Tailoring AC magnetic properties of FeCoNi(MnSi) (0 ≤ x ≤ 0.4) high-entropy alloys by the addition of Mn and Si elements

In this work, we investigate the evolution with x of the microstructure and alternating current (AC) magnetic properties of FeCoNi(MnSi)x (0 ≤ x ≤ 0.4) high-entropy alloys (HEAs) with the motivation of exploring the potential applications of soft magnetic HEAs. The suitable addition of MnSi improves AC remanence (AC Br), AC coercivity (AC Hc) and especially specific total loss (Ps) while it suppresses amplitude permeability (μa) and AC maximum magnetic flux density (AC Bm), which suggests that the HEAs can be used as a new soft magnetic material with low Br and low Hc. Ps can be divided into two parts: hysteresis loss (Ph), eddy current loss (Pe), and further studies show that the Ph plays an important role at the frequency of 50 Hz, while the Pe is dominant in the total losses when the frequency is 950 Hz. This provides the direction of efforts to reduce the Ps. The XRD, SEM and TEM results show that these alloys contain simple FCC structure, but a new Mn6Ni16Si7 intermetallic compound appears when x ≥ 0.3, and it has a big influence on the AC magnetic properties of HEAs.