High-temperature internal-friction peak in as-quenched bamboo crystalline aluminium

Soon after the discovery of the bamboo internal-friction peak (the BB peak) in bamboo crystalline aluminium, a new high-temperature internal-friction peak (designated the HT peak) was observed at a higher temperature when the specimen was quenched from high temperatures. Previous experiments with internal friction measured by the free-decay method showed that this peak is characterized by its high relaxation strength and high activation energy and it exhibits an anomalously amplitude-dependent effect. In this paper, these manifestations are critically studied by measuring the internal friction with the forced-vibration method. This HT peak is found to consist of two subpeaks, designated the HT-1 and HT-2 peaks respectively. The activation energy of the HT-1 peak is found to be 1.4 eV and the activation energy of the HT-2 peak is 2.1 eV. On the basis of the results of the transmission electron microscopy observation, it is suggested that the higher-temperature subpeak (the HT-2 peak) is attributed to the climb of straight edge dislocation segments in the network structure and the lower-temperature subpeak (the HT-1 peak) is attributed to the gliding of the logged screw dislocation segments. The anomalous amplitude effect is suggested to be a manifestation of the HT-1 peak.