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Al x CoCrFeNi High Entropy Alloys (HEAs), also referred to as multiprincipal element alloys, have attracted significant interest due to their promising mechanical and structural properties. Despite these attributes, Al x CoCrFeNi HEAs are susceptible to phase separation, forming a wide range of secondary phases upon aging, including NiAl–B2 and Cr-rich phases. Controlling the formation of these phases will enable the design of age-hardenable alloys with optimized corrosion resistance. In this study, we examine the critical role of Al additions and their concentration on the stability of the CoCrFeNi base alloy, uncovering the connections between Al composition and the resulting microstructure. Addition of 0.1 mol fraction of Al destabilizes the single-phase microstructure and results in the formation of Cr-rich body-centered-cubic (bcc) phases. Increasing the composition of Al (0.3–0.5 mol fraction) results in the formation of more complex coprecipitates, NiAl–B2 and Cr-rich bcc. Interestingly, we find that the increase of the Al content stimulates the formation of NiAl–B2 phases, increases the overall density of secondary phases, and influences the content of Cr in Cr-rich bcc phases. Density functional theory calculations of simple decomposition reactions of Al x CoCrFeNi HEAs corroborate the tendency for precipitate formation of these phases upon increased Al composition. Additionally, these calculations support previous results, indicating the base CoCrFeNi alloy to be unstable at low temperature. This work provides a foundation for predictive understanding of phase evolution, opening the window toward designing innovative alloys for targeted applications.
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This content will become publicly available on October 14, 2026
Characterization of phase-specific constitutive behavior based on representative volume element for dual-phase microstructures
Multi-phase alloys may achieve superior performance over single-phase alloys through synergistic combinations of the properties of the individual phases. An understanding of the individual phase properties aids in alloy design and optimization. However, experimental methods for directly characterizing the constitutive behavior of individual phases are limited. In this work, an inverse analysis based on representative volume element (RVE) finite element simulations was used to extract phase-wise constitutive behavior based on micrographs and macroscale constitutive response of two-phase microstructures. Both 2D and 3D RVE simulations were performed and compared to identify the most appropriate boundary conditions for the more time-efficient 2D simulations. The proposed method for extracting phase-specific constitutive behavior was validated by determining phase properties in a range of two-phase materials, including dual phase steel, steel welds, and Al-Ni alloys. This approach provides a means for extracting phase-specific mechanical properties using the microstructure, experimental tensile test data, and phase elastic moduli as input, providing insight into the contributions of individual phases to properties of multi-phase alloys toward new alloy development or microstructure optimization.
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- Award ID(s):
- 2050069
- PAR ID:
- 10680635
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Materialia
- Volume:
- 44
- Issue:
- C
- ISSN:
- 2589-1529
- Page Range / eLocation ID:
- 102581
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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