INTERNAL-FRICTION DUE TO TWINNING DISLOCATIONS IN CU-GE SOLID-SOLUTION ALLOYS

Anelastic behaviour of Cu-Ge solid solution alloys has been studied by low frequency internal friction measurements. Plastic deformation giv es rise to characteristic internal friction in the temperature range b etween 80 K and 350 K,which is attributed to the motion of twinning di slocations. By using single-crystal specimens of a Cu-8%Ge alloy, the dependence of the magnitude of the internal friction on the crystal or ientation and the degree of deformation has been examined. The results suggest that the internal friction is due to local oscillatory motion of individual twinning dislocations. The internal friction is suppres sed completely by electron irradiation, which can be explained in term s of pinning of the dislocations by point defects.