Fe-based Soft Magnetic Alloys Research Articles

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.

The Effects of Si Substitution with C on the Amorphous Forming Ability, Thermal Stability, and Magnetic Properties of an FeSiBPC Amorphous Alloy

The Effects of Si Substitution with C on the Amorphous Forming Ability, Thermal Stability, and Magnetic Properties of an FeSiBPC Amorphous Alloy

Mass Production and Vast Application States of Bulk Metallic Glasses

Since the first synthesis of bulk metallic glasses (BMGs) by copper mold casting in 1990, much effort has been devoted to the searching of new BMG composition, the clarification of fundamental and engineering properties for BMGs and their industrialization. At present, BMGs have been formed in a large number of multicomponent alloy systems where the empirical three component rule is satisfied. Nowadays, commercialized BMGs are classified to Zr-based and Fe-based alloy groups. When we look at the industrialization of Zr-Al-Ni-Cu-based BMGs, the first commercialization was made for golf clubs in Japan in 1998, followed by watch parts etc. Since then, Zr-based BMGs have been used continuously up to 2013, though their application scale was in a limited state. Since 2014, the application scale was significantly extended in collaboration with the rapid developments of smartphones and electric vehicles. At present, the mass production facilities for Zr-based BMGs have been significantly developed and variety of BMG products have been produced. On the other hand, Fe-based soft magnetic BMGs were found in 1995. Their BMGs have also been used on a huge number of pieces in various kinds of electronic-magnetic instruments. These recent application states for Zr- and Fe-based BMGs are introduced together with new nanocrystalline Fe-based soft magnetic alloys developed through the derivation of alloy composition from Fe-based BMGs.

Plasticity and brittleness of Fe-based amorphous alloy strips assessed via a single abrasive impact method

Fe-based soft magnetic amorphous alloys represent the next generation of magnetic core materials and are expected to replace silicon steel sheets in many applications. An economical and fast methodology for the study of the plasticity and brittleness of this material is however necessary to permit its widespread use. Abrasive water jetting is a cold processing technique that has great potential for use in the fabrication and inspection of Fe-based amorphous alloy parts. However, research on this technique is currently lacking. In order to assess the plasticity and brittleness of Fe-based amorphous alloys by considering abrasive impacts, this work investigates the effect of impact speed and impact angle on the removal process in Fe-based amorphous alloys and establishes the corresponding abrasive erosion mechanism. It is found that Fe-based amorphous alloys exhibit four primary responses: shear slip, viscous flow, shear crack formation, and brittle fracture; the plasticity and brittleness of Fe-based amorphous alloys are assessed by considering the impact morphology and mechanism.

Superior high-frequency performances of Fe-based soft-magnetic nanocrystalline alloys

Soft-magnetic nanocrystalline alloys with ultralow power loss are strongly desired for high-frequency power electronic applications. In this work, an industrial ultrathin FINEMET alloy (Fe73.5Si15.5B7Cu1Nb3) ribbon, with 14 μm in thickness, was fabricated by using a roller thermal conductivity-controlled cooling strategy coupled with a bottom blowing argon technique. A magnetic core made of the ultrathin ribbon exhibits excellent high-frequency soft-magnetic properties, with super high permeability of 48,000 at the condition of 1 A/m and 100 kHz and an ultralow core loss of 94 kW/m3 at the condition of 0.2 T and 100 kHz. It is found that the excess loss accounts for the largest proportion in power loss, and this proportion increases with decreasing thickness. The finest grain of nanocrystals, narrowest magnetic domain width, weakest transverse field-induced anisotropy, and considerably increased electrical resistivity (188 μΩ cm) synergistically contribute to the superior soft-magnetic performances at 100 kHz of the ultrathin alloy. This work demonstrates the attractive high-frequency application prospects of ultrathin nanocrystalline alloys in power electronics and information communication due to their excellent performance and huge energy-saving effects, and provides new and comprehensive insights into the power loss of ultrathin nanocrystalline alloys.

Resource-saving production of Fe-based amorphous alloys from carbothermal reduction of high-phosphorus oolitic iron ore

Energy-saving and resource-friendly production of Fe-based soft-magnetic materials is of paramount importance for the development of green economy. In this study, an innovative process for fabricating Fe-based amorphous alloys from high-phosphorus oolitic iron ore was developed with the combination of ironmaking and melt-spinning techniques. By using the developed process, iron and phosphorus in high-phosphorus oolitic iron ore can be simultaneously utilized. During the direct carbothermal reduction process of high-phosphorus oolitic iron ore, oolitic hematite and apatite were first reduced to form liquid iron phase and absorb P2 gas, resulting in the enrichment of P element in iron phase. Fe-P alloys with different P and C content can be easily obtained by tailoring the C/O ratio. The reduced Fe-P alloys with high εFe of 96.4% and εP of 70.7% are ideal raw materials for preparing Fe-based soft-magnetic alloys. Fe80P10C9Si1 amorphous alloy was successfully obtained after composition adjustment. The high AFA of rod sample with diameter up to 1 mm and good magnetic softness of the ribbon samples including high Bs of 1.54 T, low Hc of 3.6 A/m, high μe of 30 × 103 with excellent frequency stability prove the effectiveness of the designed process. These findings are of great significance to lay the foundation for the recycling of resources and preparation of high performance soft-magnetic alloys from iron ores.

