The kinetics of nanocrystallization and microstructural observations in FINEMET, NANOPERM and HITPERM nanocomposite magnetic materials

McHenry, Michael E.; Johnson, Frank B.; Okumura, Hideyuki; Ohkubo, T.; Ramanan, V. R. V.; Laughlin, David E.

doi:10.1016/s1359-6462(02)00597-3

Cited by 165 publications

(82 citation statements)

References 24 publications

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“…respectively. These values are similar to those found for NANOPERM and HITPERM alloys [1,[22][23][24]. The value of the Avrami exponent of the nanocrystallization process is close to 1 for all the studied alloys.…”

Section: Methodssupporting

confidence: 87%

Section: Methodsmentioning

confidence: 97%

“…The value of the Avrami exponent of the nanocrystallization process is close to 1 for all the studied alloys. This value is characteristic for the kinetics of the nanocrystallization of metallic amorphous alloys [1,22,23].The shape of the peak of the second transformation stage is clearly asymmetric for the alloys with Ge (much clearer for the alloy with 20 at. % of Co), while it is sharp and symmetric for the alloys without Ge.…”

mentioning

confidence: 89%

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Partial substitution of Co and Ge for Fe and B in Fe–Zr–B–Cu alloys: microstructure and soft magnetic applicability at high temperature

et al. 2005

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The partial substitutions of Co for Fe and Ge for B are studied for a Fe 83-x Co x Zr 6 B 10-y Ge y Cu 1 alloy series (x = 0, 5 and 20; y = 0 and 5) as a possible way to enhance the high temperature applicability of NANOPERM alloys. The devitrification process, the nanocrystallization kinetics and the nanocrystalline microstructure are similar for all the studied alloys. Good soft magnetic properties are observed even at a high crystalline volume fraction of bcc -Fe nanocrystals, which are stable up to ~1000 K. The partial substitution of Co for Fe is very effective to increase the Curie temperature of the residual amorphous matrix (T C AM ). Although the substitution of Ge for B is ineffective to increase T C AM , a clear increase of the saturation magnetization with respect to the Ge-free alloy can be observed. These nanocrystalline compositions have a high concentration of Fe and a typical composition: Fe-M-ET-(Cu), where M is a metalloid and ET is an early transition metal. The addition of metalloids, such as B, P, Si, etc., is necessary to enable the production of a precursor amorphous alloy by rapid quenching techniques, from which the nanocrystalline microstructure is obtained after controlled crystallization. It is important to distinguish two different kinds of metalloids: those highly soluble in the -Fe phase (e.g. Si) and those whose solubility in this phase is very restricted (e.g. B). The former elements will be generally dissolved in the crystalline phase, increasing the crystalline volume fraction but deteriorating some magnetic properties like the saturation magnetization and the Curie temperature of the crystalline phase. The latter elements will remain in the amorphous matrix and will diminish the maximum volume fraction of nanocrystals, although preserving the purity of the -Fe phase.The early transition metals (Zr, Nb, Hf, etc.) have a very low solubility in the -Fe phase and, consequently, will remain in the amorphous matrix. However, due to the very slow diffusivity of these elements in the amorphous phase, they pile up at the crystal-matrix interface and constrain the growth of the crystalline phase to the nanocrystalline scale. was proposed mainly because of the strong increase of the Curie temperature of the residual amorphous phase (T C AM ) due to the partial substitution of Co for Fe with respect to the Cofree NANOPERM alloy [7]. In fact, the exchange coupling between nanocrystals is transmitted through the ferromagnetic residual amorphous matrix and thus, at temperatures above the Curie temperature of this residual amorphous matrix, the nanocrystals become exchange uncoupled and, consequently, the outstanding soft magnetic properties of these In this work, the combined effect of partial substitution of Co for Fe and Ge for B on the microstructure and the magnetic properties of nanocrystalline alloys is studied. The maximum Co concentration studied in the alloys is 20 at. %, in order to search for a new showed that this parameter is seriously deteriorated for higher Co con...

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Section: Methodssupporting

confidence: 87%

Section: Methodsmentioning

confidence: 97%

mentioning

confidence: 89%

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Partial substitution of Co and Ge for Fe and B in Fe–Zr–B–Cu alloys: microstructure and soft magnetic applicability at high temperature

et al. 2005

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“…where x(t) the crystallized volume fraction, s the logarithmic time, n the Avrami exponent, and k a kinetic coefficient which is influenced by the temperature, given by [32]:…”

Section: Crystallization Mechanism Of Primary A-fe Phasementioning

confidence: 99%

Phase precipitation and isothermal crystallization kinetics of FeZrB amorphous alloy

et al. 2013

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The crystallization process of Fe 78 Zr 7 B 15 (at%) amorphous ribbon was investigated by X-ray diffraction (XRD), differential scanning calorimetry and scanning electron microscopy (SEM). The fully amorphous structure of as-quenched (Aq) ribbons was confirmed by XRD pattern. The saturation magnetization (M s ) and Curie temperature of the Aq ribbon were measured as 124.3 (AÁm 2 )/kg and 305°C with vibrating sample magnetometer (VSM), respectively. When the ribbons was annealed at 550°C near the first onset temperature (T x1 = 564.9°C), the M s was increased by 17 %, which was caused by the formation of a dual phase structure. The isothermal crystallization kinetics and crystallization mechanism of primary a-Fe phase in the dual phase structure were studied by Arrhenius and Johnson-Mehl-Avrami-Kolmogorov equations respectively. The results showed that the crystallization of a-Fe phase was a diffusion-controlled surface nucleation growth process, and the nucleation rate decreased with longer crystallization time.

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“…Soft magnetic materials with low core losses, high magnetization, and low cost are the key components for transformer with improved energy efficiency, especially in the higher frequency operation and elevated temperature conditions 6,7 . Since the 1970s, the greatly reduced coercivity has been achieved in amorphous and nanocrystalline alloys [8][9][10][11][12] . Conventional methods of improving the intrinsic and extrinsic soft magnetic properties have focused on tailoring the composition, controlling the microstructure with varied heat treatment environments.…”

Section: Introductionmentioning

confidence: 99%

The Effects of High Magnetic Field Annealing on the Structural Relaxation of Fe71(Nb0.8Zr0.2)6B23 Bulk Metallic Glass

Jia

Wang

2015

Mat. Res.

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The kinetics of nanocrystallization and microstructural observations in FINEMET, NANOPERM and HITPERM nanocomposite magnetic materials

Cited by 165 publications

References 24 publications

Partial substitution of Co and Ge for Fe and B in Fe–Zr–B–Cu alloys: microstructure and soft magnetic applicability at high temperature

Partial substitution of Co and Ge for Fe and B in Fe–Zr–B–Cu alloys: microstructure and soft magnetic applicability at high temperature

Phase precipitation and isothermal crystallization kinetics of FeZrB amorphous alloy

The Effects of High Magnetic Field Annealing on the Structural Relaxation of Fe71(Nb0.8Zr0.2)6B23 Bulk Metallic Glass

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