ON DISLOCATION LINK LENGTH STATISTICS FOR CONSTANT STRAIN-RATE DEFORMATION

A model based on the dislocation link length statistics of the three-dimensional dislocation network structure is used to analyse high-temperature constant strain rate deformation of crystalline materials. In particular, the strain rate change during steady-state constant strain rate deformation is studied in some detail. It is shown that the corresponding change in the flow stress, Delta sigma, associated with an instantaneous change, Delta epsilon, in the imposed strain rate of an otherwise constant strain rate, epsilon, at a given temperature follows the Haasen relation in that the (Delta sigma/Delta 1n epsilon) versus sigma plot is linear with the slope being equal to the strain rate sensitivity, m (Cottrell-Stokes law). The material parameters are also examined in the light of the model results and previous mechanical measurements. It is shown that the model produces constant strain rate sensitivity values for constant strain rate deformation. Agreement between model predictions and reported data is reasonably good.