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<p>NiCrFe superalloys are widely used in critical components under extreme environments such as aerospace and chemical engineering due to excellent high-temperature strength, corrosion resistance, and workability. However, nanocrystalline metals generally suffer from the inherent trade-off between strength and ductility. Grain boundary segregation engineering is considered an effective atomic-scale strategy to overcome this bottleneck. This study employs molecular dynamics to investigate the effects of Cr GB segregation (20%, 30%, and 40%) on the mechanical properties and deformation mechanisms of nanocrystalline NiCrFe alloys. The results show that GB segregation does not monotonically improve performance. The alloy with 30% Cr segregation achieves optimal strength-ductility synergy, with increases of 3.2% in tensile strength and 4.8% in average flow stress compared to the 20% Cr case. Increasing Cr to 40% reduces tensile strength by 5% but further enhances ductility. Microstructural analyses reveal that 30% Cr enhances GB stability, promotes dislocation networks and intersecting stacking faults, effectively pinning dislocations. Meanwhile, Shockley partial dislocations glide to form HCP stacking faults, collectively improving strength and work hardening. For 40% Cr, excessive Cr induces local lattice distortion and inhibits early dislocation sources, decreasing strength. However, stabilized GBs promote deformation twinning, improving plasticity. The 20% Cr model shows insufficient GB stability, leading to GB migration and loss of intersecting stacking faults, resulting in poor mechanical performance. This study provides atomic-scale insights into how Cr segregation concentration regulates the strength-ductility balance in NiCrFe alloys, offering a theoretical foundation for optimizing nanocrystalline metals via grain boundary segregation engineering.</p>

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Effect of segregation structure on mechanical properties of NiCrFe alloys

  • 期刊论文

  • 发表日期：

    2026年7月12日

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  • Yajie Shi,
  • Kexin Zhang,
  • Akbar Pushanov,
  • Shuying Liu,
  • Yuandong Li,
  • Xuefeng Lu

摘要

NiCrFe superalloys are widely used in critical components under extreme environments such as aerospace and chemical engineering due to excellent high-temperature strength, corrosion resistance, and workability. However, nanocrystalline metals generally suffer from the inherent trade-off between strength and ductility. Grain boundary segregation engineering is considered an effective atomic-scale strategy to overcome this bottleneck. This study employs molecular dynamics to investigate the effects of Cr GB segregation (20%, 30%, and 40%) on the mechanical properties and deformation mechanisms of nanocrystalline NiCrFe alloys. The results show that GB segregation does not monotonically improve performance. The alloy with 30% Cr segregation achieves optimal strength-ductility synergy, with increases of 3.2% in tensile strength and 4.8% in average flow stress compared to the 20% Cr case. Increasing Cr to 40% reduces tensile strength by 5% but further enhances ductility. Microstructural analyses reveal that 30% Cr enhances GB stability, promotes dislocation networks and intersecting stacking faults, effectively pinning dislocations. Meanwhile, Shockley partial dislocations glide to form HCP stacking faults, collectively improving strength and work hardening. For 40% Cr, excessive Cr induces local lattice distortion and inhibits early dislocation sources, decreasing strength. However, stabilized GBs promote deformation twinning, improving plasticity. The 20% Cr model shows insufficient GB stability, leading to GB migration and loss of intersecting stacking faults, resulting in poor mechanical performance. This study provides atomic-scale insights into how Cr segregation concentration regulates the strength-ductility balance in NiCrFe alloys, offering a theoretical foundation for optimizing nanocrystalline metals via grain boundary segregation engineering.