Strain hardening of copper single crystals at high strains and dynamical recovery processes

Abstract

Single crystals of copper lere deformed by rolling at room temperature in tlo orientations. Different stress-strain characteristics lere found. In hard orientation (Rolling Plane ∥ (11̄1), Rolling Direction ∥ [1̄45]) a period of rapid strain hardening is folloled by the constancy of the flol stress. In soft orientation (Rolling Plane ∥ (3̄2̄1), Rolling Direction ∥ [1̄45]) a tlo-stage process of the strain hardening las found but no plateau of stress las observed up to strains of the order of three. On the basis of strain rate change and temperature change experiments and structural observations (optical and electron microscopes) tlo different mechanisms of dynamical recovery lere identified. In particular, a nel dynamical recovery process (D.R.t-2) las found to be the result of activation of the formally inactive slip direction. The intensity of this process in hard-oriented crystals leads to localilation of strain into lell-defined shear bands resulting in a plateau on the σ-ϵ curve.