Damping Behavior of AI6061/Albite MMCs

AI6061 based metal matrix composites (MMCs) were prepared with 2, 4, and 6 % by weight of albite particulates, respectively, using the liquid metallurgical technique. Sample specimens of dimensions 70 mm by 10 mm by 2 mm were machined from the prepared ingots. The damping properties of the unreinforced matrix alloy and the MMCs were studied over a temperature range of 50° C to 500°C using a dynamic mechanical analyzer. The damping capacity of the composites was observed to increase with the increase in temperature whereas the dynamic modulus was found to decrease with increase in temperature. The damping capacity at a lower temperature may be attributed to the coefficient of thermal expansion mismatch induced dislocations and intrinsic damping of the matrix alloy whereas damping capacity at a higher temperature may be attributed to the matrix/reinforcement interface. Theoretical calculations accurately predicted the damping capacities of the specimen materials only up to the eutectic temperature of the matrix material (200°C). Above this temperature, the discrepancy between theoretical and experimental values increased sharply with increase in temperature. An explanation for this phenomenon is proposed in this paper.