Soft Magnetic Alloys Research Articles

The influence of the granulometric composition of powders of steels and precision alloys and their melting modes by LPBF ON porosity

The results of the experimental study of powder materials of various brands and classes (stainless steel, precision soft and hard magnetic alloys) are presented, the influence of their parameters (particles, fracture, fluidity, bulk density) on the properties of finite additive samples is evaluated. The impact of melting parameters on the porosity of additive samples has been studied.

Influence of heat treatment on phase and structure formation and magnetic properties of soft magnetic alloy 80NKhS manufactured by additive technology

The evolution of the structure and phase composition of the soft magnetic alloy 80NKhS, produced by selective laser melting and annealed at different temperatures, was studied by light and electron microscopy, X-ray spectral and X-ray structural analyses. It has been established that a weakening of structural anisotropy and an increase in the average grain size occurs only at temperatures of 1250°C, associated with the oxides of Al, Ti, Si, Mn, Cr and nickel silicide previously formed during additive alloying. These phases have high thermal stability and inhibit grain growth, limiting the magnetic permeability of the alloy. To achieve the required level of magnetic properties, the soft magnetic alloy 80NKhS, manufactured by the additive method, must be annealed at higher temperatures than specified in GOST 10160–75.

Reducing the annealing heating rate sensitivity of Fe83.5Si3B10P2Cu1.5 soft magnetic nanocrystalline alloy by adjusting the melt spinning cooling rate

Reducing the annealing heating rate sensitivity of Fe83.5Si3B10P2Cu1.5 soft magnetic nanocrystalline alloy by adjusting the melt spinning cooling rate

Interface-driven microwave absorption enhancement in Mn-optimized Co2FeAl1-xMnx Heusler alloys

To address the urgent need for efficient and stable electromagnetic wave absorbing materials for electromagnetic interference (EMI) protection, we synthesized Co2FeAl1−xMnx Heusler soft magnetic alloys using a high-energy planetary ball milling method. We comprehensively analyzed their structural characteristics, surface morphology, magnetic properties, and electromagnetic parameters to explore their potential in electromagnetic wave absorption. The results show that incorporating manganese (Mn) significantly changes the alloys' crystal structure, surface morphology, and magnetic properties, greatly enhancing their wave absorption performance. The Mn doping specifically alters the surface morphology, which plays a crucial role in influencing the wave absorption characteristics of the Heusler alloys. When the Mn content increased to 25 %, the sample exhibits superior wave absorption, achieving the maximum reflection loss of −44.83 dB at 13.68 GHz with a thickness of 1.5 mm and an effective absorption bandwidth of 5.52 GHz. With a significant increase in the aspect ratio and noticeable changes in surface morphology, the sample with 75 % Mn content shows exceptional performance with an effective absorption bandwidth of 5.68 GHz, representing the highest effective absorption bandwidth in single-phase Heusler alloys. The Mn doping strategy effectively improves the material's impedance matching by adjusting its permittivity and permeability, facilitating multiple polarization relaxation mechanisms and significantly enhancing the alloys' electromagnetic wave absorption efficiency. Our study provides detailed experimental data for optimizing the electromagnetic wave absorption characteristics of Heusler alloys, verifies their practical application potential, and paves the way for developing new high-performance electromagnetic wave absorbing materials.

Correlation of microstructure and magnetic softness of Si-microalloying FeNiBCuSi nanocrystalline alloy revealed by nanoindentation

Abstract Compared to the commercial soft-magnetic alloys, the high saturation magnetic flux density (B s) and low coercivity (H c) of post-developed novel nanocrystalline alloys tend to realize the miniaturization and lightweight of electronic products, thus attracting great attention. In this work, we designed a new FeNiBCuSi formulation with a novel atomic ratio, and the microstructure evolution and magnetic softness were investigated. Microstructure analysis revealed that the amount of Si prompted the differential chemical fluctuations of Cu element, favoring the different nucleation and growth processes of α-Fe nanocrystals. Furthermore, microstructural defects associated with chemical heterogeneities were unveiled using the Maxwell-Voigt model with two Kelvin units and one Maxwell unit based on creeping analysis by nanoindentation. The defect, with respect to a long relaxation time in relaxation spectra, was more likely to induce the formation of crystal nucleus that ultimately evolved into the α-Fe nanocrystals. As a result, Fe84Ni2B12.5Cu1Si0.5 alloy with refined uniform nanocrystalline microstructure exhibited excellent magnetic softness, including a high B s of 1.79 T and very low H c of 2.8 A/m. Our finding offers new insight into the influence of activated defects associated with chemical heterogeneities on microstructures of nanocrystalline alloy with excellent magnetic softness.

