Nanostructured soft magnetic materials synthesized via mechanical alloying: a review

Abstract

Soft magnetic materials are widely used in electrical and electronic industries due to their desirable electromagnetic features, i.e. relatively high electrical resistivity and low eddy current loss at high frequencies. From industrial point of view, once the size of grains is reduced to micron scale regimes, their performance is only narrowed to a few megahertz frequencies, due to their higher conductivity and domain wall resonance. Thus, one way to resolve this issue and utilize these materials at high frequency applications, is to reduce the size of grains from micron to sub or nanoscale before they are being compacted for sintering. In this aspect, however, several methods are employed to synthesize these nanoparticles, a mechanical alloying is found to be a proven route to produce a vast variety of materials with both non-equilibrium and equilibrium phases in a controlled size and shape of powder particles at desired tonnages. Mechanical alloying (MA) is a solid-state powder metallurgy route which involves a repeated action of fracturing and re-welding of powder particles in a high-energy ball mill. The final products characteristics are strongly dependent on the variable parameters of the process, i.e. milling time, ball-to-powder weight ratio, rotation speed, grinding media and milling atmosphere. Thus, this work reviews the key role of these parameters on the structure and magnetic behaviors of soft magnetic materials. Eventually, the mechanism of mechanical alloying and effect of diffusivity are also highlighted.