Breaking the strength-ductility trade-off in titanium matrix composites via heterogeneous sunflower-like architectures

Traditional titanium matrix composites (TMCs) invariably suffer from a substantial loss of ductility when high strength is achieved. This study proposed a one-step powder metallurgy sintering strategy to construct a sunflower-like architecture for superior strength-ductility synergy in TMCs. Specifically, small-size Ti6Al4V (TC4_S) powders, reinforced with in-situ synthesized CNTs, were blended with large-size TC4_L powders. Spark plasma sintering (SPS) was subsequently employed to form TMCs with sunflower-like hierarchical architecture. The heterogeneous TMCs feature multiple well-bonded interfaces. Within the fine-grained regions, in situ-formed TiC particles along with residual CNTs constitute a reinforcing network, resulting in significant grain refinement and efficient load transfer. During mechanical deformation, the composites demonstrate hetero-deformation-induced (HDI) strengthening. This is attributed to the plastic incompatibility between heterostructured components and the impediment of dislocation motion by hard reinforcing phases (CNTs/TiC) at interfaces. Additionally, the activation of <c + a> dislocations and the presence of multiple types of interfaces synergistically coordinate deformation. Ductility is enhanced by these interfaces through the effective facilitation of crack deflection and blunting. This design strategy successfully breaks the strength-ductility trade-off in TMCs, providing valuable insights into the development of high-performance TMCs.