Fe-based amorphous ribbons produced through rapid solidification method may undergo surface crystallization. The surface crystallization behavior of the ribbons, resulting from preferred oxidation or a slow cooling rate, is usually suspected to impair the magnetic properties. However, the connection between surface microstructure and magnetic properties is still a critical aspect that demands systematic exploration. This study revealed that the surface crystallization of Fe-Si-B-C amorphous ribbons during the melt-spinning process was due to poor amorphous-forming ability rather than oxidation. Moreover, an oxide layer could develop under low-vacuum annealing conditions, resulting in a surface oxide/crystallization layer (similar to 50 nm thick), with composition including a dense oxide layer (similar to 20 nm) and a crystallized/amorphous layer (15-28 nm thick). This structure could reduce out-of-plane anisotropy and improve the soft magnetic properties during short annealing durations. These findings may extend comprehension of the crystallization mechanism and support the development of excellent soft magnetic amorphous ribbons with industrially acceptable manufacturability.

This study synthesized a (Fe₀.₇₅Co₀.₂₅)₆₀Ni₃₁Al₉ Medium-Entropy alloy and systematically investigated the effects of different post-rolling heat treatment temperatures on its phase composition, microstructure, mechanical properties, and soft magnetic performance. The results indicate that the Fe-based soft magnetic medium-entropy alloy undergoes a phase transformation from a single FCC structure to a duplex FCC + BCC structure. Moreover, the heat treatment temperature plays a critical role in regulating the microstructural evolution, thereby optimizing both mechanical and soft magnetic properties. AN2 alloy exhibited the best comprehensive performance, achieving a yield strength of 509.05 MPa and a fracture elongation of 38%, reflecting an excellent synergy between strength and ductility. In terms of soft magnetic properties, AN2 alloy exhibits a high saturation magnetization of 1.73 T and a coercivity of 143.71 A/m. Compared with other heat-treated samples, its dM/dH curve exhibits a smaller full width at half maximum and better magnetization homogeneity. This is attributed to the precipitation of fine B2-NiAl phases, which increase the overall magnetic moment of the alloy and thus enhance its saturation magnetization. This work provides an in-depth understanding of the relationship between microstructural evolution and the mechanical and soft magnetic properties of the Fe-based soft magnetic medium-entropy alloy offering valuable experimental and theoretical insights for the process optimization and performance enhancement of multi-component medium-entropy magnetic alloys.

Fe-based nanocrystalline alloys exhibiting excellent soft magnetic performance are highly desirable for broad applications in electrical and electronic engineering. Here, Mo was added to Fe-Si-B-P-Cu nanocrystalline alloys with a thickness of approximately 16 mu m, which were produced using a single-roller melt-spinning process at a wheel rate of 60 m/s. The alloy with 1 at.% Mo addition exhibits superior soft magnetic properties, including fine nanocrystals with an average size of 16.7 nm, resulting in a high effective permeability of 17487 at 1 kHz, a high saturation magnetic flux density of 1.74 T, and a low coercivity of 2.3 A/m after annealing under optimal conditions. An excessive Mo content (2 and 3 at.%) inevitably leads to the deterioration of the soft magnetic properties. During the annealing process of the amorphous ribbon, Mo promotes nanocrystal nucleation and effectively suppresses nanocrystal growth, thereby facilitating the formation of a fine, uniform nanocrystalline structure dispersed within the amorphous matrix. As a result, these effects lead to a reduction in magnetic anisotropy and an enhancement in soft magnetic properties after annealing under optimal conditions. Furthermore, during annealing for different durations, Mo reduces the thermal sensitivity of the nanocrystals and effectively inhibits the rapid growth of nanocrystalline grains. The present study may provide valuable insights into addressing the challenges associated with the industrial production of ultrathin nanocrystalline alloys.

In the present study, the Fe82Si1B12C5 amorphous alloys, cast at 1150, 1300, and 1400 degrees C had been studied. The corrosion behaviors were evaluated in a 3.5 wt% NaCl solution through structural characterization analysis, surface topography analysis, and electrochemical tests. The results showed that as melt temperatures increased, the structure of Fe82Si1B12C5 amorphous alloy gradually became more disorder. Alloys cast at higher melt temperatures exhibited micro/nano pits on their etched amorphous surfaces, which resulted in a lower corrosion potential and higher current density. The corrosion morphology revealed that the macro-pit corrosion was less pronounced in amorphous alloys cast at lower melt temperatures compared to those cast at higher melt temperatures. Additionally, potentiodynamic polarization and hardness measurements of annealed alloys cast at higher melt temperatures showed improved corrosion resistance. This enhancement was attributed to their more homogeneous structure, reduced free volume, and lower residual internal stress, all of which contributed to the increased effectiveness of the passive film. Since the amorphous alloy is typically used in the annealed state, optimal properties are usually achieved by carefully controlling the temperature. Therefore, it is essential to avoid prolonged exposure to corrosion-prone conditions before the amorphous alloys undergoes annealing, to prevent issues such as burst leakage.

