Electric Discharge Machining of 10 vol% Al2O3/Al Metal Matrix Composite - An Experimental Study

Abstract

The particle reinforced metal matrix composite have hard particles dispersed in matrix which make them difficult to machine with conventional machining methods. Electric discharge machining (EDM) is an effective tool for machining such materials. This experimental study was undertaken to identify the significant factors that affect the output responses while machining of 10 vol%Al2O3/Al composite material. The material removal rate (MRR) and tool wear rate (TWR) have a direct relationship with current and an inverse relationship with pulse on-time. Appropriate levels of current and pulse on time levels can be chosen while roughing and finishing operations. Normal polarity between terminals had higher MRR than with reverse polarity. The recast layer had a non-uniform and wave-like morphology and cracks penetrated into the matrix phase resulting in high residual stresses exceeding the ultimate tensile strength of the material. Pulse on-time has greater influence on recast layer thickness than current. The reinforced particles were all clustered under the machined surface with very few in the recast layer which results in a low strength of the machined surface. The presence of reinforced particles in recast layer is very rare, so it is desirable to remove it. Keywords: electro-discharge, machining, aluminum matrix composites, material, removal, tool, wear, roughness, recast, layer