The effects of Cu addition on microstructure, mechanical properties and damping capacity of Mg-3%Ni based alloy were investigated by using tensile tests, X-ray diffraction, scanning electron microscope and dynamic mechanical analyzer. The results show that Cu addition could reduce the size of -Mg dendrites and a new binary phase Mg2Cu can be identified, which mostly distributes among the inter-dendrites in the form of typical lamellar-like eutectic microstructure and improve the mechanical properties. In low strain amplitude, with the increase of Cu addition, the damping capacities of Cu contained alloys change little, while in high strain range, the internal friction values decrease gradually with the grain refinement and increasing content of eutectic phase.

The influence of Y on the microstructure and damping capacity of AZ91D based alloys was investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and dynamic mechanical analysis. The results show that, with increasing Y content, the grain size of α-Mg matrix decreases tremendously and the distribution of β-Mg17Al12 phase is transformed from discontinuous network to fine particles. Meanwhile, a needle-shaped Al4MgY phase mainly distributing at the grain boundaries is identified. The damping capacity of the studied alloys shows sustained enhancement with increasing temperature. As to the strain dependent damping capacity, with the increase of Y content, the damping value of AZ91D alloy decreases gradually before Y content reaches to 0.5wt.%, and fluctuates when Y addition is between 0.5wt.%~0.9wt.%. G-L dislocation model was employed to explain the effects of parameters on damping capacity of magnesium alloy.