Nanocrystalline Alloy Ribbons Research Articles

Microstructure evolution, stress state and electromagnetic performance of Fe-based nanocrystalline alloy induced by stress-annealing

Stress-induced anisotropy has been applied for FeSiBCuNb nanocrystalline alloy ribbons in transformers with large direct current (DC) component. However, the physical mechanism of anisotropy induced by stress annealing during crystallization remains controversial. Here, a systematic study was conducted on the microstructure, residual stress state, dynamic domain structure and properties of the stress-annealed FeSiBCuNb nanocrystalline ribbons. Present results demonstrate that, the increase of the applied stress greatly increases the residual tensile stress and induces lattice distortion, which acts as pinning site during magnetization, resulting in enhanced domain-wall energy and narrower wall width. Meanwhile, stress annealing promotes the flattening of hysteresis loops and decreases the effective permeability, which improves the DC-bias characteristics of the ribbons, thereby promoting the transition from “hard saturation” to “soft saturation” behavior. Also, stress-induced grain refinement is beneficial to obtaining high hardness. Owing to the stress-induced anisotropy, the stress-annealed sample with applied stress of 113 MPa exhibits excellent combined properties, including low constant effective permeability of 438 at wide frequency range (1 kHz–8 MHz), high DC-bias capability of 74% (30 Oe), low power loss of 49 kW/m3 (100 mT, 100 kHz), and high hardness of 644 HV. This discovery provides an insightful understanding of stress-induced anisotropy mechanism on the high-performance Fe-based nanocrystalline alloys.

XGBoost algorithm-assisted prediction of amorphous formability of Fe-based nanocrystalline precursor

The completely amorphous structure in the precursor is a significantly important prerequisite for obtaining the perfect amorphous-nanocrystalline duplex structure and the excellent soft magnetic properties of Fe-based nanocrystalline alloy ribbons (FNR). However, the correlation between the amorphous formability (AFA) and the key parameters of FNR precursors is not clear. Herein, a data-preprocessed dataset was established, consisting of 158 FNR samples with amorphous and crystallized precursors. This dataset includes features such as elements, thermal parameters, and calculated parameters. Pearson correlation analysis was performed to assess the linear correlation between any two features, resulting in the removal of eight features. Then the features importance was ranked by random forest (RF) algorithm, and top five key features (e.g., ΔT, VEC1, VEC, P, and B) were retained. A classification predictive model in that the structure of FNR precursors is amorphous or crystalline was constructed based on XGBoost algorithm. The accuracy of the classification model by confusion matrix analysis is up to 97.9 %. Furthermore, SHAP (SHapley Additive exPlanations) results reveal that crystallization temperature intervals (ΔT), valence electron concentration without Fe, Ni, and Co elements (VEC1), as well as valence electron concentration (VEC) play an important role in affecting AFA of FNR precursors. When ΔT > 142 °C, VEC1 > 0.69, and VEC >7.27, the FNR precursors readily obtain a fully amorphous structure. The outstanding classification accuracy and the elucidated correlation between the key features and AFA could guide the discovery of novel fully amorphous FNR precursors.

Magnetostriction of Fe-rich FeSiB(P)NbCu amorphous and nanocrystalline soft-magnetic alloys

