Effects of temperature and strain rate on the mechanical behaviour and deformation mechanisms of hierarchical nanotwinned structures

Hierarchical nanotwinned (HNT) structures offer a promising pathway for overcoming the strength-ductility trade-off in nanostructured metals. While prior research has extensively examined the intrinsic strengthening mechanisms of HNT structures, the influence of external loading conditions remains relatively unexplored. This work employs molecular dynamics simulations to investigate the effects of temperature, ranging from 77 to 700 K, and strain rate, ranging from 1 × 108-5 × 1010 s−1, on the mechanical properties and deformation mechanisms of HNT copper. Results demonstrate that elevated temperatures attenuate the additional strengthening effect by weakening grain boundary blocking and promoting uniform plastic flow, which reduces the stress disparity between the primary and secondary twin-bounded regions. In contrast, high strain rates enhance strength through increased dislocation slip resistance and intensified dislocation-dislocation interactions, with grain boundaries playing a diminished role. These findings elucidate the distinct atomic-scale mechanisms governing the temperature and strain-rate sensitivity of HNT metals, providing crucial insights into their performance optimisation under diverse service conditions.