The dislocation cell size and dislocation density in copper deformed at temperatures between 25 and 700°C

Abstract

A dislocation cell structure was developed in polycrystalline OFHC copper by deforming tensile specimens 10 per cent, one at each of the following temperatures: 25, 250, 400, 500, 550, 600, 650 and 700°C. The dislocation cell size and the dislocation density were measured by transmission electron microscopy. The mean cell diameter increased with increasing temperature from 1.4 μ at 25°C to 6.0 μ at 700°C. The dislocation density ρ decreased with increasing temperature, from 118.0 × 10 8cm/cm 3 at 25°C to 8.5 × 10 8 cm/cm 3 at 700°C. The thickness of the cell walls decreased with increasing temperature of deformation. It was found that the mean cell diameter d was related to the dislocation density ρ through the relation d = 16ρ −1 2 . The occurrence of such a relation supports a theory in the literature of dislocation cell formation. The flow stress τ was given by τ = 10.5 Gb/ d and τ = 0.57Gb ρ 1 2 where G is the shear modulus and b is the Burgers vector.