Strengthening Nanotwinned Al by Twin Boundary Orientation and Spacing: A Molecular Dynamics Simulation Study

High strength is essential for structural materials to avoid sudden failure. Extensive research has highlighted the critical role of nanotwins in strengthening metals. However, it is experimentally challenging to apply loading in a specific direction, achieve the lower limit of twin boundary spacing, and exclude the effects of conventional grain boundaries. Therefore, this study employed molecular dynamics simulations to examine nanotwinned single-crystal Al under uniaxial tension in three representative directions. The results show a maximum strength of 2.27 GPa when loaded along ⟨112⟩, with intermediate and minimum strengths along ⟨111⟩ and ⟨110⟩, respectively. A strength crossover between the ⟨111⟩ and ⟨112⟩ loading directions occurs between λ = 35.07 Å and λ = 42.09 Å, due to variations in the model's ability to generate and maintain Stair-rod dislocations. The findings provide a theoretical foundation for designing high-performance nanotwinned metals.