The Effect of Increasing Nickel Content on the Microstructure, Hardness, and Corrosion Resistance of the CuFeTiZrNi(x) High-Entropy Alloys

In recent years, high-entropy alloys (HEAs) that contain fine grains of intermetallic compounds (IMCs) have gained increasing attention as they have been shown to exhibit both high mechanical strength and strong corrosion resistance. One such class of HEAs is that of CuFeTiZrNi alloys. In this study, we have investigated the effect of increasing Ni content on the microstructure, hardness, and corrosion resistance of the CuFeTiZrNi(x) alloys (where x = 0.1, 0.3, 0.5, 0.8, 1.0 in a molar ratio). The alloys used in this study were prepared in an arc melting furnace and then annealed at 900 °C. First-principles calculations of the bulk modulus were also performed for each alloy. The results revealed that increasing the Ni content had several effects. Firstly, the microstructure of the CuFeTiZrNi(x) alloys changed from B2_BCC and Laves_C14 in the CuFeTiZrNi(0.1) and CuFeTiZrNi(0.3) alloys to FCC, B2_BCC, and Laves_C14 in the CuFeTiZrNi(0.5) alloys; and to FCC, B2_BCC, Cu(51)Zr(14), and Laves_C14 in the CuFeTiZrNi(0.8) and CuFeTiZrNi(1.0) alloys. Secondly, IMCs arising from a combination of the refractory elements (Ti and Zr) and atomic size differences were found in the interdendritic region. Thirdly, as the Ni content in the CuFeTiZrNi(x) alloys increased, the hardness decreased, but the corrosion resistance increased.