Papers by Keyword: Grain Boundary Relaxation

Abstract: The features of grain boundary relaxation of a (wt.%)Fe-25Cr-5Al alloy have been investigated using a multifunction internal friction apparatus. The grain boundary relaxation peak appears at about 630oC on the internal friction-temperature curves for the alloy. The peak temperature shifts toward high temperature with increasing frequency. In terms of Arrihenius relation, the activation energy is calculated to be 4.07(±0.15)eV and the pre-exponential factor is 6.2×10^-24±1s. Grain boundary relaxation strength remarkably decreases with increasing grain size. When grain size reaches 520μm, the grain boundary relaxation peak almost disappears.

Abstract: 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.