Microstructure and Properties of Ni_xAlTiCrFeCoCu High Entropy Alloys

A series of Ni_xAlTiCrFeCoCu (x=0.5, 1.0, 1.5, 2.0, 2.5, 3.0) high entropy alloys were prepared by vacuum arc furnace. The microstructures,compressive property and corrosion resistance of as-cast high entropy alloys were analyzed. The results indicate that the phases of these alloys were mainly composed by solid solution of body-centered cubic structure and face-centered cubic structure. There were four typical cast structures including petal shaped organization(α-phase), chrysanthemum shaped eutectic structure, intergranular organization which is rich of copper and Ni-riched phase. With the increase of Ni content, petal shaped α-phase reduced and even disappeared when x was 2.0, then the Ni-riched phase appeared. The yield strengths of all other alloys were higher than 1.5 GPa and the compressive strengths were about 2 GPa except NiAlTiCrFeCoCu alloy, and the fractures of these high entropy alloys showed brittle fracture. High entropy alloy had the best performance of corrosion resistance in H₂SO₄ solution when x was 2.0, and the corrosion resistances of high entropy alloys were better than that of 304 stainless steel in NaCl solution when x were 1.5, 2.0 and 3.0.