Iron-based Amorphous Alloys Research Articles

Effect of composition on the structural relaxation of amorphous iron-based alloys

The structural relaxation of iron-based amorphous alloys upon changes in their relative electrical resistance and magnetic moments upon a rise in temperature is investigated. The presence of Nb in Fe(Cu, Nb)–Si,B alloys stabilizes amorphous states, lowering the Curie temperature T C am and raising the temperature of the paramagnetic–ferromagnetic magnetic phase transition.

非晶薄带横向均匀性的研究

非晶薄带横向均匀性是影响非晶软磁器件性能的关键因素。本文通过分析单辊快淬法制备铁基非晶合金薄带过程中冷却铜辊热膨胀、表面弯曲程度等影响单辊快淬法制备铁基非晶合金薄带横向均匀性的关键因素，采用调节喷嘴弧度来补偿冷却铜辊在制带过程的受热膨胀，消除因铜辊膨胀而引起的薄带横向非均匀性。通过不同宽度薄带所需喷嘴弧度的工艺参量总结，揭示了非晶薄带宽度与喷嘴弧度的一般性关系式，该关系式对于非晶薄带生产实际的工艺设计具有重要的指导意义。 The transverse uniformity of amorphous ribbons is a key factor affecting the properties of amor-phous soft magnetic devices. In this paper, we analyze the factors such as the thermal expansion of the cooling copper roller and surface bending degree, which affects the transverse uniformity of iron-based amorphous alloys. For ribbons prepared by single roller melt-spun method, the nozzle diameter is adjusted to compensate for the thermal expansion of the copper roller in order to elim-inate ribbon’s transverse uniformity caused by the expansion of copper roller. Summarizing the process parameters of different nozzle diameters for different ribbon-width reveals the generalized formula for amorphous ribbon-width and the nozzle diameter, the obtained formula has an im-portant guiding significance for amorphous ribbon preparation process design.

The ductile-to-brittle transition and the temperature and temporal stability of amorphous alloys

The ductile-to-brittle transition of amorphous iron-based alloys is considered. A criterion of mechanical degradation (embrittlement) in the range of climatic temperatures is developed on its basis. Time intervals of the stability of some multicomponent iron-based quenched melt amorphous alloys of the metal–metalloid type are estimated. The proposed criterion of temperature and temporal stability is compared to an independently developed criterion based on measuring the relaxation spectra of heat generation.

Relaxation of bending stresses and the reversibility of residual stresses in amorphous soft magnetic alloys

The reversibility of residual bending stresses is revealed in ribbon samples of cobalt- and iron-based amorphous alloys Co69Fe3.7Cr3.8Si12.5B11 and Fe57Co31Si2.9B9.1: the ribbons that are free of applied stresses and bent under the action of residual stresses become completely or incompletely straight upon annealing at the initial temperatures. The influence of annealing on the relaxation of bending stresses is studied. Preliminary annealing is found to sharply decrease the relaxation rate of bending stresses, and the initial stage of fast relaxation of these stresses is absent. Complete straightening of preliminarily annealed ribbons is shown to occur at significantly higher temperatures than that of the initial ribbons. Incomplete straightening of the ribbons is explained by the fact that bending stresses relaxation at high annealing temperatures proceeds due to both reversible anelastic deformation and viscous flow, which is a fully irreversible process. Incomplete reversibility is also caused by irreversible processes, such as the release of excess free volume and clustering (detected by small-angle X-ray scattering). The revealed differences in the relaxation processes that occur in the cobalt- and iron-based amorphous alloys are discussed in terms of different atomic diffusion mobilities in these alloys.

