BELHAS Saida University of Batna

Relaxation Effect Observed at Low Frequency in Al-Cu Alloy

Co-authors BELAMRI Chérif, BENYAHIA Nawel, RIVIERE André, GERLAND Michel

Al-5 wt% Cu alloys have been studied by isothermal mechanical spectroscopy. The used samples were quenched and matured at room temperature. Experiments were performed in a very large frequency range (10-4 Hz – 50 Hz) between room and solidus temperatures. During heating, for each temperature of measurement, experiment started after a hold time long enough for a complete stabilization of the microstructure. In fact the sample has reached stability such as its hardness does not evolve and therefore the transient effects due for instance to  and  precipitation were not observed. Nevertheless, a relaxation effect was obtained in the reversion temperature range. This effect is not thermally activated. The maximum of its peak is at about 0.1 Hz and its amplitude increases with the temperature of measurement. It completely disappears after annealing at solid solution temperature and successive slow cooling and therefore is linked to the  precipitates. Indeed, the experimental conditions are the fact of the gradually formation of the  precipitates at the grain boundaries of the phase α.