The compositional effect of magneto-elastic and magnetostriction properties of Fe-rich Fe81B15−xPxSi2Nb1Cu1 (ii) Fe82B14−xPxSi2Nb1Cu1 and (iii) Fe83B13−xPxSi2Nb1Cu1 (x = 0, 4, 8) amorphous and annealed nanocrystalline alloy ribbons were investigated. The present study adds knowledge to the limited magnetostriction literature available for Fe-rich nanocrystalline alloys by systematically varying the Fe and P content. A combination of Becker-Kersten and small angle magnetization rotation (SAMR) techniques has been employed for the magnetostriction (λs) evaluation. Both the as-quenched and nanocrystalline ribbons exhibit large positive magnetostriction and show strong compositional dependence to the P content. In the as-quenched condition, 4 at% P addition shows maximum magneto-elastic response and magnetostriction constant, with Fe81B11P4Si2Nb1Cu1 alloy exhibiting a maximum of + 52 ppm and P-free Fe83B13Si2Nb1Cu1 alloy exhibiting a minimum of + 27 ppm. In the nanocrystalline state, a slight reduction of magnetostriction is seen for all alloys, with a maximum of + 32 ppm (4 at% P) and a minimum of + 22 ppm (P-free) in Fe83 at% alloys. The unusual large magnetostriction of optimally annealed samples is attributed to the relatively low crystal volume fraction (30–45%) of nanocrystalline ribbons. The lowest magnetostriction of Fe83B13Si2Nb1Cu1 alloy in both as-quenched and annealed state is explained based on ribbon structural heterogeneity consisting of crystal nuclei and textured α-Fe surface crystallization. The study reveals a contradictory response of magneto-crystal anisotropy (grain size reduction) and magneto-elastic anisotropy to the P addition and ribbon structural heterogeneity. The study discusses the implications of the large magneto-elastic anisotropy associated with Fe-rich nanocrystalline ribbons and the way forward for improving their magnetic softness.

Preparation and Electromagnetic Absorption Properties of Fe73.2Si16.2B6.6Nb3Cu1 Nanocrystalline Powder.

In order to decrease and control electromagnetic pollution, absorbing materials with better electromagnetic wave absorption properties should be developed. In this paper, a nanocrystalline alloy ribbon with the composition of Fe73.2Si16.2B6.6Nb3Cu1 was designed and prepared. Nanocrystalline alloy powder was obtained by high-energy ball milling treatment. The effects of ball milling time on the soft magnetic properties, microstructure, morphology, and electromagnetic wave absorption properties of alloy powder were investigated. The results showed that, as time increased, α-(Fe, Si) gradually transformed into the amorphous phase, and the maximum saturation magnetization (Ms) reached 135.25 emu/g. The nanocrystalline alloy powder was flakelike, and the minimum average particle size of the powder reached 6.87 μm. The alloy powder obtained by ball milling for 12 h had the best electromagnetic absorption performance, and the minimum reflection loss RLmin at the frequency of 6.52 GHz reached −46.15 dB (matched thickness was 3.5 mm). As time increased, the best matched frequency moved to the high-frequency direction, and the best matched thickness decreased, while the maximum effective absorption bandwidth ΔfRL<−10 dB was 7.22 GHz (10.78–18 GHz).

Effects of Nb and Mo additions on thermal behavior, microstructure and magnetic property of FeCoZrBGe alloy* *Project supported by the National Natural Science Foundation of China (Grant No. 51301075) and supported by Sinoma Institute of Materials Research (Guang Zhou) Co., Ltd.

Both Nb and Mo additions play a vital role in FeCo-based alloys and it is crucial to understand their roles and contents on thermal behavior, microstructural feature and magnetic property of alloys. Nanocrystalline alloy ribbons Fe40Co40Zr9 – y M y B10Ge1 (y = 0–4; M = Nb, Mo) were prepared by crystallizing the as-quenched amorphous alloys. The effects of Nb and Mo additions on structures and properties of the Fe40Co40Zr9B10Ge1 alloy are investigated systemically and compared. With increasing Nb or Mo content, the primary crystallization temperature, grain size of α-Fe(Co) phase and coercivity H c all decrease. Moreover, the effect of Mo addition on thermal behavior, microstructure and magnetic properties of the FeCoZrBGe alloy is greater compared to Nb addition. The gap between primary and secondary crystallization peaks of Mo-containing alloys is wider than that of Nb-containing alloys. Both grain size and H c of Mo-containing alloys are smaller than those of Nb-containing alloys. For Fe40Co40Zr9B10Ge1 alloy, high Mo addition proportion is better compared to high Nb addition proportion.

