Effect of dielectric medium on electro-discharge machining of aluminium metal matrix composites

Abstract

Aluminium Metal Matrix Composites (AMMCs) are used in several engineering demands because it has a higher strength-to-weight ratio. In this study, aluminium grade 7075 composites have been machined using an unconventional EDM machine. The reinforcements of SiC and Al2O3 with 2 %, 4 %, 6 %, and 8% are used for producing aluminium MMC using an electronically controlled bottom die pouring stir casting machine. The effect of dielectric mediums like liquid nitrogen and deionized water on the electro-discharge machining of aluminium MMC has been analyzed. Gap voltage, pulse-on time, pulse-off time, and current were the controllable input parameters. Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (SR) are considered the machining output parameters for this work. The result revealed that MRR, TWR, and SR values have less while machining silicon carbide (SiC) reinforcements than alumina for both dielectric mediums. MRR has been gradually declining as the SiC reinforcement fraction on aluminium matrix material has increased. This is due to the presence of SiC ceramic particles in the aluminium matrix material, which reduce the mobility of electrons within the workpiece. The microstructure results presented that the liquid nitrogen EDM techniques produced fewer globules and damaged layers than the deionized water EDM approaches.