Machinability and production of aluminium alloy composites

Ill MACHINABILITY AND PRODUCTION OF ALUMINIUM ALLOY COMPOSITES (M.Sc. Thesis) Gökhan SUR GAZI UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY January 2002 ABSTRACT In this work, an electrical furnace for production of metal matrix composites (MMCs) by molten metal mixing method has been designed and MMCs reinforced with SiCp have been produced. The MMCs containing of various particle sizes and 10 wt.% and 20 wt.% SiCp were prepared using vortex method under argon gas. In the production stage, the stirring was carried out with graphite impeller during the addition of particles. The slurry was poured into a die when the stirring was completed and MMCs were produced by applying hydraulic pressure. Optical microscopic examination, hardness, density and machinability studies were carried out on the composites. It was observed that there was reasonably uniform dispersion of SiC particles in the matrix alloy. The hardness of the composites increased with increasing particle contents and decreasing the particle sizes. The density of the composites increased linearly with increasing particle content and porosity level reduced with increasing reinforcement content and applying the pressure. Moreover, the composites produced were machined on a CNC lathe at 20, 40, 60, 80 m/min cutting speeds, 0.6 mm depth of cut and with 0.08, 0.12, 0.16 mm/rev feed rates using different cutting tools. The results showed that tool life decreased considerably with increasing particle size, reinforcement content and cuttingIV speed. Among cutting tools, Insert A showed good performance in machining of 10% wt. SiCp reinforced composites with Lower particle sizes. However, Insert B at lower cutting speed and Insert D at higher cutting speed indicated better performance in machining the small size particle reinforced composites. Furthermore it was observed that abrasive wear and built up-edge formation were the main mechanisms for the cutting tools when machining the MMCs. Science code Key words Page number Adviser : 62615 : Metal matrix composites, machinability of composites, vortex method, SiC, aluminium matrix : 148 : Assoc. Prof. Dr. Yusuf ŞAHİN