Effects of Nb and Mo additions on thermal behavior,microstructure and magnetic property of FeCoZrBGe alloy

Both Nb and Mo additions play a vital role in FeCo-based alloys and it is crucial to understand their roles and contents on thermal behavior,microstructural feature and magnetic property of alloys.Nanocrystalline alloy ribbons Fe40Co40Zr9?yMyB10Ge1(y=0–4;M=Nb,Mo)were prepared by crystallizing the as-quenched amorphous alloys.The effects of Nb and Mo additions on structures and properties of the Fe40Co40Zr9B10Ge1 alloy are investigated systemically and compared.With increasing Nb or Mo content,the primary crystallization temperature,grain size ofα-Fe(Co)phase and coercivity Hc all decrease.Moreover,the effect of Mo addition on thermal behavior,microstructure and magnetic properties of the FeCoZrBGe alloy is greater compared to Nb addition.The gap between primary and secondary crystallization peaks of Mo-containing alloys is wider than that of Nb-containing alloys.Both grain size and Hc of Mo-containing alloys are smaller than those of Nb-containing alloys.For Fe40Co40Zr9B10Ge1 alloy,high Mo addition proportion is better compared to high Nb addition proportion.     

Effect of Yttrium Addition on Glass Forming Ability of ZrCuAlSi Alloy

The effect of yttrium addition on glass formation of a ZrCuAlSi alloy is investigated. The maximum diameter 8mm of the glassy rods for （Zr46.3Cu43.3Al8.9Si1.5）100-xYx alloy with x = 2.5 is obtained by copper mould casting. Apparent enhancement of the glass formation ability is found with addition of yttrium, mainly due to the purification of the alloy melt and the suppression of formation of the primary phases by yttrium.     

A comparative study of the structure and crystallization of bulk metallic amorphous rod Pr60Ni30Al10 and melt-spun metallic amorphous ribbon Al87Ni10Pr3

Pr-based bulk metallic amorphous （BMA） rods （Pr60Ni30Al10） and Al-based amorphous ribbons （Al87Ni10Pr3） have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Thermal parameters deduced from differential scanning calorimeter （DSC） indicate that the glass-forming ability （GFA） of Pr60Ni30Al10 BMA rod is far higher than that of Al87Ni10Pr3 ribbon. A comparative study about the differences in structure between the two kinds of glass-forming alloys, superheated viscosity and crystallization are also made. Compared with the amorphous alloy Al87Ni10Pr3, the BMA alloy Pr60Ni30Al10 shows high thermal stability and large viscosity, small diffusivity at the same superheated temperatures. The results of x-Ray diffraction （XRD） and transmission electron microscope （TEM） show the pronounced difference in structure between the two amorphous alloys. Together with crystallization results, the main structure compositions of the amorphous samples are confirmed. It seems that the higher the GFA, the more topological type clusters in the Pr-Ni-Al amorphous alloys, the GFAs of the present glass-forming alloys are closely related to their structures.     

Magnetic and Distribution of Magnetic Moments in Amorphous Fe89.7P10.3 Alloy Nanowire Arrays

Binary amorphous Fe89.7P10.3 alloy nanowire arrays in been fabricated in an anodic aluminium oxide template diameter of about 40nm and length of about 3μm have by electrodeposition. Magnetic properties of the samples are investigated by mean of vibrating sample magnetometer, transmission Mossbauer spectroscopy and conversion electron Mossbauer spectroscopy at room temperature. It is found that the nanowire arrays have obvious perpendicular magnetic anisotropy, and are ferromagnetic at room temperature, with its Mossbauer spectra consisting of six broad lines. The average angles between the Fe and 28° at the end of the amorphous Fe89.7P10.3 alloy magnetic moment and the wire axis are about 14°inside nanowire arrays, respectively. The magnetic behaviour is decided by the shape anisotropy and the dipolar interaction between wires. In addition, the magnetic moments distribution is theoretically demonstrated by using the symmetric fanning mechanism of the spheres chain model.     

