Understanding of the duplex high entropy of FeCoNiCuAl alloys magnetic properties dependence on the CuAl amount and annealing temperature

Abstract

High entropy alloys (HEA) FeCoNi(CuAl)x=0.8 and FeCoNi(CuAl)x =1.6 were studied in the form of small arc melted samples (x = 0.8) and also in successfully obtained hot forged strips (x = 1.6). High annealing temperature of 1200 °C was applied to the alloys. The magnetic properties as saturation magnetization (Ms), magnetostriction, coercive field (Hc) and remanent induction (Br) as well as electrical resistivity were measured and correlated to the alloy’s microstructure. The thermomechanical process due to hot rolling as well as the annealing at high temperature kept the FCC phase as the majority phase in the duplex alloy and caused changes in the magnetic properties. The unexpected Ms improvement of the alloy with x = 1.6 compared to the one with x = 0.8 was attributed to the Cu segregation originating Cu rich nanoprecipitates, which in turn cause the increase of magnetic elements in the duplex phases. The FeCoNi(CuAl)x=1.6 strip has Hc = 260 A/m, Br = 0.162 T, an initial susceptibility (χin) of 240 and a resistivity of 100 μΩ.cm. The alloy had smaller Hc and higher χin values compared to other FeCoNi(CuAl)x alloys with 0 ≤ x ≤ 1.2.