Mechanical Spectroscopy of Ultrafine Grained Copper
Temperature and amplitude dependent internal friction (TDIF and ADIF) in ultrafine-grained copper (99.95% Cu) processed by 1, 4, or 8 passes of equal channel angular pressing (route BC) and then subjected to annealing was investigated by means of mechanical spectroscopy. A dynamical mechanical analyzer DMA Q800 was used. The tests covered the temperature range from -100 to 550 °C, the strain amplitude range from 10-6 to 10-3, and the frequency range from 0.05 to 100 Hz. Two internal friction peaks were observed. They were explained by structural relaxation due to the recrystallisation process and by thermally activated grain boundary relaxation with a broad distribution of relaxation times. Increased amplitude dependent damping in ultrafine-grained copper is believed to be associated with a dislocation mechanism, rather than a grain boundary mechanism.
Jing Tao Wang, Roberto B. Figueiredo and Terence G. Langdon
I. S. Golovin and Y. Estrin, "Mechanical Spectroscopy of Ultrafine Grained Copper", Materials Science Forum, Vols. 667-669, pp. 857-862, 2011