DISLOCATION INTERNAL FRICTION PEAKS WITH ANOR- MALOUS AMPLITUDE EFFECT IN Al-Mg ALLOY

Abstract

Two low frequency internal friction peaks have been observed at 243 K and 333 K respectively in Al-0.03 at% Mg alloy during the process of temperature going up after the specimen was stretched in situ with a tensile strain of 0.5% at 208 K. Such two peaks appeared also at the same temperatures when the measurement was made in the subsequent cooling from 353 K. The dependence of internal friction on the amplitude was determined and the amplitude internal friction peaks were observed in the temperature range of the peaks. The relationship between these two kinds of peaks was analysed and the effective activation energies of the temperature internal friction peaks were found to be about 0.32 eV for the 243 K peak and 0.22 eV for the 333 K peak. It was suggested that the two peaks at 333 K and 243 K may be respectively associated with the dragging of the solute atoms and the "Mg atom-vacancy" pairs, which may be produced through the sidewise motion of the kinks on the dislocations formed during the low temperature cold working.