| Summary: | This work dealt with the damping performance and its underlying mechanism in SiC nanoparticles reinforced AZ91D composite (SiCnp/AZ91D) processed by cyclic extrusion and compression (CEC). It was found that the CEC process significantly affects the damping performance of the composite due to alterations in the density of dislocations and grain boundaries in the matrix alloy. Although there would be dynamic precipitation of the Mg17Al12 phase during processing which increases the phase interface and limits the mobility of dislocations and grain boundaries. The results also showed that the damping capacity of 1%SiCnp/AZ91D composite continuously decreases with adding CEC pass number and it consistently increases with rising the applied temperature. Considering the first derivative of the tanδ–T curve, the dominant damping mechanism based on test temperature can be divided into three regions. These three regions are as follows (i) dislocation vibration of the weak pinning points (≤Tcr), (ii) dislocation vibration of the strong pinning points (Tcr∼TV), and (iii) grain boundary/interface sliding (≥TV).
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