The effect of dispersed phases upon dislocation distributions in plastically deformed copper crystals

Abstract

Abstract The effect of dispersions of either cobalt or silica upon the dislocation distributions in deformed copper crystals has been investigated. The crystals were deformed in tension, and three-stage stress-strain curves, similar to those of single-phase copper, were obtained. However, the precipitates caused an increase in the yield stress and in the rate of hardening in stage I. Electron microscopy of sections cut from crystals deformed into stage I showed the alignment of primary dislocation loops, helices, jogs and dipole ends in the direction of the primary Burgers vector, and these effects are interpreted in terms of dislocation cross-slip at the particles. The incidence of particle shearing in the copper-cobalt crystals causes these features to be less pronounced than in the copper-silica crystals. Electron microscopy of crystals deformed into stage II shows that the precipitate causes lattice misorientations to be decreased, and less inhomogoneous dislocation structures than in single-phase crystals to occur.