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The FexCoNiCuCr ( x = 0·2, 0·5, 0·8, 1 and 2) high entropy alloys were prepared by arc melting in an argon atmosphere. The effects of the Fe content and heat treatments on the microstructure and hardness of the alloys were investigated using X-ray diffraction, scanning electron microscope, and hardness tests. The as cast alloys consist of two FCC solid solution structures, and display a typical dendrite microstructure with Cu-rich in the interdendrite (ID) region. The heat treatment has no obvious effect on the phase constituents of the alloys, meaning that the alloys have very good thermal stability. At the annealing temperature of 1000°C, the submicrometre-size particles were observed in the dendrite region, while a further high annealing temperature of 1200°C results in the formation of the discontinuous ID phase and ball shape Cu-rich particles. The hardness of the alloys become smaller after being heated at the temperature from 400-1000°C for 5 h. [ABSTRACT FROM AUTHOR]

The (Zr0·55Al0·1Ni0·05Cu0·3)100−xNbx alloys have been prepared using an in situ suck casting method in a copper mould. The effect of Nb on the microstructure, mechanical and corrosion properties of the (Zr0·55Al0·1Ni0·05Cu0·3)100−xNbx alloys has been investigated using X-ray diffraction, scanning electron microscopy, compressive and corrosion tests. It has been found that the appropriate addition of Nb enhanced the formation of the crystalline phases. All the alloys had excellent corrosion resistance in the alkaline solution. An appropriate addition of Nb greatly improved the corrosion resistance of the alloys in the 1N HCl solution. The average corrosion rate in the 1N HCl solution was 4·57 μg cm−2 h−1 for the Zr55Al10Ni5Cu30 alloy, 0·95 μg cm−2 h−1 for the (Zr0·55Al0·1Ni0·05Cu0·3)99Nb1 alloy, and 0·071 μg cm−2 h−1 for the (Zr0·55Al0·1Ni0·05Cu0·3)95Nb5 alloy. [ABSTRACT FROM AUTHOR]