| Grain boundary structures play a very important role in determining materials properties. In this work grain boundary structures in polycrystalline aluminum have been investigated either by high resolution microscopy or by weak beam imaging. It found the grain boundary structures were material processing dependent. Under extreme processing condition the structure could be away from the equilibrium state. The low angle 7° tilt grain boundary was found to be composed of 60° dislocations instead of lomer dislocations and these 60° dislocations might be moving during the annealing. A very high energy mirror symmetric structure was also observed along a Σ = 3 coherent twin boundary. This structure corresponds to a rigid body translation of translation vector 1/6[112]. This structure may be caused by the processing condition.; Not only did the grain boundary structures change with the processing procedure but also the grain boundary misorientation distribution. The titanium and hafnium textures were determined by the processing procedure. The misorientation distributions varied during different annealing processes.; The results from this thesis show that it is possible to manipulate the material properties by controlling the grain boundary structure. |
