Strain path change effect on dislocation microstructure of multicrystalline copper sheets

Abstract

In this study, coarse-grained copper sheets were subjected to tension-rolling and rolling-tension strain path sequences. In both cases, two different types of strain path change were studied: the tensile and rolling directions were parallel and normal to each other. TEM observations of deformed samples showed the typical dislocation structures for the prestraining paths in tension and rolling. Special microband features, not observed during prestrain, were found during the second strain path, whatever the sequence and type of strain path change. The microstructure observed during reloading is discussed in terms of the sequence and type of strain path change, parallel or normal. The frequency of appearance of microbands is discussed in terms of the activity of new slip systems, i.e. not active during the prestrain path and connected with the number of the active slip systems after reloading. The results from this study, obtained for coarse-grained multicrystalline copper sheets, are compared with previous ones for fine and medium-grained copper.