| METALS AND METAL MATRIX COMPOSITES |
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| Molecular Dynamics Study on the Influence of Boundary Layer Spacing on Mechanical Properties of Nanostructured Al Metal |
| CHEN Jingjing*, CHEN Sha, JIANG Yanqing, ZHAN Huimin, LUO Zeyu
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| Mechanical Friction Wear and Protective Lubrication Research Center on Surface/Interface, Nanchang Institute of Technology, Nanchang 330044, China |
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Abstract Overcoming the incompatibility between strength and plasticity in conventional structural metallic materials has long been a major challenge, and it thus remains a key scientific issue in both engineering and academic fields. From the perspective of boundary engineering, this study investigated the strong correlation between microstructural evolution and mechanical properties of twin-crystalline aluminum (Al) during plastic deformation-considering different boundary layer spacings and extreme service temperatures-based on molecular dynamics simulations. The enhancement of mechanical properties was modulated by the nanoconfinement effect induced by twin boundaries, and the underlying mechanism of this mechanical property enhancement was revealed at the atomic level. It was found that the nanoconfinement effect strongly pins mobile dislocations to twin boundaries, leading to the cross-linking and entanglement of mobile dislocations within the confined domains. This phenomenon results in a significant increase in mobile dislocation density in the confined channels, which is the fundamental reason for the remarkable improvement in the mechanical properties of nanostructured Al. Furthermore, the results demonstrate that the mechanical properties of twin-crystalline Al gradually improve with the reduction of twin boundary layer spacing, and its strengthening trend is dependent on extreme service temperatures. In addition, the high stress concentrated in confined channels directly drives the migration and proliferation of mobile dislocations, as well as the occurrence of structural phase transformations; these two processes collectively dominate the plastic deformation of nanostructured Al. Meanwhile, mismatched defect sites at the surface of nanostructured Al and within twin boundaries lead to the accumulation of high stress in damaged regions, which become the source of mobile dislocation nucleation and emission. Moreover, higher service temperatures intensify shear strain deformation around the contact zone, which weakens the boundary contact stiffness, increases boundary contact mass, and enhances the adhesion effect. In contrast, reducing the twin boundary layer spacing can improve boundary contact stiffness, effectively decrease the number of contact atoms, and mitigate boundary contact mass—thereby enhancing the toughness of nanostructured Al. This study provides an important theoretical basis and academic reference for regulating the strengthening and toughening properties of nanostructured metallic materials via the engineering design of boundary layer spacing.
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Published: 10 November 2025
Online: 2025-11-10
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