Damping characterization and its underlying mechanisms in CNTs/AZ91D composite processed by cyclic extrusion and compression

The proper combination of strength and damping performance has been a major challenge for the wide use of Mg alloys/composites in many fields. In this regard, this research focused on the effect of the CEC process and the CNTs addition on the damping behavior of AZ91D alloy. The damping capacity of CEC-processed CNTs/AZ91D composite is significantly improved compared with the initial solid-solution state. Also, although 0.5 wt% addition of CNTs to AZ91D decreases the room-temperature damping of the base alloy, its performance can be improved by the addition of 2.0 wt% CNTs. Besides, the addition of CNTs, regardless of its amount regularly increases the high-temperature damping behavior compared to the base alloy. For the solid-solution alloy/ composite, when the test temperature is lower than the critical temperature, the damping is mainly advanced by the movement of dislocations between a large number of weak pinning points and a low amount of strong pinning points. Contrarily, the damping mechanism of the same material at higher than critical temperatures is mainly progressed by grain boundary sliding.