First-principle simulation on the crystallization tendency and enhanced magnetization of Fe76B19P5 amorphous alloy

Iron-based amorphous alloys have attracted a growing interest due to their potential in the application of magnetic coil production. However, the magnetization of this kind of material is usually low due to the lack of long range ordering and high alloying element content. In this paper, an Fe76B19P5 amorphous alloy was simulated with ab initio molecular dynamics based on a previous simulation work on an Fe76Si9B10P5 amorphous alloy exhibiting that electron absorbers such as B and P can help enhance the magnetization of nearby Fe atoms. The present simulation results show that replacing Si with B can destabilize the amorphous structure, making it easier to crystallize, but no separate α-Fe participation can be observed in experiments during annealing due to its high B/P content. The results also show an increase in saturation magnetization by 8% can be expected due to the intensified electron transfer from Fe to B/P, and the glass forming ability decreases correspondingly. The idea of enhancing electron transfer can be applied to the development of other Fe-based amorphous alloys for the purpose of larger saturation magnetization.

Development of Nanostructure Formation of Fe<sub>73.5</sub>Cu<sub>1</sub>Nb<sub>3</sub>Si<sub>13.5</sub>B<sub>9</sub> Alloy from Amorphous State on Heat Treatment

Iron-based amorphous alloys have attracted technological and scientific interests due to their excellent soft magnetic properties. The typical nanocrystalline alloy with the composition of Fe73.5Cu1Nb3Si13.5B9 known as FINEMENT has been studied for structural properties analysis. Recently, it is found that after proper annealing the amorphous alloy like Fe73.5Cu1Nb3Si13.5B9 has a transition to the nanocrystalline state, thus exhibiting good magnetic properties. The alloy in the form of ribbon of 10 mm width and 25mm thickness with the composition of Fe73.5Cu1Nb3Si13.5B9 was prepared by rapid quenching method. The prepared ribbon sample has been annealed for 30 min in a controlled way in the temperature range 490℃ - 680℃. By analyzing X-ray diffraction (XRD) patterns, various structural parameters such as lattice parameters, grain size and silicon content of the nanocrystalline Fe(Si) grains, crystallization behavior and nanocrystalline phase formation have been investigated. In the nanocrystalline state, Cu helps the nucleation of α-Fe(Si) grains while Nb controls their growth, Si and B has been used as glass forming materials. Thus on the residual amorphous, the nanometric Fe(Si) grains develops. From broadening of fundamental peaks, the optimum grain size has been determined in the range of 7 - 23 nm.

The thermal and magnetic properties of the Fe89.8Ni1.5Si5.2B3C0.5 and Fe81B13Si14C2 amorphous alloys

This paper investigates the thermal and magnetic properties of two iron based amorphous alloys with different Fe-content: Fe89.8Ni1.5Si5.2B3C0.5 and Fe81B13Si14C2. The XRD results show that the thermal induced structural changes occur in the temperature range of 3000C - 8500C for the Fe89.8Ni1.5Si5.2B3C0.5 amorphous alloy. The appearance of the first crystallization peaks on DSC thermograms of Fe81B13Si4C2, amorphous alloy is perceived already at 4500C. The initial magnetization curves of the as-cast sample of the Fe89.8Ni1.5Si5.2B3C0.5 amorphous alloy, obtained at the frequencies of 50 Hz, 400 Hz and 1000 Hz show the excellent match. The maximum relative magnetic permeability for Fe89.8Ni1.5Si5.2B3C0.5 alloy sample is achieved at magnetic field strength of about 20 A/m for all frequencies, whereas the values of about 7000 were obtained at the frequencies of 50 Hz and 400 Hz. The influence of frequency on total power losses, for both alloys exhibits the increase of core losses with frequency increase. The amorphous alloy Fe89.8Ni1.5Si5.2B3C0.5 toroidal core exhibits about 3 time higher total power losses.

Nature of the deformation crystallization of iron-based amorphous alloys upon megaplastic deformation

Specific features of the crystallization of amorphous alloys Fe83Cr13B4, Fe80B13Si7, Fe76Cr16Zr4.5B3C0.5, Fe58Ni25B17, Fe57Co24Cr16B3, and Fe50Ni33B17 during megaplastic deformation (MPD) in a Bridgman chamber have been studied at room temperature. It is found that the volume fraction of the crystalline phase formed in each of the amorphous alloys during deformation increases when its crystallization temperature decreases. The obtained results are explained on the assumption of adiabatic heating in a shear band and also the hypothesis regarding an increase in the concentration of excess free volume regions in shear bands during deformation.

