LAUSR

Abstract The present work was conducted to examine the grain boundary character distribution in a rare earth elements bearing magnesium alloy during thermomechanical processing (TMP). To this end, the friction stir processing was applied as an effective TMP scheme through single and completely overlaid three-pass trials. The results indicated that along with the progressive substructure development and significant grain refinement, the fractions of coincidence site lattice boundaries were also increased in processed materials. The twin based special boundaries (holding 15b character) and the perfect coincidence ones (holding 13a character) were found as the most common coincidence site lattice boundaries. These were directly resulted from the occurrence of twinning induced dynamic recrystallization and progressive lattice rotation, respectively. The higher strain accumulation at the twin based boundary indicated the higher instability of them in comparison to the perfect coincidence one. The deformed microstructures were also consisted of a new specific kind of high angle grain boundary holding the rotating axis of . The tilt nature of the boundary plane distribution was well approved the relatively stable character of this new type of special boundary. The micro-textures of the processed materials were also examined and the preferred orientation of developed special boundaries were characterized.