Abstract
The aim of the present study is to examine how severe plastic deformation techniques: compression with oscillatory torsion and multi-axial compression, alter the microstructure and properties of metal, and what is the efficiency of the mentioned methods. For this reason the deformed microstructure of Cu was characterized quantitatively by use of electron backscattered diffraction and transmission electron microscopy techniques. The mechanical properties were determined using an MTS QTest/10 machine equipped with digital image correlation. The results show that severe plastic deformation through compression with oscillatory torsion and multi-axial compression leads to a refinement of the Cu to ultra-fine scale. The final structure of samples after compression with oscillatory torsion consists of cellular/subgrain structure with a low value of misorientation. The multi-axial compression technique is effective in generating high angle boundaries. The samples after compression with oscillatory torsion exhibit a higher strength compared with multi-axial compression.

Key words
severe plastic deformation, copper, fine-grained microstructure, EBSD, TEM

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