Fe–B–Si–Zr soft magnetic bulk glassy alloys

The present work is devoted to fabrication of Fe–B–Si–Zr multi-component bulk glassy alloys with good mechanical and soft magnetic properties. Glass formation in Fe–B system is first considered with an empirical cluster-plus-glue-atom model. A basic composition formula [B–B₂Fe₈]Fe is proposed as the framework for multi-component alloy design. Considering the structural stability of the model glass, Si and Zr are introduced to the [B–B₂Fe₈] cluster to replace the center B and shell Fe atoms, from which a series of Fe–B–Si–Zr alloys with composition formulas [Si–B₂Fe_8−xZr_x]Fe (x = 0–0.6) are derived. Copper mold casting experiment shows that bulk glassy alloys are formed within the Zr content range of x = 0.2–0.6, and the largest glass-forming ability appears at [Si–B₂Fe_7.6Zr_0.4]Fe with a critical size of 2.5 mm. The bulk glassy alloys exhibit high fracture strength as large as 3850 MPa. Magnetic property measurement indicates that these alloys exhibit good magnetic softness with high saturation magnetization (1.26–1.48 T) and low coercive force (1.6–6.7 A/m). The alloying effects of Si and Zr on bulk glass formation, thermal glass stability and magnetic softness are discussed with the empirical model.     

Martensitic transformation and magnetic properties in Ni–Fe–Ga–Co magnetic shape memory alloys

Ni–Fe–Ga–Co is a promising system for magnetic shape memory alloy applications, due to its good ductility, mobile twin boundaries and high transformation temperatures. Unlike previous studies which focused on compositions with a Ga content of 27 at.%, here the martensitic transformation and magnetic properties over a large composition range of Ni_54−xFe₂₀Ga₂₆Co_x, Ni_54−xFe₁₉Ga₂₇Co_x, Ni_56−xFe₁₇Ga₂₇Co_x and Ni_54−xFe₁₈Ga₂₈Co_x (x = 0, 2, 4) are investigated. The martensitic transformation temperature T_m and the Curie temperature T_c can be tailored in a wide range by changing composition and heat treatment. A coupling of martensitic and magnetic transformations at ∼90 °C is found for Ni₅₂Fe₁₇Ga₂₇Co₄. Additionally, the effect of thermal cycling on the martensitic transformation of single- and two-phase Ni–Fe–Ga–Co alloys is discussed. Furthermore, an intermediate face-centered cubic phase induced by powderization and transformed into a body-centered cubic phase by aging is reported. The saturation magnetization is significantly decreased by powderization, while recovered by the subsequent aging.     

The characterization of structure,thermal stability and magnetic properties of Fe–Co–B–Si–Nb bulk amorphous and nanocrystalline alloys

Recently bulk amorphous alloys have attracted great attention due to their excellent magnetic properties. The glass-forming ability of bulk amorphous alloys depends on the temperature difference (ΔT_x) between glass transition temperature (T_g) and crystallization temperature (T_x). The increase of ΔT_x causes a decrease of the critical cooling rate (V_c) and growth of the maximum casting thickness of bulk amorphous alloys. The aim of the present paper is to characterize the structure, the thermal stability and magnetic properties of Fe₃₆Co₃₆B₁₉Si₅Nb₄ bulk amorphous alloys using XRD, Mössbauer spectroscopy, DSC and VSM methods. Additionally the magnetic permeability μ_i (at force H ≈ 0.5 A/m and frequency f ≈ 1 kHz) and the intensity of disaccommodation of magnetic permeability Δμ/μ(t₁) (Δμ = μ(t₁ = 30 s) ? μ(t₂ = 1800 s)), have been measured, where μ is the initial magnetic permeability measured at time t after demagnetisation, the Curie temperature T_C and coercive force H_c of rods are also determined with the use of a magnetic balance and coercivemeter, respectively.Fe–Co–B–Si–Nb bulk amorphous alloys were produced by pressure die casting with the maximum diameters of 1 mm, 2 mm and 3 mm.The glass transition temperature (T_g) of studied amorphous alloys increases from 807 K for a rod with a diameter of 1 mm to 811 K concerning a sample with a diameter of 3 mm. The crystallization temperature (T_x) has the value of 838 K and 839 K for rods with the diameters of 1 mm and 3 mm, respectively. The supercooled liquid region (ΔT_x = T_x ? T_g) has the value of about 30 K. These values are presumed to be the origin for the achievement of a good glass-forming ability of the Fe–Co–B–Si–Nb bulk amorphous alloy. The investigated amorphous alloys in the form of rods have good soft magnetic properties (e.g. M_s = 1.18–1.24 T). The changes of crystallization temperatures and magnetic properties as a function of the diameter of the rods (time of solidification) have been stated.     

