A thermodynamic description of the Co-Cr-Fe-Ni-V system for high-entropy alloy design

To increase the strength of representative equiatomic CoCrFeMnNi HEAs (high entropy alloys), many researchers have attempted to generate a secondary phase or to maximize solid-solution hardening effects. The addition of vanadium (V) could be an effective way to achieve both effects because V is a strong sigma (σ) and body-centered cubic (bcc) phase stabilizer and has a relatively large atomic size. The amount of secondary phase material formed is directly related to mechanical properties. Therefore, the ability to predict phase equilibria could guide decisions about V-added HEA design. Although the CALculation of PHAse Diagram (CALPHAD) approach can be an effective tool for predicting the phase equilibria, a thermodynamic database is still required. Therefore, the present paper aims to provide a thermodynamic description of the Co-Cr-Fe-Ni-V HEA system by developing thermodynamic descriptions of the Co-Cr-Fe, Co-Cr-V, Co-Fe-V, and Co-Ni-V systems. The reliability of the thermodynamic description developed for the Co-Cr-Fe-Ni-V quinary system is experimentally confirmed using newly designed Co-Cr-Fe-Ni-V HEAs.