Influence of annealing temperature on nanocrystalline alloy’s excess loss parameters

In this paper, both nanocrystalline alloy (Fe73.5Cu1Nb3Si15.5B7) ribbon samples and toroidal samples (wound ribbon) are annealed at different temperatures in order to consider the influence of inner stress on the magnetization properties. Then the AC magnetization properties of these samples are measured. Combined with the measured results, the influence of inner stress on nanocrystalline alloy’s microstructure is analyzed quantitatively based on the loss separation principle and the statistical theory of loss. By comparing measured macroscopic magnetization characteristics and excess loss, the equivalent stress state of the toroidal sample is evaluated. Furthermore, two kinds of samples’ excess loss under different annealing temperatures are analyzed, and the effectiveness of stress relief at optimal annealing temperature is validated.

Significant improvement of soft magnetic properties for Fe-based nanocrystalline alloys by inhibiting surface crystallization via a magnetic field assisted melt-spinning process

Abstract Fe-based soft-magnetic amorphous and nanocrystalline ribbons made with a single-side fast-cooling process always suffer from the surface crystallization which deteriorates the magnetic properties and inhibits the wide applications. In this study, a static magnetic field assisted melt-spinning process was employed to prepare the typical Fe84.75Si2B9P3C0.5Cu0.75 alloy ribbon with an attractive application prospect. According to the comparative investigations of the crystallization behavior, structural evolution process and magnetic properties, it is found that the applied magnetic field can effectively inhibit the formation of compound phases and decrease the size of textured α-Fe grains in the surface layer of the as-spun ribbon. The Fe84.75Si2B9P3C0.5Cu0.75 samples made with low purity raw materials and under an optimal field exhibit superior magnetic properties, including a high saturation magnetization (Bs) over 1.82 T, low coercivity (Hc) of 8.5 A/m, high permeability (μ) of 2.76 × 104 at 1 kHz and much lower losses, after nanocrystallization by annealing. The apparent effect of the applied magnetic field was discussed from the disturbance of a Lorentz force of the fast-moving molten alloy and a magnetic force of preformed grains in a magnetic field during the melt-spinning process. These results provide a novel solution of surface crystallization and an effective route for improving magnetic properties of Fe-based amorphous and nanocrystalline alloy ribbons.

FeNbBP type nanocrystalline alloy with high B s of 1.64 T optimized by sputtered thin film method

The increasing of saturation magnetic flux density (Bs) in FeNbB type nanocrystalline alloy has been widely studied. The influence of additional element to improve Amorphous Forming Ability (AFA) in precursor was investigated using substrate temperature controlled sputtering method at 523K. The AFA was improved by the addition of P, Si, V, or Mo, was decreased by the addition of Y, Cu, or Ge. Especially, the addition of 1 at% P exhibited a good effect of obtaining 85 at% of maximum Fe content with high stable amorphous precursor. The addition of P or C increased Bs. The Fe85Nb6B8P1 nanocrystalline alloy ribbon showed stable amorphous phase as quenched, exhibited a homogeneous nanocrystalline structure composed of grains with 10 to 20 nm in diameter after nanocrystallization. The ribbon exhibited high Bs of 1.64T and low coercivity of 10 A/m.

Development of Block Cores Comprising High-&lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$B_{s}$ &lt;/tex-math&gt; &lt;/inline-formula&gt; Nanocrystalline Alloy Ribbon

Soft magnetic properties of block cores comprising Febal.Cu1Mo0.2Si4B14 nanocrystalline alloy ribbons (HBN core) were investigated. The HBN core shows a magnetic flux density at 2000 A/m (B2000) of 1.73 T, which is about 0.2 T higher than that of the core comprising Fe-based amorphous alloy ribbons (Fe-AM core). The core loss at 200 mT and 10 kHz is 8.5 W/kg, two thirds of that of the Fe-AM core. The coefficient of the excess eddy current loss for the HBN core is one half of that of the Fe-AM core; the difference in core loss is prominent at higher frequencies.

