Nanocomposites and nanomaterials
Structure and properties of CoCrFeNiMnBe high-entropy alloy films obtained by liquid quenching 
Bashev V.F., Kushnerov O.I., Ryabtsev S.I.
Department of Experimental Physics, Oles Honchar Dnipro National University. Gagarin ave., 72, Dnipro, 49010, Ukraine. 
E-mail: kushnrv@gmail.com
In recent decades, a new class of metal compounds has been developed - the so-called high-entropy alloys (HEAs) with multiple principal elements. HEAs have received more and more attention due to their unique structure and excellent properties in hardness and wear resistance, exceptional high-temperature strength, good structural stability, radiation, and corrosion resistance. Each principal element in HEA should have a concentration between 5 and 35 at.%. Because of the high mixing entropy of HEAs (12-19 J/(K·mol)), they usually consist of some simple solid solutions, instead of complex phases. 
In this study, a new nanostructured CoCrFeNiMnBe high-entropy alloy films were synthesized by the means of liquid quenching (LQ) technique, which consisted of rapid cooling of melt drops upon their collision with the internal heat-conducted surface of a rapidly rotating (~8000 RPM) hollow cylinder. The estimated cooling rate was ~106 K/s. 
The analysis of the XRD patterns allowed us to establish that the investigated HEA in the as-cast state has a multiphase structure in which there is the FCC phase with lattice parameter a=0.3588 nm and the coherently scattering domain size (crystallite size) estimated by the Sherer formula L =20 nm, BCC phase (a=0.2872 nm, L =19 nm), and B2 type intermetallic compounds BeNi(Co) (a=0.2616 nm,  L =20 nm). At the same time, the LQ sample has a structure consisting of the FCC phase (a=0.3599 nm, L = 15 nm) and the BeNi(Co) phase (a=0.2610 nm, L = 18 nm). The microhardness in the as-cast state is Hµ=3400 MPa, while in the LQ state Hµ=5600 MPa. So, the addition of Be significantly improves the mechanical characteristics of the studied HEA as compared with the original Сantor alloy (CoCrFeNiMn). The fact that the LQ HEA of the Co-Cr-Fe-Ni-Mn-Be system is characterized by higher values of Hµ than as-cast alloys is not unexpected, since the microstructure and the phase composition of the as-cast alloy after decomposition are in a more equilibrium multiphase state, while LQ alloy yields a higher level of microstrains, dislocation density and smaller grain sizes.
The magnetic properties of the films were measured by a vibrating sample magnetometer. For the as-cast CoCrFeNiMnBe HEA the saturated magnetizations (Ms), and coercivity force (Hc) were 5.1 A·m2/kg and 2800 A/m, while for the LQ films – 2.7 A·m2/kg and 4000 A/m respectively.