Kink dynanmics in F.C.C. metals

In 1956 the Bordoni relaxation observed by internal friction measurements was attributed by Seeger to the thermally activated kink pair formation (KPF) on dislocations. From the relaxation energy of the internal friction peak the Peierls stress can be evaluated. The obtained values are considerably larger than those expected from the low-temperature behaviour of the critical resolved shear stress. In a first part the main results obtained by internal friction measurements on the Bordoni relaxation will be discussed. In the second part results obtained by the newly developed two waves acoustic coupling method will be analysed. It is shown that the results are in very good agreement with the prediction of the KPF model and confirm this model. In the last part results obtained after cold work at a very low temperature show that a short circuit mechanism can occur which could explain the discrepancy between the expected high values of the critical resolved shear stress at low temperatures and the observed low values.