Machinability Analysis and Optimization of Electrical Discharge Machining in AA6061-T6/15wt.% SiC Composite by the Multi-criteria Decision-Making Approach

An investigation was made on AA6061-T6/15wt.% SiC composites fabricated by stir casting method to study its machinability carried out by electrical discharge machining (EDM) method and optimize process parameters by the multi-criteria decision-making (MCDM) method. For experimentation, Taguchi-based L₂₇ orthogonal array was used. EDM machining process parameters selected for this study were current (IP), pulse on time (T_on), and gap voltage (V) which were investigated by material removal rate (MRR), tool wear rate (TWR), circularity (CIR), and cylindricity (CYL). For the multi-objective optimization criteria on machining, entropy method weights incorporated with combinative distance-based assessment (CODAS) methodology to estimate the optimum level of input parameters. Objective-based entropy weight-age method was used to assign weights for output responses. Entropy weights were 0.164, 0.128, 0.402, and 0.306 for MRR, TWR, CIR, and CYL. From the CODAS assessment scores, optimal conditions were achieved at the (ninth) experiment having an IP of 9A, 100 μs of T_on, and gap voltage of 40 V with a relative assessment score of 13.720. The machined surface was examined using a scanning electron microscope. Poor surface finish and micro-voids with craters were achieved by increasing IP and T_on.