Variations in ultrasonic attenuation were measured in 5N-purity polycrystalline specimens at room temperature. It was found that, at first, the ultrasonic attenuation decreased and the strain increased. It then reached saturation with increasing time. The ultrasonic attenuation could be divided into 2 parts. An initial decrease was attributed to interactions between dislocations and point defects, and final equilibrium was caused by interaction between dislocations alone. When the applied constant tensile stress was less than 0.9MPa, there was no dislocation multiplication.

G.T.Fei, Z.G.Zhu, P.Cui: Journal of Materials Science, 1996, 31[10], 2725-8