In this paper, a series of FCC + BCC heterostructure CrFeNiAl0.28Si0.12-xCux as-cast HEAs with different Cu/Si ratios (0.2, 1, 2) were designed for tuning distribution of constituent phases for balancing strength-ductility synergy. It is found that, with the increase in Cu/Si ratio, the FCC phase significantly coarsens from fine sideplates to large-size dendrites, and the BCC phase becomes more sparsely distributed to reduce connection, while the distribution of orientation relationship (OR) between neighboring FCC and BCC phases has prominent trend to deviate from K-S OR. Moreover, increasing Cu/Si ratio from 0.2 to 2 is beneficial for enhancing uniform elongation (UE) from 15.6 % +/- 2.5 % to 29.8 % +/- 2.2 %, while reducing yield strength (YS) and ultimate tensile strength (UTS) of this series of as-cast HEAs from 583 +/- 34 MPa and 1039 +/- 30 MPa to 436 +/- 32 MPa and 902 +/- 32 MPa. However, it is interesting that, the production of strength and plasticity (YS x UE, UTS x UE and (YS + UTS)/2 x UE) for the composition with Cu/Si ratio of 2 that possessing coarse FCC phase and segregated micron-scale BCC phase are generally over 40 % higher than the ones with Cu/Si ratio of 1 when they have similar strength values, while the diversity of the values is much smaller (<11 %) between the ones with Cu/Si ratio of 1 and 0.2. Such phenomenon possibly correlates with the appropriate distribution of deformation and aggregation of dislocations in different phases. This work indicates that avoiding the connection of BCC phase in heterostructure HEAs containing FCC phase with proper size would be effective for optimization of mechanical properties considering the production of strength and plasticity, which is beneficial for further development of this series of as-cast HEAs.

The compressive mechanical behavior and deformation mechanisms of Fe-rich medium-entropy alloys with different phase structures were investigated under quasi-static (10_ 4-10_2 s_ 1) and high strain rates (1500-6000 s_ 1) conditions. The results indicated that no fractures or cracks occurred in any of the compressed specimens of the single-phase Fe57Ni18Cr15Si7Al3 and dual-phase Fe62Ni13Cr15Si7Al3 alloys. Under quasi-static conditions, both alloys exhibited low strain rate sensitivity, with deformation primarily characterized by high-density dislocations and minimal deformation twins or stacking faults. At high strain rates, the yield strength increased significantly. The strain rate sensitivity coefficients (md) for the single-phase and dual-phase alloys were 0.081 and 0.089, respectively. In the single-phase alloy, deformation was accompanied by high-density dislocations, deformation twins, and the presence of deformed NiAl precipitates. The dual phase alloy exhibited a more pronounced transformation-induced plasticity effect. At a strain rate of 6000 s_ 1, the adiabatic temperature rise reached 178 K for the single-phase alloy and 149 K for the dual-phase alloy. These findings indicated that Fe-rich medium-entropy alloys possessed excellent strength and plasticity under high strain rates, ensuring their reliability in dynamic impact environments.

Forsterite films play an important role in enhancing the adhesion of the insulation layer and the magnetic properties of grain-oriented silicon steel. To clarify the microstructure evolution of forsterite film, an experiment involving high-temperature annealing at different temperatures ranging from 850 degrees C to 1150 degrees C was performed. Additionally, the reaction processes between MgO and the oxides formed in the decarburization oxide layer, such as SiO2 and Fe2SiO4, were investigated. The initial formation temperature of the forsterite film is found to be within the range of 900 degrees C - 950 degrees C. The composition analysis reveals a decrease in the magnesium content from the surface toward the interior of the oxide layer. Up to 1100 degrees C, there is no longer a transition region between MgO and Fe2SiO4 in the uppermost oxide layer, showing that the surface of oxide layer is composed entirely of forsterite. Simultaneously, with the diffusion of Mg2+, SiO2 in the subsurface region reacts with Mg2+ and is thus transformed into forsterite. The enrichment of aluminum, silicon, and oxygen in the bottom part of the oxide layer at 1100 degrees C implies the potential formation of mullite. These findings provide valuable insights to tune and control the forsterite film in grain-oriented silicon steel.

