Developing nacre-inspired laminate-reticular 2024Al/B4C composites with high damage resistance by adjusting compositional wettability

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·m1/2, 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.