MULTIPLE TWINNING AND SPECIFIC PROPERTIES OF SIGMA = 3N BOUNDARIES IN FCC CRYSTALS

The dominant role of multiple twinning (appearance of the spectrum of SIGMA = 3n boundaries) in the formation of recrystallization texture of materials with a low stacking fault energy (stainless steel, high purity copper, silicon) has been determined. The importance of the formation, development and disappearance of twins as "channels" of the decrease of the system energy during annealing of deformed high purity aluminium is shown. The processes of structure self-organization during annealing, namely, the formation of stable groups of SIGMA = 3n boundaries, new types of metastable defects of polycrystals, such as multiple junctions (MJ), multiple nodes (MN), unequiaxial stable grain forms are considered. The crystallography classification, symmetry properties, topology and energetic estimation of the stability of (MJ) and (MN) have been performed.