Damping behavior of ultrafine-grained pure aluminum L2 and the damping mechanism

Ultrafine-grained pure aluminum L2 with a mean grain size of 1.0 μm was produced by equal channel angular pressing (ECAP) and annealing at 150°C for 2 h. Damping behavior of the alloy was measured using a dynamic mechanical thermal analyzer. The alloy had an excellent damping capacity Q-1 with the ambient value being 9.8 × 10^-3 at 1.0 Hz when the strain amplitude was 2.0 × 10^-5. The damping behavior of the alloy showed a non-linear damping variation tendency, that is, with an increase in temperature and a decrease of frequency, the damping capacity of the alloy increased. The damping capacity increased with the strain amplitude when the strain amplitude was less than 4.6 × 10^-5. When the strain amplitude was higher than 4.6 × 10^-5, the damping capacity became a constant and independent of strain amplitude. The high damping capacity was attributed to dislocation unpinning and a drag of dislocation on pinning points.