Aluminum matrix composites (AMCs) are difficult to machine due to increased tool wear. AA7075/(0-12 wt%) TiB 2 in situ AMCs were prepared and turned in a modified conventional lathe using polycrystalline diamond cutting tool. A central composite rotatable design comprising of four process parameters and five levels was utilized to limit the actual experiments required for prediction. The turning parameters such as cutting speed, feed rate, depth of cut and TiB 2 particulate content were counted as variables for the experiments. Two empirical relationships were formed for the prediction of the outcome of variable parameters on cutting force and surface roughness. The cutting force showed a downward trend with an increase in cutting speed and TiB 2 content. The advancement in feed rate and depth of cut increased the requirement of cutting force. The predicted trends were correlated with the morphology of the tool rake face and the turned surface. The development of builtup edge increased the cutting force requirement and reduced the surface finish due to deposition on the newly turned surface.
Reinforced aluminum composites are the basic class of materials for aviation and transport industries. The machinability of these composites is still an issue due to the presence of hard fillers. The current research is aimed to investigate the drilling topographies of AA7075/TiB2 composites. The samples were prepared with 0, 3, 6, 9 and 12 wt.% of fillers and experiments were conducted by varying the cutting speed, feed, depth of cut and tool nose radius. The machining forces and surface topographies, the structure of the cutting tool and chip patterns were examined. The maximum cutting force was recorded upon increase in cutting speed because of thermal softening, loss of strength discontinuity and reduction of the built-up-edge. The increased plastic deformation with higher cutting speed resulted in the excess metal chip. In addition, the increase in cutting speed improved the surface roughness due to decrease in material movement. The cutting force was decreased upon high loading of TiB2 due to the deterioration of chips caused by fillers. Further introduction of TiB2 particles above 12 wt.% weakened the composite; however, due to the impact of the microcutting action of the fillers, the surface roughness was improved.
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