The methodology detailed herein provides a framework for incorporation of results from atomistic-scale models of dislocation creep and diffusion.
Finally, effects of microstructural length scales on dislocation structures are briefly discussed.
Still, the DDD model can help elucidation of plastic deformation at the scale of discrete dislocations, which can assist the development of an appropriate continuum constitutive theory.
In the present paper we use a simple method for the quantitative evaluation of characteristic length scales of some dislocation and surface topographical structures in mechanically deformed metals by means of linear integral transforms (in particular, the Fast Hartley Transform, FHT).
The results for the MA07 model are consistent with the known slip geometry of Zr, suggesting that it offers significant advantages for large-scale atomic simulation of dislocation behaviour.
The velocity stress dependence of screws has been measured at the scale of a single dislocation source, and compared with macroscopic activation areas.
We show that indentation size effects at the micrometer scale can be understood in terms of the hardening associated with strain gradients and geometrically necessary dislocations, while indentation size effects at the nanometer scale involve the concepts of dislocation starvation and the nucleation of dislocations.
Although the good relation between the model and the experimental points is not a fully evidence, it strongly suggests that, as the hardness scale decreases, the increase of dislocation density and the increase of the surface-to-volume ratio of the plastically deformed region are the most important causes for the observed indentation size effect.
HR-TEM performed on various areas confirms on a more local scale the absence of dislocations (Figure 2b), indicating a full accommodation of the lattice misfit by elastic deformation.
Both experimental observations and theoretical analyses revealed differences in plasticity and fracture mode between the two types of metallic multilayers and the relevant physical mechanism transition due to length scale constraint and interface/boundary blocking of dislocation motion.
