Experimental studies of regularities of occurrence and development of substructural and orientational heterogeneity of polycrystalline copper foils with different twin structure in the process of their deformation in conditions of active tension have been carried out. It is shown that by selecting the regime of thermal treatment of fine-grained copper foil three types of samples with different twin structure can be obtained. The first type is characterized by the presence of twins, which differ

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... in size, shape and type of boundaries. Samples of the second type contain twins with faceted boundaries. Samples of the third type contain parallel twins with rectilinear boundaries. Such a variety of twin structures not only predetermines the difference of mechanical characteristics for samples of different types but also regularities of substructure and orientation changes accompanying the plastic deformation of samples. The use of a highly sensitive imaging method that allows in situ characterization of substructural and orientational heterogeneity during deformation and other methods (optical and raster microscopy, interferometry) allowed us to detect specific features of the course of relaxation processes in samples of different types.