Enhanced strength and toughness in TC4-(GNPs/TC4) composites via heterogeneous multi-scale lamination design

Simultaneously achieving high strength and toughness for Ti alloys or Ti matrix composites is highly desirable but remains a great challenge. The present study reports a heterogeneous multi-scale laminated (HML) TC4-(GNPs/TC4) composites fabricated by field assisted sintering (FAST) and hot rolling (HR). The alternating combination of GNPs/TC4 layers and TC4 layers formed the primary laminated architecture. Within the GNPs/TC4 layer, the secondary laminated architecture was constructed through the parallel distribution of GNPs. No interface delamination was observed. In particular, the as-designed composites with 1:1 thickness ratio and 250 μm layer thickness exhibited the enhanced strength without sacrifice in ductility. In-situ tensile tests revealed that the soft layer in the primary laminated architecture possessing a high strain-bearing capacity, deflected and blunted the microcracks originated from the hard layer. Moreover, the secondary laminated architecture preferred to transform the two-dimensional cracks into three-dimensional cracks, thereby effectively increasing the crack propagation path. The synergistic effect of these mechanisms noticeably enhanced the toughness of the composites. Together they act in concert to render outstanding mechanical performance. This study highlights a simple and feasible route towards well balance between strength and ductility in Ti matrix composites, and informative for achieving high-performance in GNPs/Ti system.