Dislocation Damping at High Strain Rates in Aluminum and Aluminum‐Copper Alloy

Impact shear tests have been used to study the dependence of shear stress with shear‐strain rate at strain rates ranging from 0.5×104 to 2.2×104 sec−1 in pure Al, prestrained Al, and Al‐2 at. % Cu alloy. Within this strain‐rate range a linear relationship was found between shear‐stress and shear‐strain rates, indicating the presence of a viscous drag on dislocations. The dependence on temperature of this viscous damping was investigated between 10° and 293°K. The results are discussed in terms of theories of phonon viscosity and phonon scattering, and of electron viscosity at low temperatures.