Spark plasma forging and network size effect on strength-ductility trade-off in graphene reinforced Ti6Al4V matrix nanocomposites

Abstract

Architecting tightly bonded interface microstructure is the principal guarantee for increased mechanical properties of titanium matrix composites (TMCs). Adopting an effective technique to modulate interface structure is desirable to break through the trade-off of strength-ductility. Herein, a strategy is applied to establish interlocking interface in multilayer graphene (MLG) reinforced Ti6Al4V (TC4) matrix TMCs by spark plasma sintering (SPS) with subsequent spark plasma forging (SPF). By this technique, 3D network-structured composites of 0.35 wt% MLG/TC4 with tailored network size are fabricated via varied TC4 particle sizes (2–15 μm, 15–53 μm, 63–97 μm, 120–150 μm), then their microstructure and mechanical properties are explored systematically. Results depict that enhanced interface bonding and oriented configuration of reinforcements are generated in inhomogeneous network architecture with diminished internal defects by minimizing agglomerations after deformation, simultaneously enhancing the strength and ductility. Among the different network sizes, SPFed composite with 15–53 μm TC4 powder displays the better maintained tensile ductility (ε, 10.2%) with remarkably higher yield strength (YS, σ0.2) of 1089 MPa (27.52% higher than TC4), resulting in excellent strength–ductility synergy. Strengthening mechanisms and corresponding contributions are further discussed systematically. The work provides a valuable and facile pathway to prepare high-performance TMCs with outstanding interface microstructure.