Synergistic strength-ductility enhancement in carbide-free FeMnCoNiC high entropy alloys via interstitial carbon solution

侵入型固溶炭素による炭化物フリーFeMnCoNiCハイエントロピー合金の強度・延性協調向上

Fang, W.*; Liu, C.*; 吉田 周平*; Peng, T. X.*; 徐 平光   ; Han, Y.*; Li, J.*; Yin, F.*; 辻 伸泰*

Fang, W.*; Liu, C.*; Yoshida, Shuhei*; Peng, T. X.*; Xu, P. G.; Han, Y.*; Li, J.*; Yin, F.*; Tsuji, Nobuhiro*

Interstitial alloying is an effective strategy for enhancing the mechanical properties of high-entropy alloys (HEAs). However, in carbon-containing HEAs, the coexistence of interstitial carbon and carbides complicates the investigation of interstitial carbon's individual effects on strength and ductility. To address this, a carbide-free interstitial strengthened HEA, FeMnCoNiC, was designed by incorporating elements with low carbon affinity, enabling a clear assessment of the role of interstitial carbon. The results demonstrate that interstitial carbon solution simultaneously improves strength, ductility, and work hardening capability. Synchrotron radiation experiments reveal that the interstitial carbon containing alloy sustains higher lattice elastic strain, dislocation density, and stacking fault probability during tensile deformation, with the increased dislocation density being the primary contributor to enhanced work hardening. First principles calculations further elucidate the lattice distortion, chemical inhomogeneity and electronic localization effects induced by interstitial carbon, as well as their potential influence on strength and ductility. This study highlights the importance of carbide-free interstitial carbon-strengthened HEAs for a fundamental understanding of carbon's influence on mechanical properties.