Effect of length scale of alumina particles of different sizes on the damping characteristics of an Al–Mg alloy

Pure Al was reinforced with alumina particles with size ranging from micro to nano-size dimension. Magnesium was added to the Al matrix to enhance the wettability of alumina particles. Synthesis of materials was accomplished using the solidification route viz., disintegrated melt deposition technique. Energy dissipation in the form of damping capacity was determined using free–free type suspended beam arrangement coupled with circle-fit approach. Three samples with Al–4 wt.% Mg matrix were prepared that were reinforced by alumina particles whose size ranged from μm to nm length scale (viz., 10, 0.3 μm and 50 nm and with a volume percentage of 10.13, 1.47 and 0.94, respectively). Damping per unit volume percentage of alumina particles in the Al–Mg matrix increased by 58%, 30% and 3% for the alumina particles size of 50 nm, 0.3 and 10 μm, respectively, with respect to the monolithic Al–Mg specimen. Such increase in damping can be rationalized in terms of microstructural changes that arise due to the presence of the alumina particles in the composite samples compared to that of unreinforced sample.