Microstructure and properties of nanocrystalline Fe–Zr–Nb–B soft magnetic alloys with low magnetostriction

We have investigated the microstructure–property relationship of nanocrystalline Fe₈₅Zr_1.2Nb_5.8B₈ and Fe_85.5Zr₂Nb₄B_8.5 soft magnetic alloys in order to understand the origin of drastic change in the permeability regardless of the zero magnetostriction in these two alloy compositions. Plan-view and cross-section transmission electron microscopy (TEM) observations showed strongly textured α-Fe particles on the free surface of the Fe₈₅Zr_1.2Nb_5.8B₈ alloy ribbon, while uniform nanocrystalline microstructure was observed in the Fe_85.5Zr₂Nb₄B_8.5 alloy ribbon. The high Zr content of the latter improves the glass forming ability, thereby suppressing the surface crystallization, resulting in higher permeability. By adding Cu in the Fe–Zr–Nb–B alloy, uniform nanocrystalline microstructure was obtained, from which superior soft magnetic properties with zero magnetostriction was achieved.     

Preparation technology and magnetic properties of Nd9.5Fe77B6Co5Zr2.5 nanocomposite magnets

The preparation technology and magnetic properties of Nd9.5Fe77B6Co5Zr2.5 nanocomposite magnets were investigated by melt spinning and crystallization process. The nonuniform composition and grain size can be induced by nanocomposite magnet prepared by arc-melt-spinning process, which will decrease the magnetic properties. These can be avoided by modification of preparing process. Induction-melt-spinning furnace was designed successfully and applied to prepare nanocomposite magnets. The bonded magnet with Br=0.736, Hcb=418 kA/m, Hcj=630 kA/m, Mr/Ms=0.7 and （BH）max=82.4 kJ/m^3 was prepared by this technology.     

Effect of composition and heat treatment on the structure and properties of Fe−Ni−Be invar alloys

Conclusions Addition of Be (0.5–1%) to Fe–Ni invar alloys provides dispersion hardening after quenching and aging, with retention of a low (close to invar) value of LCTE. Increase of the Be concentration in alloy 36N is accompanied by an increase in LCTE in the quenched as well as the aged condition, and increase of the Ni concentration to 38–41% at a fixed concentration of Be leads to a decreased value of LCTE in the aged alloys, approaching that of the alloy 36N. The optimum composition range for Fe–Ni–Be alloys in which the best combination of properties can be obtained — low value of LCTE (3.10^–6, K^–1) and higher strength (_0.2910 N/mm², _u1100 N/mm²) — was determined to be (39–40% Ni, 0.7–0.8% Be). The alloy 40NL (40% Ni, 0.8% Be) is proposed as a high strength invar alloy.I. P. Bardin Central Scientific-Research Institute for Ferrous Metallurgy (TsNIIChERMET). Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 33–36, February, 1992.     

Crystallization kinetics and induced magnetic properties of bulk （Fe,Co）-Zr-Nd-B metallic glass

Crystallization kinetics and phase transformation of bulk Fe64 Co7 Zr6 Nd3B20 metallic glass were studied by X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Based on the Kissinger analyses, the activation energies for the nucleation and growth during the first, second and third crystallization-stages of the metallic glass are determined to be 294, 475 and 365 kJ/mol, respectively, and the activation energy for the glass transition is determined to be 1 242 kJ/mol. The Johnson-Mehl-Avrami (JMA) analysis under the isothermal condition reveals that the crystallization process is a three-dimensional controlled growth of nuclei at a constant nucleation rate. The crystalline grains are in the size of less than 50 nm after the selected annealing treatments. In the completely crystallized state, the alloy exhibits the maximum coercivity (Hc) of 34.8 kA/m and corresponding energy product of 11 kJ/m^3.     

