Evolution of the anomalously amplitude dependent internal friction peaks in AlMg solid solutions and the discovery of a new peak

The anomalously amplitude-dependent internal friction peak (P peak) previously observed in cold-worked and partially annealed dilute AlMg alloys is found to shift toward lower temperature when the specimen is further twisted. Annealing at an intermediate temperature or aging at room temperature for a longer period shifts the peak back to a higher temperature. Meanwhile a new peak (P0 peak) appears at the lower temperature side of the P peak. A physical model is suggested to explain the origin of the P0, P, and P peaks which are observed simultaneously. The shift of the P′1 peak by twisting is explained in terms of the increase of the interaction force between the kinks in a kink chain created by the bowing out of pinned dislocation segments under the action of the localized internal stress introduced by successive twisting.