Laser powder bed fusion of a nanocrystalline Finemet Fe-based alloy for soft magnetic applications

The aim of this work is to explore the laser powder bed fusion (LPBF) processability window of the nanocrystalline soft magnetic Finemet alloy. With that purpose, several laser power and scan speed values and a meander scanning strategy were probed to process simple geometry specimens. Good dimensional accuracy was obtained within the entire processing window investigated. Relative densities as high as 89% were achieved for processing conditions including high laser power and low scan speeds. The fraction of amorphous phase, which peaked at 49%, was found to be mostly dependent on the scan speed and only slightly influenced by the laser power. The microstructure of the crystalline domains is formed by ultrafine, equiaxed grains with random orientations. Irrespective of the processing conditions, the LPBF-processed samples exhibit a similar saturation magnetization, lower permeability, and higher coercivity than fully amorphous melt-spun ribbons of the same composition. The coercive field of the additively manufactured specimens is fairly independent of the relative density and exhibits a moderate inverse variation with the amorphous fraction. Consistent with earlier works, this study suggests that the average grain size is an important contributor to coercivity.

Composition and microstructure engineering of Fe–Si–Co soft magnetic alloys with enhanced performance

Composition and microstructure engineering of Fe–Si–Co soft magnetic alloys with enhanced performance

Magnetization processes features in the tapes of cobalt-based amorphous alloy

Studies of the amorphous cobalt-based soft magnetic alloy AMAG-172 (Co–Ni–Fe–Cr–Mn–Si–B) from different manufacturers have shown that in the as-quenched state there is nonuniformity of the magnetic characteristics, and therefore the level of internal stresses across the width of the tape produced by MSTATOR (Borovichi) significantly lower. However, similar to the tape produced by NIIMET (Kaluga), there is nonuniformity of the tape in thickness, which contributes to the formation of a bimodal field dependence of magnetic permeability.This may be a consequence of the non-uniform concentration along the width of the tape of hydrogen and oxygen atoms embedded in its surface during interaction with atmospheric vapor and the presence of temperature gradients during the manufacturing process. A stepwise shape of the initial sections of the magnetization curves in the region of the first maximum of magnetic permeability was discovered. The abrupt nature of the magnetization processes in the region of weak fields allows us to conclude that in the samples of tape produced by MSTATOR, the formation of the first maximum of the field dependence is associated with an independent magnetization reversal of the surface layer, while the main layer of the tape participates in the formation of the second maximum. The smoothed shape of the stepped initial section of the magnetization curve of samples produced by NIIMET corresponds to the gradual involvement of the main layer of the tape in the processes of magnetization and remagnetization. A comparison of the hysteresis loops of both parts of the tape, measured in the same magnetic field region, shows that the field shift of the hysteresis loops is associated with the interlayer interaction of the surface and volume of the tape, and the formation of asymmetric hysteresis loops occurs with the participation of the second layer with its gradual involvement in the processes of magnetization and magnetization reversal.

