Amorphous-nanocrystalline Alloys Research Articles

Effect of cryogenic thermal cycling treatment on the mechanical properties of FINEMET amorphous nanocrystalline alloy

The brittleness of FINEMENT amorphous nanocrystalline alloys caused by annealing is an urgent problem to be solved because it limits the scope of their engineering application. We are herein to investigate the rejuvenation behavior of the as-annealed samples that not only are in a relaxed state but also the nanocrystals are precipitated in the amorphous matrix. The results show that the thermal temperature for cryogenic thermal cycling (CTC) treatment should not be larger than 483 °C in order to recover the enthalpy of relaxation. Further, the more suitable temperature for CTC treatment differs with the time that the as-annealed ribbon is employed. Meanwhile, the improvement of mechanical properties of the rejuvenated samples was examined with the help of hardness, flat plate bending, and nanoindentation experiments, and the results correspond well to the maximum of the relaxation enthalpy recovery. In addition, molecular dynamics simulations were used to visualize the changes in the local structure and found that the increased local five-fold symmetric clusters have increased the amorphousness of the amorphous nanocrystalline ribbon through CTC treatment.

Study on microwave absorbing properties of reduced graphene oxide@Co/Fe81.5Si3B9P3C1Cu1Ti1.5 amorphous nanocrystalline composite

Electromagnetic pollution problems and military stealth technology need to be solved, the development of new wave absorbing materials has been imminent. In this study, reduced graphene oxide@Co (rGO@Co) powder is obtained by alcoholthermal method, afterwards the different contents of rGO@Co powders are also compounded with Fe81.5Si3B9P3C1Cu1Ti1.5 nanocrystalline powder by high-energy ball milling, obtaining rGO@Co/Fe81.5Si3B9P3C1Cu1Ti1.5 nanocrystalline composite powder, and powder morphology, the nuclear layer structure, soft magnetic properties and corresponding absorbing properties of the materials are studied. The research results are that rGO coats Co and Fe-based nanocrystalline of double magnetic cores in the composite powder, which realizes the synergy of the two magnetic cores to enhance the magnetic loss, is also compatible with the dielectric loss of rGO, and also improves the impedance matching. The minimum reflection loss (RLmin) is −44.18 dB, and the maximum effective absorption bandwidth (EAB) is 5.03 GHz in the amorphous nanocrystalline alloy matrix. When the addition of rGO@Co powder is 1 wt%, the RLmin of composite powder is −52.41 dB (3 mm), which is increased by 18.6 %. The EAB is 6.07 GHz (2 mm), which is increased by 20.7 %.

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.

Effect of the structure and volume fraction of nanophase on the mechanical properties of (FeNi)86B14 amorphous nanocrystalline alloys

The influence of precipitated nanophases on the mechanical properties of Fe-based amorphous nanocrystalline alloys is an urgent issue to be explored. Two amorphous nanocrystalline alloys, i.e., (Fe0.9Ni0.1)86B14 and (Fe0.7Ni0.3)86B14 containing nanophase of the body-centered cubic and face-centered cubic structures, respectively, were selected to investigate the effect of the structure and volume fraction of nanophase on their mechanical properties. The results of nanoindentation experiments and the calculation of the volume and size of the shear transition zone reveal that the two alloys show different mechanical properties. When the volume fraction of the nanophase in (Fe0.9Ni0.1)86B14 is larger than 50%, the elastic modulus is increased suddenly and the volume and size of the shear transition zone is decreased dramatically, while no dramatic change occurs in (Fe0.7Ni0.3)86B14. Moreover, it was found by using molecular dynamics simulations that the main reason for these abnormal mechanical properties is the change of cluster type in the system due to the incorporation of nanophases with different structures.

