Structure and Magnetic Properties of Mechanically Synthesized [.sub.75][C.sub.25] Nanocomposites

X-ray diffraction, Mossbauer spectroscopy, and magnetic measurements have been used to study the phase formation in [([Fe.sub.1-x][Ni.sub.x]).sub.75][C.sub.25] (with x = 0-0.20) nanocomposites upon severe plastic deformation in a planetary ball mill and subsequent annealings. It has been shown that...

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Bibliographic Details
Published in:Physics of metals and metallography 2017-07, Vol.118 (7), p.691
Main Authors: Ul'yanov, A.I, Chulkina, A.A, Volkov, V.A, Ulyanov, A.L, Zagainov, A.V
Format: Article
Language:English
Subjects:
Analysis
Annealing
Carbides
Intermetallic compounds
Iron compounds
Magnetic properties
Magnetization
X-ray diffraction
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Summary:X-ray diffraction, Mossbauer spectroscopy, and magnetic measurements have been used to study the phase formation in [([Fe.sub.1-x][Ni.sub.x]).sub.75][C.sub.25] (with x = 0-0.20) nanocomposites upon severe plastic deformation in a planetary ball mill and subsequent annealings. It has been shown that the mechanical synthesis results in the formation of mainly a nickel-alloyed nanocrystalline (Fe, Ni)3C cementite with a distorted crystal lattice and an amorphous Fe-Ni-C phase. During heating above 300[degrees]C, the amorphous phase crystallizes with the formation of cementite, which is characterized by a higher Ni content compared to that in mechanically synthesized cementite. The mechanically synthesized samples exhibit low coercive force (equal to several tens ampere per centimeter). In the course of annealing at temperatures of up to 500-550[degrees]C, crystal lattice distortions are removed; this results in reliving the magnetic anisotropy constant and high-coercivity state of cementite. At the same time, Ni-rich cementite areas decompose with the formation of [gamma]-(Fe, Ni, C) phase (austenite); as a result, the average nickel content in the cementite substantially decreases. Annealings at higher temperatures cause the complete decomposition of cementite and lead to an abrupt decrease in the coercive force ([H.sub.c]) of samples. Alloying with nickel leads to an increase in the Curie temperature of cementite and a decrease in its specific saturation magnetization, coercive force, and thermal stability. Keywords: mechanical synthesis, Ni-alloyed cementite, Mossbauer spectroscopy, X-ray diffraction, structure and phase transformations, magnetic properties, coercive force
ISSN:0031-918X
DOI:10.1134/S0031918X17050143