Surface quality evaluation of electrical discharge machined AZ31 magnesium alloy

This research optimizes electrical discharge machining (EDM) of AZ31 magnesium alloy by investigating pulse-on time (6.4–400 μs) and peak current (12–48 A) by the aid of image processing technique and phase identification. Higher energy inputs increased material removal and tool wear rates but also raised crack density (up to 5.2 %) and surface roughness (R a up to 16.41 μm). Crucially, pulse-on times below 10 μs eliminated surface cracks entirely. Minimal roughness (R a = 1.53 μm) occurred at 12A/6.4μs, while surface hardness rose to 152 HV at high energies due to alloying. Metastable Mg 2 C 3 carbide was identified via XRD as a product of rapid EDM cooling. Multi-objective optimization recommends 24A/25μs for balanced efficiency (MRR: 4.2 mm 3 /min) and surface quality (R a : 2.87 μm, 0.3 % cracks), while 12A/6.4 μs is ideal for biomedical implants.