Additively manufactured FeCoNiSi0.2 alloy with excellent soft magnetic and mechanical properties through texture engineering

High-entropy alloys are widely used as structural materials and hold potential as functional materials. This study aims to develop a soft magnetic medium entropy alloy FeCoNiSi0.2 (Si0.2 MEA) with excellent soft magnetic properties and higher ductility using additive manufacturing technology. The microstructure of Si0.2 MEA is characterized by texture and large grains, with a single FCC phase structure. The texture strength of MEA initially increases and then decreases with the addition of Si, with Si0.1 MEA exhibiting the strongest fiber texture. Among the four FeCoNiSix MEAs, Si0.2 MEA demonstrates the best tensile properties (i.e. δ ∼39 %, σ0.2–287 MPA, σb∼551 MPa). The correlation generalized stacking fault energy calculation model indicates that Si0.2 MEA has the lowest generalized stacking fault energy (∼7 mJ/m2), suggesting superior ductility. The synergistic effect of texture and large grains promotes the formation of a magnetization “easy axis”, which makes Si0.2 MEA exhibit the best soft magnetic properties (Ms:150emu/g, Hc:1.04Oe). These results provide a new paradigm for developing laser additively manufactured soft magnetic medium entropy alloy.

Tailoring microstructure in a soft-magnetic Fe-based amorphous-nanocrystalline alloy for high resistivity according to electrical percolation threshold

Superior soft-magnetic materials are necessary for the development of modern magnetic devices with energy-saving and high-power density requirements. However, improving the magnetism by nanocrystallization always brings about the sacrifice of resistivity, presenting a common trade-off in Fe-based amorphous-nanocrystalline alloys. Here, the comprehensive merits of both superior soft-magnetic properties (high saturation magnetization of 1.81 T and low coercivity of 3.8 A/m) and high resistivity of 117.2 μΩ·cm were obtained by precisely tailoring amorphous-nanocrystalline microstructure close to electrical percolation threshold for a Fe82.5B12P2C1Cu0.5Co2 amorphous alloy. The soft-magnetic properties are attributed to the low magnetic anisotropy stemming from high nuclei number density and ultrafine nanocrystalline grains of 9.2 nm. The high resistivity is associated with the electrical percolation behavior with a nanocrystalline volume threshold of 14.8 % in the composite alloy. The results provide an effective strategy to overcome the trade-off in traditional amorphous-nanocrystalline alloys, significant for applications in high-frequency, high-power, and energy-saving devices.

Exploring Microstructure and Magnetic Domain Evolution in the As-cast Soft Magnetic Fe74B20Nb2Hf2Si2 Alloy: A Comprehensive Study Using STEM, Lorentz TEM, and LM-STEM DPC Microscopy

This study delves into subtle changes in the microstructure and domain arrangement of a Fe74B20Nb2Hf2Si2 soft magnetic amorphous alloy. Utilizing transmission electron microscopy in Lorentz mode, low-magnification STEM, and differential phase contrast analysis (DPC), the research explores both the as-cast state and annealed samples. The results confirmed the formation of α-Fe, Fe23B6, Fe2(Hf, Nb), and Fe2B crystalline phases with increasing annealing temperature. Consequently, these crystallization stages induce significant alterations in magnetic domain size and spatial distribution due to microstructural changes. As the crystallization temperature rises, the volume fraction of crystalline phases increases, leading to modifications in the arrangement and size of magnetic domains. The decrease in magnetic domain size, associated with the formation of pinning sites during heat treatment, leads to alterations in soft magnetic properties. This includes an increase in coercivity (Hc) up to 40 A/m in the sample annealed at the temperature range of the third crystallization stage compared to the as-cast sample (1.5 A/m). Furthermore, as the annealing temperature rises, there is a corresponding increase in saturation magnetization (Ms), which reached to 1.71 T in the sample annealed within the temperature range of the third crystallization stage. These findings hold substantial implications for the practical applications of the Fe-based soft bulk metallic glasses (BMGs) alloy across various industries.

Integrative approach to enhance the soft magnetic properties of Co35Cr5Fe10Ni30Ti20-xAlx (x= 10, 15, 20) high entropy alloys

