Effect of granularity of reinforcing particles Al2O3 on EDM process of aluminium matrix composites

The study discusses issues related to the process of electro-discharge machining (EDM) composites based on Al + 20% Si + 5% Fe + 3% Cu + 1% Mg matrix manufactured using a powder metallurgy method. Ten percent by volume of Al2O3 grains of 3, 9, 23 and 53?m sizes with irregular sharp edges represented the reinforcing phase. EDM was performed with a machine equipped with a RLC generator using different (computational) discharge energies varied in steps within the 0.044 - 2.268 mJ range. The tests measured volumetric productivity of EDM (Vw) and roughness (Ra) of the machined surface. In addition, the researchers provided selected SEM images of ED-machined surfaces with some results of X-ray microanalyses of chemical composition performed in cavities and on the surfaces of irregularities. They also provided SEM images of Al2O3 grains adhering to the machined surface of the composite, showing the mechanism of erosion of dielectric particles in EDM conditions. They demonstrated that the energy of single discharges (Ei) was the main parameter effecting the process and results of EDM. The volumetric productivity of the process (Vw) and roughness of the machined surface (Ra) increase with growth of energy (Ei) and, at the same time, surface integrity (SI) changes.