Design of a Microfluidic Chip System Based on Magnetoelastic Sensors for Blood Coagulation Measurement

Blood coagulation measurement can provide the valuable indicators for diagnosing the hemorrhagic and thrombus disease, observing the curative effect of dissolving thrombus as well as preventing clotting. The novel design of a microfluidic chip system based on the magneto-elastic sensors for blood coagulation measurement is presented in this paper. Firstly, several thick films of iron-based amorphous alloy with the different specifications were selected to compose a magnetoelastic sensor group. Then this sensor group was packaged and bonded in a PDMS microfluidic chip to form a plurality of detection channels that can be used to simultaneously detect the multiple coagulation factors. The whole chip was fixed into a coil through a specific mold. Once the reagent and sample flow path was connected, the magneticelastic detection system could be used to measure multiple parameters including prothrombin time (PT), thromboplastin time (APTT), prothrombin time (TT). The preliminary experimental results have verified the feasibility of the design. The magnetoelastic sensor exhibits the wireless, passive, easily miniaturized and integrated features. These are combined with the microfluidic chip detection technology in this design to realize the multi-channel simultaneous detection of multiple parameters. Therefore, it has great potentials for clinic applications.

Interaction of surface of ribbons of amorphous soft-magnetic iron-based alloys with vapor

The interaction with water vapor of the surface of ribbons of amorphous soft-magnetic iron-based alloys with positive saturation magnetostriction and an effect of the interaction on the magnetization distribution and magnetic properties have been investigated. The results of the investigation showed that, during in-air heat treatment, the interaction of the surface of ribbons of amorphous soft-magnetic alloys with water vapor upon the heating of samples and at the initial stage of isothermal holding exerts a substantial effect on the magnetization distribution and the level of magnetic properties formed. Preliminary room-temperature treatment of the ribbon surface in the as-quenched state with water vapor favors an increase in pseudo-uniaxial tensile stresses along the ribbon axis because, during annealing, the enhanced concentration of hydrogen and oxygen atoms introduced into the ribbon surface is formed in this direction. When certain regimes of heat treatment are used, this leads to an increase in the volume of domains with magnetization oriented along the axis of the ribbon in its plane and allows a significant enhancement in the efficiency of the in-air heat treatment.

Nano-crystallization and magnetic mechanisms of Fe85Si2B8P4Cu1 amorphous alloy by ab initio molecular dynamics simulation

Iron-based amorphous and nano-crystalline alloys have attracted a growing interest due to their potential in the application of magnetic coil production. However, fundamental understanding of the nano-crystallization mechanisms and magnetic features in the amorphous structure are still lack of knowledge. In the present work, we performed ab initio molecular dynamics simulation to clarify the ionic and electronic structure in atomic scale, and to derive the origin of the good magnetic property of Fe85Si2B8P4Cu1 amorphous alloy. The simulation gave a direct evidence of the Cu-P bonding preference in the amorphous alloy, which may promote nucleation in nano-crystallization process. On the other hand, the electron transfer and the band/orbital features in the amorphous alloy suggests that alloying elements with large electronegativity and the potential to expand Fe disordered matrix are preferred for enhancing the magnetization.

Enhancement of wear and corrosion resistance of iron-based hard coatings deposited by high-velocity oxygen fuel (HVOF) thermal spraying

Fe-based alloy material is widely used in the corrosive environment of seawater. It is replacing expensive cobalt and nickel-based alloys. Amorphous iron-based (Fe-based) alloy coatings can be deposited on stainless steel by high-velocity oxygen fuel (HVOF) thermal spraying. Following spraying, coatings were heat-treated at 500, 600, 700, 800, and 900°C for up to three hours in a vacuum furnace. The microstructures of such coatings were analyzed herein using an optical microscope (OM) and scanning electron microscope (SEM) to monitor the morphologies of both powders and coatings of Fe-based alloy. Phase analysis was performed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The goal of this work on the modification of Fe-based alloy feedstock powder is to enhance the corrosion and wear properties of these coatings. The results of this investigation reveal that adding a cobalt material to Fe-based alloy yields coatings with enhanced corrosion and tribological characteristics.

