The Effect of B and Si Additions on the Structural and Magnetic Behavior of Fe-Co-Ni Alloy Prepared by High-energy Mechanical Milling (original) (raw)
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Nanostructured alloys have considerable potential as soft magnetic materials. In these materials a small magnetic anisotropy is desired, which necessitates the choice of cubic crystalline phases of Fe, Co, Ni, etc. In the present work, Fe-50 at.-%Co alloys were prepared using mechanical alloying (MA) in a planetary ball mill under a controlled environment. The influence of milling parameters on the crystallinity and crystal size in the alloys was studied. The particle size and morphology were also investigated using SEM. In addition, a thermal treatment was employed for partial sintering of some of the MA powders. The crystal size in both MA powders and compacted samples was measured using X-ray diffraction. It was shown that the crystal size could be reduced to less than 15 nm in these alloys. The nanocrystalline material obtained was also evaluated for magnetic behaviour.
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FeNi-based alloy powders are interesting in their applications as soft magnetic materials with low coercivity and high permeability. Their magnetic properties are closely related to their microstructure and particle size. In this study, nanocrystalline Fe-45%Ni alloy powders were prepared using a planetary ball mill. The effects of ball milling speed (the vial rotation speed (ω) and the disc rotation speed (˝)) on the microstructure and particle size of Fe-45%Ni alloy powders have been studied. The face-centered-cubic (FCC) ␥-(Fe, Ni) solid solution phase was identified by X-ray diffraction (XRD). The lattice parameter, lattice strain, grain size and quantitative amount of ␥-(Fe, Ni) phase have been estimated from Rietveld's powder structure refinement analysis of XRD data. The powder morphology and particle size were examined using scanning electron microscopy (SEM). The results showed that the FCC ␥-(Fe, Ni) phase could be observed completely at the vial rotation speed of 350 rpm and the milling time of 24 h. We also found that the higher milling speed leads to higher milling energy, larger lattice parameter, larger particle size and lower grain size of the investigated system.
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The mechanical alloying process has been used to prepare nanocrystalline Fe70−xCuxCo30 (x = 0, 3, 6, and 10) alloy from powder mixture. The structure and magnetic properties were investigated through powder X-ray diffraction (XRD), electron microscopy and magnetization measurements. The XRD patterns show a bcc crystal structure with lattice constant 0.2865 nm and crystallite size (D) of 15 nm evolves on 60 h milling in the case of Fe–Co alloy. But it is found that Cu speeds up the formation of bcc phase with finer microstructure (D = 7 nm for x = 10). Increase in microstrain is observed with the milling time and also with Cu concentration. The magnetic measurements show a contrasting saturation magnetization and coercivity (HC) for the case of samples having lower (x ≤ 3) and higher (x > 3) Cu content in Fe–Co alloys. These variations are explained on the basis of crystallite size and strain variations in the samples during milling. Present results indicate that a nonmagnetic inc...