The complementary effects of Fe and metalloids on the saturation magnetization of Fe-based amorphous alloys

Developing Fe-based amorphous alloys with high saturation flux density (Bs) have been challenging topics for a long time. Metalloid elements like B, Si, C, and P are key elements for Fe-based amorphous alloys, but the addition of multiple metalloids would significantly complicate the effects of each metalloid on saturation flux density. Herein, Fe83-85(B, C, Si)14–16P1 amorphous alloys with high Bs of 1.61–1.71 T and low coercivity (Hc) of 2.2–8.7 A/m were successfully developed. Fe and metalloids were found to have strong interrelated effects on the total magnetic moment and the strength of magnetic exchange interaction, which largely determine the Bs of Fe-based amorphous alloys. It was revealed that for Fe-rich amorphous alloys, the effects of metalloids on Bs are much more significant than that of Fe, and the effects are largely dependent on Fe content. The complementary effects of metalloids on Bs and the Fe-sensitive behavior of these effects, as well as the underlying mechanisms, have been revealed. These results pave a new way to understand the composition-property relationship, and would help design and develop high-performance Fe-based soft magnetic amorphous alloys.

Composition design for Fe-based soft magnetic amorphous and nanocrystalline alloys with high Fe content

For composition design of amorphous and nanocrystalline alloys, prediction of their properties has been a long-sought goal. In this study, we reveal the quantitative relationship between composition and crystallization behavior in Fe-rich FeB based amorphous alloys. Furthermore, we demonstrate that after using the mixing enthalpy as the threshold, the atomic size difference can be utilized as an indicator for amorphous-forming ability (AFA). By employing the correlations between composition and crystallization behavior/AFA, we developed new strategies for designing high-Bs (saturation flux density) Fe-rich Fe-based amorphous/nanocrystalline alloys from thermodynamic, topological and comprehensive perspectives. These new strategies have the potential to be a universal guide on composition design for high-Bs Fe-based soft magnetic amorphous/nanocrystalline alloys.

High performance Fe-based nanocrystalline alloys with excellent thermal stability

Fe-based alloys are an important soft magnetic material that plays a pivotal role in a variety of energy-related industrial applications, such as electric transformers, motors and converters. However, the trade-off between magnetic softness and saturation magnetization (Bs) has been hindering the development of next-generation Fe-based soft magnetic materials. In this work, we demonstrate a facile route to obtain nanostructured Fe-based alloy out of a marginal glass former, which exhibits a core-shell like nanostructure and a synergetic increase of Bs, magnetic permeability (μe) and hardness upon thermal annealing, giving rise to a unique combination of Bs > 1.83 T, μe ∼25000 and ultrahigh hardness of ∼15 GPa. In terms of the combined magnetic/mechanical properties, the nanostructured Fe-based alloy outperforms the variety of Fe-based soft magnetic alloys hitherto reported. Furthermore, compared to the existing high performance soft magnetic Fe-based nanocrystalline alloys, the core-shell like nanostructure in our Fe-based nanocrystalline alloy displays an excellent thermal stability, which offers a large time window which would facilitate materials processing for future large-scale industrial production.

Research progress and application prospect of Fe-based soft magnetic amorphous/nanocrystalline alloys

Amorphous alloy is a kind of metallic materials prepared by rapidly cooling the alloy melt through hindering crystallization in cooling process. Due to the unique structure of atomic random packing, Fe-based amorphous alloys exhibit not only structural and property isotropy, but also small structural correlation length, small magnetic anisotropic constant, and then small coercivity Hc. Like crystalline Fe-based alloys, Fe-based amorphous alloys also possess high saturation induction Bs. As a result, research on engineering applications of Fe-based amorphous alloys has been promoted by their excellent soft magnetic properties. Now Fe-based soft magnetic amorphous/nanocrystalline alloys have been produced and applied to various areas on a large scale. Here in this paper, the processes of discovery, development and application of Fe-based soft magnetic amorphous alloys are reviewed, and the effects of chemical composition, structure and preparation technology on the soft magnetic properties are introduced and discussed. The obtained theoretic results and the technological innovation show that the great contributions have been made to the development and application of Fe-based soft magnetic amorphous/crystalline alloys. Based on the progress of structure and soft magnetic property and our understanding, the development process of the fundamental research and the application progress of Fe-based soft magnetic amorphous alloys could be divided into three periods. In addition, the present challenge topics in their researches and applications are proposed.

