Interface control and mechanical properties of Al₂O₃–Ni laminated composites that were prepared through gel casting and hot pressing

Abstract

The use of ceramic–metal laminated composites is an efficient way to improve the toughness of brittle ceramics. Uniform multilayered Al₂O₃–Ni laminated composites were prepared through a combined method of gel casting and hot pressing, which is less cumbersome than the traditional sequential lamination method. The wettability, diffusion and chemical reaction between Al₂O₃ and Ni were controlled through surface oxidation treatment of the Ni sheets. The results show that when the surface-oxidized Ni sheets were used, the microstructure of the Al₂O₃–Ni interface changed with the hot-pressing temperature. As the hot-pressing temperature was increased from 1150 to 1300 °C, a straight and clean interface formed, the interface became interlocked and, finally, a stable layer of NiAl₂O₄ formed at the interface. The interlocked microstructure was especially beneficial for interfacial bonding, and the plastic deformation of the Ni layers was restrained, thereby leading to slip steps rather than dimple formation on the fracture surfaces of the Ni layers. In addition, the toughening effects of plastic deformation and crack deflection in the Al₂O₃–Ni laminated composites were significant, which resulted in ductile fracture rather than brittle fracture. As a result, the Al₂O₃–Ni laminated composite that was prepared using the oxidized Ni sheets and the combined method of gel casting and hot pressing achieved a higher work of fracture than laminated composites that were prepared via other methods.