Cyclic deformation of pure aluminum bicrystals

The dynamic behavior of 〈112〉-tilt grain boundaries in aluminium bicrystals under the influence of cyclic stresses at elevated temperatures is reviewed. Bicrystals, containing low- and high-angle grain boundaries within a wide range of misorientation angles, were deformed at several combinations of stress, temperature, and number of cycles. The grain-boundary (GB) displacement and the deformed structure of bicrystals were framed using standard optical microscopy. The grain orientations were measured using the electron backscatter diffraction (EBSD) technique with a scanning electron microscope (SEM), before and after the deformation. There is distinct evidence of a sharp transition angle between low- and high-angle grain boundaries, with respect to the ability of the boundaries to move under the given parameters. The experimental observations lead to the conclusion that a difference in the dislocation structure in two grains causes the driving force for GB migration.