Nanocomposites and nanomaterials
Structure and properties of nanostructured metallic glass of the Fe-B-Co-Nb-Ni-Si high entropy alloy system
Kushnerov O.I., Bashev V.F., Ryabtsev S.I.
Department of Experimental and Metal Physics, Oles Honchar Dnipro National University. Gagarin ave., 72, Dnipro, 49010, Ukraine. 
E-mail: kushnrv@gmail.com

In recent years, high entropy alloys (HEAs) have attracted considerable attention of researchers in the field of materials science. The HEAs are composed of at least 5 major components with equiatomic or nearly equiatomic concentrations which are between 5 and 35 at. %. The HEAs are characterized by unique structures and show promise as materials for application in electronics, atomic power engineering, transportation equipment, space-rocket hardware, etc.  In contrast to HEAs, metallic glasses (MGs), known as another type of advanced materials, usually contain more than two kinds of elements but only one, sometimes two principal constituents. Due to their considerably different characteristics in structure and composition rules, the HEAs and MGs have been studied independently until the HEAs with an amorphous structure, namely high entropy metallic glasses (HE-MGs) were successfully synthesized. The developed HE-MGs provide a new strategy to design and synthesis MGs. The HE-MGs possess excellent mechanical and physical properties inherited from the advantages of both HEAs and MGs and show great potential for practical applications. In particular, MGs usually possess excellent soft magnetic properties. 
In this study, a new nanostructured Fe25B17.5Co21.35Nb3.65Ni25Si7.5 (at.%) HE-MG was synthesized by the means of splat-quenching (SQ) technique. The estimated cooling rate was ~106 K/s. The coherently scattering domain size (crystallite size) of  HE-MG estimated by the Sherer formula was  ~ 3 nm.
The coercive force (Hc) of the SQ films of investigated HE-MG alloy was measured with a B–H loop tracer and reaches a relatively low value of 40 A/m, which is much smaller than in the crystallized as-cast alloy. So in accordance with the measured values of Hc the SQ alloy exhibit a typical soft magnetic hysteresis characteristic. The origin of the lower Hc can be attributed to the low number density of the domain-wall pinning sites resulting from the high degree of amorphicity and structural homogeneity proceeding from the high glass forming ability. Such behavior is typical for alloys in the amorphous state. The Fe25B17.5Co21.35Nb3.65Ni25Si7.5 HE-MG exhibits also high saturation magnetization of 74 A·m2/kg, measured by a vibrating sample magnetometer at room temperature. SQ films demonstrate high microhardness value ≥ 8000 MPa indicating good mechanical properties of Fe25B17.5Co21.35Nb3.65Ni25Si7.5 HE-MG.