Microstructure property correlations and electrical discharge machining response of TiC-reinforced AZ31B magnesium composites using response surface methodology

Magnesium matrix composites have low density and high specific strength, but their machinability under electrical discharge machining (EDM) is rarely studied together with the thermomechanical processing route. AZ31 B was reinforced with 5, 10, 15 and 20 wt.% TiC by stir casting under an Ar + SF 6 atmosphere, and the cast billets were forged at two temperatures: hot (approximately380°C) and warm (approximately175°C, called cold-forged in keeping with prior MMC literature). The cold-forged AZ31B-15%TiC composite gave the best combination: 1.97 g cm −3 density, 110.8 HV hardness, 260 MPa UTS (155 MPa yield) and 2.1 × 10 −5 mm 3 N −1 m −1 wear rate; clustering beyond 15 wt.% caused a hardness reversal. Machinability was modelled with a face-centred half-fraction central composite design — six factors, three levels, 52 runs. To the authors’ knowledge this is the first Mg-TiC EDM-RSM study that treats tool material and workpiece composition as categorical factors in the same model. Adjusted R 2 were 0.998 (MRR) and 0.945 (TWR). Desirability optimisation (weights 0.6/0.4) gave T on = 120 µs, T off = 58 µs, V = 20 V, I = 16 A, Cu electrode and AZ31B-15%TiC workpiece, with validation error below 6%; MRR follows the I 2 T on electrothermal scaling.