Dislocation structures in copper matrix after constant stres cycling of copper/tungsten composites

Abstract

Abstract Composites consisting of single crystal copper matrix containing 10 per cent volume fraction of uniaxially aligned tungsten fibres were subjected to constant stress cycling and the dislocation structures produced were studied by the etch-pitting technique. It was found that plastic deformation started in the soft region of the copper matrix away from the fibre. Dislocations piled up against the pre-existing sub-boundaries and cell walls. On cycling, progressively less permanent plastic strain was obtained. The cell structure seemed to be better defined. At stabilisation ( i.e. closed loop) the cell structure was fairly well developed thoughout the matrix although not of a uniform size. Cycling beyond stabilisation led to a greater rearrangement of dislocations into a metastable cellular structure. The stress cycling thus tended to make the copper matrix of a uniformly high dislocation density distributed in a more or less uniform cellular structure.