On the formation of deformation bands in fatigued copper single crystals

The features of the deformation bands (DBs) in copper single crystals under cyclic straining were surveyed. A simple model was proposed to account for the formation of DBs. In this model, both crystal rotation and dislocation density variation induced by cyclic straining were considered. The gradual lattice rotation caused by tension and compression irreversibility is the main driving force for the formation of DBs. The drastic release of mobile dislocations resisted by the primary slip bands is the direct trigger for the formation of DBs. From this analysis, one may understand why the formation of DBs is easier in copper single crystals with double- and multiple-slip orientations than that with single-slip orientation. At the same time the effect of the dislocation avalanche factor on the formation of DBs was discussed.