Systematic investigations were performed to characterize the Charpy impact behavior of Fe-based medium-entropy alloys (Fe-MEAs) with single-phase face-centered cubic (FCC) (Fe57Ni18Cr15Si7Al3) and dual-phase FCC + body-centered cubic (BCC) (Fe62Ni13Cr15Si7Al3) structures in this work. The results reveal that both alloys possess a fine-grained microstructure with average grain sizes of 1.6 mu m and 1.7 mu m, respectively, accompanied by nanoscale precipitates and well-defined annealing twins. Notably, the dual-phase alloy exhibits excellent impact properties; specifically, it demonstrates remarkable impact toughness values of 138.3 J/cm(2) at 298 K and 138.8 J/cm(2) at 77 K, which are similar to 2.1 and similar to 2.6 times higher than those of the single-phase Ni18 alloy. This superior mechanical performance can be explained in terms of the synergistic strengthening contributions arising from four principal factors, i.e., microstructural refinement, dual-phase FCC + BCC crystalline structure, nanoscale precipitates, and transformation-induced plasticity (TRIP). Especially, the stress-induced phase transformation taking place during plastic deformation is predominantly localized in the notch root regions, which are subjected to triaxial stress, and it exhibits different divergent evolution patterns during crack initiation and propagation. Furthermore, the crack propagation energy accounts for over 70 % of the total absorbed energy, which demonstrates its critical role in determining the impact resistance of the alloy. These findings provide fundamental insights into how to optimize the mechanical properties of Fe-MEAs through a combination of multi-phase architecture and TRIP effects and thus offer significant guidance for the development of advanced impact-resistant materials for use in extreme environments.

In this study, Fe60Co10-xNi15Cr15Six (x = 0, 4, and 8) powders were successfully prepared using the aerosol method and employed to produce high-entropy coatings on Q235 steel via laser cladding. The microstructure and phase composition of the coatings were analyzed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Corrosion resistance and potential were evaluated through electrochemical analysis and Kelvin probe force microscopy. The results show that the Fe60Co10-xNi15Cr15Six coatings exhibit excellent metallurgical bonding with no visible porosity or cracks. The coating primarily consists of an FCC structure; however, as the Si content increases, the structure transitions to a mixed FCC + BCC phase. The addition of Si also refines the grain size in the alloy system. Electrochemical analysis reveals that the Si0 and Si4 coatings exhibit similar corrosion behavior, while the Si8 coating shows a significant drop in corrosion potential, reducing its corrosion resistance. As the Si content increases, grain refinement leads to more grain boundaries, but the corrosion resistance decreases due to the lower corrosion performance of Si compared to Co. Considering both cost and corrosion resistance, the Si4 coating offers a balance of low cost and excellent corrosion resistance.

Fe–Si–B–P–Cu alloys with high Fe content have excellent soft magnetic properties (SMPs), yet they have low amorphous formation ability (AFA) and the thermodynamic behavior is unstable. The addition of Nb is an effective way to improve the SMPs of Fe–Si–B–P–Cu nanocrystalline alloys and to overcome the harsh nanocrystalline technique due to its nature of rapid crystallization kinetics. Here, the role of Nb addition on structure and magnetic properties of Fe81.3Si6B8P4Cu0.7 nanocrystalline alloy was investigated, and the underlying mechanism was discussed in term of the crystallization kinetics. It was found that the inclusion of Nb significantly raises the nucleation activation energy (Ea) of Fe-(B, P) phase and enhances the thermal stability of the alloy system, easing the harsh nanocrystalline technique of NANOMET alloys. The addition of Nb can facilitate the formation of dense, homogeneous, and fine-grained α-Fe nanocrystals, thereby contributing to excellent SMPs of the nanocrystalline alloys. As a result, comprehensively excellent SMPs, including coercivity (Hc) of 4.52 A/m, effective permeability (µe) of 15,848.6 (at 1 kHz), and saturation magnetic induction (Bs) of 1.68 T after annealed at 793 K were achieved in Fe81.3Si4.4B8P4Cu0.7Nb1.6 nanocrystalline alloy.

