Formation and magnetic properties of nanocrystallifie 78.5-permalloy by mechanical alloying

摘要

An intermetallic alloy of 80-NiFe known as permalloy is used as magnetic core, magnetic shielding etc. due to its very high magnetic permeability and low coercivity. Mechanically alloyed permalloy has a superior property as it forms a FeNi3 Phase. In our study we have fabricated Ni78 5Fe2i.5 which is widely known as 78.5-permalloy by mechanical alloying. Metal powders of appropriate amounts were mixed and milled in a high energy planetary ball mill for different milling hours. A FeNi3 phase was obtained after 4hr of milling. This powder was annealed at 600K for 4 hours. Phase formation was determined by X-ray diffraction (XRD) analysis. Lattice parameter and theoretical density was determined from the XRD peak and they were found to vary with milling time. Mean crystallite size was calculated by Scherrer formula. Microstructure of the powder sample was studied by scanning electron microscopy (SEM). Mean crystallite size was found to be in the order of few nanometers and the particle size was found to be in the order of micrometer. Magnetic property was studied by vibrating sample magnetometer (VSM) and was found to vary with milling time and heat treatment.