The effect of Nb addition on the thermal stability and magnetic properties of Fe—based amorphous alloys with a wide supercooled liquid region

We have examined the effect of Nb addition on the thermal stability of the supercooled liquid before crystallization,the glass-forming ability and magnetic properties for the amorphous alloyn series Fe73NbxAl5-xGe2P10C6B4 and Fe63Co7NbxZr10-xB20.The supercooled liquid regions (ΔTx=Tx-Tg) have maximum values of 66 and 79K,respectively,for Fe73Nb1Al4Ge2P10C6B4 and Fe63Co7Nb4Zr6B20 alloys.The saturation magnetization σs of the Fe73NbxAl5-xGe2P10C6B4 alloy system is much higher than that of the Fe63Co7NbxZr10-xB20 alloy system,and is almost unchanged with an increasing Nb content from 0 to 3 at%.But the σs of the Fe63Co7NbxZr10-xB20 alloys decreases linearly with increasing Nb content.The coercive force Hc of the two alloy series can have a minimum value of 31A/m for Fe73Nb1Al4Ge2P10C6B4 and 37A/m for Fe63Co7Nb4Zr6B20.All these values are for the ribbons annealed at 773 and 873K for 15min in vacuum.     

Development of soft magnetic amorphous alloys with distinctly high Fe content

This paper reports on the preparation of Fe_(82.7-85.7)Si_(2-4.9)B_(9.2-11.2)P_(1.5-2.7)C_(0.8) soft magnetic amorphous alloys with a distinctly high Fe content of 93.5-95.5 wt.% by component design and composition adjustment. All alloys can be readily fabricated into completely amorphous ribbon samples with good surface quality by the single copper roller melt-spinning method. These alloys show good bending ductility and excellent magnetic properties after annealing, i.e., low coercivity(H_c) of 3.3-5.9 A/m, high permeability(μ_e)of 5000-10000 and high flux saturation density(B_s) of 1.63-1.66 T. The mechanism of the good glass forming ability(GFA) and soft-magnetic properties are explored. The amorphous alloys with the high Fe content comparable to that of the desired high Si alloy can be promising candidates for the potential application in electric devices.     

Glass Formation Ability and Kinetics of the Gd55A120Ni25 Bulk Metallic Glass

We report a new bulk glass-forming alloy GdssA12oNi25. The bulk sample of the alloy is prepared in the shape of rods in diameter 2ram by suction casting. The rod exhibits typical amorphous characteristics in the x-ray diffraction pattern, paramagnetic property at 30OK, distinct glass transition and multi-step crystallization behaviour in differential scanning calorimetry traces. The gJass formation ability of the alloy is investigated by using the reduced glass transition temperature Trg and the parameter γ- Kinetics of glass transition and primary crystallization is also studied. The fragility parameter m obtained from the Vogel-Fulcher-Tammann dependence of glass transition temperature Tg on In φ （φ is the heating rate） classifies the bulk metallic glasses into the intermediate category according to Angell＇s classification.     

Glass-Forming Ability of an Iron-Based Alloy Enhanced by Co Addition and Evaluated by a New Criterion

A new Fe-based alloy that can be cast into a fully amorphous rod with a diameter of at least 16mm by the conventional copper-mould casting technique is obtained by partially replacing Fe with Co in a previously reported Fe-based bulk metallic glass. The preliminary thermodynamic analysis indicates that the Co-containing alloy has a significantly lower Gibbs free energy difference between the undercooled melt and the corresponding crystalline solid, compared to the Co-free alloy, reflecting the dramatic role of the Co addition in stabilizing the supercooled melt and facilitating glass formation in iron-based alloys. Here, a new criterion, derived from the classical nucleation and growth theory, is introduced to evaluate the glass-forming ability of Fe-based bulk metallic glasses.     

Effects of Mo additions on the glass-forming ability and magnetic properties of bulk amorphous Fe-C-Si-B-P-Mo alloys

Glass formation, mechanical and magnetic properties of the Fe76-xC7.0Si3.3B5.0P8.7Mox (x=0, 1 at.%, 3 at.% and 5 at.%) alloys prepared using an industrial Fe-P master alloy have been studied. With the substitution of Mo for Fe, glass-forming ability (GFA) was significantly enhanced and fully amorphous rods with a diameter of up to 5 mm were produced in the alloy with 3% Mo. The Mo-containing amorphous alloys also exhibited high fracture strength of 3635–3881 MPa and excellent magnetic properties including a high saturation magnetization of 1.10–1.41 T, a high Curie temperature and a low coercive force. The unique combination of high GFA, high fracture strength and excellent magnetic properties make the newly developed bulk metallic glasses viable for practical engineering applications.     