Effect of 0.5 at. % Cu addition on the crystallization behavior and soft magnetic properties of Fe83B11C1Si2P3 alloy

In order to gain insight into how the addition of Cu element affects the crystallization mechanism of amorphous nanocrystalline alloys and soft magnetic properties, the crystallization behavior of (Fe0.83B0.11Si0.02P0.03C0.01)100-xCux (x = 0 and 0.5) amorphous ribbons was investigated based on kinetic and thermodynamic behavior under non-isothermal and isothermal annealing conditions. The results show that under non-isothermal annealing conditions, the Cu0.5 amorphous ribbon not only favors the formation of the amorphous structure, but also enlarges the temperature window for annealing and improves the thermal stability of the α-Fe(Si) phase. At the same time, the Cu0.5 amorphous ribbon shows slow kinetic and is insensitive to heating rate change during annealing treatment. Under isothermal conditions, the addition of Cu decreases the nucleation activation energy (En) and increases the growth activation energy (Eg). This further indicates that the nucleation of α-Fe(Si) grains is easier than the growth process, which is conducive to the formation of a homogeneous nanostructure and improves the soft magnetic properties of the alloy. Compared to Cu0 amorphous ribbon, it is also shown that the Cu0.5 amorphous ribbon changes the crystallization mechanism from diffusion-controlled one-dimensional to two-dimensional growth when the crystallization volume fraction x is 10–30 vol%. While three-dimensional growth become dominated when x is reaches 60 vol% for both ribbons. Therefore, the kinetics of crystallization as well as microstructure supports that the Cu0.5 ribbon is able to exhibit uniformly fine nanocrystalline structures. Further, the Cu0.5 nanocrystalline ribbon shows a higher Bs of 1.85 T and a lower Hc of 2.55 A/m, respectively, and the favorable (100) orientation of α-Fe(Si) grains formed after annealing is another factor to increase Bs.

The effect of the volume fraction of nanocrystals on the brittleness of Fe-based amorphous/nanocrystalline alloys simulated by molecular dynamics

The effect of the volume fraction of body-centered cubic (BCC) crystal in Fe-based amorphous nanocrystalline alloys on room temperature brittleness was investigated via molecular dynamics simulations. Seven model samples with embedded BCC nanocrystal contents ranging from 0 to 33.4 vol.% were obtained. The indentation tests were carried out by spherical rigid indenter to investigate the microstructural evolution and the mechanical properties of those Fe-based amorphous/nanocrystalline alloys in terms of the indentation force, hardness, von Mises shear strain, atomic displacement vector as well as surface morphology. It is found virtually that the plasticity shows a gradient decrease tendency for the three types of samples with 0, less than 16, and more than 20 vol.% nanocrystal, respectively, which is caused by the free volume decreases via monitoring the Voronoi polyhedra.

Tailoring the thermal stability and soft magnetic properties of Fe80-xNixSi7B8P4Cu1 amorphous nanocrystalline alloys based on the magnetic domain structure

Structure, crystallization behavior, dynamic domains, and magnetic properties of as-quenched and annealed Fe80-xNixSi7B8P4Cu1 (x = 0, 1, 2, 3 and 4) alloy ribbons have been investigated. It finds that the partial substitution of Ni for Fe promotes the formation of amorphous structure. We have determined the critical spinning speed for the formation of pre-existing α-Fe cluster structures. In addition, a little increase in Ni content effectively inhibits the excessive growth of the α-Fe grains, which contributes to the reduction of grain size and Hc. Moreover, the role of Ni on the magnetic domain structures and its correlation medel was established. After proper annealing treatment, the Fe79Ni1Si7B8P4Cu1 nanocrystalline alloy exhibited excellent soft-magnetic properties including a high Bs of 1.58 T, a low Hc of 2.48 A/m and a high μe of 16400, which is closely related to the high volume fraction of α-Fe grains and uniform refinement of magnetic domains which is more conducive to the migration and rotation of magnetic domains.

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.

Effect of miscible and immiscible element microalloying on crystallization behavior and soft magnetic properties of Fe-P-C-B amorphous alloy

Microalloying is an efficient strategy to promote nano-crystallization of Fe-based amorphous alloys to improve soft magnetic properties. Here, the Fe-P-C-B amorphous alloy is selected as a typical system to investigate the effect of microalloying of immiscible elements (In and Sn) and miscible elements (Al, Ga and Ge) in Fe on crystallization behavior and soft magnetic properties of Fe-based amorphous alloys. Microalloying of immiscible elements leads to slightly increased energy barrier for α-Fe nuclei growth as evaluated by Kissinger equation, yielding fine and uniform α-Fe nanograins and low coercivity after annealing. In contrast, miscible elements cause high growth energy barrier, resulting in few huge α-Fe grains and large coercivity. This work suggests a strategy of obtaining amorphous-nanocrystalline alloys with good magnetic properties by microalloying of immiscible elements.

