Microstructural, mechanical and damping analysis of Al/Gr composites produced via friction stir processing: effect of rotational speed
K. Venkateswara Reddy, Guttikonda Manohar, C. Ravikanth Reddy
Abstract
The primary objective of this study is to improve the damping capacity of the Al6061-T6 alloy to reduce vibrations by adding 10 vol.% graphite (Gr) particles to its surface through friction stir processing (FSP). The FSP was performed using a tool that had a conical pin measuring 4 mm in length and a shoulder diameter of 15 mm. Surface composites were fabricated at rotational speeds of 800, 1100, and 1400 rpm, with a constant traverse speed of 30 mm/min. Microstructural analysis was performed using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Grain refinement was achieved, reducing the average grain size from 45 μm to 4.52 μm. Hardness measurements revealed a decrease in the stir zone, attributed to the inherent softness of graphite compared to the aluminium matrix. Samples were obtained from the stir zone and their damping characteristics were studied using dynamic mechanical analyzer. Damping capacity increased from 1.1 × 10−3 to 7.3 × 10−3 at room temperature. In comparison to the base metal, the Al/Gr composites demonstrated a superior damping capacity. The damping mechanisms of the composites were analyzed in relation to the microstructural changes in the stir zone.