Metallurgical and magnetic characterisation of mechanically milled Sm(Co0.9−xFexCu0.1)4.8 alloys

An attempt has been made to develop nanocomposite Sm(Co_0.9−xFe_xCu_0.1)_4.8 (x=0 and 0.1) alloy powder by mechanical milling and subsequent annealing. The samples have been characterised by X-ray diffraction, scanning electron microscopy, differential scanning calorimetry and magnetic measurements. Evidence of exchange coupling between the magnetic phases has been observed in Sm(Co_0.8Fe_0.1Cu_0.1)_4.8 alloy.     

Effect of Al on microstructure and magnetic properties of mould-cast Nd60Fe40−xAlx alloys

Mould-cast Nd₆₀Fe_40−xAl_x (x=0, 5, 10) alloys were studied to clarify the effect of Al on the structural and magnetic properties. For binary Nd₆₀Fe₄₀, the metastable hard magnetic A₁ phase forms along with the Nd₂Fe₁₇ equilibrium phase. Partial substitution of Fe by Al favours the formation of the hard magnetic metastable A₁ phase manifested by a large magnetization.     

Phase transformation behavior and mechanical properties of Ti50Ni49−x Fe1Co x shape memory alloys

In this article, the influence of Co addition on phase transformation behavior and mechanical properties of TiNiFe shape memory alloy was investigated extensively. Differential scanning calorimetry (DSC) measurements shows that martensitic start transformation temperatures (Ms ) decrease drastically with increasing Co content, while the R phase transformation start temperatures (Rs ) vary slightly. Nevertheless, the substitution of Ni with Co does not exert substantial influence on the two-stage transformation behavior of the TiNiFe alloy. The results from stress-strain curves indicate that higher critical stress for stress-induced martensitic transformation (rSIM ) has been obtained because of Co addition. In such cases, the Ti50Ni48Fe1 Co1.0 alloy maintains a good shape memory effect, and a maximum recoverable strain of 7.5 % can be obtained.     

Structure and magnetic properties of TbCu_7-type melt-spun Sm–Fe–B alloys

The melt-spun SmFe_(12)B_x(x = 0, 0.50, 0.75,1.00, 1.25 and 1.50) ribbons were prepared at 40 m·s~(-1),and their structure and magnetic properties were studied by powder X-ray diffraction(XRD), vibrating sample magnetometer(VSM) and transmission electron microscopy(TEM). XRD results indicate that SmFe_(12)B_x alloys with 0.50 ≤ x ≤ 1.00 are composed of single-phase TbCu_7-type structure. Moreover, it is found that the boron addition can inhibit the emergence of soft magnetic phase a-Fe and result in the increase in the axial ratio c/a. After annealing at 650 ℃ for 0.5 h, the metastable phase TbCu_7 initially decomposes into the stable phase Sm_2Fe_(14)B(Nd_2Fe_(14)B-type) and a-Fe. The value of magnetic moment per Fe atom increases slightly from 1.75 uB for boron-free sample to 1.80 uB for the x = 0.75 sample and then decreases again.In addition, the best magnetic properties of maximum energy product [(BH)_(max)] of 14.56 kJ·m~(-3), coercivity(H_(cj))of 172.6 kA·m~(-1) and remanence(B_r) of 0.45 T are obtained for the SmFe_(12)B_(1.00) alloy. Based on transmission electron microscopy(TEM) results, the average size of grains is around 197 nm for B-free sample and decreases to 95 nm for x = 1.00 sample, indicating that the addition of boron can refine grains.     