Exceptionally High Saturation Magnetic Flux Density and Ultralow Coercivity via an Amorphous-Nanocrystalline Transitional Microstructure in an FeCo-Based Alloy.

High saturation magnetic flux density (Bs ) of soft magnetic materials is essential for increasing the power density of modern magnetic devices and motor machines. Yet, increasing Bs is always at the expense of high coercivity (Hc ), presenting a general trade-off in the soft magnetic material family. Here, superior comprehensive soft magnetic properties, i.e., an exceptionally high Bs of up to 1.94 T and Hc as low as 4.3 A m-1 are unprecedentedly combined in an FeCo-based alloy. This alloy is obtained through a composition design strategy to construct a transitional microstructure between amorphous and traditional nanocrystalline alloys, with nanocrystals (with < 5 nm-sized crystal-like regions around) sparsely dispersed in an amorphous matrix. Such transitional microstructure possesses extremely low magnetic anisotropy caused by the annihilation of quasi-dislocation dipoles, and a strong magnetic exchange interaction, which leads to excellent comprehensive magnetic properties. The results provide useful guidelines for the development of the next generation of soft magnetic materials, which are promising for applications of high-frequency, high-efficiency, and energy-saving devices.

Structure and properties of amorphous-nanocrystalline alloy Fe77,5Ni3,5Mo1Si2B16, obtained by controlled annealing from the amorphous state

For amorphous alloy Fe77,5Ni3,5Mo1Si2B16 the possibility of obtaining the amorphous-nanocrystalline state by controlled annealing of source alloy is evaluated. Based on theory of high-temperature stability of amorphous alloys the temperature interval in which the condition of growth of frozen-in crystallization centers is fulfilled, but the process of intensive crystallization has not yet begun, is calculated. With proposed method alloy in the amorphous-nanocrystalline state is obtained, that is confirmed by the results of X-ray diffraction and electron microscopic studies. Using the highly sensitive dilatometric technique, the onset temperatures of intense crystallization for the source amorphous alloy and for alloy in the amorphous-nanocrystalline state have been determined. It has been shown that the proposed heat treatment reduces the onset temperature of intense crystallization by 15°С. Calculated according to the dilatometric experiment, the part of the nanocrystalline phase in the obtained amorphous-nanocrystalline specimen does not exceed 24%. In the paper the micromechanical and electrical properties of obtained alloy in the amorphous-nanocrystalline state are investigated.

Effect of Hydrogenation on the Glass Formation Ability and Magnetic Properties of the Fe79Si9B6Nb5Cu1 Amorphous Nanocrystalline Alloys

Effect of Hydrogenation on the Glass Formation Ability and Magnetic Properties of the Fe79Si9B6Nb5Cu1 Amorphous Nanocrystalline Alloys

Structural Heterogeneity of an Amorphous-Nanocrystalline Alloy Fe77Cu1Si16B6 in the Nanometer Range

In this article, an alloy of the Finemet type Fe77Cu1Si16B6 obtained by quenching from a liquid state (spinning method) in the initial state is investigated. The main research methods were scanning and transmission electron microscopy. Methods for describing multiscale structural heterogeneities in amorphous-nanocrystalline alloys have been developed, allowing the structural state to be described and its influence on the physicochemical and technical properties to be determined depending on the technological conditions for obtaining these alloys. Representation of electron microscopic images in the form of Fourier spectra made it possible to reveal the nature of the formation of short- and middle-order in amorphous-nanocrystalline alloys according to the principle of self-similar spatial structures. The analysis of electron microscopic images by integral Lebesgue measures revealed density fluctuations over the alloy volume, which corresponds to the hierarchical representation of structural inhomogeneities in amorphous metallic alloys.

