Tailoring the Microstructure of Soft Magnetic Composites for Electric Motor Applications

Abstract

Soft magnetic composite (SMC) material has been fabricated using 9 different powder particle fractions (smallest fraction: <;50 μm and largest: >400 μm). The microstructure features and resulting magnetic properties have been quantified and correlated. A specific focus lies on simultaneous consideration of the effects of particle size and internal grain size. Analysis has been carried out on samples in green condition and samples annealed between 400 °C and 600 °C. Electron backscatter diffraction technology brings about a substantially additional value to characterize deformations inside the grains. By detailed advanced microstructure analysis, it is shown that the deformation and recrystallization behavior is significantly different for different particle sizes used. Particle sizes between 100 and 200 μm show grain size distributions with the largest grains (d50 ~ 44 μm) in the volume of the particles resulting in the lowest hysteresis losses (PH ~ 4 W/kg, 1 T, 50 Hz). The relationship between particle and internal grain size distribution has been analyzed to enable further improvement of SMC materials concerning hysteresis loss reduction.