Graphene nanosheets networking: A novel material design strategy to enhance ultra-precision machining of titanium alloys and composites

Positive efforts (e.g., cryogenic machining, vibration assistance, and laser assistance) have been proposed to address the challenges of low thermal conductivity and the heterogeneous structure in titanium alloys and titanium metal matrix composites (Ti-MMCs) during ultra-precision machining. However, these techniques often require complex auxiliary equipment with high costs and stringent precision control precision control, posing a major challenge to the sustainable production of titanium alloys and Ti-MMCs. Unlike other existing methods relying on external assistance, this study introduces a novel material design strategy to intrinsically improve the machinability of titanium alloys and Ti-MMCs by incorporating networked graphene nanosheets (GNSs) as internal reinforcement. To systematically evaluate this approach, three Ti-6Al-4V (Ti64) alloy-based materials: the matrix alloy, a composite reinforced with randomly dispersed GNSs (GNSs/Ti64 composite), and a composite reinforced with a networked GNSs structure (networked GNSs/Ti64 composite), were respectively designed and employed as workpiece in ultra-precision micro-cutting tests. The results reveal that the networked GNSs/Ti64 composite exhibits significantly reduced machining vibration induced by machining force, enhanced surface integrity, and more uniform chip formation compared to both the Ti64 alloy and GNSs/Ti64 composite. In-depth material characterization and mechanistic analysis attribute this improvement to the networked GNSs structure that optimizes the occurrence of shear fracture in the primary shear zone, leading to more uniform serrated chips for chip formation. This research effectively improves the ultra-precision machinability of titanium alloys and Ti-MMCs, which lays the foundation for the subsequent fabrication of advanced products from titanium alloys and composites.