Fe Cr Si Research Articles

Revealing the microstructural evolution and mechanical response of repaired Fe–Cr–Si based alloy by directed energy deposition

This study investigates the microstructure and mechanical properties of wear-resistant hardfacing structures fabricated on an AISI 1045 carbon steel substrate using a specially designed Fe–Cr based powder for directed energy deposition (DED). Electron backscatter diffraction (EBSD) analysis reveals that the texture predominantly consists of cube rotated {001}<110> and cube {001}<110> textures, in addition to weaker Brass {112}<111> texture components. These textures contribute to the random orientations of martensitic grains and facilitate the tracing of austenite reconstruction. Notably, the as-printed samples exhibited superior yield strength (999.4 ± 86.3 MPa) and ductility (9.6 ± 2.6%) along the build direction (BD), compared to conventional samples, which demonstrated a tensile strength of 790 MPa and ductility of 2%. This improvement is primarily attributed to the hardening effects associated with a low volume fraction of retained austenite and the precipitation of Cr carbides. Comprehensive mechanical response, nanoindentation hardness profile across the interface, and microstructural analyses were conducted to confirm the feasibility of using a Fe-based hardfacing alloy for DED. The findings underscore the outstanding balance of strength and ductility exhibited by as-printed hardfacing alloy, further enhanced by its high printability, highlighting its potential in producing wear-resistant structures for repair applications.

Improving magnetic properties of Fe–Si–Cr-based soft magnetic composites through precise adjustment of salt dosage based on interface engineering

Herein, the composite powder with a core–shell heterostructure (Fe–Si–Cr magnetic particles as the core and ZnSO4 as the shell) was synthesized using hydrothermal method, and Fe–Si–Cr-based soft magnetic composites (SMCs) with an insulation layer of ZnO·SiO2·Cr2O3 (ZSC) composites were successfully prepared via powder heat treatment and cold pressing. The formation mechanism of the ZSC composite insulation layer was thoroughly investigated, and the impact of varying amounts of ZnSO4 on the Fe-Si-Cr/ZSC SMCs’ microstructure and magnetic properties was analyzed. ZnSO4 released oxygen during thermal decomposition and oxidation reaction occurred at the core–shell heterogeneous interface, forming ZSC composite insulation layer. The incorporation of ZnSO4 significantly influenced the homogeneity and thickness of the composite insulation layer, effectively modulating the magnetic properties of Fe–Si–Cr/ZSC SMCs. This SMCs had the best magnetic properties after the addition of 2 wt% ZnSO4. Under 10 mT and 300 kHz, the relative permeability was 37.7, with a total loss of 248.8 kW/m3 The method proposed in this study is beneficial for facilitating the advancement of SMCs towards high frequency and further optimizing its performance.

Investigating the Effect of Carbonyl Iron Powder Doping on the Microstructure and Magnetic Properties of Soft Magnetic Composites

This study proposes the thermal decomposition of salt compounds and doping of carbonyl iron powders (CIPs) to optimize the preparation of an insulating layer through the solid-phase interface reaction. First, (Fe–Si–Cr + CIPs)/ZnSO4 composite powders were synthesized using the hydrothermal method and (Fe–Si–Cr + CIPs)/ZnO·SiO2·Cr2O3 SMCs with a ZnO·SiO2·Cr2O3 composite insulation layer were prepared through heat treatment and cold pressing. The effect of the CIP doping content on the microstructure and magnetic properties of the (Fe–Si–Cr + CIPs)/ZnO·SiO2·Cr2O3 SMCs were then investigated. During the heat treatment, ZnSO4 decomposed into solid ZnO and gaseous SO2 and O2. The O2 drives the solid-phase reaction, prompting the migration of nonmagnetic Si and Cr atoms from the interior of the Fe–Si–Cr soft magnetic powder to the surface insulation layer, finally forming the ZnO·SiO2·Cr2O3 insulation layer. The doped CIPs also show good plasticity during the coating process, combining with the coating layer to fill the internal pores of SMCs. Moreover, as the particles are small with a high surface area, they increase the number of reaction sites for ZnSO4 decomposition and facilitate the growth of the composite insulation layer, promoting its uniform distribution on the surfaces of the soft magnetic powders and CIPs. The lattice mismatch between the insulation layer and soft magnetic powder is reduced while the magnetic-phase content is increased, allowing the effective doping of CIPs sin the insulation layer. The magnetic properties of SMCs can be precisely regulated by changing the doping amount of CIPs. Unlike other insulating layer–preparation strategies based on the interfacial solid-phase reaction, the proposed method exploits the high plasticity and specific surface area of CIPs and removes the lattice mismatch between the insulation layer and soft magnetic powder.

