Machinability and Surface Morphology of TiB₂ Reinforced Al 7075 MMC During EDM with Cryogenic Treated Cu Electrode

This work accentuates investigation of machinability of TiB₂/Al 7075 metal matrix composite (MMC) while electrical discharge machining (EDM) with cryogenic treated Cu electrode, following Taguchi L₆₄ design of experiments (DOE). Influences of peak current (I_P), pulse on time (T_ON) and gap voltage (V_G) on material removal rate (MRR), tool wear rate (TWR) and average surface roughness (R_a) were studied. Morphology of the machined surfaces was also explored through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and elemental mapping. Results revealed increment of MRR (by about 55%) and TWR (by about 75%) on increasing I_P (from 4 A to 10 A at T_ON = 100µs at V_G = 55 V), but these responses reduced (by about 70% and 9%, respectively) on increasing V_G (from 55 V to 80 V at I_P = 4 A and T_ON = 100µs). R_a was influenced significantly by the I_P and T_ON levels. At 4 A of I_P, 200µs of T_ON and 55 V of V_G, SEM micrograph of the machined surface revealed craters, re-solidified regions, voids and cracks. On increasing the current level to 6 A keeping the other parameters constant, significant reduction of debris with larger craters were observed. On further increasing the current level to 10 A, minimal amount of debris, thicker ridges and deeper craters were witnessed from the machined surface microstructure.