Optimization Of Soft Magnetic Properties Research Articles

Optimizing soft magnetic properties by reducing internal defects and residual stress of Fe85-xSi9.6Al5.4Snx soft magnetic composites

In this work, Fe85-xSi9.6Al5.4Snx (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) Soft magnetic powder cores (SMPCs) were prepared by Sn doping, and the effects of the doping on the microstructures and soft magnetic properties were systematically investigated. With the increase of Sn content, the dislocation density of SMPCs decreases from 0.53 × 1014 m−2 to 0.29 × 1014 m−2, so does the degree of lattice distortion and the residual stress. These changes optimize the soft magnetic properties of Fe85-xSi9.6Al5.4Snx SMPCs. Based our experiments, the effects of the crystal grain size, grain orientation, and magnetic domain motion on the magnetic properties are also discussed. At last, the best soft magnetic performance was obtained, when Sn doped with 0.8 wt.%. Fe85-xSi9.6Al5.4Snx SMPCs designed by Sn doping have excellent soft magnetic properties, which expands their application advantages in the field of power electronics, the composition design also provides an effective method for the optimization of soft magnetic properties of FeSiAl SMPCs.

Electron beam welding with in situ heat treatment: An effective method for optimization of soft magnetic properties of permalloy

Considering the deterioration of the soft magnetic properties of permalloy welded joints, a method of electron beam welding with in-situ heat treatment was investigated which provided improved soft magnetic properties. After in situ heat treatment, the initial permeability was considerably increased from 3.15 mH/m (71% of base metal) to 5.58 mH/m (130% of base metal), and the saturation flux density was also increased to 746.8 mT higher than that of base metal (703.7 mT). The tenacity of the joint with in situ heat treatment was improved, indicating that the elongation was increased from 32% to 40% after in situ heat treatment. Both soft magnetic property and mechanical property of the joint were optimized after in situ heat treatment. The underlying reason for the property optimization of welded joint with in situ heat treatment was the decrease in dislocations.

Development of Magnetically Soft Amorphous Microwires for Technological Applications

Amorphous magnetic microwires can be suitable for a variety of technological applications due to their excellent magnetic softness and giant magnetoimpedance (GMI) effect. Several approaches for optimization of soft magnetic properties and GMI effect of magnetic microwires covered with an insulating, flexible, and biocompatible glass coating with tunable magnetic properties are overviewed. The high GMI effect and soft magnetic properties, achieved even in as-prepared Co-rich microwires with a vanishing magnetostriction coefficient, can be further improved by appropriate heat treatment (including stress-annealing and Joule heating). Although as-prepared Fe-rich amorphous microwires exhibit low GMI ratio and rectangular hysteresis loops, stress-annealing, Joule heating, and combined stress-annealed followed by conventional furnace annealing can substantially improve the GMI effect (by more than an order of magnitude).

The percolation effect and optimization of soft magnetic properties of FeSiAl magnetic powder cores

In this paper, a new magnetic percolation phenomenon between the green compact density ρ and effective permeability μe in FeSi9.6Al6.5 magnetic powder cores, was discovered. The Magnetic Percolation Area of ρ is the range of 5.6 g/cm3∼5.78g/cm3, and the percolation threshold is 5.78g/cm3. As a result of the guidance of the percolation theory, the best comprehensive magnetic properties have been optimized through adjusting the distribution of powders. The special distribution of the magnetic powder cores with the best comprehensive magnetic properties was as follows: the content 60% with the particle size distribution of 100–200 mesh, the content 20% with the particle size distribution of 200–325 mesh and the content 20% with the particle size distribution of ≥400 mesh. When the green compact density ρ of cores was 5.79g/cm3, and the frequency was in the range of 1kHz∼100kHz, the best comprehensive magnetic properties were as follows: μe=91, ∆μ=0.61%, μe(H80 Oe)=43, μe(H100 Oe)=33, μe(H120 Oe)=26, Pc(50mT/20kHz)=30.58kW/m3, Pc(50mT/50kHz)=76.85kW/m3, Pc(50mT/100kHz)=178kW/m3. Not only have those cores the excellent constant magnetic properties with frequency, the excellent DC superposition characteristic and the lower loss at high frequency, but also the effective permeability outstandingly goes up, which has important significance for the miniaturization of inductance components.

