Low frequency relaxation effect observed on 2024 aluminium alloy

摘要

2024 Aluminium alloy has been studied by isothermal internal friction after quenching and annealing at different temperatures. Experiments were performed in a very large frequency range (10~(-4)-50 Hz) between room temperature and 823 K. At each measuring temperature, the experiment was started after complete stabilization of the microstructure and therefore the transient effects due to 0' and 0" precipitation were not observed. Nevertheless, a new relaxation effect was obtained in the reversion temperature range. This effect is not thermally activated, has a maximum at about 0.1 Hz and increases with the measuring temperature. It disappears completely after annealing at 823 K and successive slow cooling; it is therefore related to the 0 precipitates.