High Entropy Alloys (HEAs) are advanced materials having multi-functional properties. These materials have the potential to overcome the shortcomings of conventional soft magnetic alloys. In this study, an integrative approach is adopted to enhance the magnetic and electrical properties of CoCrFeNiTi-based HEA by the addition of Al in different content for Ti and annealing for different temperatures and durations. Firstly, Co35Cr5Fe10Ni30Ti20-xAlx (x= 10, 15, 20) HEAs were synthesized through mechanical alloying and investigated for phase formation and magnetic properties. Major fcc with minor bcc and intermetallic R phase has formed for Co35Cr5Fe10Ni30Ti10Al10 and Co35Cr5Fe10Ni30Ti5Al15 HEAs. However, the mixture of fcc and bcc phase with a minor fraction of σ phase has been found for Co35Cr5Fe10Ni30Al20 HEA. The value of Ms is slightly decreased for Co35Cr5Fe10Ni30Ti5Al15 HEA as compared to Co35Cr5Fe10Ni30Ti10Al10 HEA, but for Co35Cr5Fe10Ni30Al20 HEA, the value of Ms has drastically decreased when Ti completely removed for Al. Among these three synthesized HEAs, the highest value of Ms is found for Co35Cr5Fe10Ni30Ti10Al10 HEA (Ms=78 emu/g). Further, we investigated the effect of annealing at different temperatures for 2 h on phase evolution, microstructure, and their correlation with magnetic properties of Co35Cr5Fe10Ni30Ti10Al10 HEA. Among annealed HEA, 700°C annealed Co35Cr5Fe10Ni30Ti10Al10 HEA has high Ms (104 emu/g), and the value of Hc was found to be 29 Oe. The long-duration annealing is also performed at 700°C for 10 h to improve the magnetic properties of the as-synthesized Co35Cr5Fe10Ni30Ti10Al10 HEA and found good soft magnetic behaviour (Ms=103.5 emu/g and Hc=13 Oe). Moreover, the electrical resistivity of the long-duration annealed Co35Cr5Fe10Ni30Ti10Al10 HEA is also recorded in the temperature range 2–350 K, and the value of electrical resistivity at 2 K and 300 K is found to be 180.2 ×102 µΩ.cm and 200.80 ×102 µΩ.cm, respectively. The found value of electrical resistivity is the highest value of resistivity reported so far in the case of soft magnetic HEA.

Influence of annealing treatment on grain growth, texture and magnetic properties of a selective laser melted Fe-6.5 wt% Si alloy

The high-density Fe-6.5 wt% Si soft magnetic alloy samples were prepared using selective laser melting (SLM) technology. Annealing treatments with different temperatures were employed to promote grain growth. The microstructure, texture and magnetic hysteresis loops were characterized, aiming to investigate the relationship between microstructure and magnetic properties. The as-printed Fe-6.5 wt% Si alloy had weak texture and low density of ordered phases, and was featured by coarse grains in the top-view section and columnar grains in the side-view section. After annealing at 800 °C–1000 °C, the textures were slightly weakened, while the grain growth was not significant. Increasing the annealing temperature to 1100 °C led to abnormal grain growth behaviors. The grains of the as-printed Fe-6.5 wt% Si alloy showed randomly abnormal growth behaviors rather than oriented growth, which may be related to the low stored energy and initial size advantage before annealing. After annealed at 1100 °C for 1 h, the abnormal grain growth and the formation of large Goss ({110}<001>) and Cube ({100}<001>) grains resulted in microstructure coarsening and texture optimization. Thus, the corresponding ring-shaped sample exhibited excellent magnetic performance. The magnetic induction B8 is 1.21 T, the maximum relative permeability is 14.71 × 103 and the core loss P10/50 is 11.69 W/kg.

Study on the soft magnetic properties, corrosion, and wear resistance of Ni–Co–W coatings deposited via laser-assisted electrochemical technique: Potential applications in advanced electromagnetic devices

