Effect of Silicon Particles on the EDM Characteristics of Al-Si Alloys

Abstract

The second phase of the Aluminum-Silicon (Al–Si) alloy embedded in microstructure includes primary silicon particles and hypereutectic silicon particles. Variations in the area fraction of these silicon particles significantly influences Electro Discharge Machining (EDM) characteristics. The area fraction of these silicon particles is proportional to materials removal rate (MRR). Experimental data obtained using Scanning electron microscope (SEM) revealed that discharge craters were formed as a ridge on the EDMed surface. The increased average surface roughness (Ra) resulted in an increased EDM rate. The area fraction of second phase silicon particles, and the ridge density on the rapidly resolidified layer of the EDMed surface tended to increase. However, most silicon particles were found on the peaks on the sub-layer of the EDMed surface, formed by rapidly solidification of molten fluid during discharge melting. Therefore the presence of silicon particles in the rapidly resolidified layer was largely governed by the formation of discharge peaks. The formation of peaks was governed by EDM conditions and silicon content. The electrodes showed stable wear during EDM when the pulse duration exceeded 150 \\microsecond. Wear increased as the area fraction of silicon particles increased.