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Damping capacity and shear elastic modulus measurements have been carried out during precipitation in AlMgSi alloys. After the specimen has been aged at the temperature corresponding to the lowest thermoelectric power, both damping and elastic modulus increase comparing with the as-quenched state. The effect of strain amplitude was investigated in specimens aged at different temperatures. A critical strain amplitude, E,, has been observed. For strain amplitudes higher than E,, the damping capacity increases strongly with strain amplitude. In addition a relaxation peak appears around 420K after ageing. The strong damping-amplitude effect and the relaxation peak are attributed to the breakaway of the dislocation from the solute atoms at low temperature and to the dragging of these solute atoms by the dislocations at high temperature respectively.

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