Contribution of Defect Dragging to Dislocation Damping. II. Experimental

Abstract

Detailed internal-friction and Young's-modulus measurements have been made in electron-irradiated copper. The measurements confirm the defect-dragging-model calculations presented in the previous paper. In particular, an initial increase and subsequent decrease in logarithmic decrement $\ensuremath{\delta}$ is observed. This peaking effect is shown to be highly structurally dependent, vanishing after a suitable high-temperature annealing treatment. The proportionality of $\ensuremath{\delta}$ to the modulus defect $\frac{\ensuremath{\Delta}E}{E}$ is demonstrated. This dependence, contrary to previous expectations that $\ensuremath{\delta}\ensuremath{\propto}{(\frac{\ensuremath{\Delta}E}{E})}^{2}$, is consistent with the dragging model. Agreement with the dragging model is quite complete if two types of dislocations are assumed, as has been reported by other investigators.