In recent years, high-entropy alloys (HEAs) have attracted considerable attention in materials engineering due to their unique phase stability and mechanical properties compared to conventional alloys. Since the inception of HEAs, CoCrFeMnNi alloys have been widely investigated due to their outstanding strength and fracture toughness at cryogenic temperatures. However, their lower yield strength at room temperature limits their structural applications. The mechanical properties of HEAs are greatly influenced by their processing methods and microstructural features. Unlike traditional melting techniques, powder metallurgy (PM) provides a unique opportunity to produce HEAs with nanocrystalline structures and uniform compositions. The current review explores recent advances in optimizing the microstructural characteristics in CoCrFeMnNi HEAs by using PM techniques to improve mechanical performance. The most promising strategies include grain refinement, dispersion strengthening, and the development of heterogeneous microstructures (e.g., harmonic, bimodal, and multi-metal lamellar structures). Thermomechanical treatments along with additive manufacturing techniques are also summarized. Additionally, the review addresses current challenges and suggests future research directions for designing advanced HEAs through PM techniques.

1. Introduction of high entropy alloys
    1.1. Definition of HEAs
    1.2. Core effects of HEAs
2. Fabrication of HEAs by powder metallurgy route
    2.1 Mechanical alloying
    2.2. Gas atomization
    2.3. Sintering techniques
3. Microstructural evolution in CoCrFeMnNi alloy using powder metallurgy techniques
    3.1 Grain boundary strengthening
    3.2. Dispersion strengthening
    3.3. Heterogeneous structures
4. Conclusions and future directions
Funding
Conflict of Interest
Data Availability Statement
Author Information and Contribution
Acknowledgments
References

• K. Raja Rao(Department of Materials Science and Engineering, Ajou University, Suwon 16499, Republic of Korea, Department of Mechanical Engineering, Mandsaur University, Mandsaur, Madhya Pradesh 458001, India)
• Cheenepalli Nagarjuna(Department of Materials Science and Engineering, Ajou University, Suwon 16499, Republic of Korea)
• Sheetal Kumar Dewangan(Department of Materials Science and Engineering, Ajou University, Suwon 16499, Republic of Korea)
• Hansung Lee(Department of Materials Science and Engineering, Ajou University, Suwon 16499, Republic of Korea)
• Byungmin Ahn(Department of Materials Science and Engineering, Ajou University, Suwon 16499, Republic of Korea, Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea) Corresponding author
• Eunhyo Song(Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea)