Mechanical loss spectrum of aged Al-Mg-Si alloys

摘要

The low-frequency internal friction and elastic modulus have been measured as functions of temperature at different strain amplitudes in wrought Al-Mg-Si (6082) alloys after quenching and after ageing. The damping spectrum exhibits a relaxation peak located at about 420 K in over-aged specimens. This damping peak, with an activation enthalpy H = 1.57 +/- 0.04 eV and a limit relaxation time tau = 2.6 x 10(19+/1) s, may be attributed to the dragging of solute atoms by the dislocation loops. A strong damping-amplitude effect has been observed at lower temperature. This phenomenon, which leads to a high damping capacity at high strain amplitudes, may be interpreted by a breakaway mechanism. Damping would be due to the increase in the dislocation loop length by depinning and to the work done to overcome the binding energy between the dislocations and the solute atoms. [References: 26]