Effect of Graphite Addition on Surface Roughness during Turning of AA 7075-ZrB2 In-situ Metal Matrix Composites

This project work involves the study of surface roughness during turning of AA 7075-ZrB 2 in-situ metal matrix composites. The composites of AA 7075 alloy, AA 7075-3% ZrB 2 and AA 7075-3%ZrB 2 -1% Gr were manufactured using in-situ liquid metallurgy route. This in-situ method involves formation of reinforcements within the matrix by the chemical reaction of two or more chemical compounds that produces some changes in the matrix material within the vicinity. The samples were turned in CNC high speed turning machine with three independent input parameters of cutting speed, feed rate and depth of cut. The TiN coated carbide tipped tool inserts were used to carry out the turning process. The microstructures of the fabricated samples were taken using optical microscope. The mechanical properties in terms of hardness and flexural strength were also examined. The response of the surface roughness was measured after turning of every independent input parameter. It was observed that good surface finish was obtained for AA 7075-3%ZrB 2 -1% Gr hybrid in-situ composites when compared to other AA 7075-3%ZrB 2 and AA 7075 alloy. This was due to self-lubricating properties of Gr which helps to improve the machinability.