Machining Parameter Optimisation Of Al Sic Gr Hybrid Metal Matrix Composites

Abstract

The density of MMCs is approximately one-third of steel, due to this potentially attractive property MMCs contend with super-alloys, ceramics, plastics and steel parts in various aerospace and automotive applications. The objective of this work is to investigate the effect of graphite addition to Al/SiC composites prepared by stir casting process. Al6061 has been used as matrix base material. Three types of hybrid composites are prepared with Al6061 alloy with 5 wt.% SiC and varying percentage of graphite are used for this study. The reinforcement content of graphite was varied from 2.5 wt.% to 7.5 wt.% in a step of 2.5 wt.%. Al/SiC/Gr composites are used in bearings and pistons due to features like self-lubrication, low wear rate and less friction. The inclusion of both strong reinforcement like SiC and smooth reinforcement like graphite enhances hardness and wear resistance of aluminium composites. The microstructure results exposed an uneven spread of graphite particles in all the three manufactured composites; their theoretical and experimental densities were compared. EDAX outcome show the existence of Aluminium and SiC particles as major and minor peaks, respectively. Vickers hardness decreases for Al/SiC/Gr hybrid composites when the percentage of graphite content increases and chip formation studies are also done. High-speed machining of Al/SiC/Gr was carried out in CNC machine using PCD insert with cutting speed of 300, 400 and 500 m/min. From ANOVA analysis, cutting speed (48.76 %) is the critical factor influencing surface roughness. Grey Relational analysis was done for simultaneous improvement of Material Removal Rate and surface roughness. Roughness values were predicted by Taguchi method and predicted values are verified with experimental results. Surface roughness values obtained range from 0.5275 - 1.161 µm. Fuzzy rule based modeling is used for predicting surface roughness. The defuzzified final surface roughness value is 1.07 µm. PCD tools produce smoother surfaces compared to tungsten carbide