Deciphering eutectic (FCC/B2) formation in Al-Co-Cr-Fe-Ni system using a novel CALPHAD-based alloy design model

Abstract

Two-phase (FCC/B2) selection rules were established for the design of eutectic high entropy alloys (EHEA) similar to as-cast AlCoCrFeNi_2.1 using; (a) the phase-formation capabilities of the alloying elements of the reported FCC/B2-structured Al-Co-Cr-Fe-Ni alloys using CALPHAD and (b) computational exploration of the Al-Co-Cr-Fe-Ni alloy space. The presented selection rules are developed as a relationship between (Ni+Co)/Al-ratio, Co/(Ni+Co)-ratio and Cr/(Fe+Cr)-ratio and unveils large unexplored FCC/B2 eutectic-phase field. A combination of low (Ni+Co)/Al-ratio and high Cr/Al-ratio within the developed relationship may be the key to the design novel as-cast Al-Co-Cr-Fe-Ni-based EHEAs such as Al₁₅Co_9.5Cr₁₈Fe₂₉Ni_28.5 alloy with ultra-high yield strength of 856 MPa.