Correlation of the applied strain rate with the operative mean slip and dislocation velocities

The theories of dislocation dynamics of plastic flow are based on the mean velocity of dislocations, whereas, the experimental results are correlated to the applied strain rate. The mutual dependence of velocity, strain rate and structure (v-γ̇-Σ) is usually assumed to be given by the Orowan relation γ̇=ρmνb where ρm is the mobile dislocation density and b the magnitude of the Burgers vector. Since ρm is not directly accessible, it is related to the total dislocation density, ρt, by ηρt where, η is less than 1. The mean slip velocity, λ̇, derived from slip kinematics conforms to the requirements of the rate of power dissipation. Using this definition and its correlation to γ̇, an independent measure of v can be calculated and compared with that from the Orowan relation. The resulting values for rolled copper and aluminum at room temperature indicate that the onset of dynamic recovery increases λ̇ with strain.