Study on the deformation mechanisms of gradient grains based on molecular dynamics

W Wang and LP Chen and T Wang and FR Yang and C Qi and XY Mao, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, 33, 045013 (2025).

DOI: 10.1088/1361-651X/add7f6

This study employs molecular dynamics simulations to compare the mechanical properties and deformation mechanisms of gradient nano- grained (GNG) Fe and uniform NG Fe. The results show that the maximum stress of GNG Fe (8.05 GPa) is significantly higher than that of NG Fe (7.30 GPa), indicating that the gradient structure contributes to enhancing the material's strength. Furthermore, the GNG structure exhibits both high strain hardening and high strain softening rates. The fine-grained region of GNG Fe is more prone to plastic deformation, and the stress concentration is more evenly distributed to the coarse- grained region, forming a stress gradient that improves crack resistance and toughness. Microstructural analysis reveals that, at 5% strain, the higher dislocation density in GNG Fe (increased by 5 x 1015 m-2 compared to NG Fe) enhances its strain hardening capability. At 15% strain, the twin boundaries in GNG Fe effectively inhibit dislocation motion in the coarse-grained regions, thereby improving the material's ductility. As strain increases further, cracks primarily nucleate and propagate in the coarse-grained regions of GNG Fe, while the fine-grained regions effectively suppress crack propagation.

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