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Deformation mechanisms of the Al3(TiTaZrNbHf) high entropy intermetallic compound under tensile loading were studied using molecular dynamic simulations. To this end, the site occupancy of the five constituent atoms that form the high entropy sublattice of Al3(TiTaZrNbHf) was first determined by simulating the near-equilibrium melting/crystallization process. It is shown that nuclei of intrinsic stacking faults are formed under early plastic deformation due to dislocation nucleation and glide, which further contribute to the formation and growth of twin boundaries. Twinning and 1/6<112> Shockley partial dislocations are key components in the plastic deformation of Al3(TiTaZrNbHf) at room and elevated temperatures, which is in good agreement with the experimental observations for D022-structured materials. The tensile strength of Al3(TiTaZrNbHf) is 4.6 GPa at 300 K and slightly decreases to 4.34 GPa at 1000 K, highlighting the unique properties of high entropy intermetallic compounds in retaining their mechanical properties at elevated temperatures. The derived results provide grounds for understanding the atomic-scale origin of deformation mechanisms in high entropy intermetallic compounds. They also show potentials for tailoring the chemical composition of intermetallic compounds to overcome the problem of low ductility, paving the way to their industrial applications. [ABSTRACT FROM AUTHOR]

Abstract—The microstructure, phase composition, and oxidation resistance of as-cast high-entropy alloys (HEAs) Al0.25CoCrFeNi and Al0.25CoCrFeNiCuAgx (x = 0, 0.1, 0.2) have been studied. Oxidation was carried out at 700°C for 50 h in air. During the experiment, curves for the dependence of the specific weight gain on the exposure time were plotted. It has been shown that the introduction of copper has a slight effect on the resistance of the base Al0.25CoCrFeNi HEA to oxidation, while additional (to copper) alloying with silver worsens the resistance of the samples to high-temperature gas corrosion. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) consisting of five or more components in an equimolar ratio are attracting increasing attention due to a unique combination of various properties. Doping HEAs with small amounts of certain elements (most often rare earth, trace or noble metals) is a promising way to improve the characteristics of such alloys and to control their properties. This paper reports the results on the microstructure, phase composition, and microhardness of as-cast AgxAl0.5CoCrCuyFeNi HEAs (x = 0, 0.1; y = 0.5, 1.0). The effect of silver addition on the oxidation behavior of the studied HEAs at 700°C was determined. The morphology, phase and chemical composition of the resulting oxide film were studied. It was shown that the introduction of silver improves the mechanical characteristics of the alloys, but deteriorates the oxidation resistance due to the formation of copper-silver eutectic in the alloy microstructure, leading to a change in the morphology and phase composition of the formed oxide layer. Along with the solid solution of (Al, Cr)2O3 oxides and CuCr2O4, NiCr2O4 spinels, the addition of silver leads to the formation of copper oxide CuO and a small amount of silver oxide Ag2O in the surface film. [ABSTRACT FROM AUTHOR]

Large single crystals of high-entropy oxides with the M-type hexaferrite structure, the chemical composition of which can be described by the formula BaFe12–x(Ti, Mn, In, Ga)xO19, are obtained for the first time by spontaneous crystallization from a solution. The actual compositions of the samples are determined: BaFe1.20Ti0.22Mn0.76In0.58Ga0.23O19, BaFe8.71Ti0.44Mn1.16In1.25Ga0.44O19, BaFe7.14Ti0.57Mn1.77In1.79 Ga0.73O19, BaFe5.6Ti0.64Mn2.48In2.52Ga0.76O19. These crystals have a special shape for hexaferrites and are characterized by a fairly uniform distribution of elements in their structure. A significant quantitative difference in the ability of various metal ions to transfer from a melt to a growing crystal is found. A change in the initial ion concentration in the solution has practically no effect on this ability. The influence of crystal compositions on their unit cell parameters is considered. Some increase in these parameters correlates with a decrease in the iron content in the samples. This is mainly due to an increase in the weighted average ionic radius of ions forming the crystals. The configuration mixing entropies within the sublattice formed by Fe, Ti, Mn, In, and Ga for the target compositions and the compositions of actually obtained crystals are calculated and compared. [ABSTRACT FROM AUTHOR]