Persistent slip bands: Similitude and its consequences

The similitude properties of persistent slip bands (PSBs) in cycled copper and nickel crystals are determined with optimal accuracy from three published sets of experimental data covering a wide temperature range. These properties are analyzed in terms of Brown's bowing and passing model for screw dislocations, which predicts that PSB channels should follow similitude. Several unexpected original features are obtained. The PSBs and the PSB channels follow similitude relations. The maximum temperatures for the occurrence of a saturation plateau appear to be related to the emergence of secondary dislocations in the microstructure. The flow stresses of the channels were found comparable to predicted values. They are, however, somewhat smaller than the saturation stresses. Thus, the bowing and passing model can accommodate a small resistance opposed by internal stresses and/or various defects to the motion of screw dislocations in PSB channels. Finally, it seems confirmed that the measured temperature and material dependencies of PSB channel properties arise from the thermally activated annihilations of screw dislocations.

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