First principle study on the Si effect in the Fe-based soft magnetic nano-crystalline alloys

The contributing effects of Si inclusion on the fabrication and performance of the Fe-based amorphous/nano-crystalline alloys were extensively studied with the first principle molecular dynamics simulation method. Si is found to have complicated impact on the formation of amorphous structure as it is structurally preferred to crystallize with Fe but energetically beneficial to stabilize the amorphous when reaching high concentration. The inclusion of Si is also found to cause the increase of the crystallization temperature and give rise to better controllability of the nano-crystallization process for better magnetic softness. Magnetically, Si can always reduce the saturation magnetization in the Fe-based alloy but also can indirectly help decreasing the overall coercivity of the Fe-based nano-crystalline alloy.

Magnetically soft FeCoTiZrB alloys with high saturation magnetization

Soft magnetic materials are ubiquitously utilized in various applications such as motors, actuators, sensors, and so forth. The requirements for efficient cores in electric power transmission devices include low core loss and high saturation magnetization. Here we report the magnetic properties of Fe-based soft magnetic alloys with the compositions Fe67-xCo20Ti7Zr6Bx (x = 0, 2, 4, and 6 at.%) produced by melt-spinning. The highest saturation magnetization achieved is 190 emu g−1 (1.79 T) for the Fe67Co20Ti7Zr6 system. This performance is attributed to the uniform distribution of nanometer-sized α-Fe nanocrystals. In addition, the experimentally measured magnetic properties are reproduced well by micromagnetic simulations.

Investigation on the crystallization mechanism difference between FINEMET® and NANOMET® type Fe-based soft magnetic amorphous alloys

In this article, the atomic behaviors of Nb and P in Fe-based amorphous alloys during nano-crystallization process were studied by the combination of ab initio molecular dynamics simulations and experimental measurements. The inclusion of Nb is found to be tightly bonded with B, resulting in the formation of diffusion barrier that could prevent the over-growth of α-(Fe, Si) grains and the promotion of larger amount of α-(Fe, Si) participation. The P inclusion could delay the diffusion of the metalloids that have to be expelled from the α-(Fe, Si) crystallization region so that the grain growth could be reduced with fast but practically achievable heating rates. The combined addition of P and Nb in high Fe content amorphous alloys failed in exhibiting the potential of good magnetic softness with slow heating (10 K/min) annealing at various temperatures. The sample with optimum crystallization process with confined grain size was annealed at 653 K, with the grain size of 31 nm and a coercivity of ∼120 A/m, much too large to meet the application requirements and to be compared with the currently well-studied alloy systems. This attempt suggests that the inclusion of early transition metal elements might not be effective enough to suppress grain growth in crystallizing high Fe content amorphous alloys.

Fe-Based Magnetic Alloy Electrodeposition for Thin Films and Template Based Nanostructures

The electrochemical fabrication of the Fe-based soft magnetic CoFe alloy and the shape memory active Fe-Pd alloy is reported. We examine the influence of electrolyte composition and deposition regime or post treatment on morphology, composition and structural development of the deposits. Up to 10 µm thick CoFe films with 55 at.% Fe were achieved from simple and additive adjusted electrolytes by potentiostatic or alternating potential deposition regime. Micropatterned deposits of smooth surface morphology and high saturation magnetization applicable as magnetic field gradient generator can be prepared best by the combination of SDS additive and alternating potential regime. The Fe-Pd alloy has been deposited and heat treated to achieve a composition with 30 at.% Pd and to adjust the crystal structure. For thin films and nanowires the transition from bcc to fcc phase is accomplished. This represents a good starting point towards shape memory active materials and their further physical characterization.

FeCo-based soft magnetic alloys with high Bs approaching 1.75 T and good bending ductility

Fe-rich amorphous alloys with FeCo contents above 85 at% were formed by partial replacement of Fe by Co in Fe-Si-B-P alloy system. The resulting alloys exhibit good soft magnetic properties and bending ductility after stress relief annealing. Moreover, the maximum magnetic flux density (Bs) approaches 1.75 T, which is higher than those for previous reported Fe-rich Fe-metalloid alloys. Thus, the partial substitution of Fe by Co caused both Curie temperature (TC) and Bs exceeding those for the Fe-Si-B-P alloys. Any compositional modification so as to raise TC was found to be effective for the further increase in the previous maximum value of Bs for the Fe-metalloid amorphous alloy system reported to date. Based on this concept, it is expected that further high Bs exceeding largely 1.75 T is obtained for Fe-based soft magnetic alloys with higher total ferromagnetic element content.