Core loss analysis of Finemet type nanocrystalline alloy ribbon with different thickness

Nanocrystalline soft magnetic materials are widely used in power electronic applications due to their high permeability, magnetization and low core loss. In this paper, Fe73.5Cu1Nb3Si15.5B7 (at%) nanocrystalline alloy ribbons, with ultra-thin thickness of 14µm, and also 18 and 22µm, were prepared by a planar flow casting method with a single roller device. Soft magnetic properties of these ribbons were analyzed after nanocrystallization annealing. The experiments were conducted on toroidal samples using IWATSU B-H Analyzer over a frequency range of 10–100kHz, at induction amplitudes of 100–500mT, at room temperature. It was found that the excess eddy current loss Pex was the dominant factor in the overall core loss above 10kHz. The toroidal samples made of the 14µm thickness ribbon exhibit very low total core loss of 48W/kg at a frequency of 100kHz and magnetic flux density of 300 mT. The ratio of the Pex was up to 89% at 100kHz. The ribbon with lower thickness exhibits lower Pex and therefore lower total core loss. The domain structure evidences were found. It indicates that the ribbons with small thickness are preferable for application in high frequency condition.

High B s Fe-based nanocrystalline alloy with high impurity tolerance

High B s Fe82.5Si3B13P0.5C0.2Cu0.8 alloys with high impurity tolerance were successfully developed and prepared into ribbons with fully amorphous and uniform nanocrystalline microstructure. By comparing samples made with industrial grade and pure raw materials, it is found that the impurities in the commonly used industrial grade raw materials mainly affect the amorphous forming ability and amorphous structure of the as-spun ribbons. The effects of impurities on crystallization behaviors and magnetic properties can be inhibited in the amorphous ribbon production process for the alloys with a high impurity tolerance. The Fe82.5Si3B13P0.5C0.2Cu0.8 nanocrystalline alloy ribbons prepared with industrial grade raw materials exhibit excellent magnetic properties, containing high B s over 1.79 T, low H c of 9.5 A/m and maximum permeability (μ m) of 4 × 104, which are similar to the samples made with pure raw materials with unacceptable high cost. Combining the low cost of raw materials, good manufacturability and excellent magnetic properties, the present Fe82.5Si3B13P0.5C0.2Cu0.8 alloy will become a promising candidate for mass production and also provide a good reference for future development of high B s nanocrystalline alloys.

Effect of surface crystallization on magnetic properties of Fe82Cu1Si4B11.5Nb1.5 nanocrystalline alloy ribbons

In this study, Fe82Cu1Si4B11.5Nb1.5 nanocrystalline alloy ribbons with completely amorphous structure and surface crystallization were prepared using melt-spinning technique with wheel speeds of 45m/s, 35m/s and 25m/s. The effect of surface crystallization layers on the soft-magnetic properties, core loss and dynamic magnetization process were systematically investigated. Moreover, the permeability-frequency spectra were measured as a function of the AC magnetic field, ranging from 1 to 75A/m. It was found that decreasing the melt-spinning wheel speed can widen the annealing temperature range and the coercivity increases with the increase of surface crystallization. Excessive crystallization layers will increase the pinning field (Hp), which will lead to an increase of magnetic anisotropy constant K and eventually decrease the effective permeability. The crystallization mechanism of the Fe82Cu1Si4B11.5Nb1.5 nanocrystalline alloy ribbons with surface crystallization layers was discussed from the aspects of diffusion and competitive processes, which is helpful for further understanding the nanocrystallization process.

