First-principles study on the stability of interstitial carbon and nitrogen and their influence on the plastic deformation mechanisms in a Co–Cr–W–Ni quaternary alloy

Kai Hiyama; Nana Ito; Ryoji Sahara; Kyosuke Ueda; Takayuki Narushima

doi:10.1016/j.mtcomm.2026.115937

Journal article First-principles study on the stability of interstitial carbon and nitrogen and their influence on the plastic deformation mechanisms in a Co–Cr–W–Ni quaternary alloy

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Kai Hiyama, Nana Ito, Ryoji Sahara, Kyosuke Ueda, Takayuki Narushima. First-principles study on the stability of interstitial carbon and nitrogen and their influence on the plastic deformation mechanisms in a Co–Cr–W–Ni quaternary alloy. Materials Today Communications. 2026, 55 (), 115937. https://doi.org/10.1016/j.mtcomm.2026.115937

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Carbon (C) and nitrogen (N) are critical elements for improving the mechanical properties of Co–Cr-based biomedical alloys and medium/high-entropy alloys. However, owing to the complex local atomic configurations in multicomponent alloys, the effects of interstitial C/N elements on the generalized stacking fault energy (GSFE) and underlying plastic deformation mechanisms remain poorly understood. In this study, we investigated the stability of interstitial C/N atoms and their effects on the GSFE of a Co–Cr–W–Ni quaternary alloy using first principles calculations combined with special quasi-random structures and supercell methods. Formation energy analyses revealed that, relative to Co, the presence of W and Ni in the first nearest-neighbor shell tends to destabilize the C/N atoms, whereas Cr acts as a stabilizer. N exhibits pronounced stabilization by Cr, suggesting the formation of Cr–N short-range order (SRO). Furthermore, GSFE analysis demonstrated that both C and N addition increased the intrinsic stacking fault energy. The addition of C and N also tended to enhance twinnability. N addition is expected to provide a greater increase in yield strength than C addition owing to SRO formation. Both C and N additions are expected to suppress the γ-to-ε strain-induced martensitic transformation, a mechanism known to contribute to higher ductility. Simultaneously, the promotion of deformation twinning suggests a potential pathway toward an exceptional balance of ultimate tensile strength and ductility, providing valuable insights for advanced alloy design.

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