Effect of the substitution of Fe by Co on the magnetic properties and microstructure of nanocrystalline (Fe1−xCox)86Hf7B6Cu1 alloys (original) (raw)
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Structure and high temperature magnetic properties of nanocrystalline (Fe0.6Co0.4)86Hf7B6Cu1 alloy
Materials Science and Engineering: A, 2006
The crystallization process, structure and high temperature magnetic properties of (Fe 0.6 Co 0.4 ) 86 Hf 7 B 6 Cu 1 alloy have been investigated. The alloy after annealing at 550 • C for 1 h exhibits the good soft magnetic properties with both small local coercivity and large magnetization. Furthermore, the coercivity measured at heating temperature point of this nanocrystalline alloy holds the value below 40 A/m until the onset of secondary crystallization corresponding to the formation of high coercivity phases. Nanocrystalline (Fe 0.6 Co 0.4 ) 86 Hf 7 B 6 Cu 1 alloy is one of the excellent candidates for soft magnetic materials used at high temperature applications with the range of 500-550 • C.
High-temperature magnetic behavior of FeCo-based nanocrystalline alloys
Physical Review B, 2002
The soft magnetic response of nanocrystalline Fe 73.5Ϫx Co x Si 13.5 B 9 Cu 1 Nb 3 ͑xϭ0, 30, and 45͒ samples are analyzed above room temperature through the temperature evolution of the magnetic permeability and the associated loss factor. Moreover, the actual structure and composition of the crystalline phase is analyzed through neutron-diffraction studies. The results show that the inclusion of Co atoms give rise to an improvement in the soft magnetic behavior at high temperatures with respect to the Fe-based sample as a consequence of the increase in the Curie temperature of the precipitated crystallites. However, the role of the residual amorphous matrix cannot be disregarded and the decrease in its Curie temperature for the Co richest sample gives rise to a deterioration of the high-temperature soft magnetic response. The observed temperature evolution is analyzed within the framework of the random anisotropy model and associated with the temperature dependence of the magnetic coupling between the ferromagnetic crystals.
Journal of Magnetism and Magnetic Materials, 2006
Amorphous ribbons Fe73.5−xMnxSi13.5Nb3Cu1 (x=1, 3, 5) were prepared by rapid quenching on a single rotated copper wheel. The X-ray patterns show that the as-cast samples are amorphous. The measurements of thermomagnetic curves indicated that the Curie temperature of the amorphous phase of the samples decreased with increasing Mn content. The optimal heat treatment was performed at Ta=535°C for 1h and
Development of Co-Fe Based Nanostructured Soft Magnetic Materials for High Temperature Applications
2011
Nanocrystalline FINEMET type alloys derived from amorphous precursors exhibit superior soft magnetic properties suitable for various types of applications like transformer cores, choke coils, magnetic sensors etc. However these materials lose their ferromagnetic stability at elevated temperature due to their low Curie temperature (below 700K) and hence are unsuitable for high temperature applications. To overcome this limitation, additional effort has been made to develop materials with high Curie temperature coupled with superior soft magnetic properties. It is observed that crystalline CoFe based alloy (HIPERCO) exhibits high Curie temperature. Hence, Willard et al. introduced a series of CoFe based alloys by the incorporation of cobalt in amorphous FeZrB alloy systems, which resulted in optimum material composition of Co44Fe44Zr7B4Cu1 termed as HITPERM alloy. Even though this type of alloy had fairly high Curie temperature but its soft magnetic properties tended to deteriorate du...
