OPTIMIZATION OF OUTPUT RESPONSES DURING EDM OF AZ91 MAGNESIUM ALLOY USING GREY RELATIONAL ANALYSIS AND TOPSIS

Abstract

Unconventional machining of magnesium alloys through die sinking and Wire Electrical Discharge Machining (WEDM) processes are preferred over conventional machining processes to overcome the rapid loss in strength and affinity that occurs with tool materials at high temperatures. In the present study, AZ91 magnesium alloy is machined in EDM using a prepared alloy tool (copper alloyed with titanium diboride). Based on Taguchi's L27 orthogonal array, a total of 27 experiments have been conducted by varying the process parameters such as pulse on time (Ton), gap voltage (Vg) and current (Ip) with three different levels. Techniques for Order Preference by Similarity to Ideal Solution (TOPSIS) and Grey Relational Analysis (GRA) have been applied to optimize the response parameters of EDM to obtain maximum Material Removal rate (MRR) and minimum Tool Wear Rate (TWR) and Surface Roughness (SR). Analysis of variance (ANOVA) is carried out based on F-test at a confidence interval of 95% to confirm the significant influence of individual parameters. From the above two optimization techniques, the obtained optimal values are current 15 A, gap voltage 55 V, pulse on time 30 ìs and an error of less than 5% is observed from the confirmation experiments. Scanning Electron microscope (SEM) images revealed that there is no formation of cracks but micro pits and holes are observed.