Producing thin-walled tube of pure copper by severe plastic deformation of shear extrusion

A severe plastic deformation method entitled shear extrusion (SE) was proposed to form thin-walled tubular components. This process was validated by experiments in which a pure copper tube was used as investigation object. The effect of SE on grain refinement and strength improvement was assessed. The results of optical microscope observation show a significant grain refinement as well as the increased grain misorientations for the samples processed by four passes of SE. The TEM analysis shows that the dislocation refinement of shear strain is the main reason during the SE process, followed by strain localization leading to dynamic recrystallization. The hardness of undeformed copper cube sample is ~400 MPa, while that of as extruded sample is up to ~1070 MPa. The increase of the hardness is mainly caused by the dislocation generation.