Arma models applied to prediction of the dislocation patterns in nanostructured materials

Abstract

Nanostructured materials by severe plastic deformation have attracted much interest in the last decade due to their size-dependent unique mechanical, physical and chemical properties. During plastic deformation of metals and alloys, dislocations arrange in ordered patterns. When deformed plastically, line defects (dislocations) are introduced into the lattice of each grain. These defects organize into dislocation boundaries separating (nearly) dislocation-free regions with almost perfect lattices, which we term subgrains. Understanding the arrangement of dislocations is essential for science and industry, because their patterns determine many physical and mechanical properties, such as electrical rezistivity of semiconductors or strength anisotropy and fatigue failure of metals. In nanostructured materials, plasticity is caused by the dislocations generated by dislocation sources between grain boundaries. These dislocation spread out, interact with the pre-existing structures, so that an important part of them mutual annihilate each other. Based on the overlapped dislocations concept at the grain boundary frontier, the Hall-Petch relation shows an increase of the restrict flow value when decreasing grain boundaries size.