Nanoindentation of porous bulk and thin films of La0.6Sr0.4Co0.2Fe0.8O3−δ

In this paper we show how reliable measurements on porous ceramic films can be made by appropriate nanoindentation experiments and analysis. Room-temperature mechanical properties of the mixed-conducting perovskite material La_0.6Sr_0.4Co_0.2Fe_0.8O_3?δ (LSCF6428) were investigated by nanoindentation of porous bulk samples and porous films sintered at temperatures from 900 to 1200 °C. A spherical indenter was used so that the contact area was much greater than the scale of the porous microstructure. The elastic modulus of the bulk samples was found to increase from 33.8 to 174.3 GPa and hardness from 0.64 to 5.32 GPa as the porosity decreased from 45% to 5% after sintering at 900–1200 °C. Densification under the indenter was found to have little influence on the measured elastic modulus. The residual porosity in the “dense” sample was found to account for the discrepancy between the elastic moduli measured by indentation and by impulse excitation. Crack-free LSCF6428 films of acceptable surface roughness for indentation were also prepared by sintering at 900–1200 °C. Reliable measurements of the true properties of the films were obtained by data extrapolation provided that the ratio of indentation depth to film thickness was in the range 0.1–0.2. The elastic moduli of the films and bulk materials were approximately equal for a given porosity. The 3-D microstructures of films before and after indentation were characterized using focused ion beam/scanning electron microscopy tomography. Finite-element modelling of the elastic deformation of the actual microstructures showed excellent agreement with the nanoindentation results.     

Microstructure,tribological behavior and magnetic properties of Fe−Ni−TiO2 composite coatings synthesized via pulse frequency variation

The Fe−Ni−TiO₂ nanocomposite coatings were electrodeposited by pulse frequency variation. The results showed that the nanocomposite with a very dense coating surface and a nanocrystalline structure was produced at higher frequencies. By increasing the pulse frequency from 10 to 500 Hz, the iron and TiO₂ nanoparticles contentswere increased in expense of nickel content. XRD patterns showed that by increasing the frequency to 500 Hz, an enhancement ofBCC phase was observed and the grain size of deposits was reduced to 35 nm. The microhardness and the surface roughness were increased to 647 HV and 125 nm at 500 Hz due to the grain size reduction and higher incorporation of TiO₂ nanoparticles into the Fe−Ni matrix (5.13 wt.%). Moreover, the friction coefficient and wear rate values were decreased by increasing the pulse frequency;while the saturation magnetization and coercivity values of the composite deposits were increased.     

Magnetism and transport properties of Nd6Fe13−xAl1+x crystals

Nd₆Fe_13−xAl_1+x (x=2.2 and 3.5) crystals were grown by the self-flux method, and their crystallographic, magnetic and electric properties were investigated. Nd₆Fe_13−xAl_1+x, which crystallizes in a tetragonal structure of space-group I4/mcm, shows peculiar successive magnetic transitions. In particular, Nd₆Fe_9.5Al_4.5 shows transitions at 20 K, 56 K and 128 K, and the spontaneous magnetization M_s at 5 K (87.5 emu/g) can be explained by assuming ferromagnetic Fe sublattices (4d↑16k↑16l₁↑16l₂↑) and ferrimagnetic Nd sublattices (8f↓16l↑). Nd₆Fe_9.5Al_4.5 seems to adopt ferrimagnetism in which the spontaneous magnetization is parallel to the 〈100〉 directions at temperatures below 20 K. A small ferromagnetic moment component, which is induced by canting of the antiferromagnetically coupled spins along the [001] direction, exists in the [100] direction at temperatures of 20 K<T<56 K. At temperatures of 56 K<T<128 K, an antiferromagnetic spin configuration exists along the [001] direction. A first-order magnetization process was observed in the magnetization curve measured in the [001] direction in the temperature ranges 20 K<T<56 K. The electrical resistivity showed anomalies at the temperatures of each magnetic transition. Moreover, a remarkable hysteresis was observed in the field dependence of resistivity. The magnetic phase transitions seem to have significant effects on the transport properties.     

Manufacturing of the bulk amorphous Fe61Co10Zr2+xHf3−xW2Y2B20 alloys (where x = 1, 2, 3) their microstructure,magnetic and mechanical properties

In this paper the microstructure, magnetic properties and mechanical studies results for Fe₆₁Co₁₀Zr_2+xHf_3?xW₂Y₂B₂₀ (for x = 1, 2 or 3) alloys are presented. The samples used in the investigations were obtained by a suction-casting method. The samples were produced in the forms of rods with diameter of 1 mm and length of about 20 mm and plates with thickness of 0.5 mm and surface area of about 100 mm². The results show that the best soft magnetic properties were achieved by Fe₆₁Co₁₀Zr₃Hf₂W₂Y₂B₂₀ amorphous alloy in the form of a plate. This sample has the highest value of saturation magnetization (1.09 T) and the smallest values of coercivity (H_C = 1.5 A/m) and core losses. All investigated samples of amorphous alloys were characterized by substantially greater values of microhardness and, unfortunately, slightly lower values of wear resistance compared with their crystalline counterparts.     

