The evolution of microstructure, micromechanical and magnetic properties of FeCoNiAlSi alloys with peritectic structure processed by high-pressure solidification

In this work, we examined the microstructure evolution, as well as the micromechanical and magnetic properties of FeCoNiAlSi high-entropy alloys (HEAs) under high pressure solidification (HPS). According to the results, FeCoNiAlSi alloy solidified at 0.1 MPa (atmospheric pressure) contains three kinds of phases: grain boundary (GB)phases, peritectic phases, and primary phases. As the solidification pressure increases to 7 GPa, the volume fraction of GB phases and peritectic phases decreases, while the volume fraction of primary phase increases by 82.8%. In addition, the Fe of the primary phase increases by 63.6 %, which enhances the ferromagnetism and exchange coupling properties of the alloy. Furthermore, HPS also reduces the magneto-crystal anisotropy of the GB phases and the pinning effect of boundaries on domain movement. Additionally, with the increasing solidification pressure, the FeCoNiAlSi HEAs shows stronger ferromagnetic. When solidified at 7Gpa, a reduction of 51.5 % in intrinsic coercivity(HMC) was observed, as was an increase of 106 % in magnetic polarization strength (Js). As well, HPS significantly increased the high temperature magnetic properties of FeCoNiAlSi alloy as well as the microhardness(i.e. from 8.25 GPa to 10.15 GPa). According to these results, HPS is an effective method for developing new functional applications for FeCoNiAlSi HEAs.