Ni–Co–W alloy possesses several advantages, including exceptional hardness, outstanding wear resistance, and remarkable high-temperature resistance. The coating exhibits favorable soft magnetic performance when the Co content is high. This study combines the introduction of Co element and laser irradiation to explore the changing mechanisms in the soft magnetic properties, corrosion resistance, and wear resistance. Coatings are electrochemically deposited on copper substrates employing a pulsed current, and a Ni–Co–W coating is assisted-deposited utilizing a picosecond laser with a single pulse energy of 10μJ. The experimental results reveal that when 12 g/L of CoSO4·7 H2O is added to the electrolyte, the Co elements significantly improve the soft magnetic properties of the Ni–Co–W alloy. Meanwhile, the reduction of WO42− is also promoted and the W content is increased (nearly 2.6 times, 1.95 Wt%), thereby obtaining microhardness, corrosion resistance, and wear resistance superior to Ni–W. Laser irradiation effectively increases the W content (nearly 2.3 times, 4.52 Wt%) while reducing surface defect. The increased W content alters the internal crystal structure and refines the grain. Moreover, laser irradiation significantly improves the soft magnetic properties (a 33.17 % increase in Ms, a 12.97 % increase in Hc, and a 5.66 % increase in Mr). This study achieves soft magnetic coatings with excellent corrosion and wear resistance through a laser electrochemical deposition process. It provides new processing ideas and methods for preparing soft magnetic alloy coatings and has broad application prospects in magnetic thin film storage devices and high-frequency electromagnetic devices.

Indirect effect of Si on the ferromagnetic transformation of Mn in FeCoMnAlSi high-entropy soft magnetic alloy

In this study, we examined the indirect impact of Si on the ferromagnetic transformation of Mn in (Fe0.8Co0.2)80-xMn10Al10Six (x = 0, 1, 2, 3, 4, & 5 at%) high-entropy soft magnetic alloys. Our findings indicate strong correlation between Si and the ferromagnetic transformation, substantiated by simulation calculations. With Si content increasing the saturation magnetization of the system exhibits a distinctive trend of an initial increase followed by a subsequent decrease. Notably, the coercivity consistently decreases with x increases. Remarkably, when x equals 3, the soft magnetic properties of the system reach an optimal state, characterized by a saturation magnetization of 186.5 emu·g−1 and a coercivity of 1.6 Oe. The density of states and magnetic moment of the system are obtained by simulation calculation. Notably, the average atomic magnetic moment of Mn (1.642 μB) surpasses that of Co (1.434 μB), suggesting the excellent soft magnetic properties inherent in the system.

Design of quaternary FeSiCoNi soft magnetic alloys towards large-power and high-frequency applications

The growing trend of large power and high frequency in electromagnetic conversion applications urges advancements in the saturation magnetization (Ms), effective permeability (μe) and core loss (Pcv) of soft magnetic composites (SMCs). Such performance depends largely on the Ms and coercivity (Hc) of the magnetic alloys as the main component of the SMCs. It is however, difficult to simultaneously achieve large Ms and low Hc via binary and ternary alloy systems. Here, quaternary Fe81-xSi15Co4Nix (x = 0, 3, 6 at%) soft magnetic alloys have been designed with the effect of Ni addition on the microstructure and magnetic properties of the alloy revealed. On one hand, rational incorporation of Co and Ni maintains the relatively large Ms. On the other hand, the Ni enters into the A2 lattice and promotes its transition into DO3 ordered phase as confirmed by both experimental characterization and first-principles calculations. Such microstructural evolution gives rise to initially decreased magnetocrystalline anisotropy (K1) followed by increasing due to the competitive reduction effect of Ni addition and increment effect of DO3 formation. The magnetostriction constants (λs) increases monotonously from negative to positive values with raised Ni content. This is accompanied with the decrease in 90° domain walls and increase in 180° domain walls as revealed by Lorentz microscopy. Combined lowest K1 and λs as well as optimized domain structure result in the lowest Hc for the Fe78Si15Co4Ni3 alloy. The corresponding SMCs exhibit excellent performance with the μe of 160.6 and the Pcv of 288.4 mW/cm3 (50 mT, 100 kHz) combined with high Ms of 177.3 emu/g, superior to other FeSi-based SMCs.

