Microstructure Evolution, Phase Composition, Tensile and Hardness Properties Investigation of CrCuFeNi2Tix-Based High-Entropy Alloys

CrCuFeNi2Tix high-entropy alloys (HEAs) (x = 0.1 ~ 0.7) are prepared and studied in this paper to investigate the effect of titanium on the microstructure, phase composition, and mechanical properties of the CrCuFeNi2Tix-based system. Microstructural studies using scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that the addition of titanium could induce the formation of a body-centered cubic lattice (BCC) and intermetallic compounds (Ni3Ti) of the CrCuFeNi2Tix-based system. The practical formation of the phases meet the theory of the atomic size difference δ, mixing enthalpy ΔHmix, mixing entropy ΔSmix, valence electron concentration (VEC), and electronegativity difference Δχ. Additionally, the tensile and hardness properties of the CrCuFeNi2Tix-based system are investigated in this study. Generally, CrCuFeNi2Tix HEAs show low stiffness and good flexibility in mechanical properties. When the x value is relatively small, the HEAs show good ductility in the tensile test, which is the result of a face-centered cubic lattice (FCC) in the phase composition at this stage; when the x value becomes larger, due to the formation of the intermetallic compounds Ni3Ti, the HEAs show high hardness