Deformation bands in cyclically deformed copper single crystals

The characteristics of the deformation bands (DBs), formed in cyclically de formed copper single crystals with various orientations, were summarized sy stematically. The Formation mechanism of DBs was also explored. It was show n that the apperance of DBs seems to be a general phenomenon in cyclically deformed copper single crystals with various slip orientations, especially with double- or multiple-slip orientations, for which the critical plastic strain amplitude needed for the formation of DBs is rather low (about 10(-3 )). The DB denoted by DBI develops roughly along the primary slip plane {11 1}, and the habit piano of DBII is close to the conventional kink plane {10 1}. The habit planes of DBI and DBII are strictly perpendicular to each oth er. An analysis based on the crystallographic deformation geometry showed t hat the local irreversible rotation of crystal which exists during symmetri cal push-pull loading may be responsible for the Formation of DBI and DBII. When a certain crystallographic geometrical condition is satisfied, DBI an d DBII are very hard to form coincidentally. In addition, a favourable macr oscopic state of stress might also be responsible for the occurrence of oth er types of DB, such as (001) DB in the [011] crystal. Finally, the disloca tion structure relevant to DBs was observed tentatively by electron channel ling contrast in scanning electron microscopy. It was revealed that the DBs formed in copper single crystals during cyclic straining may exhibit quite different microstructures, depending upon the crystallographic orientation .