Microstructural Evolution and Mechanical Properties of Non-Equiatomic (CoNi)74.66Cr17Fe8C0.34 High-Entropy Alloy

You Sub Kim; Hobyung Chae; E-Wen Huang; Jayant Jain; Stefanus Harjo; Takuro Kawasaki; Sun Ig Hong; Soo Yeol Lee

doi:10.3390/ma15041312

Microstructural Evolution and Mechanical Properties of Non-Equiatomic (CoNi)_74.66Cr₁₇Fe₈C_0.34 High-Entropy Alloy

Materials (Basel). 2022 Feb 10;15(4):1312. doi: 10.3390/ma15041312.

Authors

You Sub Kim¹, Hobyung Chae¹, E-Wen Huang², Jayant Jain³, Stefanus Harjo⁴, Takuro Kawasaki⁴, Sun Ig Hong¹, Soo Yeol Lee¹

Affiliations

¹ Department of Materials Science and Engineering, Chungnam National University, Daejeon 34134, Korea.
² Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30013, Taiwan.
³ Department of Materials Science and Engineering, Indian Institute of Technology Delhi, New Delhi 110016, India.
⁴ J-PARC Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.

Abstract

In this study, we manufactured a non-equiatomic (CoNi)_74.66Cr₁₇Fe₈C_0.34 high-entropy alloy (HEA) consisting of a single-phase face-centered-cubic structure. We applied in situ neutron diffraction coupled with electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) to investigate its tensile properties, microstructural evolution, lattice strains and texture development, and the stacking fault energy. The non-equiatomic (CoNi)_74.66Cr₁₇Fe₈C_0.34 HEA revealed a good combination of strength and ductility in mechanical properties compared to the equiatomic CoNiCrFe HEA, due to both stable solid solution and precipitation-strengthened effects. The non-equiatomic stoichiometry resulted in not only a lower electronegativity mismatch, indicating a more stable state of solid solution, but also a higher stacking fault energy (SFE, ~50 mJ/m²) due to the higher amount of Ni and the lower amount of Cr. This higher SFE led to a more active motion of dislocations relative to mechanical twinning, resulting in severe lattice distortion near the grain boundaries and dislocation entanglement near the twin boundaries. The abrupt increase in the strain hardening rate (SHR) at the 1~3% strain during tensile deformation might be attributed to the unusual stress triaxiality in the {200} grain family. The current findings provide new perspectives for designing non-equiatomic HEAs.

Keywords: high-entropy alloy; mechanical property; neutron diffraction; stacking fault energy.

Abstract

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