Friction and wear behavior under oil lubrication conditions of amorphous-nanocrystalline composite coatings deposited via HVAS

To prolong the service life of heavy-duty vehicle engine parts subject to wind and sand exposure, a FeCrMoWBRe amorphous-nanocrystalline composite coating was prepared via high-velocity arc spraying for its higher wear resistance than the traditional one. The adhesive strength of the coating is approximately 60.5 MPa, the hardness is approximately 13.3 GPa, and H 3 /E r 2 is 0.07 GPa, indicating that the coating has excellent wear resistance. Under the condition of oil lubrication, the wear rates of the coating under different loads (50–150 N) are in a range of (0.993–250) × 10 −7 mm 3 ·N −1 ·m −1 ; the coating performance is most stable under low and medium loads (50–100 N). It is proved that, abrasive and fatigue wear are the predominant wear mechanisms under low and medium loads (50–100 N), while abrasive, fatigue, and delamination friction as well as wear mechanisms are the dominant under higher loads (e.g., 125 and 150 N) for the coating. After adding abrasive particles, the wear rates of the coating under different loads are in the range of (3.6–259) × 10 −7 mm 3 ·N −1 ·m −1 ; the wear amount is not significantly increased under higher loads (125 and 150 N). The wear mechanism is almost the same under this condition. These results indicate that the coating performs stably under low and medium loads and shows resistance to abrasive particles, especially under higher loads. • A Fe-based amorphous-nanocrystalline alloy composite coating with excellent wear resistance was prepared by HVAS. • The influences of load and the third-body abrasive particles on the wear resistance were investigated. • The results have guiding significance to the wear resistance of heavy-duty vehicle engine parts in high wind-sand area.

Application direction of amorphous and nanocrystalline alloy materials and the evaluation of venture capital value

At present, the country vigorously calls for the use of green, energy-saving and environmentally friendly materials in various fields, especially in electronic power systems that require the use of low-loss soft magnetic alloy materials. Amorphous nanocrystalline alloy materials that have received widespread attention have excellent high magnetic permeability and low loss performance. Therefore, this material has become a power system with energy saving, environmental protection and excellent efficiency. Among them, soft magnetic alloys have the most application prospects. In this paper, various amorphous/nanocrystalline samples have been successfully prepared by vacuum arc melting and rapid cooling. Using XRD, HV and SEM testing and analysis methods, the structure, hardness, mechanical properties, magnetic properties and other alloys were successfully prepared. Mo element improves the ability to form glass from amorphous nanocrystalline alloys, the alloy with alloy composition has the best glass forming ability. The addition of Mo deteriorates the soft magnetic properties of the alloy. The saturation magnetic flux density Ms of the alloy is reduced from 81 to 59 emu/g, but the coercive force is not significantly improved. By increasing the Fe content, the amorphous forming ability and heat the stability decreases, the Vickers hardness and corrosion resistance decrease, and the saturation magnetization and coercivity increase. It can reduce the cost of the alloy and improve the magnetic properties of the alloy.

Heterogeneously structured FeCuBP amorphous–nanocrystalline alloy with excellent dye degradation efficiency

Fe-based amorphous alloys have drawn wide attention in dye degradation due to the superior properties and adjustable compositions. As a new component of Fenton-like catalyst, Fe80Cu4B14P2 amorphous alloy with few nanocrystals has been prepared by melt spinning method without additional process for the first time in this paper. Furthermore, Fe80Cu4B14P2 amorphous–nanocrystalline alloy shows the better degradation performance than fully amorphous and crystalline counterparts, which is originated from structural and chemical inhomogeneities in nanoscale. Two distinct types of galvanic cells are formed between copper-rich nanocrystals and amorphous matrix, iron-rich and iron-poor regions, respectively, accelerating the transfer of electrons and the production of ·OH radicals in Fenton-like system. Besides, the formation of special three-dimensional (3D) network structures on ribbon during degradation is also an important reason for the high degradation efficiency. This work not only proposes novel and promising FeCuBP amorphous–nanocrystalline alloy as catalyst in the wastewater treatment field, but also provides a new perspective on heterogeneous materials designing and fabricating.

The Magnetic Properties and Glass Formation Ability of the Fe80Si8B6Nb5Cu Amorphous-Nanocrystalline Alloys with Different Phosphorus Addition

We prepared Fe80Si8B6Nb5Cu amorphous-nanocrystalline strips with different phosphorus addition by the melt spinning method, and their nanocrystalline magnetic powder core was obtained after a series of processing. Then, the microstructure, micromorphology, thermal behavior, and magnetic properties were studied. The results show that the atomic radius difference (σ) affected the glass formation ability; thus, first, the grain size and coercivity decreased and then increased. The (Fe80Si8B6Nb5Cu)99P nanocrystalline core has the better comprehensive magnetic properties than those of Fe80Si8B6Nb5Cu; its μe (75.93) is 5% higher, and Pcm (370 W/kg) is 14% lower than those of Fe80Si8B6Nb5Cu (i.e., 72.98 and 431.2 W/kg, respectively).

