Crystallisation progress in Si-rich ultra-soft nanocomposite alloy fabricated by melt spinning (original) (raw)
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Magnetic Softening of Nanocrystalline Fe74Cu1.5Nb2.5Si12B10 Alloy by the Process of Annealing
Advanced Science Focus, 2014
Nanocrystalline amorphous FINEMET alloy with a nominal composition Fe 74 Cu 1.5 Nb 2.5 Si 12 B 10 prepared by a rapid solidification method was annealed in a controlled way in the temperature range 475-650 C for 15 minutes in order to study the structural parameters such as grain size, Si content and lattice parameter of the nanocrystalline Fe(Si) nanograins developed in the residual amorphous matrix. The effect of structural parameters on the initial permeability and coercivity of the material was also investigated. The Curie temperature, T c of the amorphous ferromagnetic alloy was found to be 425 C. With the appearance of the nanocrystalline phase, the T c of the residual amorphous matrix gradually decreases with the increase of the annealing temperature. The room temperature coercivity of the alloy decreases with the increase of the annealing temperature and reaches a minimum value of 0.623 Oe at an annealing temperature of T a = 550 C which indicates the magnetic softening of the material. With further increase of the annealing temperature a magnetic hardening takes place with the manifestation of a higher coercivity.
Journal of Bangladesh Academy of Sciences, 2016
To observe the impact of the annealing time on the alloy structure and ultra-soft magnetic properties of Fe 75.5 Si 13.5 Cu 1 Nb 1 B 9 , the alloy was annealed in a controlled way in the temperature range 475-600°C for different annealing time from 5 to 30 min. Amorphosity of the ribbon and nanocrystalline state was evaluated by X-ray diffraction. Grain size and Si content increase with increasing annealing temperature and time; on the other hand lattice parameter decrease with increasing annealing temperature and time. The maximum permeability was observed at annealing temperature Ta = 525°C for 15 min, and thereafter it starts to decreases. Saturation magnetization increases with annealing temperature Ta for the samples and finally decreases during annealing at a temperature much higher than peak crystallization temperature. The results of the experimental observations are explained on the basis of existing theories of nanocrystalline amorphous metallic ribbons.
Structural and soft magnetic properties of a new nanocrystalline Fe-based and B-free alloy
Journal of Applied Physics, 2008
A new nanocrystalline Fe-based soft magnetic alloy is discussed here. Ingots of nanocrystalline alloys ͑FeCu͒ 80 Zr x Si 20−x ͑x = 5, 6, and 8͒ were prepared by arc melting. The ingots were remelted and cast into 25-30 m thick ribbons by a single roller melt spinning method. X-ray diffraction ͑XRD͒ revealed the as-spun ribbons to be amorphous. The structural evolution of these samples was studied by XRD and transmission electron microscopy ͑TEM͒ after annealing at 450, 480, and 550°C. XRD shows the primary nanocrystallization product to be the ␣-Fe͑Si͒ phase. The grain size was observed by TEM to be ϳ10 nm after annealing at 480°C for 1 h and 14 nm after 550°C for 1 h. ac soft magnetic properties were measured using a Walker AMH 401 ac permeameter. The core loss at an exciting frequency f = 100 kHz and maximum induction B m = 1 kG was determined to be less than 19 W / kg.
Effect of crystallization on soft magnetic properties of nanocrystalline Fe80B10Si8Nb1Cu1 alloy
Journal of Magnetism and Magnetic Materials, 2014
The crystallization processes that occur in amorphous melt-spun ribbons of nominal ۱ composition Fe 80 B 10 Si 8 Nb 1 Cu 1 during preparation and heat treatment affect the soft magnetic ۲ properties of this alloy. Fe 80 B 10 Si 8 Nb 1 Cu 1 alloys are prepared by different quenching rates (wheel ۳ speeds of 10, 20 and 40 m/s) and their soft magnetic properties are studied. The XRD data reveal ٤ that as the wheel speed increases, the fraction of crystallinity and the Fe-Si grain size both decrease. ٥ These data also show that the sample prepared by the wheel speed of 10 m/s exhibits α-Fe particles ٦ on its free surface. The data for the samples prepared by the wheel speed of 20 and 40 m/s are in ۷ good agreement with the HRTEM images. VSM measurements show these nanostructured samples ۸ exhibit coercivity in the range of 3 to 21 A/m and magnetic saturation in the range of 1.55 to 1.78 ۹ T.
Iranian Journal of Materials Science and Engineering, 2019
In the present research, rapidly solidi ed Fe 85.3 B 11 P 3 Cu 0.7 ribbons were prepared by melt spinning process. The microstructural variation, as well as magnetic properties of the as-spun and annealed ribbons, were characterized by X-ray diffraction (XRD), transmission Mossbauer spectroscopy and alternating gradient eld magnetometer (AGFM). The results showed two separated distinct exothermic peaks during heating, resulting from the phase transition from amorphous to -Fe and then to Fe 3 B, respectively. The study of magnetic properties in the amorphous and nanocrystalline states revealed that annealing the amorphous ribbons at 440 ̊C for 10 minutes gives rise to a signi cant increase in saturation magnetization (220 emu/g) which makes this alloy a good candidate for power applications.
