 mass% Si has been recognized as a promising core material for high frequency applications. When producing high silicon steel by the continuous chemical vapor deposition (CVD) siliconizing process, materials with a gradient Si concentration in the sheet thickness direction have been found to display superior high-frequency iron loss.

Chill sensitiveness and thermal analysis parameters relationship in hypo-eutectic, Ca and Ca-La inoculated commercial grey cast irons

Previous experiments showed a specific distribution of Al, La, and Ca on the section of complex (Mn,X)S compounds, found as major nucleation sites for graphite flakes in low-S cast irons (&lt; 0.03%S), and a possible contribution of La to improve their capacity to nucleate graphite, avoiding carbides formation. In the present work, standard thermal [cooling curves] investigations were undertaken to explore Ca and La-Ca bearing FeSi alloys inoculation effects [10 measurements for each inoculant], in 3.7 ? 3.8%CE and optimum S and Mn relationship [0.046 ? 0.056%S, (%Mn) x (%S) = 0.024 ? 0.029]. Representative temperatures on the cooling curves and under-cooling degrees referring to the meta-stable eutectic temperatures were determined and correlated with the chill [carbides/graphite formation sensitiveness], in different solidification conditions [cooling modulus, wedge shape castings, resin sand mould]. Supplementary addition of La to Cabearing inoculants had limited, but specific benefits in these cast irons: lower eutectic recalescence and maximum recalescence rate, higher GRF1 and lower GRF2 graphitizing factors, and lower value of the first derivative at the end of solidification. Consequently, it resulted in a premise for lower shrinkage sensitiveness and lower chill (carbides) sensitiveness, especially at the highest solidification cooling rate (thin wall castings).

Cathodoluminescence Analysis for the Nondestructive Evaluation of Silica Scale on an Iron-Based Alloy

Information on the composition, morphology, and thickness of surface oxide scale helps to control the performance of heat-resistant alloys. Currently, there is a lack of adequate analytical methods that allow the rapid and nondestructive evaluation of these properties. In this study, we demonstrate a nondestructive method for identifying silica (SiO2) scale and evaluating its morphology and thickness within 1 min by acquiring the cathodoluminescence (CL) images and spectra of SiO2 scale on an Fe–5%Si alloy heated to 900 °C. SiO2 scale emitted yellow–orange, violet, or red luminescence, whereas the other scale products that form on Fe–Si alloys, such as FeO, Fe3O4, Fe2O3, and Fe2SiO4, did not. Thus, we can identify SiO2 scale and observe its morphology on the basis of luminescent color in the CL image. The thickness of SiO2 scale can be correlated to the intensity of the CL peak at 645 nm. Therefore, the acquisition of CL images and spectra is a novel analytical method, which allows one to control the performance of SiO2-forming Fe–Si alloys.

Phase, microstructure, and wear behavior of Al2O3-reinforced Fe–Si alloy-based metal matrix nanocomposites

In the present work, phase, microstructure, and wear properties of Al2O3-reinforced Fe–Si alloy-based metal matrix nanocomposites have been studied. Composites using 2 wt.% and 5 wt.% of Si and rest Fe powder mix were synthesized via powder metallurgy and sintered at different temperature schedules. Iron–silicon alloy specimens were found to have high hardness and high wear resistance in comparison to pure iron specimens. Addition of 5 wt.% and 10 wt.% alumina reinforcement in Fe–Si alloy composition helped in developing iron aluminate (FeAl2O4) phase in composites which further improved the mechanical properties i.e. high hardness and wear resistance. Formation of iron aluminate phase occurs due to reactive sintering between Fe and Al2O3 particles. It is expected that the improved behavior of prepared nanocomposites as compared to conventional metals will be helpful in finding their use for wide industrial applications.

Properties of Fe2SiO4/SiO2 coated Fe-Si soft magnetic composites prepared by sintering Fe-6.5wt%Si/Fe3O4 composite particles

In this work, Fe2SiO4/SiO2 coated Fe-Si soft magnetic composites (SMCs) have been prepared successfully via ball milling Fe-6.5wt%Si/Fe3O4 composite particles combined with subsequent spark plasma sintering (SPS) process. The formation mechanism of Fe2SiO4/SiO2 insulating layer and effect of Fe3O4 coating content on the microstructure and properties for the Fe-Si SMCs were investigated in detail. It is interesting that high temperature SPS process would lead to the occurrence of redox reactions between Fe3O4 and Si from Fe-Si alloy cores, and resulted in the transformation from Fe3O4 coating layer to Fe2SiO4/SiO2 insulating layer. As a consequence, the novel Fe-Si SMCs exhibited superior performances including high saturation magnetization (190.4 emu/g) and low core loss (9.02 mW/cm3 at 10 kHz) decreased by 89.1% compared to that of the uncoated Fe-Si SMCs (83.08 mW/cm3 at 10 kHz). The results indicated that the method of preparing insulating layer by the redox reactions is a simple and effective way to synthesize new SMCs with high performance for electro-magnetic energy conversion equipments.

Electrochemical Mechanism for the Preparation of Fe-Si Alloys by Melts Electrodeposition

Abstract The melts dissolution characteristics and reaction process during the preparation of Fe-Si alloys by the melts electrochemical method were studied. The thermodynamic calculations and experimental results showed that the solubility of SiO2 in KCl-NaCl-NaF melts was 0.24 mas% at 1073 K. The cyclic voltammetry data showed that the reduction of SiO2 on a Pt electrode was a one-step electron process; when SiO2 accounted for 0.24 mas% of the NaCl-KCl-NaF melts, the Fe-Si alloy was prepared by electrodeposition at 1073 K. When the deposition time was 30 min, Fe3Si was formed.