Fabrication, Characterization and Micro-machinability of Stir-Cast Al6061/GNPs + Mg Nanocomposite

The present work deals with the mechanical and microstructural characterization of Al6061/3 wt% Graphene nanoplatelets (GNPs) fabricated through the bottom pouring stir casting technique. Magnesium (Mg) as a wetting agent (1 wt%) was incorporated to reduce the aggregation and increase the uniform dispersion of GNPs in the matrix. The grain structure, microhardness, tensile strength, and fractured surfaces of Al6061-based nanocomposites were investigated to better understand the effect of GNPs on the microstructure and mechanical properties of the manufactured specimens. The microchannels were machined using a 500 µm TiSiN-coated carbide end mill tool. The machinability analysis was conducted to investigate the impact of micromachining parameters on surface roughness, burr formation, and cutting force during dry machining. An image processing method was used to analyze the slot and burr widths of the fabricated microchannels. The measurements were acquired by a user-defined subroutine using scanning electron microscope (SEM) images. The SEM micrographs revealed the dendritic microstructures with reduced casting defects. The fabricated nanocomposite showed a 35% and 267% improvement in microhardness and ultimate tensile strength, respectively. SEM fractograph of the nanocomposite revealed a mixed-mode ductile–brittle failure mechanism. The optimum machining condition displayed a 52% and 36% decrease in feed force Fy and surface roughness Ra, respectively, compared to the lowest process parameter. Optimum parameters revealed a 78% decrease in up-milling side burrs and a 54% improvement in slot width compared to the lowest process parameter. ANOVA results revealed feed rate as a significant factor, which contributed 83% and 93% in thrust force Fz and Ra, respectively. Material adhesion and abrasion were identified as the primary tool wear mechanisms.