Synthesis and characterization of permalloy-reinforced Al2O3 nanocomposite powders by mechanical alloying

Intermetallics of Fe and Ni, which are known as permalloy, are under attention due to their excellent magnetic performance. Besides, mechanical properties of the materials can be improved by decreasing crystallite size of FeNi intermetallics or by reinforcing them with hard secondary phases such as Al₂O₃. In this study, FeNi–Al₂O₃ nanocomposite powders with three different compositions were successfully synthesized through mechanical alloying of Fe₂O₃, Ni, and Al powders mixture. Characterization of the samples was accomplished by scanning electron microscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy and X-ray diffraction. Effects of various parameters such as chemical composition of received materials, milling time, and annealing on the phase evolution, morphology, and microhardness of samples were investigated. It was found that by the addition of Fe as diluent, the required milling time for formation of FeNi intermetallic increased. By increasing milling time, mean crystallite size of FeNi decreased and reach to about 28 nm for FeNi-30 wt% Al₂O₃ nanocomposite powder sample. TEM observations also showed that in situ-formed Al₂O₃ particles, with particle size of about 65 nm, were uniformly dispersed within FeNi matrix.