Optimization of Soft Magnetic Properties in Fe-Ni-Based Magnetic Microwires

We studied the correlation between the magnetic softness and the magnetostriction coefficient of as-prepared and annealed Fe-Ni rich microwires. We found that the hysteresis loops as well as the magnetostriction coefficients of Fe47.4Ni26.6Si11B13C2 microwires can be tailored by annealing. Varying the annealing conditions, we observed the changes of the character of hysteresis loops. These changes correlate with the evolution of the magnetostriction coefficient.

Optimization of Soft Magnetic Properties in Nanocrystalline Fe-Rich Glass-Coated Microwires

We have studied Hitperm-type and Finemet-type glass-coated microwires with a nanocrystalline structure. In Hitperm-type microwires where the nanocrystalline structure has been obtained directly after melt quenching using the Taylor–Ulitovsky fabrication technique, we observed rectangular hysteresis loops and studied the domain wall propagation. We measured and analyzed the switching field dependence on the frequency in as-prepared and annealed Hitperm-type microwires. A conventional annealing results in a drastic change of the frequency dependence of the switching field. This effect might be interpreted considering the stress relaxation process. We have also studied the correlation of magnetic properties, structure, and giant magnetoimpedance (GMI) effect in Finemet-type FeCuNbSiB microwires prepared by the Taylor–Ulitovsky technique. We observed that both GMI effect and magnetic softness of Finemet-type glass-coated microwires can be tailored by heat treatment, and after annealing a considerable magnetic softening of studied samples has been achieved. This magnetic softening correlates well with the devitrification of amorphous samples. Amorphous Fe-rich microwires exhibit a low GMI effect (GMI ratio below 1%). A considerable enhancement of the GMI effect (GMI ratio up to 100%) has been observed in heat-treated microwires developing a nanocrystalline structure.

On the optimization of soft magnetic properties of high Bs Fe83.7B14.8Cu1.5 nanocrystalline alloy

Influence of thermal annealing as a function of temperature and time, in Fe83.7B14.8Cu1.5 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 (Hc) and saturation magnetization (B2000) 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 oC/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 Fe23B6 phase.

Magnetic properties of Fe76X2B22 (X=Cr,Zr,Nb) amorphous alloys

The paper contains experimental results referring to optimization of soft magnetic properties and crystallization in the Fe 76 X 2 B 22 (X=Cr,Zr,Nb) amorphous alloys. We have used measurement of thermomagnetic balance, magnetic permeability, coercive field and also HREM and X-ray diffraction techniques. It was shown that Zr and Nb alloying additions cause a slowing down of diffusion processes and an increase of the annealing for 1 hour optimization temperature of about 50 and 100 K, respectively. Activation enthalpies of the crystallization process were determined as: 2.0 eV (X=Cr), 2.6 eV (X=Zr) and 4.4 eV (X=Nb).

Optimization of soft magnetic properties in nanoperm type alloys

In the present paper, it was shown that soft magnetic properties of the group of amorphous alloys Fe–X2–B22 (X=Cr, Zr and Nb) can be optimized (magnetic permeability increases about five times) by applying 1-h annealing at temperatures: 600, 600, 650 and 700 K for the Fe78B22, Fe76Cr2B22, Fe76Zr2B22 and Fe76Nb2B22 alloys, respectively. This effect is attributed to annealing out of free volumes formed into material during fabrication and for the Fe76Zr2B22 alloy also to a formation of a nanocrystalline phase. Using isothermal measurements of magnetization (magnetic balance), it was shown that the process of formation of nanocrysalline phase can be described by Johnson–Mhel–Avrami kinetic. Activation enthalpy of this process was deduced as 3.2 eV and the power law exponent 3.4.

Optimization of Soft Magnetic Properties in Fe-B and Fe-B-Si Amorphous Alloys Obtained by Melt Spinning Method

In the present paper the process of optimization of soft magnetic properties have been studied by applying different experimental techniques (magnetic measurements, electric measurements, X-ray analysis, and high-resolution electron microscopy observations). It has been shown that an increase in magnetic permeability after optimization annealing can be mainly attributed to annealing out of microvoids.

On the optimization of soft-magnetic properties of metallic glasses by dynamic current annealing

A dynamic relaxation process has been developed that allows optimization of the soft-magnetic properties of ferromagnetic amorphous tapes during the winding process using Joule heating. Best magnetic properties of commercial FeSiB amorphous tapes are attained after only about ten seconds of annealing in air far below the crystallization temperatures but above the Curie temperature. It is found that structural and stress relaxation phenomena follow nearly the same temperature dependences in this annealing range. >