A new kind of persistent slip band (PSB) structure, designated as PSB II, has been found in cyclically deformed polycrystalline copper. Like the classic PSBs, designated as PSBs I, PSBs II show persistent slip behaviour and strain localization, are transformed from a vein structure, consist of multipolar walls and dislocation-free channels and are hounded by {111} slip planes of the primary dislocations of the walls. The differences between the dislocation wall structure of PSBs II and I are firstly the primary dislocations of a PSB II and its neighbouring veins have different Burgers vectors; secondly the multipolar walls in PSBs II have irregular configurations; thirdly the spacing between walls is not regular; fourthly the multipolar walls have non-edge orientation. The nucleation of a PSB II involves the annihilation of vein dislocations and the generation of multipolar walls. It is suggested that new slip system(s) are generated by the incompatible stress between neighbouring vein blocks; the new slip system(s) then cause the annihilation of edge dipoles in veins and the generation of multipolar walls. The complexity of the wall structure in PSBs II may cause the properties of PSBs II to vary from band to band. [References: 28]
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