Mechanically Alloyed FeNi and Fe Powders Crystalline Size, Phase Formation, and Morphology: Investigation on Milling Time Impact

The present paper is devoted to study the structural, morphological, and magnetic behavior of Fe50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{50}$$\end{document}Ni50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{50}$$\end{document} alloy and pure Fe powder prepared by mechanical alloying. The powder has been milled with high-energy ball milling process with 24 h and 32 h for FeNi and Fe powders, respectively. The x-ray diffraction, scanning electron microscopy, M & ouml;ssbauer spectroscopy, and vibrating sample magnetometer techniques have been employed to identify the characteristics of the milled powders. The first x-ray diffraction results show that increasing milling time for pure Fe exhibits bcc-type reflections, with rapid decrease in crystallite size and a slight increase in lattice, and no other phase appears during milling, while for Fe50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{50}$$\end{document}Ni50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{50}$$\end{document} alloy, fcc phase appears after 8 h of milling with disappearance of Fe peaks. SEM and FE-SEM results have shown morphological changes are appearing in the structures where crystallite size for Fe50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{50}$$\end{document}Ni50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{50}$$\end{document} is 33.49 nm and the one for pure Fe is 15 nm. M & ouml;ssbauer spectroscopy proved that during the mechanical alloying process, the hyperfine field of Fe50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{50}$$\end{document}Ni50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{50}$$\end{document} decreases from 33 to 32 T, 31, and 29 T, respectively after 2, 8, and 24 h of milling. For the FeNi alloy, Vibrating Sample Magnetometer (VSM) at room temperature has been used, and the Hysteresis cycles has been plotted for several times of milling. The magnetic coercivity increased and the saturation magnetization decreased after the first two hours due to the morphological changes in particles leading to considerable changes in remanent magnetization and squareness ratio. These changes have disappeared during milling operations where particles sizes become equal. During FeNi milling, morphological changes lead to change the Hysteresis loops after 2 h of milling. At the end of milling, a remanent magnetization of 0.118 emu and coercivity of 32.85 G have been noted. The magnetic moment in Bohr magnetron for the alloy is 0.1338.