Effect of simultaneous improvement of plasticity and microhardness of an amorphous-nanocrystalline material based on Co, as a result of laser processing of nanosecond duration

Experimental investigations of the properties of nanostructured materials are of large practical significance. Physical and chemical properties of nanocrystalline and amorphous-nanocrystalline alloys are currently being actively researched. Yet, the practical use of such materials is complicated by the lack of an optimal set of physical and mechanical properties. Classical processing methods are not effective enough. Laser processing is a promising method for forming specified mechanical properties. Amorphous-nanostructured materials, as a result of local and ultrafast exposure to high temperatures and pressure, retain their structure almost unchanged. At the same time, plasticity and microhardness can remain at a high level, and in some cases even increase during processing. The relevance of the presented work lies in the study of the regularities of the simultaneous increase in plasticity and microhardness of an amorphous Co-based nanocrystalline metal alloy, due to its processing with nanosecond laser pulses. The relevance of the presented work lies in the study of the patterns of the simultaneous increase in plasticity and microhardness of an amorphous Co-based nanocrystalline metal alloy due to its processing with nanosecond laser pulses.

Nanoporous metallic-glass electrocatalysts for highly efficient oxygen evolution reaction

High anode overpotential of the oxygen evolution reaction (OER) restricts the upscale applications of water electrolysis. We attempt to address such technical challenges through the design and preparation of a group of nanoporous (Fe–Ni–Co)-based metallic glasses (NP–FeNiCo-MGs) as electrocatalyts of OER. The nanoporous structure is yielded through electrochemical selective dissolution of active Fe solid solution phase in free-surface layer of (Fe–Ni–Co)-based amorphous-nanocrystalline alloys (FeNiCo-ANs). Electrochemical tests reveal that integral composite electrodes combining with a catalytic layer of NP-FeNiCo-MGs and a current collector of FeNiCo-ANs exhibit high catalytic activity towards water oxidation in 1 M KOH solutions, which only requires an overpotential of 274 mV to yield a current density of 10 mA cm−2. Studies of electrochemical states and electrode-electrolyte reaction process of the NP-FeNiCo-MGs during OER unveil plausible working mechanisms driving such promising catalytic activities. Based on the merits of a broad tunable range of compositions of active elements for OER, homogeneous distribution of metastable atoms, and high-surface-area nanoporous structure strongly combining with high-conductive substrate, the proposed nanoporous metallic-glass composite electrodes are of great significance for a variety of applications for clean energy.

Bulk-nano spark plasma sintered Fe-Si-B-Cu-Nb based magnetic alloys

Iron-based soft magnetic alloys (FeSiB, FeSiBNb, FeSiBCu, and FeSiBNbCu (Finemet)) have been fabricated via mechanical alloying followed by spark plasma sintering (SPS) process. FeSiB alloy powder was obtained by high energy ball milling of an elemental blend Fe, Si, and B powders. The effect of milling time on crystallite size and phase transformation was studied. Additionally, FeSiBCu, FeSiBNb, and FeSiBCuNb alloy powders were milled to study the effect of Cu and Nb on phase transformation, mechanical, and magnetic behavior. The mechanically alloyed powders were sintered via SPS process to achieve full densification. The microhardness and magnetic permeability of sintered FeSiB alloys were found to be increased monotonically with milling time primarily due to the smaller crystallite size and more uniform microstructure. Interestingly, the alloying of Cu or (and) Nb to FeSiB resulted in higher saturation magnetization and lower coercivity mainly due to large volume fraction of α-Fe3Si nanocrystals. Overall, these alloys exhibit reasonably good soft magnetic behavior along with excellent microhardness. Mechanical alloying followed by spark plasma sintering opens up a new avenue of processing amorphous-nanocrystalline alloys into bulk shape with good mechanical and magnetic properties.