The Effect of Reverse Strain on Microstructure and Strengthening of Copper Fabricated by Severe Plastic Deformation of Torsion Process

Abstract

The unidirectional single torsion process of commercially pure copper was followed by different number of reverse turns of torsion deformation. The effect of reverse strain on the material refinement and hardening was investigated. It is found that the grain refinement is significantly blocked in the reverse torsion strain in comparison with that only suffered in monotonic torsion strain. The strengthening slightly decreases with the torsional direction change. This phenomenon is interpreted in terms of the average dislocation density. A qualitative assumption is proposed to explain the retarded phenomenon of material refinement and hardening in the reverse torsion process. The reverse strain maybe improves the uniformity and stress-strain equilibrium of severe plastic deformation induced material.