On the strain-rate dependence of flow stress in crystals with high intrinsic lattice friction

An analytical expression for the strain-rate (<(gamma)over dot>) dependence of the critical resolved shear stress (CRSS) (tau) of crystals with high intrinsic lattice friction has been derived within the framework of a kink-pair nucleation model of flow stress. It predicts a linear relationship between tau(1/2) and ln <(gamma)over dot> at a given deformation temperature, as embodied in tau(1/2) = C + D ln <(gamma)over dot>, where C and D are positive constants. Comparison of theory and experiment, using the wealth of data available in the literature, shows an excellent agreement between the predicted and the observed response of the CRSS to the strain rate. Evaluation of the low-temperature slip parameters of the model leads to identification of the slip system responsible for yielding of crystals.