High strain rate measurements reported recently for several tantalum and copper crystal/polycrystal materials were shown to follow dislocation mechanics-based constitutive relations, first at lower strain rates, for dislocation velocity control of the imposed plastic deformations and, then at higher rates, transitioning to nano-scale dislocation generation controlled by twinning or slip. For copper, there was the possibility of added-on slip dislocation displacements to be accounted for from the newly generated dislocations.

High Rate Straining of Tantalum and Copper. R.W.Armstrong, F.J.Zerilli: Journal of Physics D, 2010, 43[49], 492002