New Fe-based soft magnetic amorphous alloys with high saturation magnetization and good corrosion resistance for dust core application

Fe-rich amorphous dust core alloys with minor-addition of Mo and/or Cr were synthesized because of the industrial request of mass production of high efficient low core loss Fe-based dust cores. It was found that the present Fe-(Cr, Mo)-P-B-Si-(C) amorphous alloy ribbons exhibit good soft magnetic properties of above 1.5 T for saturation magnetization, below 10 A/m for coercivity and rather good corrosion resistance in 3%NaCl aqueous solution. Besides, the amorphous alloy ribbons exhibit good bending ductility in as-spun and optimally annealed states. It is noticed that these characteristics are much superior to those for commercial Fe-Cr-Nb-P-B-Si soft magnetic dust core alloy (SENNTIX). In addition, the annealing treatment was noticed to cause the improvement of corrosion resistance without detriment to bending ductility. The new Fe-based soft magnetic alloys with good combined characteristics are expected to be used as the basic material as high-efficient soft magnetic dust cores in a high frequency range.

Characterization of a Fe-Based Soft Magnetic Alloy System with High Saturation Magnetization.

The ratios of Fe/Co and Fe/B in a ferromagnetic alloy system, Fe(87-x-y) Co(x) Ti7 Zr6 By (x = 20, 30, and 40 at% and y = 2 and 4 at%), which was produced by the melt-spinning technique in the form of thin ribbons, were investigated to improve the saturation magnetization. The thermal properties T(x) were in the range of 792.0 K to 838.0 K, and it decreased by decreasing Fe/Co ratio. In the as-spun amorphous ribbons, the saturation magnetization and coercivity ranged from 137.5 emu/g to 164.2 emu/g and from 0.027 Oe to 1.245 Oe, respectively. The optimum Fe/Co ratio for the Fe(83-x) Co(x) Ti7 Zr6 B4 system was determined to be 64:36. In other words, the optimum system was Fe60 Co25 Ti7 Zr6 B2, which exhibited robust soft magnetic properties, such as a low coercivity of 0.252 Oe, and high saturation magnetization of 164.2 emu/g (1.55 T). Also, in this system, magnetic properties such as the saturation magnetization and coercivity increased with decreasing Fe/Co ratio.

B23-P-04High glass forming ability Fe-based soft magnetic amorphous alloys

Amorphous alloys, or so called bulk metallic glass, are well known as a functional material with high strength, good wear and corrosion resistance, and excellent soft magnetic properties. Among all the compositions, Fe-based and Co-based amorphous alloys exhibit high maximum magnetic flux, high permeability, low loss, and low coercivity, are high grade soft magnetic materials. In addition, Fe-based soft magnetic amorphous alloys perform higher maximum magnetic flux and lower cost than Co-based alloys. However, the glass forming ability (GFA) of Fe-based soft magnetic amorphous alloys is a stumbling block to limit the critical size and the application field. In the previous research, increasing metalloid content is benefit for GFA but is tend to be harmful for the maximum magnetic flux and thus lower the performance. In this study, the goal is to increase the GFA of Fe-based soft magnetic amorphous alloys by trace element adding. Meanwhile, to maintain the excellent soft magnetic properties. The amorphous nature, morphologies of the porous metallic glasses, and mechanical properties are examined by X-ray diffraction (XRD), and scanning electron microscopy (SEM). In addition, the GFA of Fe-based alloys are analysis by differential scanning calorimetry (DSC). All of the results included magnetic properties will be discussed in details. B23-P-03 doi:10.1093/jmicro/dfv277

Syntheses and corrosion behaviors of Fe-based amorphous soft magnetic alloys with high-saturation magnetization near 1.7 T

Abstract

Fe-based soft magnetic amorphous alloys with high saturation magnetization above 1.5 T and high corrosion resistance

Fe-rich amorphous alloys with minor-addition of Cr and/or Nb were examined with the aim of developing Fe-based amorphous alloys exhibiting simultaneously high saturation magnetization above 1.5 T and good corrosion properties. Fe82Cr2B8P4Si3C and Fe82NbB9P4Si3C amorphous alloys were found to exhibit high saturation magnetizations of 1.49 T and 1.57 T, respectively, and rather good corrosion resistance in 3.5 mass% NaCl solution at 298 K. The minor-addition of Cr or Nb enables the formation of amorphous alloy particles without harmful oxide layer by water atomization process which makes these alloys suitable for applications as soft magnetic core materials. The addition of 1 at% Nb improved the corrosion resistance through the increase in Ecorr value, which makes easy to reach passive state, and the suppression of pitting corrosion. Besides, it has been proved that the simultaneous addition of Nb and Cr has an effect on forming protective passive film.