Temperature and amplitude dependent internal friction (TDIF and ADIF) in ultrafine-grained copper (99.95% Cu) specimens processed by equal channel angular extrusion by route BC in 1, 4, and 8 passes and then subjected to annealing is investigated by means of dynamical mechanical analyzer DMA Q800 in the temperature range from -100 to 550 °C, amplitude range from 10-6 to 10-3, and frequency range from 0.05 to 100 Hz. Two IF peaks were registered and explained by structural relaxation due to the recrystallisation process and by thermally activated grain boundary relaxation with broad distribution of relaxation times. Increase in amplitude dependent damping in ultrafine-grained copper is due to dislocation but not grain boundary contribution.
Grain boundary contribution to recoil loop openness of exchange-coupled nanocrystalline magnets