Influence of mechanical alloying on the particle size, microstructure and soft magnetic properties of coarse Fe-based amorphous powders prepared by gas atomization

Abstract

The aim of this work is to refine the particle size of the coarse Fe-based amorphous powders by ball milling process without destroying the amorphous characteristics, thermal stability and soft magnetic properties. The gas atomized Fe-based amorphous powders were sieved, and the powders larger than 75 μm were selected as the raw materials. The effects of ball milling on the particle size, morphology, amorphous rate, thermal stability and soft magnetic properties of the Fe-based amorphous powders were systematically investigated. The results showed that the particle size of the Fe-based amorphous powders decreased as the ball milling time increased, and the mass median diameter (D50) of the powders was reduced by almost 80% after ball milling of 9 h compared with that of the initial powders (D50 reduced from 138.4 μm to 24.22 μm). The nanocrystallization and amorphization induced by the microstructural breakdown and intensified inter-diffusion of elements during the ball milling improved the amorphous rate of Fe-based powders. The ball milling reduced the saturation magnetization of the Fe-based amorphous powders, and had little effect on the coercivity. As a result, ball milling not only refined the particle size, but also improved the amorphous phase content of the Fe-based amorphous powders without changing the thermal stability and soft magnetic properties.