Effect of Alloying Compositions on the Stacking Fault Energy and Elasticity of FeNiCrAlCo and FeNiCrAlCu: A First-principles Study for Fe-based High Entropy Superalloy Design

Abstract

High Entropy Superalloy (HESA) is a classification of materials with promising properties extensively developed to improve performance, resource sustainability, and cost efficiency in high-temperature applications. The need for computation on HESA is due to its time and cost superiority over experiments while maintaining good accuracy. However, thermodynamic data of some rare elements like Zr has not existed in publications based on a phase diagram calculation. First-principles is then used to investigate further the effect of decreasing Ni while adding Cu and Zr on lattice parameters, elasticity, stacking fault energy (SFE), and electronic structure of Fe-based HESA FeNiCrAlCo and FeNiCrAlCu. Adding Cu increases the SFE and ductility while decreasing Ni and adding Zr decreases the SFE and increases the strength but slightly reduces the ductility. Electronic structure analysis showed that adding Zr increases charge accumulation and decreases density of states, then interatomic bonding weakened, interlayer distance increased, and SFE decreased. The Fe-based HESA design can be optimized by reducing Ni concentration and increasing Cr concentration to decrease SFE to significantly increase strength, ductility, and hardness, especially at high temperatures, or adding Zr to decrease SFE value to the maximum. This study will help develop low-cost high entropy superalloys with desired performance.