Impurity Effects on the Recovery of Copper Studied by Ultrasonic Attenuation Measurements under Cyclic Bias Stress

High purity Cu single crystals doped with Mg, Ag, Pb, Sb, Bi (20-50 ppm) were isochronally annealed between 373 K and 923 K after 0.12% deformation at room temperature. After each annealing step the dependence of sound attenuation on frequency (10 200 MHz) and bias stress (cyclic compression/tension; peak amplitudes below plastic yield) was measured. From the latter experiment specific information on the solute diffusion towards the dislocations and their pinning strength is obtained. From the frequency dependence of attenuation the dislocation pinning point density and the recovery of dislocation density as a function of temperature and type of solute is derived.