Second Phases’ Distribution of FeCoNiSi High-Entropy Alloy Solidified Under High Pressure and Its Effect on Magnetic Properties

The phase evolution and magnetic properties of FeCoNiSi high-entropy alloy prepared by high-pressure solidification were investigated. The results showed that the Ni-rich second phases (SPs), dispersed in the FeCoNiSi alloy matrix during the initial application of 0.1 MPa solidification pressure, aggregated as the pressure was further increased. In addition, we observed an increase in saturation magnetization
$M_{s}$
(from 77 to 86 emu/g) and a decrease in the intrinsic coercivity
$H_{\mathbf {MC}}$
(from 75 to 49 Oe) when the alloy solidification pressure increased from 0.1 MPa to 7 GPa. Based on the micromagnetic calculations, the dispersed SPs separate the continuous magnetic moment in the matrix and delay the magnetization process. The reversed domain is prone to nucleate at the interface of the SPs and matrix due to its low domain wall energy and demagnetization energy during magnetization. Therefore, the dispersed SPs demonstrate a pinning effect on magnetic domains in the matrix compared with aggregated SPs.