Internal friction of gamma-TiAl alloys at high temperature

Polycrystalline internal oxidize copper alloy with CuAlO particles has been studied by isothermal mechanical spectrometry, above room temperature. The frequency range was 10-4 to 30 Hz and the maximum strain 2×10-5. Experiments were carried out on a sample after 18% cold-rolling and successive annealings at various temperatures. The internal friction spectra obtained between 290 and 400 K exhibit only a low frequency background superimposed to a non thermally activated maximum. After annealing at 400 K, the background decreases, a relaxation peak appears and its maximum rises progressively as temperature increases. The relaxation parameters, obtained from the frequency shift of the maximum with temperature, leads to Ea=0.9 eV, and tau 0=6.9×10-10 s. These values are similar to those described in the literature for a relaxation peak assigned to dislocation motion inside grains.