High-entropy alloys (HEAs) have been reported to have better properties than conventional materials; however, they are more expensive due to the high cost of their main components. Therefore, research is needed to reduce manufacturing costs. In this study, CoCrFeMnNi HEAs were prepared using metal injection molding (MIM), which is a powder metallurgy process that involves less material waste than machining process. Although the MIM-processed samples were in the face-centered cubic (FCC) phase, porosity remained after sintering at 1200°C, 1250°C, and 1275°C. In this study, the hot isostatic pressing (HIP) process, which considers both temperature (1150°C) and pressure (150 MPa), was adopted to improve the quality of the MIM samples. Although the hardness of the HIP-treated samples decreased slightly and the Mn composition was significantly reduced, the process effectively eliminated many pores that remained after the 1275°C MIM process. The HIP process can improve the quality of the alloy.

1. Introduction
2. Experimental
    2.1. Powder materials
    2.2. MIM process
    2.3. HIP process
    2.4. Microstructure characterization & mechanical testing
3. Results and Discussion
    3.1. Optical microscopy analysis
    3.2. Microhardness with the grain size
    3.3. Microstructure and chemical composition
4. Conclusion
Conflict of Interest Declaration
Author Information
Acknowledgments
References

• Eun Seong Kim(Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea)
• Jae Man Park(Department of mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea)
• Do Won Lee(Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea)
• Hyojeong Ha(Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea)
• Jungho Choe(Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea, Nano Materials Research Division, Korea Institute of Materials Science (KIMS), Changwon, Republic of Korea)
• Jaemin Wang(Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea)
• Seong Jin Park(Department of mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea)
• Byeong-Joo Lee(Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea)
• Hyoung Seop Kim(Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea, Graduate Institute of Ferrous & Eco Materials Technology (GIFT), Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea, Institute for Convergence Research and Education in Advanced Technology, Yonsei University, Seoul, 03722, Republic of Korea, Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan) Corresponding author