Impact of EDM process parameters on machining performance in rare-earth AE42 magnesium alloy: a Taguchi-TOPSIS based multi-objective optimisation

Magnesium alloys have attracted renewed industrial interest due to improved performance. AE42 Magnesium alloy, a rare-earth material containing 4 wt. % aluminium and 2 wt. % rare-earth elements, offers improved properties compared to conventional alloys. Non-traditional machining processes like EDM produce accurate geometry while maintaining surface integrity. In this study, AE42 Mg alloy was machined to assess its performance across operating parameters. An AE42 Mg alloy specimen machined by a copper-titanium diboride (Cu-TiB2) composite tool was utilised. The EDM parameters peak current (Ip), gap voltage (Vg), and pulse-on time (Ton) were evaluated by a three-level L27 orthogonal array to investigate nonlinear behaviour and interaction effects, thereby improving efficiency. The effects of process parameters on Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (SR) were analysed using the Signal-to-Noise (S/N) ratio to minimise noise and assess robustness. The results indicate that a peak current of 15 A, a gap voltage of 55 V, and a pulse-on time of 30 µs provide balanced machining performance. Multi-response statistical significance, assessed by ANOVA, provides a balanced optimisation framework, with peak current and pulse-on time being significant for MRR and TWR, respectively. The trends were visually validated using SEM analysis.