Structure and magnetic properties of mechanically alloyed Tb0.2Pr0.8（Fe0.4Co0.6）1.93 and magnetostriction of its epoxy composite

The C15 Laves phase with composition Tb_0.2Pr_0.8(Fe_0.4Co_0.6)_1.93 was synthesized by mechanical alloying (MA) and subsequent annealing process. The structure and magnetic properties of Tb_0.2Pr_0.8(Fe_0.4Co_0.6)_1.93 were investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer, and a standard strain technique. The effect of annealing on the structure and magnetic properties was studied. The analysis of XRD shows that the high Pr-content Tb_0.2Pr_0.8(Fe_0.4Co_0.6)_1.93 alloy with the single phase of MgCu₂-type structure can be successfully synthesized by MA method. The sample annealed at 450°C is found to have a coercivity of 196 kA/m at room temperature. An epoxy/Tb_0.2Pr_0.8(Fe_0.4Co_0.6)_1.93 composite was produced by a cold isostatic pressing technique. A large magnetostriction of 400 ppm, at an applied magnetic field of 800 kA/m, was found for the composite. The epoxy-bonded Tb_0.2Pr_0.8(Fe_0.4Co_0.6)_1.93 composite combines a high magnetostriction with a significant coercivity, which is a promising magnetostrictive material.     

Structure and magnetic properties of a multi-principal element Ni–Fe–Cr–Co–Zn–Mn alloy

A nanocrystalline alloy with a nominal composition of Ni₂₀Fe₂₀Cr₂₀Co₂₀Zn₁₅Mn₅ was produced by mechanical alloying and processed using annealing treatments between 450 and 600 °C for lengths from 0.5 to 4 h. Analysis was conducted using x-ray diffraction, transmission electron microscopy, magnetometry, and first-principles calculations. Despite designing the alloy using empirical high-entropy alloy guidelines, it was found to precipitate numerous phases after annealing. These precipitates included a magnetic phase, α-FeCo, which, after the optimal heat treatment conditions of 1 h at 500 °C, resulted in an alloy with reasonably good hard magnetic properties. The effect of annealing temperature and time on the microstructure and magnetic properties are discussed, as well as the likely mechanisms that cause the microstructure development.     

Nb-Poor Fe–Nb–B nanocrystalline soft magnetic alloys with small amount of P and Cu prepared by melt-spinning in air

The effect of the addition of P and Cu to Fe₈₅Nb₆B₉ alloy on an as-quenched structure and soft magnetic properties in a nanocrystallized state has been investigated. The Fe₈₅Nb₆B₉ alloy melt-spun in air has an as-quenched structure of an amorphous phase and α-Fe grains with 20–45 nm in size. The coarse grains should still remain in the nanocrystallized structure, which deteriorates the soft magnetic properties. The simultaneous addition of 1 at.% P and 0.1 at.% Cu to the Fe₈₅Nb₆B₉ alloy decreases the α-Fe grain size to nanoscale in an as-quenched state, and realizes a uniform crystallized structure with high saturation induction of 1.61 T as well as high permeability of 41,000.     

Influence of heat treatment on the structure and magnetic properties of amorphous Co–Ni–Fe–Cr–Si–B alloy and its thermal stability

The causes of changes in the magnetic properties of an amorphous Co–Ni–Fe–Cr–Si–B alloy obtained by melt spinning in the form of a thin ribbon subjected to heat treatment and subsequent action of temperatures corresponding to various conditions of its exploitation have been analyzed. We have established the regimes of heat treatment that provide for the highest values of the maximum magnetic permeability of the alloy and the shielding factor of a magnetic shield made from the alloy. We have analyzed changes in the magnetic properties, shielding properties, and total magnetization distribution in an alloy ribbon at a temperature well below the crystallization temperature. We have found the temperature ranges that determine the practical application of this alloy.     

Effects of quenching speed and Joule heating on the magnetic properties of Nd9Fe86B5 ribbons

1 IntroductionNanocomposite two-phase magnets are an im-portant type of permanent magnetic materials that have attracted much attention in recent years. Com-bining the high coercive force of the hard magnetic phase and the large saturation magnetization o…