X-Ray Magnetic Circular Dichroism Measurement of Fe-Co Alloy Films Prepared by Electrodeposition

The macro- and micro-magnetic properties of Fe-Co alloy films eletrodeposited on CaAs（100） are studied by synchrotron radiation x-ray magnetic circular dichroism （XMCD） in combination with the magneto-optical Kerr effect （MOKE） measurements and magnetic force microscopy （MFM）. The orbital and spin magnetic moments of each element in the Fe-Co alloy are determined by the sum rules of XMCD. Element-specific hysteresis loops （ESHL） are obtained by recording the La MCD signals as a function of applied magnetic field. MOKE results reveal that the amorphous films are magnetically isotropic in the surface plane. The MFM image shows that the dimension of the magnetic domains is about 1-2 #m, which is much larger than that of the grains, indicating that there are intergranular correlations among these grains. Both ESHL and MOKE hysteresis loops indicate the strong ferromagnetic coupling of Fe and Co in the alloy films.     

Grain growth process of two-phase nanocrystalline soft magnetic materials

In order to clarify the origin of the high thermal stability of the microstructure in bcc-Fe/amorphous two-phase nanocrystalline soft magnetic materials, we have investigated the changes in the magnetic and microstructural properties upon isothermal annealing at 898 K for an Fe₈₉Zr₇B₃Cu₁ alloy by means of transmission electron microscopy, Mössbauer spectroscopy and DC magnetometry. The mean grain size was found to remain almost unchanged at the early stage of annealing. However, rapid grain coarsening was evident at an annealing time of 7.2 ks where the intergranular amorphous phase begins to crystallize into Fe₂₃Zr₆. The grain growth process with a kinetic exponent of 1.6 is observed for the growth process beyond this annealing time, reflecting the disappearance of the intergranular amorphous phase. Our results confirm that the thermal stability of the bcc-Fe/amorphous two-phase nanocrystalline soft magnetic alloys is governed by the residual amorphous phase.     

Cr对Fe-Zr基非晶合金电阻率及压力效应的影响

 在0.000 1~2.5 GPa范围不同静水压下，用四探针法详细测量了七种非晶态Fe_90-xCr_xZr₁₀合金（x=2、4、7、10、13、16、20）的电阻率。结果表明：（1）常压室温电阻率ρ₀与FeZr基非晶合金中Cr含量成N形曲线关系；（2）当静水压增加时，七种非晶合金的约化电阻率（ρ/ρ₀）都单调下降，x越大则电阻率下降的幅度越小；（3）非晶Fe_90-xCr_xZr₁₀合金电阻率的压力系数对x的变化相当敏感；（4）为方便查值，给出了六种典型静水压下ρ/ρ₀与x的曲线关系。最后，讨论了四种物理模型的选用以及相干交换散射在高压下的行为。     

Effect of Gd and Fe doping on magnetic properties of Al87Y5Ni8 amorphous alloy

In this paper we present and discuss magnetic properties of the Al₈₇Y₅Ni₈, Al₈₇Y₄Gd₁Ni₈, Al₈₇Gd₅Ni₈, Al₈₇Y₄Gd₁Ni₄Fe₄ and Al₈₇Gd₅Ni₄Fe₄ amorphous alloys. The examinations have been concentrated on a possible magnetic ordering at low temperatures and its modification by amorphous surroundings as well as different magnetic moment of alloying additions. It was shown that magnetic properties of the Al₈₇Y₅Ni₈ amorphous base alloy correspond to a superparamagnetic body with Ni magnetic clusters. Magnetic moment of Ni atom in amorphous aluminum matrix is found to be 0.3 μ_B that corresponds to less than 50 Ni atoms per one cluster. Gd doping of the base alloy leads to a decrease of the resultant magnetic moment of Ni clusters that can be explained by some antiferromagnetic coupling Ni-Gd and Ni-Ni within magnetic clusters.     

Microstructure investigations and magnetic after-effect in amorphous and nanocrystalline Fe–Zr–Ti–B–Cu alloy

The microstructure evolution and low field magnetic properties i.e. initial magnetic susceptibility, stabilization field and magnetic after-effect as disaccommodation of the amorphous and nanocrystalline Fe₈₀Zr₄Ti₃B₁₂Cu₁ alloy were investigated. The heat treatment of the as-quenched Fe₈₀Zr₄Ti₃B₁₂Cu₁ alloy at 773 K for 1 h leads to its nanocrystallization. It was stated that initial magnetic susceptibility increases and intensity of disaccommodation decreases with increasing of annealing temperature. The magnetic after-effect of the investigated nanocrystalline samples is connected with relaxation processes that occur in the amorphous matrix.     

