The effect of depinning on the dislocation damping peak associated with pinning-point drag

Abstract

The effect of depinning on the position and shape of the dislocation damping peak associated with point-defect drag is considered. Although this peak exhibits a standard Debye form as a function of frequency, a significant narrowing of the damping versus temperature maximum, as well as a shift towards lower temperatures, results from the interference of depinning. The effect depends on the heating rate. A similar behaviour of the differentiated modulus defect is predicted. However, in both cases the peak narrowing remains hidden in the apparent activation energy, conventionally derived from the peak temperature displacement upon frequency variation, is used in evaluating the peak width instead of the true activation energy for the underlying relaxation process. The analytical results obtained suggest a procedure for revealing the true peak narrowing by determining the true activation energy for point-defect diffusion along with the dislocation. A method for experimentally 'decoupling' this activation energy from the activation energy for superimposed depinning is proposed. This method is based on measuring the peak temperature displacement when varying both the frequency and the heating rate.