Magnetic and mechanical properties of Fe-based α-Fe2O3/nano-sized MgO-coated composites

Abstract

Fe-based α-Fe2O3/nano-sized MgO-coated soft magnetic composites were fabricated by powder metallurgy with 800 MPa pressure at room temperature, and then annealed at 400 ℃. A layer of iron oxide α-Fe2O3 was generated on the iron surface by passivation treatment. The processed iron powders were coated with nano-sized MgO by mixing method. The soft magnetic composites with sandwich structure (Fe + iron oxide + nano-sized MgO) resulted in an increased permeability at a higher frequency, and higher eddy current loss compared to that of the resin layer by the two-step annealing method, which indicates that the sandwich structure for the soft magnetic composites exhibited noticeably higher frequency stability. The relationship between compressed load and displacement for two kinds of soft magnetic composites implied that the density and stress release for iron play a leading role in the mechanical properties. The stress field analysis of the internal microstructure by finite element method shows that the cracks and pores are two important factors that affect the mechanical strength for the whole material.