A new kind of persistent slip band structure was identified in cyclically deformed polycrystalline material. Like normal persistent slip bands, the new bands exhibited persistent slip behavior and strain localization, transformed from a vein structure, consisted of multi-polar walls and dislocation-free channels and were bounded by {111} slip-planes of the primary dislocations of the walls. The differences between the dislocation-wall structures of both types of persistent slip band were mainly related to the fact that the primary dislocations of a new-type persistent slip band and its neighboring veins had different Burgers vectors. The multi-polar walls in new-type persistent slip bands also had irregular configurations. The spacing between walls was not regular, and the multi-polar walls had a non-edge orientation. The nucleation of a new-type persistent slip band involved the annihilation of vein dislocations and the generation of multi-polar walls. It was suggested that new slip systems were generated by the incompatibility stresses between neighboring vein blocks. The new slip systems then caused the annihilation of edge dipoles in veins, and the generation of multi-polar walls. The complexity of the wall structure in new-type persistent slip bands was expected to cause their properties to vary from band to band.

Dislocation Structures of Persistent Slip Bands in Cyclically Deformed Polycrystalline Copper T.Luoh, H.T.Tsai, C.P.Chang: Philosophical Magazine A, 1998, 78[4], 935-48