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<p>High-entropy alloys have garnered significant attention recently due to their exceptional mechanical properties and phase stability across a broad temperature range. However, understanding their plastic deformation mechanisms at the atomic scale remains a challenge. This study employs molecular dynamics simulations to examine the influence of grain size on the mechanical properties, microstructural evolution, and governing deformation mechanisms of polycrystalline FCC Al<sub>16.8</sub>Co<sub>20.8</sub>Cr<sub>20.8</sub>Fe<sub>20.8</sub>Ni<sub>20.8</sub> HEA with grain sizes ranging from 4.2 to 15.6&#xa0;nm. The results indicate that the elastoplastic properties of samples deteriorate with decreasing grain size, which is attributed to the critical role of grain boundary density in polycrystalline materials. It was determined that grain boundaries serve as primary nucleation sites for microstructural defects, including dislocations, stacking faults, and twins. Deformation twins are also formed through the transformation of intrinsic stacking faults into extrinsic stacking faults. Coarse-grain HEAs primarily undergo deformation via intra-grain defect activities, such as dislocation slip and twinning, while fine-grain HEAs exhibit both grain boundary-driven mechanisms and defect-induced deformation. These findings offer valuable insights into the deformation behavior of HEAs and can assist in optimizing their microstructure to enhance mechanical properties for high-performance engineering applications.</p>

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Complexity of the Plastic Deformation Mechanisms in Al-Based High-Entropy Alloys: An Atomistic Study via Molecular Dynamics Approach

  • 期刊论文

  • 发表日期：

    2026年4月2日

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  • Abolfazl Malti,
  • Mostafa Farahani,
  • Farrokh Yousefi,
  • Arash Kardani

摘要

High-entropy alloys have garnered significant attention recently due to their exceptional mechanical properties and phase stability across a broad temperature range. However, understanding their plastic deformation mechanisms at the atomic scale remains a challenge. This study employs molecular dynamics simulations to examine the influence of grain size on the mechanical properties, microstructural evolution, and governing deformation mechanisms of polycrystalline FCC Al16.8Co20.8Cr20.8Fe20.8Ni20.8 HEA with grain sizes ranging from 4.2 to 15.6 nm. The results indicate that the elastoplastic properties of samples deteriorate with decreasing grain size, which is attributed to the critical role of grain boundary density in polycrystalline materials. It was determined that grain boundaries serve as primary nucleation sites for microstructural defects, including dislocations, stacking faults, and twins. Deformation twins are also formed through the transformation of intrinsic stacking faults into extrinsic stacking faults. Coarse-grain HEAs primarily undergo deformation via intra-grain defect activities, such as dislocation slip and twinning, while fine-grain HEAs exhibit both grain boundary-driven mechanisms and defect-induced deformation. These findings offer valuable insights into the deformation behavior of HEAs and can assist in optimizing their microstructure to enhance mechanical properties for high-performance engineering applications.