Tuning AC magnetic properties of FeCoNi1+xCu1-xAl (0 ≤ x ≤ 1.0) high-entropy alloys by adjusting Ni and Cu content.

In this work, the AC magnetic properties and microstructure of FeCoNi 1+ x Cu 1- x Al (0 ≤ x ≤ 1.0) high-entropy alloys (HEAs) are studied. The results show that the total loss (P s), AC coercivity (AC H c), and AC applied field (AC H m) are improved by adjusting the amounts of Ni and Cu. When x = 0.1, P s , AC H c , and AC H m of the alloy at 50 Hz decrease by 40 %, 41 %, and 43 %, respectively. When x = 0.7, the alloy has optimised magnetic properties, and P s , AC H c , and AC H m of the alloy at 50 Hz decrease by 77 %, 78 %, and 82 %, respectively. The P s is divided into hysteresis loss (P h) and eddy current loss (P e). When f ≤ 100 Hz, P h is the dominant contributor to P s , while when f ≥ 850 Hz, P e is the dominant contributor. At the same frequency, P h is closely connected with AC H c , and AC H m , and P e is inversely proportional to ρ. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that the alloys consist of a mixture of face-centred cubic (FCC) and body-centred cubic (BCC) phases. As x increases, the elemental distributions of FCC and BCC phases clearly change. Transmission electron microscopy (TEM) shows that there are many Cu-rich nano-precipitates in the BCC phase. Compared with the alloy where x = 0, nano-precipitates of the alloy where x = 0.1 have shorter lengths, lower distribution densities, and more uniform size. Our work provides an effective approach to explore novel soft magnetic materials. • The adjustment of Ni and Cu content affects the AC magnetic properties of HEAs. • P h is closely related to AC H c and AC H m , and P e is inversely proportional to ρ. • The adjustment of Ni and Cu content changes elemental distribution of the alloys. • Reduction of Cu content makes the distribution density of nano-precipitates lower. [ABSTRACT FROM AUTHOR]