Severely deformed Cu by using compression with oscillatory torsion method

Purpose: The present study is aimed at a quantitative description of microstructural parameters as a misorientation angle of Cu deformed by using compression with oscillatory torsion. Design/methodology/approach: Cu samples were deformed at torsion frequency (f) changed from 0 Hz (compression only) to 1.8 Hz under a constant torsion angle (alpha) = 8 degrees and compression speed (v)=0.1 mm/s. Structural investigations were conducted by using transmission electron microscopy (TEM). Local misorientation have been measured by the Kikuchy pattern technique. Findings: The results of the investigations have shown that formation of ultrafine structure is seen after deformation at 0.4 Hz, where cells show broad boundaries having a diffuse dislocation arrangement, which transform to high-angle grain boundaries at higher strains (higher value of f). The subgrain interiors also contain dislocation arranged in an irregular shape. For this reason the effects must be explained by movements of dislocation, where dislocation are continuously built up to new boundaries as a deformation increase. Research limitations/implications: Reported research ought to be completed with EBSD (Electron Backsscattering Difraction) technique. Originality/value: Grain boundary misorientation is important for describing the microstructure of severe plastic deformation process and may be useful in explanation of ultrafine grains formation.