MACHINABILITY OF ALUMINIUM METAL MATRIX COMPOSITE REINFORCED WITH ALUMINA USING ELECTRO-DISCHARGE MACHINING

Aluminium metal matrix composites (AMMCs) are making inroads in various
engineering applications (aviation, marine, automotive parts as diesel engine pistons,
cylinder, and brake components) requiring higher strength and stiffness than those
offered by conventional aluminium alloys. Traditional machining of AMMCs
however is difficult due to hard reinforcement in the AMMC material which tends to
wrap around the cutting tool-bit leading to tool breakage. Electro-discharge
machining (EDM) has been successfully applied on standard aluminium alloys such
as Al 6061 but yet to be tested on 30% Al2O3 reinforced AMMC. In this study, a
specific machining performance on 30% Al2O3 reinforced AMMC is assessed in
comparison with Al 6061. The characteristics analyzed are surface roughness (Ra),
material removal rate (MRR), tool wear ratio (TWR), overcut (OC) and surface
morphology. Process parameters used, are peak current, ON-time (pulse duration) and
OFF-time (pause duration), were varied in this research to determine the
machinability of AMMC reinforced by 30% Al2O3 by using EDM. The research
methodology adopted was using design of experiment (DOE) and results from the
experiment were analyzed and interpreted. The response surface methodology (RSM)
was used to predict the machining performance and empirical mathematical models
for Ra, MRR and TWR using Design Expert software. Results showed that peak
current, ON-time and OFF-time have influenced on the EDM performance.
Machinability of electro-discharge machining of 30% Al2O3 reinforced AMMC
composite using electrolytic copper electrode has been proven feasible at certain
parameters setting. Nevertheless, EDM machining performance of Al 6061 is better
than that of AMMC. For machining at a specific material removal rate, minimal
surface roughness, and low overcut can be obtained at low peak current or short ONtime
and longer OFF-time however tool wear ratio remains high. Appropriate setting
of EDM parameters that results in optimum machining performance have been
identified in this research.