Soft Magnetic Properties of Magnetic Cores Assembled With a High $B_{s}$ Fe-Based Nanocrystalline Alloy

Soft magnetic properties of magnetic cores assembled with Fe 81.8 Cu 1.0 Mo 0.2 Si 4 B 14 nanocrystalline alloy ribbon are discussed. The nanocrystalline alloy ribbon was cast in an amorphous phase by a melt quenching method, and a nanocrystalline phase was obtained by high-heating rate annealing. A medium-size toroidal core assembled with this nanocrystalline alloy ribbon exhibits magnetic flux density B 800 at 800 A/m of 1.74 T, core loss P 16/50 at 50 Hz, and at 1.5 T of 0.29 W/kg. A racetrack-shaped core, which includes curved and straight sections in the same core, exhibits core losses at 1.0 T and at 400 Hz and 1 kHz of 1.5 and 5 W/kg, respectively. These core losses are as low as those of Fe-based amorphous alloys. A medium-size toroidal core assembled with this nanocrystalline alloy ribbon, secondarily annealed under a perpendicular magnetic field, exhibits core loss P 2/10k at 0.2 T and at 10 kHz of 2 W/kg. This value of core loss is one of the lowest values for the metallic magnetic cores, which have a saturation induction B s higher than 1.5 T. A core assembled with this material can be used in several applications from low to medium frequency ranges. Since this material exhibits a higher B s and one half of the saturation magnetostriction λ s of Fe-based amorphous alloys with comparable core losses, the most possible applications are in such applications as distribution transformers and inductors in power electronics.

Crystallization induced ordering of hard magnetic L1 phase in melt-spun FeNi-based ribbons

The microstructure of newly developed hard magnetic Fe42Ni41.3SixB12-xP4Cu0.7 (x = 2 to 8 at%) nanocrystalline alloy ribbons has been studied by transmission electron microscopy (TEM) and electron diffraction. A high-density polycrystalline grains, ∼30 nm in size, were formed in a ribbon after annealing at 673 K for 288 hours. Elemental mapping of the annealed specimen revealed the coexistence of three regions, Fe-rich, Ni-rich, and nearly equiatomic Fe-Ni, with areal fractions of 37%, 40%, and 23 %, respectively. The equiatomic L10-type ordered phase of FeNi was detected in between the Fe and Ni-rich phases. The presence of superlattice reflections in nanobeam electron diffraction patterns confirmed the formation of the hard magnetic L10 phase beyond any doubt. The L10 phase of FeNi was detected in alloys annealed in the temperature range of 673 to 813 K. The present results suggest that the order-disorder transition temperature of L10 FeNi is higher than the previously reported value (593 K). The high diffusion rates of the constituent elements induced by the crystallization of an amorphous phase at relatively low temperature (∼673K) are responsible for the development of atomic ordering in FeNi.

Amorphous FeNiCoCuSiBCr Alloys with Superior Direct Current Tolerant Characteristics

Amorphous Fe62-x Ni19Cox Cu0.1 Si3.8 B14 Cr1.1 (x = 0, 1, 5, 10) ribbons were annealed under magnetic field and tensile stress, respectively, and their magnetic properties were investigated. Fe73.5 Cu1 Nb3 Si15.5 B7 and Fe66 Ni10-Cu1 Nb3 Si11 B9 nanocrystalline alloy ribbons were also fabricated for comparison. Excellent DC tolerant property was obtained in the amorphous FeNiCoCuSiBCr ribbons after thermomagnetic treatment and the constant permeable property was improved with increasing Co content. The relative permeability was constant up to the DC bias field of approximately 6 × 10−4, 9 × 10−4, and 10 × 10−4 T and the values of relative permeability μr were 1650, 1200, and 1000 with the Co content being 0, 5 at. %, and 10 at. %, respectively. Besides, stress-annealed FeNiCoCuSiBCr alloy ribbons were proved to exhibit positive saturation magnetostriction constant λs.

