Effect of Mg Content on the Damping Behavior of Al–Mg Alloys

This article investigated the effect of Mg content (4.5, 6.5 and 9.2, in wt%) on the damping capacities of Al–Mg alloys. The results indicate that the damping behavior can be divided into three regions. Region I refers to the low strain amplitude region (ε < 5 × 10⁻⁵), where the damping capacity decreases with increasing the Mg content and has almost no relation with the strain amplitude. Region II is the middle strain amplitude region (5 × 10⁻⁵ < ε < 8 × 10⁻⁴), where the damping capacity increases rapidly with the strain. Region III refers to the high strain amplitude region (8 × 10⁻⁴ < ε < 2 × 10⁻³), where the damping capacity remains constant and is independent of the strain when the strain is high enough, but increases with the Mg content. The damping values Q⁻¹ of Al–4.5Mg, Al–6.5Mg and Al–9.2Mg alloys are 0.01501 ± 0.00032, 0.01633 ± 0.00032 and 0.01862 ± 0.00119 at the strain of 1 × 10⁻³, respectively. The damping capacity in Region I is mainly determined by the lattice distortion caused by Mg addition and the restoring force caused by pinning points and Suzuki segregation. The extended dislocations break away from the pinning effect of Mg atoms and become moveable in Region II, and the movement of extended dislocations is the dominant damping mechanism in Region III.

The damping behavior associated with the movement of extended dislocations and the force diagram of the extended dislocation segment.