Direct measurement of shear stress for dislocation transferring across {111} Σ3 grain boundary in aluminum bicrystal via in situ straining TEM

TEM in situ straining was applied to an Al bicrystal with a {111}Σ3 grain boundary. The activated slip systems in both grains were determined based on the dislocation line configurations and the crystallographic orientation of the applied load. The resolved shear stress for activation of the dislocation transfer at the GB, τgb, was directly evaluated from the dislocation motion and the simultaneously obtained stress-strain curve. The evaluated τgb value agrees with those obtained in a previous study on macroscopic tensile tests. From the geometry of the dislocation reaction, it was presumed that the pile-up lattice dislocations are dissociated into the lattice dislocations in the adjacent grain and the GB dislocation. It was determined that the activated slip system in the adjacent grain was dominated by local energetic and geometric conditions rather than the global condition such as the combination of Schmid low and applied stress.