Characterization And Microstructure And Mechanical Properties Of Y_xCoCrFeNi And Gd_xCoCrFeNiCu High-entropy Alloys

High-entropy alloys have attracted much attention for their promising mechanical properties, such as high-strength, high-hardness and high wear-resistant. High-entropy alloys possess four core effects, that is high-entropy effects, sluggish diffusion, severe lattice distortion and cocktail effects. The research topics of the high- entropy alloys focus on the alloy composition design, preparation, deformation mechanisms and mechanical properties.A new approach for the design of alloy systems with multiprincipal elements is presented in this research. The YxCoCrFeNi and GdxCoCrFeNi alloys were prepared by vacuum arc melting and casting method. The structures were investigated by X-ray diffraction and scanning electron microscopy. We studied the different microstructure of the alloys with the difference of Y and Gd content. The research results showed that the CoCrFeNi alloy is a single-phase FCC solid solution structure, whereas the YxCoCrFeNi and GdxCoCrFeNi alloys are multi-phases. Typical cast dendrite and interdendrite structures were observed in the YxCoCrFeNi and GdxCoCrFeNi alloys.We found that the hardness and the strength of the alloys increase with the increasing of Y and Gd content.But the plasticity of the alloys decreased. The corrosion resistance of the alloys was investigated by the electrochemical experiment in the sodium chloride solution.Nanoindentation measurements were performed on YxCoCrFeNi and GdxCoCrFeNi alloys to reveal the mechanical properties including the indentation hardness, the contact modulus and the indentation creep of individual phases.