Development of FeCoMnAl multi-principal element alloys and soft magnetic powder cores with excellent magnetic properties and high temperature magnetic stability

Abstract

In order to develop a multi-principal element alloy with outstanding soft magnetic properties and high thermal stability, a Fe35Co35Mn30−xAlx (x = 9, 12, 15, 18, 21, 24) alloy system was designed. The findings demonstrated that the optimal Al/Mn content ratio contributes to the formation of a BCC and B2 dual-phase structure, which leads to a significant increase in the saturation magnetic flux density (Bs) and a considerable decrease in the coercivity of the alloy. The as-cast Fe35Co35Mn15Al15 alloy with a co-lattice structure exhibits exceptional soft magnetic properties, with a resistivity of 324 μΩ·cm, a Bs of 1.46 T and a Hc of 167.2 A/m. Corresponding soft magnetic powder cores (SMPCs) were fabricated and the impact of heat treatment temperature on the properties of the SMPCs was examined. The SMPCs after annealing at 660 °C exhibits high stable permeability (μe) of 48 up to 10 MHz, a low core loss (Pcv) of 1208 mW/cm3 (at 1 MHz, 20 mT), and excellent direct current bias performance. In addition, these SMPCs possess excellent high temperature magnetic stability, and the variation of both μe and Pcv at a high frequency (1 MHz) is less than 2 % over a wide temperature range of 25–150 °C.