Tailoring microstructure and mechanical properties of nacre-architecture (TiBw-TiB2p)/Al hybrid composites by particle grading

A nacre-inspired (TiBw-TiB 2p )/Al composites with strength-toughness synergy were prepared by combination of freeze casting and squeeze casting. By adjusting the ratio of fine and coarse TiB 2 particle sizes (F/C), the microstructure, mechanical properties, heterogeneous deformation induced (HDI) strengthening, and toughening mechanisms of the (TiBw-TiB 2p )/Al composites were effectively tailored. The results indicated that the mechanical properties in the longitudinal section were superior to those in the transverse section. The F7C3 composite showed the highest longitudinal compressive strength of 771 MPa, flexural strength of 760 MPa, and plane strain fracture toughness ( K Ⅰc ) of 18.2 MPa⋅m 1/2 and crack-growth toughness ( K Jc ) of 35.1 MPa⋅m 1/2 . The peak HDI stress accounted for more than 60 % of the flow stress and thus HDI strengthening played an important role in improving the composite mechanical properties. Of these, the F10C0 composite had the highest HDI stress in the longitudinal section (431 MPa) while F0C10 had the highest HDI stress in the transverse sections (379 MPa). The outstanding fracture toughness in the longitudinal section was attributed to several toughening mechanisms, including Al deformation, crack deflection, blunting and branching, Al bridging and interfacial debonding, while the poor fracture toughness in the transverse section was mainly related to the lack of a toughening mechanism.