The microstructure and tensile properties of C-doped Fe-based medium entropy alloys with a single BCC structure were studied in this work. The addition of 0.25 at.% and 0.5 at.% C induces a significant transformation of the Fe64Ni11Cr15Si7Al3 alloy from a single-phase BCC to a dual-phase FCC + BCC structure, accompanied by the precipitation of B2 (NiAl) nanoparticles within the BCC phase. Following thermomechanical treatment, the (Fe64Ni11Cr15Si7Al3)99.75C0.25 alloy shows excellent tensile properties at 77 K, achieving a yield strength (YS) of 1550 + 34 MPa, ultimate tensile strength (UTS) of 1926 + 33 MPa, and uniform elongation (UE) of 25 + 6 %. These properties are attributed to ultrafine grains, carbon solution, high-density dislocations, B2 (NiAl) nano precipitates, and transformation - induced plasticity (TRIP). At 298 K, the same alloy retains substantial mechanical performance with a YS of 1054 + 14 MPa, UTS of 1203 + 6 MPa, and UE of 15 + 1 %, without the TRIP effect. In contrast, the (Fe64Ni11Cr15Si7Al3)99.5C0.5 alloy exhibits sudden fracture at 77 K, likely due to carbide formation. This work provides a novel strategy for overcoming cold working challenges in single BCC alloys, thereby promoting their development and potential applications in structural materials.

In the present study, the structure and properties of Fe78Si9B13 amorphous ribbons produced in an industrial production process at casting temperatures of 1500, 1450, and 1350 degrees C were investigated. The analysis focused on surface morphology, microstructure, thermal stability, and magnetic anisotropy. The results showed that, compared to the amorphous ribbon produced at 1350 degrees C, the ribbon fabricated at 1500 degrees C exhibited smoother edges, smaller thickness variation, higher thermal stability, a more uniform microstructure, and superior magnetic properties. This phenomenon could be attributed to the more uniform melt structure at higher temperatures, leading to a more homogeneous amorphous ribbon during the cooling process. A higher melt temperature enhanced the fluidity of the melt, promoting the formation of a sufficient molten pool and reducing fluctuations within the pool. A high melt temperature inhibited the precipitation of nanoclusters in the amorphous ribbons, improved atomic spacing, and enhanced atomic motion. The reduced coercivity and core loss were due to the significant decrease in interlayer eddy current losses, which resulted in excellent surface morphology. The enhanced melt fluidity at higher melt temperatures facilitated the thickness distribution of the amorphous ribbon, leading to a smoother surface morphology, consequently, superior soft magnetic properties.

To obtain an alloy with excellent mechanical properties and low cost, Fe62+xNi13-xCr15Si7Al3 (at. %) medium entropy alloys (MEAs) were designed in this work. The as-cast microstructure transformed from dual-phase BCC+FCC to single-phase BCC with Ni content decreasing from 13 to 11 at. % for Fe62+xNi13-xCr15Si7Al3 (x=0, 1 and 2). It was found that as-cast Fe63Ni12Cr15Si7Al3 alloy (BCC + very little FCC) with brittle fracture characteristics can still be cold rolled even to 85%. The facile thermomechanical treatment leads to the exceptional mechanical properties of the cast brittle Fe63Ni12Cr15Si7Al3 MEA. Specifically, its yield strength (YS) and ultimate tensile strength (UTS) at 77 K reach impressive values of 1424 and 1814 MPa, respectively, and the uniform elongation (UE) remains 36%. This is due to multi-reinforcement synergy mechanisms including ultra-fine grains, B2 nano-precipitations, annealing twins, high-density dislocations and transformation induced plasticity (TRIP) effect during deformation. Furthermore, the YS, UTS and UE of the MEA at 298 K is 882 MPa, 1077 MPa and 21%. The deformable B2 particles can contribute to both strength and plasticity during tension at 298 K, which is different from the result caused mainly by bypass mechanism at 77 K. This work provides a new idea for performance enhancement of Fe-based MEAs by designing and ascertaining critical element content.

Fe-based nanocrystalline alloys with high saturation magnetic flux density (Bs) show significant potential for electrical and electronic applications. However, their large-scale industrial production remains challenging due to limited glass forming ability (GFA). In this work, we systematically investigated the GFA, thermal stability and soft magnetic properties of Fe85-xNi2B13Cx (x = 0, 1, 2, 3, 4) alloys. The experimental results indicated that appropriate carbon addition can significantly enhance both GFA and soft magnetic properties. Specially, when the carbon content exceeds 2 at. %, the as-spun alloy ribbons retain a fully amorphous structure at a wheel speed of 40 m/s. As the carbon content increases from 0 to 4 at. %, Tx1 rises from 628 K to 688 K and Tx2 increases from 748 K to 768 K, while the C2 alloy maintains a substantial Delta T over 104 K. After rapid annealing at 753 K for 6 s, the Fe83Ni2B13C2 alloy exhibits improved soft magnetic properties, achieving Bs of 1.87 T and Hc of 8.2 A/m. This research provides valuable insights into the development and practical industrial application of Fe-based soft magnetic nanocrystalline alloys with high Bs.

