Abstract:To address the issue that B₄C ceramics are difficult to be wetted by aluminum metals in the composites, TiB₂ was introduced via an in-situ reaction between TiH₂ and B₄C to regulate their wettability and interfacial bonding. By pressure infiltration of the molten alloy into the freeze-cast porous ceramic skeleton, the 2024Al/B₄C-TiB₂ composites with a laminate-reticular hierarchical structure were produced. Compared with 2024Al/B₄C composite, adding initial TiH₂ improved the flexural strength and valid fracture toughness from (484±27) to (665±30) MPa and (19.3±1.5) to (32.7±1.8) MPa·m^1/2, respectively. This exceptional damage resistance ability was derived from multiple extrinsic toughening mechanisms including uncracked-ligament bridging, crack branching, crack propagation and crack blunting, and more importantly, the fracture model transition from single to multiple crack propagation. This strategy opens a pathway for improving the wettability and interfacial bonding of Al/B₄C composites, and thus produces nacre-inspired materials with optimized damage tolerance.

Key words: bio-inspired composites; freeze casting; titanium hydride; mechanical properties; damage tolerance