Journal of Applied Physics, 2003
The effect of Co replacement for Fe on the microstructure and soft magnetic properties of Fe 78.8Ϫx Co x Nb 2.6 Si 9 B 9 Cu 0.6 (xϭ5 -60) nanocrystalline alloys has been studied for improving the soft magnetic properties of Fe-Si-B-Nb-Cu type alloys at a high frequency range. The magnetic anisotropy constant increases with x, but the coercivity increases when x exceeds 20, indicating that magnetic softness is degraded by replacing Fe with Co. Three-dimensional atom-probe observations have revealed that the number density of Cu-enriched clusters decreases with x, thereby decreasing the number density of the heterogeneous nucleation sites for bcc-Fe primary crystals. In addition, differential scanning calorimetry measurements show that the Cu clustering temperature shifts to a higher temperature with increasing x, suggesting that the kinetics for the Cu clustering decreases as Co content. These experimental results are discussed from the thermodynamical point of view, and the optimized Cu composition to achieve a low coercivity with 40 at % Co has been found.
Journal of Applied Physics, 2003
The technological applicability of FeCoNbBCu alloys is suggested in terms of measurements of room temperature magnetoimpedance and temperature dependence of magnetic permeability r . Results for the Fe 78-x Co x Nb 6 B 15 Cu 1 alloy series show that room temperature soft magnetic properties are enhanced in the lowest Co containing alloy ( r ϳ10 500 and magnetoimpedance ratio ϳ60% at 1 MHz͒. However, permeability exhibits a smoother thermal dependence in the alloys with medium and high Co content. A tradeoff between magnetic softness and its thermal stability reveals the alloy with 39 at. % Co as the most suitable composition among those studied, characterized by a temperature coefficient of ϳ 0.02%/K from room temperature up to 900 K. This value is 1 order of magnitude smaller than those observed for FeSiBCuNb ͑FINEMET-type͒ alloys and Mn ferrites and extended over a much wider temperature range than in these materials.
Journal of Alloys and Compounds, 2010
The structure of annealed Sm(Co 0.6 Cu 0.4 ) 5 compounds, prepared with different Sm excess content, has been investigated by means of high resolution x-ray diffraction and scanning electron microscopy. The samples were also magnetically characterized by thermomagnetic analysis and M versus H curves at room temperature. Increasing Sm excess improves the compositional order of the 1 : 5 phase. The coercivity (H C ) and the Curie temperature (T C ) are both changed as a function of Sm excess content. The decrease in the structural defects density, resulting from the compositional order, is responsible for the observed magnetic behaviour.
On the optimization of soft magnetic properties of high Bs Fe83.7B14.8Cu1.5 nanocrystalline alloy
Journal of Physics: Conference Series, 2012
Influence of thermal annealing as a function of temperature and time, in Fe 83.7 B 14.8 Cu 1.5 alloy was monitored using magnetic measurements, differential scanning calorimetery (DSC), X-ray diffraction (XRD) to get information on correlation between structure, formed nano-crystalline phases and soft magnetic properties. Thermal annealing dependence of coercivity (H c ) and saturation magnetization (B 2000 ) shows that these values are affected by the structural relaxation and the presence of the precipitated nanocrystals in the amorphous phase. For the studied samples lowest coercivity of 14.6 A/m and rather high saturation induction value of 1.99 Tesla was obtained after annealing at 390 o C/1h. Activation energy of crystallization is 1.82 ± 0.48 eV. Grain diameter and volume fraction of the nanograins varies between 16.5 -29 nm and between 2 -56 % respectively. Lattice parameter suggests the presence of α-Fe and Fe 23 B 6 phase.
Characterization and Analysis of Nanocrystalline Soft Magnetic Alloys: Fe Based
Metals, 2021
Soft magnetic nanocrystalline alloys have been widely analysed and studied during the past years. However, optimisation of specific chemical compositions is still being developed. The applicability of these soft nanocrystalline alloys depends mainly on the presence of the desired nanocrystalline phases within the alloy. In this study, the analysed alloys are manufactured by mechanical alloying. The analyses performed on the samples include a microstructural analysis, a thermal analysis, and a complementary functional analysis in the form of the thermomagnetic response of some samples. Regarding Fe-based alloys, thermal stability for samples containing B was higher than those containing P (crystal growth peaks in the range between 895–905 K and 775–800 K respectively). The higher magnetization of saturation, Ms, was found in Fe–Mn alloys, whereas the addition of boron provoked a decrease of Ms and the nanocrystals size.