Effects of macroscopic graphite particulates on the damping behavior of commercially pure aluminum

The objective of present work is to investigate the effect of macroscopic graphite (Gr) particulates on the damping behavior of commercially pure aluminum (Al). Macroscopic defects are graphite particulates with sizes of the order of a millimeter (0.5–1.5 mm) and in large proportions, typically 70 vol.%. Macroscopic graphite particulate-reinforced commercially pure aluminum metal matrix composites (MMCs) were prepared by pressure infiltration process. The damping characterization was conducted on a multifunction internal friction apparatus (MFIFA). The internal friction (IF), as well as the relative dynamic modulus, was measured at frequencies of 0.5, 1.0 and 3.0 Hz over the temperature range of 25–400 °C. The microstructural analysis was performed using transmission electron microscopy (TEM). The damping capacity of the Al/Gr MMCs, with three different volume fractions of macroscopic graphite reinforcements, was compared with that of unreinforced commercially pure aluminum specimens. The damping capacity of the materials is shown to increase with increasing volume fraction of macroscopic graphite particulates. Finally, the operative damping mechanisms in the macroscopic graphite particulate-reinforced MMCs were discussed in light of internal friction measurements and microstructural studies.