Interdiffusion of Solute Elements in the &lt;i&gt;α&lt;/i&gt;-Fe Phase of the Fe–Cr–Mo and Fe–Cr–Si Ternary Systems

Interdiffusion of Solute Elements in the &lt;i&gt;α&lt;/i&gt;-Fe Phase of the Fe–Cr–Mo and Fe–Cr–Si Ternary Systems

Augmenting magnetic properties: Ectopic reconstruction of insulation layer in soft magnetic composites via coating-doping method

The doping of carbonyl iron powders (CIPs) with small particle sizes and high ferromagnetism can effectively enhance the magnetic conductivity of soft magnetic composites (SMCs). However, the poor fluidity and the direct contact between CIPs will increase the effective eddy current size, resulting in increased core loss. To address the negative effects, the ectopic reconstruction of CaCO3 insulation layer in CIPs was realized by heat treatment. A composite powder of Fe–Si–Cr matrix/CaCO3 insulation layer + CIPs was fabricated, exhibiting a unique core–shell heterostructure. Furthermore, the effect of the doping amount of CIPs on the permeability optimisation and core-loss reduction in the SMCs was investigated. Findings demonstrated that simultaneous execution of insulation coating and CIPs doping can promote the ectopic reconstruction and nucleation of the CaCO3 insulation layer on CIPs surfaces during heat treatment. This coating-doping method is expected to prevent the direct contact between different magnetic powder particles, potentially mitigating the magnetic dilution effect caused by the non-magnetic phase. The SMCs exhibited best soft magnetic performance at 15 wt% doping level, where the saturation magnetisation peaked at 185.4 emu/g, permeability increased to 38.6 and the core loss was minimised to 466.0 kW/m3 (at 30 mT and 200 kHz). Compared with conventional doping techniques, the proposed method enables CIPs doping within the insulation layer and enhances the intergranular insulation between the Fe–Si–Cr soft magnetic powders and CIPs, improving the SMCs performance.

Development of Fe–Cr–Si deposited layer manufactured by laser directed energy deposition process

In this study, the mechanical and corrosion characteristics of a corrosion-resistant layer made of stainless steel (STS) 316 L and Fe–Cr–Si alloy powder were investigated using laser-directed energy deposition (DED). In the STS 316 L deposited specimen, both the substrate and deposited layer were face-centred cubic (FCC). The deposited Fe–Cr–Si layer was clearly separated from the substrate because it was composed of body-centred cubic (BCC). Despite the phase differences, the surface of the Fe–Cr–Si-deposited layer showed a lower corrosion rate than that of the STS 316 L. All the deposited specimens exhibited typical high-temperature tensile behavior. However, the Fe–Cr–Si deposited layer at 600 °C showed a notable reduction in strength and increased elongation compared to the room temperature (RT) and 300 °C test results owing to the carbide concentration and phase transformation in the deposited layer. Because nuclear facilities mainly operate at temperatures below 600 °C, Fe–Cr–Si materials can also be used as nuclear piping coating materials. This study provides a mechanism for the high-temperature properties and corrosion resistance of the Fe–Cr–Si deposited layer and makes it competitive for application in fourth generation nuclear power systems.

Preparation of Ni–Fe–S Matte and Fe–Cr–Si Alloy by the Co-treatments of Stainless Steel Pickling Sludge and Electroplating Sludge

Preparation of Ni–Fe–S Matte and Fe–Cr–Si Alloy by the Co-treatments of Stainless Steel Pickling Sludge and Electroplating Sludge

Effect of Mg content on the microstructure and properties of high strength, high conductivity Cu–Fe–Cr–Si–Mg alloy

