In this study, seven models of pure aluminum and graphene-reinforced aluminum-based composite nanomaterials (Gr/Al nanocomposites) are constructed using molecular dynamics simulations in which 0.5% of 1–3 layers of graphene are embedded at 0° and 90° orientations. This study aims to investigate the microscopic deformation behavior of Gr/Al nanocomposites under torsional loading. The simulation results indicate that the graphene significantly influences the torsional mechanical response of aluminum matrix: graphene reduces the potential energy of the system and smoothens kinetic energy fluctuations through mechanical interlocking and electron-phonon coupling. The composites containing graphene exhibit stronger shear stress fluctuations with higher extreme values. The influence becomes more pronounced as the number of layers increase, when the graphene is embedded at 0°. Specifically, 3-layer graphene embedded at 0° (3-Gr-0°) shows prominent stress extremes near 540°–610°, indicating that 3-Gr-0° can withstand greater torsional loads.

Further research reveals that graphene embedding disrupts both the short-range and long-range orderliness of aluminum atoms. The 0° orientation exerts a stronger disruptive effect than the 90° orientation, and an increase in the number of layers exacerbates this effect. The proportion of face-centered cubic (FCC) structures decreases as torsional angle increases. A more pronounced reduction in structural stability is observed at 90° orientation and with an increase in the number of layers. The analysis of dislocations and stacking faults indicates that graphene hinders dislocation propagation, increasing the angle at which initial dislocations appear. During torsion, Shockley partial dislocations dominate. The 90° orientation of graphene is more susceptible to triggering dislocation reactions, while the 0° orientation more significantly obstructs dislocation propagation. After graphene reinforcement, the generation of intrinsic stacking faults within the composites requires a larger torsional angle, and the reduction in stacking fault energy facilitates dislocation decomposition. The 3-Gr-0° configuration predominantly features Shockley partial dislocations, with a moderate dislocation pile-up effect and a higher threshold for ISF generation. This study provides a theoretical reference for the structural design and performance optimization of such composites.