Investigation on the strengthening behaviour of micro-scale copper fiber

Abstract

Due to the size effect, the material exhibits the characteristics of "the smaller, the stronger", but there are limits to the improvement of material strength. In this paper, the 200 μm pure copper fiber is reduced to 23 μm by the cold drawing method. The stress-strain curve and microscopic analysis, it is concluded that grain boundary strengthening, texture strengthening and dislocation strengthening are the main strengthening methods of copper fiber. Cold drawing improves the fiber strength by reducing the grain size and changing the texture orientations. With the grain refinement, the texture orientation of copper fiber, gradually changed from the random distribution orientations to <001> and <111> preferred orientations. However, the evolution of the texture orientation does not always follow the same path. The increase of <101> oriented grains provide more plastic deformation space for the further refinement of copper fiber. When the fiber diameter reaches 23 μm, the grain orientation deflects to the preferred orientations of <111> and <001> again. For the copper fiber, the conditions for further refinement by orientation transformation gradually disappear, so that the strength of copper fiber approaches the critical value, which can be confirmed by the distribution of grain size at the fracture.