A new strategy for the preparation of Cu–Fe alloy with excellent comprehensive performance is proposed. This strategy combines the construction of dual-scale polymetallic second phases with the addition of trace solid-solution atoms. A series of Cu–2Fe-0.3Cr-0.2Si-xMg (x = 0.1, 0.3, 0.5) alloys are designed and prepared through multi-stage thermo-mechanical treatment. Among the reported Cu–Fe alloys with low Fe content (Fe content less than 3 wt%), the designed Cu–2Fe-0.3Cr-0.2Si-0.3 Mg alloy has the highest product of the tensile strength times the electrical conductivity (PSC). The tensile strength and PSC of the Cu–2Fe-0.3Cr-0.2Si-0.3 Mg alloy are 698 MPa and 43.9 GPa∙%IACS, respectively. The dual-scale polymetallic second phase has been successfully constructed. The submicron-scale Fe8CrSi phase triggers the generation of substructures, such as geometrically necessary dislocation boundaries in lamellar structures and random dislocation boundaries in cell shapes. The high-density low angle grain boundaries (LAGBs) of substructure evolution enhances the substructure strengthening of the alloy. The main strengthening phase in precipitation strengthening is the nanoscale Fe11CrSi4 phase. An appropriate amount of Mg reduces the ultimate solid solubility of Fe atoms in Cu alloys, promotes the formation of a dual-scale second phase and refines the grain size of the alloy. Therefore, the comprehensive performance of the design alloy is significantly improved.

Fabrication and Soft Magnetic Properties of Fe–Si–Cr Composites with Double-Insulating Layers Suitable for High-Frequency Power Applications

Soft magnetic composites (SMCs) are composed of alloy materials with the core and insulating layers as the shell. These composites exhibit high saturation magnetic sensitivity and low hysteresis loss, making them a promising material for various applications. The investigation of double layers is considered valuable as it can effectively address the issues of low resistivity and high dynamic loss that arise from non-uniform insulating layers in SMCs. In this study, Fe-Si-Cr/SiO2 particles with a core–shell heterostructure were produced via chemical vapor deposition (CVD). The Fe-Si-Cr/SiO2 materials were coated with different weight percentages (1–6%) of sodium silicate (SS). Subsequently, Fe-Si-Cr-based SMCs were synthesized through high-pressure molding and heat treatment. The effect of the SS weight percentage on microscopic changes and magnetic characteristics was investigated. These findings indicated that a concentration of 4 wt% of SS was the most effective at enhancing magnetic characteristics. The resultant SMCs exhibited high resistivity (21.07 mΩ·cm), the lowest total loss (P10 mt/300 kHz of 44.23 W/kg), a relatively high saturation magnetization (181.8 emu/g), and permeability (35.9). Furthermore, it was observed that the permeability exhibited stabilization at lower frequencies. According to these findings, the combination of CVD and double layers could lead to the further development of SMCs in a variety of applications.

Formation mechanism of periodic layered structure between Fe–Cr–Si–B cast steel with high B content and molten Al

The periodic layered structures (PLSs) have been confirmed to be formed as the Fe–Cr–B cast steels containing about 3.0 wt% B were dipped into Al melt. However, there was no PLSs formed, in terms of a novel Fe–Cr–Si–B cast steel with B content much higher. The interfacial reaction between borides contained in this novel Fe–Cr–Si–B cast steel with 8.5 wt% B content and Al at 750 °C was studied using hot dip aluminizing, thermal diffusion treatment, and subsequent SEM, TEM, and 3DAP of the obtained specimens. The PLSs were formed in situ after a long period of incubation because of the high chemical stability induced by the overstoichiometric (Cr, Fe)2B. The formation of PLSs proceeded through an intermediate state which involved transformation from disordered particles to ordered Cr–Al–B intermetallic compound. Owing to the formation of the localized melt of FeAl3–Al eutectics, the understoichiometric Cr–Al–B intermetallic compound gradually drifted to agglomerate and grew under the effects of the driving force of the lamellar growth of MAB phase and the thermal flux, along with the drag of the overstoichiometric Cr–Al–B intermetallic compound due to the interlaced structure.

