Optimal twin boundary spacing in nanotwinned monocrystalline Al under loading perpendicular to twin boundaries: An atomistic study

WC Shi and B Shao and QC Fan and C Yang and HX Liu and P Jing, MATERIALS TODAY CHEMISTRY, 46, 102728 (2025).

DOI: 10.1016/j.mtchem.2025.102728

Al foil is an important structural material in the aerospace field due to its unique thermal control performance, lightweight nature, and other merits. Introducing nanotwins is a very effective method to improve both strength and ductility. The orientation of twin boundaries in experimentally synthesized nanotwinned Al is not fixed relative to the prevailing load, making it difficult to elucidate the inherent evolution of mechanical properties under different loading directions. Molecular dynamics simulations were used to investigate the mechanical properties of nanotwinned Al under uniaxial tension perpendicular to twin boundaries at 300 K. The results reveal a transition of average flow stress from strengthening to softening around the twin boundary spacing of 21.04 & Aring;. As the twin boundary spacing decreases, the dominant deformation mechanism gradually shifts from inclined dislocations to detwinning. The detwinning ratio reaches as high as 96.6 % at the minimum twin boundary spacing of 7.01 & Aring;. A new model, developed by integrating with the CLS model, is proposed, which successfully predicts the critical twin boundary spacing for the strengthening-to- softening transition in nano-twinned face-centered cubic metals. The results provide valuable insights into the design and application of high strength and high toughness nanotwinned materials.

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