HIGH-TEMPERATURE INTERNAL-FRICTION PEAK IN AS-QUENCHED BAMBOO CRYSTALLINE ALUMINUM

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 tempe rature 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-d ependent effect. In this paper, these manifestations are critically st udied by measuring the internal friction with the forced-vibration met hod. 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 pe ak 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 micr oscopy observation, it is suggested that the higher-temperature subpea k (the HT-2 peak) is attributed to the climb of straight edge dislocat ion segments in the network structure and the lower-temperature subpea k (the HT-1 peak) is attributed to the gliding of the logged screw dis location segments. The anomalous amplitude effect is suggested to be a manifestation of the HT-1 peak.