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Network microstructure titanium matrix composites (NMTMCs), featuring Ti6Al4V as the matrix and network-distributed TiB whiskers (TiBw) as reinforcement, exhibit remarkable potential for diverse applications due to their superior physical properties. Due to the difficulty in machining titanium matrix composites, electrical discharge machining (EDM) stands as one of the preferred machining techniques for NMTMCs. Nevertheless, the compromised surface quality and the recast layer significantly impact the performance of the workpiece machined by EDM. Therefore, for the purpose of enhancing the surface quality and restraining the defects of NMTMCs, this study conducted comparative EDM milling experiments between NMTMCs and Ti6Al4V to analyze the effects of discharge capacitance, charging current, and pulse interval on the surface roughness, recast layer thickness, recast layer uniformity, and surface microcrack density of both materials. The results indicated that machining energy significantly influences workpiece surface quality. Furthermore, comparative experiments exploring the influence of network reinforcement on EDM milling revealed that NMTMCs have a higher melting point, leading to an accumulation phenomenon in low-energy machining where the reinforcement could not be completely removed. The residual reinforcement in the recasting layer had an adsorption effect on molten metal affecting the thermal conductivity and uniformity within the recasting layer. Finally, specific guidelines are put forward for optimizing the material's surface roughness, recast layer thickness, and uniformity, along with minimizing microcrack density, which attain a processing effect that features a roughness of Ra 0.9 μm, an average recast layer thickness of 6 μm with a range of 8 μm, and a surface microcrack density of 0.08 μm−1. [ABSTRACT FROM AUTHOR]

Wire electric discharge machining (WEDM) and electrical discharge machining (EDM) promise to be effective and economical methods for the machining of metal matrix composites and conducting ceramic blanks. However, the machining process of Ni-AlO functionally graded materials (FGMs) is extremely difficult because the insulating ceramic layer cannot be machined directly by EDM. In this paper, the pure AlO layer has been machined by self-induced EDM, using the conductive layers of Ni-AlO FGMs to trigger the discharges in the insulating ceramic layer. Machining experiments have been performed to investigate the effects of discharge capacitance, pulse off-time, and charging resistance on the process performance of the pure AlO layer using RC-type pulse generator. From the experimental results, the discharge waveform of pure AlO layer includes long pulse discharge waveform, in addition to conventional normal discharge of conductive layers. The shape of long pulse discharge waveform can be changed by pulse off-time. The appropriate pulse off-time not only improves the stability of EDM but also increases the material removal rate (MRR). Moreover, it was observed that the MRR increases with increasing discharge capacitance and decreasing charging resistance. The surface roughness increases with increasing discharge capacitance. Finally, a small hole with a depth-diameter ratio of 5, little tapper is machined based on the experimental analysis. [ABSTRACT FROM AUTHOR]