The flow stress behavior of OFHC polycrystalline copper

The flow stress behavior of OFHC polycrystalline copper was evaluated using cold-rolled and equal channel angular extruded materials. Prior to tensile testing at room temperature, the specimens were heat treated to obtain grain sizes ranging from 3 to 60 μm. The flow stress, when correlated with the square root of true strain, is associated with four stages of hardening. These stages, in terms of increasing strain, are attributed to: (1) dislocation source activation, possibly at annealing twin boundaries during the onset of plastic flow, (2) dislocation slip and cross slip, (3) constriction of the screw dislocation partials for cross slip continuation, and (4) dislocation annihilation and saturation as interpreted through dynamic recovery. The tensile properties and analyses are supported by observations and measurements from orientation imaging and transmission electron microscopy.