Damping capacities and tensile properties of magnesium matrix composites reinforced by graphite particles

Magnesium matrix composites reinforced by graphite particles were fabricated using stir casting with graphite particle size of 50 mu m and graphite particle volume fractions of 5, 10, 15 and 20%. respectively. The as-cast composites were extruded at 300 C with an extrusion ratio of 12:1. The experimental results reveal that the graphite particles play an important role on the tensile properties and damping capacities of the composites. The strength increases with the addition of 5% graphite particles, but decreases with further addition of graphite particles. The strain amplitude independent damping increases significantly as the graphite particle volume fraction increases from 0 to 10%, but almost keeps constant when the volume fraction exceeds 10%. Two damping peaks are found at 150 and 350 degrees C, respectively. The damping peak around 150 degrees C is considered to be caused by movable boundary slip, and the damping peak around 350 degrees C is inferred to be recrystallization peak. (C) 2010 Elsevier B.V. All rights reserved.