Microstructural, textural, and residual stress evolution alongside the magnetic properties through isothermal static recrystallization of cold-drawn Fe–Cr–Si–S–C ferritic high-alloy stainless steel and by JMAK modelling

The evolution of microstructures, textures, and residual stresses scale of cold-drawn (CD) 18%Cr ferritic stainless steels (FSS) round bars under isothermal static recrystallization annealing are investigated. As for determination of the new grains' formation, the size, growth, and orientation, as well as the nucleation of grains, alongside revealing the recrystallization fractions are studied by a mixed experimental and theoretical work. The recrystallization kinetics are calculated according to the Johnson-Mehl-Avrami-Kolmogorov theory. Electron backscatter diffraction (EBSD) analyses are applied for the actual specimens of an industrial wire drawing process with 20 and 35% reduction rates. The heat treatment has been implemented at three different set ratio temperatures of 0.65, 0.68, and 0.71, defining as a ratio between the temperatures of annealing and melting point (TRAM). According to the results, the nucleation is occurred at faster incubation time with higher temperature and reduction rate. The grain average size (AGS) increases gradually whereas the temperature increases. This is while the 0.71TRAM-scale annealed samples illustrate finer and more equiaxed recrystallized grains. Following recovery, recrystallized grains, and the grain growth, the overall varied AGS of 27–86 μm in the core region are achieved. Moreover, the JMAK model agrees well with the obtained experimental data. All in all, this 18Cr-FSS material is taken into account for the optimal industrial annealing production as well as the targeted material selection of the market applications. It is observed that the higher recrystallization leads the higher magnetic permeability, lower coercivity, and lower residual stresses compared to the unheated specimens.

Phases and Interfaces in the Cr–Fe–Si Ternary System: X-ray Diffraction and Electron Microscopy Study

The ternary Cr-Fe-Si system was investigated with X-ray diffraction, energy dispersive X-ray spectrometry, scanning and transmission electron microscopy, and electron diffraction. Samples melted at 1723 K were examined right after cooling or after annealing at 1073 K for 3 days to determine phases, grain sizes, and interphase interfaces. During annealing, a polymorphic transformation of the tetragonal α-FeSi2 to the orthorhombic β-FeSi2 phase occurs, while CrSi2 retains its hexagonal structure at high-temperature treatment. Thin layers of ε-FeSi with a cubic structure were observed and identified within the CrSi2 grains. Crystallographic orientation relationships are determined at the interphase interfaces. The contributions of lattice mismatch and thermal expansion coefficient misfit to deformation are discussed.

Effect of Ca and Ti contents on characteristics of inclusions in Fe–Si–Cr–Mn–Al–Ti–Ca–O melts

Effect of Ca and Ti contents on characteristics of inclusions in Fe–Si–Cr–Mn–Al–Ti–Ca–O melts

Effect of dual-scale FeCrSi phase on the strength and conductivity of Cu-2.5Fe-0.3Cr-0.2Si alloy

A new dual-scale (submicron and nanoscale) FeCrSi ternary second-phase has been successfully constructed in designed Cu-2.5Fe-0.3Cr-0.2Si alloy. The synergistic addition of Cr and Si promotes the transformation of the submicron Fe phase morphology from “square” to “flower” shape in as-cast alloys. The orientation relationship between nanoscale FeCrSi phase and Cu matrix is: [011] Cu//[01‾1] Fe11CrSi4 and the misorientation angle between the (200) of the Cu matrix and the (022) of the Fe11CrSi4 phase is about 4°. After three-stage thermomechanical treatment, the tensile strength and electrical conductivity of the alloy are 435 MPa and 70.52 %IACS, respectively. According to the calculated results, precipitation strengthening and substructure strengthening play an important role in the strengthening of Cu–Fe–Cr–Si alloys. With the addition of Cr and Si, the precipitation of the second phase in the alloy is promoted, which also leads to the improvement of the electrical conductivity and mechanical properties of the alloy.

Integrated phase equilibria experimental study and thermodynamic modeling of the Cr–Si–O, Fe–Cr–O and Fe–Cr–Si–O systems

Complete characterization of the Fe–Cr–Si–O system at high temperatures (700–2600 °C) is performed using integrated experimental and thermodynamic modeling research methodology. Experimental technique includes high-temperature equilibration, quenching and electron probe X-ray microanalysis (EPMA). Main challenges in the experiments are the choice of holding materials (substrate), fixing the oxygen partial pressure in a wide range, using the secondary standards for EPMA correction, overcoming slow reactions to achieve solid state equilibria. Thermodynamic modeling involves critical assessment of literature data, development of the mathematical models for the Gibbs energies of all phases in the system, and optimization of model parameters. The main modeling challenge is to obtain a self-consistent database, which requires a re-assessment of the Cr–Si–O and Fe–Cr–O sub-systems, and an accurate simultaneous description of all experimental data from literature and from the present study. There are several outcomes of the present study: a critical review of earlier work; a set of diagrams representing phase equilibria and distribution of elements among phases within the system; a set of thermodynamic model parameters for liquid and solid phases in the system. The results of the work will be applied to solve chemical engineering problems in pyrometallurgical production of copper, nickel and steel, recycling of waste electronics and designing refractory materials.

