Balancing strength and toughness of nacre-inspired (TiBw-TiB_2p)/Al hybrid composites by regulating Ti addition

To address the problem of hot cracking caused by high temperature sintering for monolithic TiB₂ particle (TiB_2p) preforms, Ti particles were added to induce the an in-situ reaction Ti + TiB₂ → TiBw to create TiB whisker (TiBw) and reduce the sintering temperature of TiB_2p preforms. Nacre-inspired (TiBw-TiB_2p)/Al composites were prepared by freeze casting and pressure infiltration, and the microstructure and mechanical properties of the composites were tailored by regulating the Ti addition content. The addition of Ti particles altered the ceramic-rich layer thickness and the type/distribution of intermetallic compounds in the composites. The effect of Ti content on the flexural strength and fracture toughness of the composites was investigated. The results showed that 5Ti composite exhibited optimum mechanical properties with flexural strength of 811 MPa, crack initiation toughness (K_Ic) of 19.1 MPa·m^1/2 and crack growth toughness (K_Jc) of 24.9 MPa·m^1/2. The enhanced strength was mainly attributed to the hetero-deformation induced (HDI) hardening, while the improved toughness was due to multiple crack branching, deflection and blunting.