Damping capacity of aluminium surface layers developed through friction stir processing

Abstract An attempt is made here to understand the role of tool rotational speed on the damping capacity of friction stir processed (PSP) commercial pure aluminium metal. The as-received metal plates were processed with a conical pin tool by keeping tool traverse speed constant and varying the rotational speed 600, 900 and 1200 rpm. Subsequently, samples extracted from the stir-zones were characterized for their microstructure, hardness, frequency-dependent and temperature-dependent damping capacities. The increase in rotational speed decreased the dislocation density and increased the average grain-size at the stir-zone, thus significantly influenced the damping capacity. The frequency-dependent damping capacity decreased with rotational speed owing to the reduction in dislocation density. High-temperature damping significantly higher for the processed samples but at the same time increase in rotational speed decreased the damping as there was an increase in grain size.