Study on Surface Modification of Fe–Si–Cr Alloy by Selective Oxidation Heat Treatment and its Corrosion Properties

Corrosion properties of the insulating oxide layer formed on the Fe–Si–Cr alloy through the selective oxidation heat treatment are evaluated to find out that the oxide layer can play a role as a barrier layer against corrosion. Preferential oxidation of Si and Cr during the selective oxidation heat treatment results in a two‐layered oxide layer. From the X‐ray photoelectron spectroscopy and transmission electron microscope results, it is revealed that the inner layer is SiO2 and the outer layer is Cr2O3, and they keep growing with the heat treatment time. The oxide layer formed by the selective oxidation heat treatment causes the ennoblement of the corrosion potential, but additional ennoblement does not occur with the growth of the oxide layer. However, the thickness of the oxide layer influences anti‐corrosion performance in terms of corrosion resistance and deterioration. The thicker the oxide layer is, the higher the corrosion resistance and the slower the deterioration become so that the protection property withstands for 3 h in the 3.5 wt% NaCl solution when the oxide layer has 44.3 nm thickness.

Influence of the Oxygen Induced Surface Segregation Process of Solutes on the Anti-corrosion Properties of the Fe–Cr and Fe–Cr–Si Alloys

Influence of the Oxygen Induced Surface Segregation Process of Solutes on the Anti-corrosion Properties of the Fe–Cr and Fe–Cr–Si Alloys

Core-loss reduction of Fe–Si–Cr crystalline alloy according to particle size in the high frequency band

We used different sizes of gas atomized Fe–Si–Cr alloy powder to produce soft magnetic composites (SMCs), this alloy has higher resistivity than existing materials used in SMCs. These powders were prepared by sieving raw materials which had an average size from less than 25 μm to over 63 μm. Our experiments show that as particle size decreases, the magnetic saturation tends to increase, the sample made from the powder with particles 25–38 μm in size recorded the highest magnetic saturation of 169.38 emu/g. Additionally, as particle size decreased, permeability increased. The sample made from powder with particles under 25 μm had a permeability of 20.7 H/m at 1 MHz. Also, the relationship between particle size and quality factor was found to be inversely proportional. Finally, the minimum core-loss was 187.26 kW/m3 at 1 MHz for the sample made from powder whose constituent particles are under 25 μm.

Relationship of isothermal solidification completion and precipitate formation with mechanical properties of Inconel 939 joints vacuum TLP bonded by an amorphous Ni–Cr–Fe–Si–B filler alloy

In this research, vacuum transient liquid phase bonding of Inconel 939 superalloy was performed using an amorphous Ni–Cr–Fe–Si–B filler alloy at different temperatures from 1060 °C to 1180 °C, and the microstructure and mechanical properties of the joints were investigated. The results showed that the bonding region can be categorized into three athermal solidification, isothermal solidification, and diffusion affected zones. The ASZ region consisted of a eutectic phase while the ISZ region included a Ni-rich gamma single-phase solid solution. Also, the DAZ involved cubic-shaped, needle-like and grain boundary-shaped borides. The width of DAZ increased with increasing the bonding temperatures, and it also led to a decrease in the ASZ/joint ratio. The ASZ was disappeared at 1180 °C. The highest hardness value was obtained for the DAZ region of the sample bonded at 1180 ᵒC, and a direct relationship was detected between the bonding temperature and ISZ hardness. The addition of bonding temperature also led to the improvement of the shear strength and joint efficiency. It was also found that an inverse relationship can be detected between the shear strength and the ASZ/joint ratio. A joint efficiency of ∼79% was obtained for the bonding temperature of 1180 °C.

Insulation Coating of Fe–Si–Cr Soft Magnetic Powder by Selective Oxidation

Insulation Coating of Fe–Si–Cr Soft Magnetic Powder by Selective Oxidation