Structured analysis of iron-based amorphous alloy coating deposited by AC-HVAF spray

The uniform and compact Fe-based amorphous alloy coating was prepared by active combustion high velocity air fuel (AC-HVAF) spray method. By tuning the parameters of AC-HVAF spray process, the influence of the spraying gun length, spraying distance, and powder feed rate on non-crystallization has been studied carefully. Results indicate that spraying gun length is the key factor in forming perfect amorphous coating. Spraying distance and powder feed rate may determine the thickness and formation rate of the coating. The prepared coatings have a tight adhesion with the substrate, low porosity, and good non-crystallization, which would effectively maintain the excellent mechanical properties of the Fe-based amorphous alloy. The coating can provide a good protection for the substrate material.

Possibilities of Application of Amorphous Fe<sub>77</sub>Cr<sub>2</sub>B<sub>16</sub>Si<sub>5</sub> Alloys in Different States of Thermal Relaxation as Magnetic Tensile Force Sensors

Paper discusses the possible of application of iron-based amorphous Fe77Cr2B16Si5 alloys for tensile force sensors. In proposed sensor uniform stresses were generated in direction of the ribbon ring core axis. As a result stresses were perpendicular to the magnetizing field direction, what increases sensor sensitivity as well as simplified analyses. The results show high magnetoelastic sensitivity of Fe77Cr2B16Si5 amorphous alloy. Moreover, this magnetoelastic sensitivity increases during the annealing process, which is connected with thermal relaxation of amorphous alloy.

Microstructure and wear resistance of spray-formed supermartensitic stainless steel

Since the early 90's the oil industry has been encouraging the development of corrosion and wear resistant alloys for onshore and offshore pipeline applications. In this context supermartensitic stainless steel was introduced to replace the more expensive duplex stainless steel for tubing applications. Despite the outstanding corrosion resistance of stainless steels, their wear resistance is of concern. Some authors reported obtaining material processed by spray forming, such as ferritic stainless steel, superduplex stainless steel modified with boron, and iron-based amorphous alloys, which presented high wear resistance while maintaining the corrosion performance1,2. The addition of boron to iron-based alloys promotes the formation of hard boride particles (M2B type) which improve their wear resistances3-9. This work aimed to study the microstructure and wear resistance of supermartensitic stainless steel modified with 0.3 wt. (%) and 0.7 wt. (%) processed by spray forming (SF-SMSS 0.3%B and SF-SMSS 0.7%B, respectively). These boron contents were selected in order to improve the wear resistance of supermartensitic stainless steel through the formation of uniformly distributed borides maintaining the characteristics of the corrosion resistant matrix. SF-SMSS 0.7%B presents an abrasive wear resistance considerably higher than spray-formed supermartensitic stainless steel without boron addition (SF-SMSS).

Magnetic Field Effects on Crystallization of Iron-Based Amorphous Alloys

The crystallization behavior of iron-based amorphous alloys has been investigated in high magnetic fields by differential thermal analysis (DTA) and magnetization measurements. DTA of Fe­Si­B amorphous alloys showed that the exothermic peaks shift toward higher temperature under high magnetic fields. At 10T, peak temperatures of the crystallizations increased approximately 3K, compared with those at a zero magnetic field. Such a variation in the crystallization peak was not observed in the Fe­B­Nb­Y bulk metallic glass (BMG). In the temperature dependence of the saturation magnetization for the Fe­Si­B amorphous alloy, the sudden increase of the magnetization was found at the crystallization temperatures. The magnetization of Fe­Si­B increased 56 and 40Am 2 kg ¹1 at the first and second crystallization temperatures, respectively. This magnetization behavior indicates the magnetic transition from the paramagnetic to the ferromagnetic state, accompanying the crystallization, whereas there is only a slight increase in magnetization at the crystallization temperature in Fe­B­Nb­Y BMG. The effect of magnetic field on the crystallization peak as observed from DTA is related to the increase in the magnetization at the crystallization temperature. [doi:10.2320/matertrans.M2012242]

