Local-Stress-Induced Detwinning in Nanotwinned Al without Shear Stress on Twin Boundaries

Enhancing the strength of nanotwinned aluminum (Al) is essential for the development of next-generation high-end chip technology. To better understand the detwinning behavior of nanotwinned Al under conditions with no resolved shear stress acting on the twin boundaries, we conducted molecular dynamics simulations of uniaxial tensile deformation in nanotwinned single-crystal Al at room temperature. Detwinning is observed only when the twin boundary spacing is 7.01 Å. At larger spacings, twin boundaries remain parallel to the loading direction, with no rotation or bending, indicating negligible migration. Detwinning is triggered by localized stress from dislocation interactions, with detwinning fraction evolving synchronously with dislocation density. In the absence of detwinning, dislocations inclined toward twin boundaries interact frequently with them, leading to a loss of coherency that intensifies with increasing twin boundary spacing. These findings enhance understanding of the plastic deformation mechanisms in nanotwinned metals at very small twin boundary spacings, supplement the conventional understanding of twin boundary stability, and therefore suggest potential pathways for designing Al-based nanostructures with enhanced stability or controllable plastic deformation.