Microstructures and Damping Capacities of AZ91D-0.7%Si Alloy

Microstructure of as-cast AZ91D alloy doped with 0.7wt% silicon was investigated, the damping capacity of the alloy was measured by cantilever beam technique, and the damping mechanism was also analyzed. The results show that after addition 0.7%Si into AZ91D alloy, the dendritic grains are refined, and Chinese script Mg2Si phase forms in the interdendritic areas. The damping capacities of the alloy are improved by Si addition, and increase with increasing of strain amplitude. The damping behavior of the alloy is mainly resulted from dislocation movement, and can be explained by the theory of Granato and Lücke.