Isothermal Crystallization of Iron-Based Amorphous Alloys in a High Magnetic Field

Isothermal crystallization of soft magnetic Fe­Si­B amorphous alloys under high magnetic fields was investigated by magnetization measurements. The increase of magnetization due to the precipitation of ferromagnetic i-Fe(Si) from the paramagnetic amorphous matrix was observed as a function of time. The magnetic field dependence of the time evolution of the crystallization was also examined. The relaxation time increases under high applied magnetic fields indicating that the suppression of the precipitated crystal growth rate occurs. Moreover, by normalizing the relaxation time of the crystallization, the time evolutions of the crystallized fraction converge to a universal sigmoidal curve regardless of the applied magnetic field strength. These behaviors indicate that the magnetic field influences the growth rate rather than the elementary processes of crystallization. [doi:10.2320/matertrans.M2013136]

Interrelation between the electrical resistance of amorphous alloys and their atomic and electronic structures

Based on the results of the investigations of temperature dependences of electrical resistance of a number of iron-based amorphous metallic alloys, a model of electrical resistance that takes into account the common features of the atomic and electronic structures of these alloys has been developd. It has been established that the alloying of these materials by elements that are located to the left of Fe in the periodic table leads to a nonlinearity, which is described satisfactorily by the T 1/2 law. This feature is explained by the phenomenon of weak localization in cluster structures formed around an alloying atom. The origin of such a localization is considered with allowance for the electron structure, which makes it possible to explain some singularities in the temperature dependences of the electrical resistance.

Magnetic Shielding Effectiveness of Iron-Based Amorphous Alloys and Nanocrystalline Composites

This paper refers to magnetic field shielding effectiveness <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$S_{\rm H}$</tex></formula> of the selected iron-based amorphous alloys and some magnetic composites. The measurement conditions were chosen regarding the potential sources such as energetic lines or electric devices. As it was shown, the shields made of amorphous and optimized (in amorphous phase) melt spun ribbons can be applied as highly efficient and flexible shields. In the group of the tested alloys, the highest <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$S_{\rm H}$</tex></formula> reveal (at <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$H=110$</tex></formula> A/m and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$f=55$</tex></formula> Hz): Fe <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{84}$</tex></formula> Cr <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\rm B}_{14}$</tex></formula> (95%) and optimized Fe <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{72}$</tex></formula> Co <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{10}$</tex></formula> Nb <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{6}$</tex></formula> B <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{14}$</tex></formula> (97%) and Fe <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{80}$</tex></formula> Nb <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{6}$</tex></formula> B <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{14}$</tex></formula> (92%). In the case of the tested composites, a significant decrease of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$S_{\rm H}$</tex></formula> was observed. The shielding effectiveness decreases with decreasing size of magnetic addition due to breaking magnetic flux circuit and dipolar interactions between particles. For the composite with magnetic flakes of 4 mm in diameter <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$S_{\rm H}$</tex></formula> is about 60%; therefore, it can be applied as coatings in order to fulfill human protective standards. For the composites with micro and nano-sized magnetic powder <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$S_{\rm H}$</tex></formula> does not depend of the composition which suggests that a response to a magnetic field is fully influenced by the demagnetization effect.

Magnetic cores made of an amorphous tape for the induction accelerator

It is proposed to use induction cells with cores wound by a thin tape made of an iron-based amorphous alloy in the linear induction accelerator for flash radiography. The comparison of pulse magnetization characteristics of the toroidal cores made with layer insulation and without it is given. The results of switching on of the injector based on the manufactured cores are presented.