Fe–Si–B–P–Cu Nanocrystalline Alloy Ribbons With High Saturation Magnetic Flux Density Prepared Using Industrial Materials

Magnetic properties and fine structure of Fe-Si-B-P-Cu nanocrystalline alloy ribbons have been investigated. The Fe84.8(Si,B,P)14Cu1.2 alloy ribbons using industrial materials are produced by a single-roller melt-spinning method in air. The Fe84.8(Si,B,P)14Cu1.2 nanocrystalline alloys exhibit low coercivity Hc of 7-20 A/m in the compositional range of Si=0-2 at% and P=2-8 at% and high saturation magnetic flux density Bs of 1.80 T or more in the compositional range of P=0-4 at%. In particular, Fe84.8Si1B10P3Cu1.2 nanocrystalline alloy annealed at 698 K exhibits both the high Bs of 1.82 T and the low Hc of 7.2 A/m. The iron loss W at 50 Hz of the Fe84.8Si1B10P3Cu1.2 nanocrystalline alloy is much smaller than oriented and nonoriented magnetic steel over the maximum induction Bm range up to 1.7 T. In addition, nanocrystalline structure of the Fe84.8Si1B10P3Cu1.2 alloy exhibits a homogeneous nanocrystalline structure composed of α-Fe grains with 5-20 nm in diameter even using industrial materials. Therefore, the Fe-Si-B-P-Cu nanocrystalline alloy has good soft magnetic properties and a large economical advantage of low material cost by using industrial materials.

High Bs nanocrystalline Fe 84−x−yCu xNb ySi 4B 12 alloys ( x=0.0–1.4, y=0.0–2.5)

In this study, Cu and Nb content dependences of magnetic properties for annealed Fe 84− x−y Cu x Nb y Si 4B 12 alloy ribbons fabricated by melt spinning were investigated. In Fe 83− x Cu x Nb 1Si 4B 12 alloy systems, the coercivity H c markedly decreases with increasing x and exhibits a minimum at around x=1.0–1.2, while the saturation magnetic flux density B s shows a slight variation. In Fe 83− y Cu 1Nb y Si 4B 12 alloy systems, H c markedly decreases at around y=0.5, while B s shows a monotonic decrease. Fe 82Cu 1Nb 1Si 4B 12 nanocrystalline alloy ribbons exhibit a high B s of 1.78 T and a low H c of 3.2 A/m. The core losses of the present alloys at 1.0 T at 400 Hz, P 10/400, and at 1.0 T at 1 kHz, P 10/1k, are 1.3 and 4.4 W/kg, respectively.

Fe-based Nanocrystalline Alloy Ribbon as Coaxial Cable Shielding Material

This paper describes the application of an Fe-based nanocrystalline ribbon as a shielding material for coaxial cable in the 10 MHz to 1GHz frequency range. A 0.01 mm thick Fe-based amorphous ribbon was converted into an Fe-based nanocrystalline ribbon by annealing it at 570 °C for 10 min. The ribbon exhibited high impedance characteristics when it was annealed in a transverse magnetic field. The noise attenuation value of cable covered with Fe-based nanocrystalline alloy ribbon annealed in a transverse magnetic field was 12.9 dB. This value exhibited 13 % higher than that of cable covered with Fe-based nanocrystalline alloy ribbon annealed without a magnetic field.

Application of Fe-Based Nanocrystalline Ribbon to a Noise Filter and a Shielded Cable

The paper describes the application of Fe-based nanocrystalline alloy ribbon to a common-mode noise filter and a shielded cable in the 10 MHz-1 GHz frequency range. A 0.01-mm-thick Fe-based nanocrystalline alloy ribbon exhibited high permeability and high impedance characteristics. The resistance of a 5.5-mm-diameter roll of Fe-nanocrystalline ribbon (12.5 mm wide and 6 cm long) increased from 1.0 /spl Omega/ at 1 MHz to 5.1 /spl Omega/ at 700 MHz. We confirmed that this filter exhibited the same noise attenuation as a conventional filter (ferrite core) but with 1/20th its volume. Moreover, the noise emission from a twisted pair cable is greatly reduced without any increase in the cable volume by employing the nanocrystalline ribbon as a shielding material.

The mechanism of magnetic relaxation in Fe-based nanocrystalline alloy ribbons investigated by permeability spectroscopy

The mechanism of magnetic relaxation in Fe-based nanocrystalline alloy ribbons investigated by permeability spectroscopy