Athermal critical stresses for dislocation propagation in nanocrystalline aluminium

Molecular dynamics simulations investigating the mechanical properties of nanocrystalline Al have revealed the importance of both dislocation nucleation at grain boundaries and subsequent propagation as possible rate-limiting microscopic plastic process. Here, we present an approach to determine the athermal stress-strain behaviour of selected dislocations as they propagate within the nanocrystalline environment. In the first case study, the critical resolved shear stress to depin resulting into a planar propagation is found to be 735 MPa. In a second case study, a pinned dislocation is found to cross-slip at a critical resolved shear stress of 372 MPa to circumvent a near unfavoured grain boundary region.