Macroscopic and Microscopic Studies of the Plastic Deformation of Copper Single Crystals during Strain-Rate Changes

The variation of the total "active dislocation length", defined as the product of the density of mobile dislocations and the active slip volume, is determined during changes of deformation rate by combining stress relaxation and strain rate change experiments. It is established that the active dislocation length is practically constant during stress relaxation SO that the true activation volume is obtained from this experiment. On the other hand the active dislocation length strongly increases with increasing strain rate changes. The dependences found for stage II are discussed qualitatively. Consequences regarding the analysis of thermally activated dislocation motion are considered.