| Dislocation boundaries are an important dislocation structure created during plastic deformation of metals. Since these are formed at the beginning of plastic deformation, they play a vital role in the creation of subsequent microstructural pattern. Considerable research has been directed towards understanding of the behavior of dislocation boundaries. Unfortunately, most of the theoretical work available in open literature considers simplified dislocation boundaries configuration leading to the use of two-dimensional models. In addition, dislocation boundaries are formed as a result of various dislocation motion processes, which are three-dimensional in nature. Therefore in order to gain a better understanding of dislocation boundary behavior, one must perform three-dimensional analysis of experimentally observed dislocation boundaries, which is the main objective of this study.; In this research, the behavior of nearly planar geometrically necessary dislocation boundaries (GNBs) is investigated. The internal dislocation structure of the dislocation boundary is determined using experimentally known dislocation boundary normal and misorientation angle/axis, which is then used to construct the dislocation boundary for a discrete dislocation (DD) analysis. A dislocation boundary constructed in this manner reflects the characteristics of the dislocation boundary in the experiments. The dislocation boundary behavior is investigated using a multi-scale model, which couples discrete dislocation plasticity with finite element. The results are presented for two different dislocation boundaries termed "21" and "10". Comprehensive analysis of a single dislocation boundary is performed to investigate various numerical factors and set guidelines for simulation of such dislocation boundaries. It is shown that the use of plausible model boundary conditions removes the 'hump' observed in the self-stress field of dislocation boundaries of finite size. Next, the interaction behavior of two dislocation boundaries is analyzed, which shows that local stress in the space between dislocation boundaries depends on the separation distance. In addition, results are presented for interaction of a mobile extrinsic dislocation with a dislocation boundary using a quasi-static method and dynamic simulations. Finally, a gradient crystal plasticity model is outlined that incorporates the effect of length scale associated with dislocation boundaries into a continuum model. |
