Ultrahigh‐Strength and Toughness Ceramic‐Metal Composites With Valence Gradient Interfaces

ABSTRACT The design of lightweight, high‐strength, and tough composites is crucial for enhancing the mechanical properties of materials. Bio‐inspired designs for brick‐and‐mortar structures can considerably enhance the strength and durability of composites. Phase interfaces are especially important, as material failures often occur at these interfaces, leading to substantial degradation in structural performance. Accordingly, building robust interfacial connections poses a crucial challenge. In this study, a ceramic‐metal bulk composite with an ordered alternating layered structure, measuring 30 mm × 30 mm × 30 mm, is fabricated by infiltrating 6061 aluminum alloy into an alumina skeleton. Using pressure infiltration technique, a robust interface is formed by constructing a valence gradient of aluminum at the interface between the alumina and the aluminum alloy layers. Benefiting from the synergistic effects of lamellar reinforcement and valence gradient interfacial reinforcement, the ceramic‐metal composite exhibits excellent properties, including high flexural strength (∼986.4 MPa) and toughness (∼45.3 MPa·m 1/2 ) as well as a low thermal expansion coefficient of ∼6.6 × 10 −6 K −1 . The valence gradient interface design strategy is also applicable to ceramic‐metal composite systems with identical elements, such as MgO‐Mg, offering a new pathway for the structural design of advanced composites.