The influence of composition and field annealing on magnetic properties of FeCo-based amorphous and nanocrystalline alloys

We report the influence of composition and very high transverse field annealing on the magnetic properties and structure of four FeCo-based amorphous and nanocrystalline alloys. The compositions (Fe₅₀Co₅₀)₈₉Zr₇B₄ and (Fe₆₅Co₃₅)₈₉Zr₇B₄ were investigated changing the Fe:Co ratio from 50:50 to 65:35. (Fe₅₀Co₅₀)₈₅Zr₂Nb₄B_8.5 was chosen to investigate Nb substitution for Zr in an FeCo-based alloy. This substitution is shown to increase the magnetostrictive constant, _λS${\lambda }_{\mathrm{S}}$, of the nanocrystalline alloy from 36×10⁻⁶ to 54×10⁻⁶. The composition (Fe₆₅Co₃₅)₈₄Cr₅Zr₇B₄ was studied to investigate the influence of Cr on intergranular coupling across the amorphous matrix. Samples of each composition were annealed in the amorphous state at 300 °C and in the nanocrystalline state at 600 °C. Field annealing was performed in 17 T transverse field in an inert atmosphere. Frequency-dependent magnetic properties were measured with an automatic recording hysteresisgraph. Static magnetic properties were measured with a vibrating sample magnetometer. The mass-specific power loss of the alloys decreased with field annealing in both the nanocrystalline and amorphous states for some frequency and induction combinations. Furthermore, the hysteresis loops are sheared after field annealing, indicating a transverse magnetic anisotropy. The nanocrystalline (Fe₅₀Co₅₀)₈₅Zr₂Nb₄B_8.5 composition has a lower relative permeability than the other compositions.     

Magnetoimpedance effect in Nanoperm alloys

The influence of isothermal annealing (1 h at 600 °C in Ar atmosphere) on the soft magnetic properties and magnetoimpedance (MI) effect has been studied in ribbons of the following Nanoperm alloys: Fe₉₁Zr₇B₂, Fe₈₈Zr₈B₄, Fe₈₇Zr₆B₆Cu₁ and Fe₈₀Zr₁₀B₁₀. A maximum MI ratio of about 27% was measured for the nanocrystalline alloy Fe₈₇Zr₆B₆Cu₁ at a driving frequency of 0.2 MHz. The thermal annealing led to magnetic softening for this alloy, while a hardening is observed for the Fe₈₀Zr₁₀B₁₀ alloy.     

Inducing anisotropy in bulk Nd-Fe-Co-Al-B nanocrystalline alloys by quenching in magnetic field

We have observed magnetic anisotropy in bulk Nd_55−xCo_xFe₃₀Al₁₀B₅ (x=10, 15 and 20) alloys prepared by copper mold suction casting method with a presence of external magnetic field (quenching field) μ₀H=0.25 T. By changing direction of the measuring field from perpendicular to parallel one in comparison with that of the quenching field, coercive force of the alloys slightly decreases while remanent magnetization and squareness of hysteresis loop increase more clearly. It is also found that the higher Co-concentration in the alloys the larger magnetic anisotropy is induced. The structure analyses manifest nanocrystalline particles embedded in residual amorphous matrix of the alloys. The size of the particles is in range of 10-30 nm and their crystalline phases consist of Nd₂(Fe,Co)₁₄B, Nd₃Co, Nd₃Al, NdAl₂ and Nd.     

Long-term stability of soft magnetic properties of amorphous and nanocrystalline alloys based on iron

In the present paper long-term stability of magnetic properties of different amorphous and nanocrystalline alloys was studied. Magnetic properties were measured for annealed samples (300<Ta<900 K) directly after annealing and after long-term aging at room temperature. It was shown that for the Fe_75.3Cu₁Zr_1.7Si₁₃B₉ alloy magnetic permeability of the optimized samples is stable during 8 years aging. For Fe_86−xNb_xB₁₄ alloys the observed long-term instability (3 years aging) is due to annealing out of free volume leading to formations of small iron clusters coherent with the amorphous surroundings.     

Amorphization Induced High Magneto-Caloric Effect of Gd55Al20Ni25 Ternary Alloy

We report the amorphization induced high magneto-caloric effect （MCE） of recently developed Gd55Al15Ni30 bulk metallic glass （BMG）. The magnetic properties of the Gd55Al15Ni30 BMG are investigated in comparison with that of its crystalline counterpart. It is found that amorphization can increase the saturation magnetization and decrease the hysteresis of Gd55Al15Ni30 alloys, which indicate the possible enhancement of MCE. The magnetic entropy changes and the refrigerant capacity of the BMG as well as the crystalline samples is calculated directly from isothermal magnetic measurements. The results show the amorphization induced high MCE of the alloy and the excellent refrigerant efficiency of Gd55Al15Ni30 bulk metallic glass.