Effect of Ti content on microstructure and mechanical properties of CuCoFeNi high-entropy alloys

We prepared (CuCoFeNi)Tix (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) high-entropy alloys (HEAs) by vacuum arc melting and then investigated the effects of Ti on their microstructure and mechanical properties. When x was inreased to 0.6, the structure of the alloy transformed from their initial single face-centered cubic (fcc) structure into fcc+Laves mixed structure. The Laves phase was found to comprise Fe2Ti and be mainly distributed in the dendrite region. With increasing Ti content, both the Laves phase and the hardness of the alloy increased, whereas its yield and fracture strengths first increased and then decreased, reaching their highest value when x was 0.8. The (CuCoFeNi)Ti0.8 alloy exhibited the best overall mechanical properties, with yield and fracture strengths of 949.7 and 1723.4 MPa, respectively, a fracture strain of 27.92%, and a hardness of HV 461.6.