Journal of Bangladesh Academy of Sciences, 1970
Structural and magnetic measurements have been performed on the FINEMET type of ribbons with nominal composition of Fe 74 Cu 0.5 Nb 3 Si 13.5 B 9 synthesized by rapid solidification technique. The crystallization behavior and the nanocrystal formation have been studied by differential thermal analysis (DTA) and X-ray diffraction (XRD). The crystallization onset temperatures determined by XRD are in good agreement with DTA results. Magnetic permeability and magnetization measurements have been carried out using inductance analyzer and vibrating sample magnetometer (VSM). Magnetic permeability sensitively depends on the annealing temperature which increases sharply with the increase of annealing temperature. Maximum permeability corresponding to optimum annealing temperature (T a) was observed at T a = 575°C. Saturation magnetization, M s, increases with T a for the sample and finally decreases for annealing at a temperature much higher than peak crystallization temperature. The results show that the amounts of Cu and Nb are very important for the soft magnetic properties of FINEMET alloys.
Scripta Materialia, 2017
The structural and magnetic properties of amorphous Fe 87 − y B 13 Cu y (y = 0 to 1.5) annealed with a range of heating rates (α) up to 150 K/s were investigated. The lowest coercivity (H c) for Fe 87 B 13 after crystallization shows a dramatic decrease from 174 A/m to 6.7 A/m when α is increased from 1.7 K/s to 150 K/s. The coercivity of Fe 87 − y B 13 Cu y annealed at 150 K/s is reduced by Cu addition and H c = 3.0 A/m is obtained at y = 1.5. Nanostructures with a grain size of 15 to 20 nm were evident in transmission electron micrographs from these rapidly annealed alloys.
Journal of Alloys and Compounds, 2006
The kinetics of crystallization of a soft magnetic amorphous Fe 40 Ni 38 B 18 Mo 4 alloy was studied by TEM, EDX and resistivity methods. The kinetic parameters were measured from TEM studies and resistivity measurements. Nanocrystals of the fcc FeNi phase were found to crystallize by a primary crystallization mechanism followed by slow growth kinetics. The volume fraction measured by TEM matches well with that calculated from resistivity results and a TTT diagram was constructed. Quantitative measurements of the nucleation and growth rates as a function of temperature and time were performed. The nucleation rate was found to decrease with an increase in heat treatment time due to an increase in boron content in the amorphous matrix as the crystallization took place. The crystal growth was found to slow down considerably due to the presence of Mo. The crystal size was calculated according to the Michels model and compared to our experimental results. Molybdenum was found to dramatically alter the energetics of crystallization, the morphology of the crystals and particularly the kinetics of crystallization. These results offer a method of creating new families of nanostructured magnetic materials by suitable molybdenum addition.
Nucleation of soft magnetic Fe 3 Si nanocrystals in Cu-free Fe 74.5 Si 15.5 Nb 3 B 7 alloy, upon rapid (10 s) and conventional (30 min) annealing, was investigated using x-ray diffraction, transmission electron microscopy, M€ ossbauer spectroscopy, and atom probe tomography. By employing rapid annealing, preferential nucleation of Fe 3 Si nanocrystals was achieved, whereas otherwise there is simultaneous nucleation of both Fe 3 Si and undesired Fe-B compound phases. Analysis revealed that the enhanced Nb diffusivity, achieved during rapid annealing, facilitates homogeneous nuclea-tion of Fe 3 Si nanocrystals while shifting the secondary Fe-B crystallization to higher temperatures resulting in pure soft magnetic nanocrystallization with very low coercivities of $10 A/m. V C 2016 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4944595\]
Nano-crystallisation and magnetic softening in Fe–B binary alloys induced by ultra-rapid heating
Journal of Physics D: Applied Physics, 2018
Magnetically soft nanostructures are known to be prepared by the primary crystallisation of Fe-based amorphous precursors containing Cu and/or Nb. These nonmagnetic additives are essential for accelerated nucleation and retarded crystal growth during crystallisation. However, it has recently been found that none of these additives are necessary for the preparation of similar nanostructures when ultra-rapid annealing (URA) is employed. As a result, a magnetically soft nanostructure with exceptionally high Fe contents is realized in a simple Fe-B binary system. An obvious question is the mechanism of the nanostructural formation in such a simple system. To answer this question, the crystallisation behaviour of amorphous precursors was investigated by means of in situ resistivity measurements with heating rates up to ~100 K s −1. The primary crystallisation temperature (T p) in Fe 86 B 14 is increased at least by ~100 K under URA. This brings T p to the vicinity of the glass transition (T g) predicted by Egami's zeroth-order approximation, suggesting that an enhanced nucleation rate near T g due to the contribution of homogeneous nucleation could be responsible for the nanostructural formation in Fe 86 B 14. Contrarily, the effect of URA is absent from Fe 80 B 14 Nb 6 , and a magnetically soft nanostructure is realized by conventional annealing because the crystallisation reaction in this alloy takes place above T g even with a low heating rate of ~1 K s −1. URA offers new possibilities for enhancing the saturation magnetization in nanocrystalline soft magnetic alloys through reductions of the amount of nonmagnetic additives.