In non-close-packed crystalline lattices, e.g. of body-centered cubic metals and intermetallic compounds, the stress-state dependence of the Peierls barrier for the motion of a screw dislocation violates Schmid’s law and led to non-associated plastic flow at the continuum level. Plasticity models based upon distinct yield and flow functions were developed for both single crystals and polycrystalline aggregates that build upon atomic-level simulations of single dislocations. For a random polycrystal, isotropic forms for those functions were proposed and used to study mechanisms of macroscopic deformation. Non-associated flow was shown to have a significant effect on strain localization. Intermittent strain bursts were predicted to arise as a consequence of non-associated flow, particularly for deformations close to the plane strain state and for nearly rate-insensitive response.

From Non-Planar Dislocation Cores to Non-Associated Plasticity and Strain Bursts. J.L.Bassani, V.Racherla: Progress in Materials Science, 2011, 56[6], 852-63