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<p>The activation volume, a key parameter in plasticity theory, quantifies the unit volume associated with microstructural changes during plastic deformation and provides critical insight into the underlying deformation mechanisms. Calculation of the activation volume enables a quantitative assessment of dislocation evolution during microscopic deformation processes. In this study, molecular dynamics (MD) simulations were performed to investigate the mechanical response of single-crystal and bi-crystal Ni<sub>75</sub>Cr<sub>15</sub>Fe<sub>10</sub> nickel-based alloys under nanoindentation. The bi-crystal models incorporated Σ3(111), Σ9(114), Σ17(334), and Σ33(554) symmetric tilt grain boundaries (GBs). The hardness, dislocation density, and activation volume were systematically evaluated, and dislocation nucleation under various conditions was analyzed. Results indicate that elevated temperatures accelerate dislocation nucleation. By determining the strain rate sensitivity and activation volume, the correlation between dislocation evolution behavior across different GBs and the activation volume was elucidated. A smaller activation volume was found to correspond to faster dislocation nucleation and mobility.</p>

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Atomic Simulation of Dislocation Nucleation and Activation Volume in the Nanoindentation Process of Nickel-Based Alloys Ni75Cr15Fe10

  • 期刊论文

  • 发表日期：

    2026年7月27日

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  • Tianyu Chen,
  • Tianxiao Liu,
  • Huaiyu Hou

摘要

The activation volume, a key parameter in plasticity theory, quantifies the unit volume associated with microstructural changes during plastic deformation and provides critical insight into the underlying deformation mechanisms. Calculation of the activation volume enables a quantitative assessment of dislocation evolution during microscopic deformation processes. In this study, molecular dynamics (MD) simulations were performed to investigate the mechanical response of single-crystal and bi-crystal Ni75Cr15Fe10 nickel-based alloys under nanoindentation. The bi-crystal models incorporated Σ3(111), Σ9(114), Σ17(334), and Σ33(554) symmetric tilt grain boundaries (GBs). The hardness, dislocation density, and activation volume were systematically evaluated, and dislocation nucleation under various conditions was analyzed. Results indicate that elevated temperatures accelerate dislocation nucleation. By determining the strain rate sensitivity and activation volume, the correlation between dislocation evolution behavior across different GBs and the activation volume was elucidated. A smaller activation volume was found to correspond to faster dislocation nucleation and mobility.