Role of Processing and Silicon Addition to CoCrCuFeNiSix High Entropy Alloys

The present chapter gives insight into the role of the processing route and silicon addition on phase evolution and mechanical properties of CoCrCuFeNiSix (x = 0, 0.3, 0.6, and 0.9 atomic ratios) high entropy alloys. The high entropy alloys were prepared through two different routes i.e., spark plasma sintering and vacuum-arc melting. The X-ray diffraction results reveal a face-centered cubic structure along with the sigma phase after spark plasma sintering, and it is also observed that the addition of silicon favors sigma phase formation, while a sample prepared by the arc melting route showed a face-centered cubic structure up to 0.6 silicon content. Further increases in silicon (0.6 to 0.9) lead to the formation of Ni₃Si. The addition of silicon (0.3, 0.6, and 0.9) favors the formation of the body-centered cubic structure during mechanical alloying. However, heating during spark plasma sintering encourages the transformation of the body-centered phases evolved after mechanical alloying to the face-centered and sigma phases. Better physical properties were obtained by spark plasma sintered samples compared to the arc melted samples due to the formation of sigma phases. Furthermore, comparative analyses were performed based on the parametric approach to study the phase evolution.