Influence of the interaction between dislocations and mobile point-defects on the damping spectrum of aluminium

The mechanical damping P-C peak is observed near 290 K in deformed samples of 5 N aluminium and is linked to the interaction between dislocations and impurities. In addition to a strong amplitude dependence, the lower part of the damping spectrum (<350 K) presents a transitory stage during the first annealing in the room-temperature range. The acoustic coupling technique has been used in similar experimental conditions to understand this behaviour. It shows the formation of solute atmospheres around dislocations and the amplitude dependence of the solute distribution profile. It also provides 'signatures' characteristic of a dragging-depinning of solute atoms. The low activation energy of the solute dragging (similar to 0.7 eV) in comparison to the solute bulk diffusion energy (similar to 1.4 eV) is explained by a core diffusion process. (C) 2000 Elsevier Science S.A. All rights reserved.