Surface plasticity effects in dispersion-hardened copper-silica single crystals

Abstract

Abstract The effect of internally-dispersed silica spheres upon the surface plasticity of copper single crystals, deformed in tension, has been investigated. It is shown that copper-silica crystals do not exhibit any crystal size-effect phenomena in their stress-strain behaviour and that they have a uniform flow-stress distribution across the crystal width. Electron microscopy studies show that the dislocation distribution is uniform throughout the bulk of a crystal except for a surface region about 0·5 μm deep where a lower density of dislocations is evident. In contrast, similar studies of the internally oxidized and annealed pure copper matrix material show pronounced size effects and a ‘soft-surface’ flow-stress distribution analogous to as-grown pure copper. This investigation provides evidence that the type of flow-stress distribution present in a f.c.c. single crystal during deformation can be modified by changing the mean-free-path of the dislocations at low strains. No evidence could be found for...