Contribution of Defect Dragging to Dislocation Damping. II. Experimental

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 δ is observed. This peaking effect is shown to be highly structurally dependent, vanishing after a suitable high-temperature annealing treatment. The proportionality of δ to the modulus defect ΔEE is demonstrated. This dependence, contrary to previous expectations that δ∝(ΔEE)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.