Development of high-performance Fe-rich Fe–P–C amorphous alloys with enhanced magnetization and low coercivity

Using melt spinning technology, we successfully synthesized a series of Fe-rich Fe–P–C amorphous alloys exhibiting high saturation magnetization (Bs), low coercivity (Hc), and excellent bending ductility. These alloys exhibit low Hc values ranging from 4.1 to 7.2 A/m, and high Bs values ranging from 1.58 to 1.68 ​T. Particularly, after annealing at 588 ​K for 900 ​s, the Fe83P11C6 amorphous alloy showed extraordinary soft magnetic properties: Bs up to 1.68 ​T, Hc only 4.7 A/m, and the core loss at approximately 1.5 ​W/kg under the condition of 0.5 ​T and 50 ​Hz, all of which surpass the reported Fe–P–C ternary amorphous and nanocrystalline alloys. These Fe-rich Fe–P–C alloy ribbon samples exhibit favorable bending ductility in both the as-spun and annealed states. Their simple alloy composition, outstanding soft magnetic properties, and excellent flexibility collectively make these soft magnetic alloys highly promising candidate materials for industrial applications.

Short-Range Order in Gallium Solid Solutions in α-Iron

Short-range order in soft magnetic FeGa alloys containing from 3 to 25 at % Ga was studied using nuclear gamma resonance (Mössbauer) spectroscopy. The Mössbauer spectra were analyzed via fitting with subspectra corresponding to different configurations of the neighborhoods of the Fe atoms with Ga in the first and second coordination shells. It has been shown that in samples of alloys containing from 3 to 17 at % gallium, the short-range order is almost independent of the heat treatment conditions (quenching from a paramagnetic state or exposure in a ferromagnetic state) and is characterized by the presence of pairs of Ga atoms in the position of the second neighbors (B2-type clusters). At a Ga content of 17 to 21 at %, the portion of B2 clusters turns out to be significantly higher after quenching than after annealing, which correlates with the observed effect of heat treatment on the magnitude of magnetostriction. As the Ga concentration (21–25 at %) further increases, the observed features in the distribution of Ga atoms indicate the appearance and growth of D03 phase regions.

A unique Fe-based soft magnetic alloy and its magnetic softening mechanism

Fe-based amorphous alloys with good glass-forming ability (GFA), superior soft magnetic properties, low cost, and a wide heat treatment window have long been pursued in the field of soft magnetic materials due to their importance for mass production and broad applications. In the present study, by strategically adjusting the composition of a low-cost Fe-Si-B-P-Cu-C alloy, we achieved a saturation magnetization (Ms) of approximately 186 emu/g and a coercivity (Hc) of about 6 A/m for the Fe82.5 alloy with a good GFA. Specifically, the limited Cu content and suitable contents of metalloid elements played pivotal roles in enhancing the nuclei barrier and stabilizing the amorphous matrix. This, in turn, facilitated the formation of a finely uniform nanocrystalline structure dispersed within the amorphous matrix, enhancing soft magnetic properties during annealing. Notably, this magnetic softening behavior occurred at a lower heating rate. Structural characterizations revealed that a transient metalloid-rich shell and a stable amorphous matrix contributed to the slow growth of the α-Fe (Si) during prolonged isothermal annealing. This is in contrast to the agglomeration of small nanograins into larger clusters at high heating rates, which enhances the versatility and potential applicability of the alloy. The successful development of this novel nanocrystalline alloy offers promising guidance for addressing the challenges associated with the mass production of soft magnetic materials.

High‑silicon electrical steel powders aimed for additive manufacturing

The Fe6.5Si soft magnetic alloy exhibits promising magnetic properties for energy applications, including near-zero magnetostriction, low magnetocrystalline anisotropy, and higher electrical resistivity than conventional electrical steels. However, its brittleness impedes industrial use. Recent advances in powder-based additive manufacturing show potential for processing high‑silicon electrical steels. This study focuses on the production cycle and properties of feedstock powder, which are crucial for such applications. Fe6.5Si alloy powders were produced via closed-coupled gas atomization. Comprehensive analysis covered mass balance, particle size distribution, powder flow, morphology, density, rheological properties, and thermal and magnetic behavior. Results suggest the feasibility of producing suitable Fe6.5Si alloy powder via gas atomization, enabling additive manufacturing of the next generation of medium/high-frequency electrical motors. The powder exhibited desirable characteristics within the size ranges applicable to laser powder bed fusion (20–75 μm) and direct energy deposition (75–106 μm), showing excellent flow behavior and morphological suitability for additive manufacturing.