Study on damping capacity of graphite particle—reinforced AZ31 magnesium matrix composites

The damping capacities of 1%, 5%, and 9% (by mass) graphite particle—reinforced AZ31 magnesium matrix (Grp/AZ31) composites and unreinforced AZ31 magnesium alloy in as-annealed and 5% Grp/AZ31 composites in the different treatment states, which included as-cast, as-quenched, as-annealed, and as-extruded ones, were investigated. The composites were synthesized by semi-continuous stir casting process. The damping capacity was respectively tested on a dynamic mechanical thermal analyzer, at a frequency of 1 Hz, at room temperature, and in a strain range of 10 -6 —10 -2 . The results show that the damping mechanics of composites can be mainly interpreted by G—L dislocation pinning theory. The addition of graphite leads to the increase of dislocation density and will be beneficial to the damping properties of Grp/AZ31 composites. The dislocation loops are pinned down by the strong pinning point precipitate after being annealed and the effective length of dislocation becomes shorter because of the grain refinement after being quenched and extruded, which leads to the decrease of damping capacity of the composites after treatments. Moreover, there is an obvious damping—strain peak in as-extruded Grp/AZ31 composites.