Effect of Electrical Discharge Machining Parameters on Microwave Heat Treated Aluminium-boron Carbide-graphite Composites

Abstract

Aluminium metal matrix composites have become the necessary materials in various engineering applications. Al 6061 is the matrix material in which boron carbide, one of the hardest material and graphite are reinforced and the composite was prepared by stir casting. Microwave post heat treatment of metal based components is a newer technique which is employed in this study. It provides unique microstructure and properties as a result of selective heating. In order to obtain solution heat treatment, the composites were heated up to 520o C and were maintained for a definite holding time at 520oC. Electrical discharge machining process was selected to machine MMC as it is difficult to machine by conventional machining. EDM machinability studies were carried out on the heat treated Al-B4C (15 vol%) graphite (5 vol%) and compared with EDM machined with conventionally heat treated composites. EDM process parameters optimization was carried out using Taguchi design with input parameter such as pulse on time, pulse off time and current density for the material removal rate (MRR) and tool wear rate (TWR) as response parameters. Microwave heat treated composite exhibited higher hardness than the conventionally heat treated composites. Pulse off time and pulse on time was a non-linear function for the material removal rate of the composite and the most influential parameters for the MRR were determined.