Reducing the core losses of motors and transformers is an important way to address the global environment and energy resource problems. Soft magnetic composites (SMCs) comprising of electrically insulated ferromagnetic powder has shown vast potential for applications at low to high applied frequencies. In this work, in -situ steam oxidation was used to coat the surface of amorphous Fe75.5Si4B6P8C6Mo0.5 powder with an insulating layer. The thickness and composition of the Fe -oxide layer were controlled by tuning the in -situ steam oxidation time, and more cracks and Fe2+ were formed on the powder surface with the extension of oxidation time. The magnetic Feoxide layer of amorphous powder not only plays an insulating role to reduce the Pe, but also affects the magnetic coupling of particles that leads to the change of Ph. And the amorphous SMCs with 10 h in -situ steam oxidation treatment exhibits good comprehensive soft magnetic properties, i.e., the magnetic loss (Pcv), effective permeability (mu e) and DC bias are 61.44 W/kg (50 mT, 100 kHz), 30.4 (to 10 MHz) and 71.5% (100 Oe), respectively.

The yield strength of face-centered cubic (FCC) alloy is insufficient, resulting in the limitation in bear-load applications and the reduced competitiveness among advanced structural materials. In this work, by modulating thermomechanical processing, the route combining dual phase and heterogeneous structure of grain is proposed to optimize the balance of strength and ductility in FeCrNi2Nb0.1 medium-entropy alloy (MEA). It is found that the processing method via cryogenic-temperature rolling and following annealing can result in heterogeneous microstructures consisting of fully recrystallized grains with annealing twins, non-recrystallized grains with highdensity of dislocation, and small-size dispersive Laves phase. The multi-scale heterogeneous microstructure of MEA exhibits an optimized strength and ductility (yield strength similar to 720 MPa, ultimate tensile strength similar to 920 MPa and uniform elongation similar to 23%), as well as considerable strain-hardening capacity. The harmonized strength and ductility can be attributed to the multiple strengthening mechanisms including grain boundary hardening, dislocation hardening, deformation twinning hardening and hetero-deformation-induced hardening. The results pay a feasible way to design dual-phase MEAs/HEAs with outstanding mechanical properties.

The industrialization of Fe-based amorphous alloys with high a saturation magnetic flux density (Bs) has been limited so far due to their inadequate amorphous forming ability (AFA). In this study, the effects of substituting Si with C on the AFA, thermal stability, and magnetic properties of Fe82Si6−xB9P3Cx (x = 0–6) alloys were systematically investigated. The experimental results demonstrate that the AFA, thermal stability, and soft magnetic properties can be significantly enhanced by the addition of C. Specifically, at a copper wheel velocity of 40 m/s, the Fe82Si6−xB9P3Cx (x = 2, 3, 4, 5 and 6) alloy ribbons exhibit a fully amorphous structure in the as-spun state. The activation energy required for the α-Fe phase crystallization process in Fe82Si6−xB9P3Cx (x = 0, 2, 4, and 6) alloys is determined to be 326.74, 390.69, 441.06, and 183.87 kJ/mol, respectively. Among all of the compositions studied, the Fe82Si4B9P3C2 alloy exhibits optimized soft magnetic properties, including a low coercivity (Hc) of 1.7 A/m, a high effective permeability (μe) of 10608 (f = 1 kHz), and a relatively high Bs of 1.61 T. These improvements may be attributed to a more homogeneous and optimized magnetic domain structure being achieved through proper C addition. This work holds significant implications for the advancement of Fe-based soft magnetic amorphous alloys with high Bs.

In this work, the surface crystallization behavior and magnetic properties of Fe81.5+xSi3B10−xP3.5C0.2Cu0.8Nb1 nanocrystalline alloys were systematically investigated. It was found that the surface crystallization phenomenon occurs at the free-side surface of the as-cast ribbon, and the temperature interval between the first and second crystallization peaks increased to 159 °C with an increase in Fe content up to 83.5 at.