Lamellar and interpenetrated Al/(Al2O3–TiC) composites prepared by bidirectional freeze casting and melt infiltration

Abstract

Unidirectional freeze casting followed by sintering and infiltration treatments has been proved to be a promising method to produce lamellar composites with good strength and toughness. However, it remains a great challenge to tailor the microstructure, particularly the lamellar orientation at the centimeter scale and the architectural features over multiple scales. Herein, we prepared Al/(Al2O3–TiC) composites with a long-range ordered lamellar architecture via bidirectional freeze-casting and melt-infiltration techniques. The incorporation of a certain amount of TiC (∼3 μm in diameter) into the Al2O3 slurry increased the solidification velocity and decreased the ceramic layer thickness. Furthermore, it greatly facilitated the infiltration of liquid Al into the interlamellar channels and in-layer cavities, thus improving the mechanical properties of the composites. The maximum flexural strength (474 ± 8 MPa) and crack-growth toughness (42.7 ± 2.7 MPa m1/2) appeared in the composite containing ∼27 vol% ceramics with Al2O3:TiC = 5:5. Moreover, the composites exhibited anisotropic mechanical properties. The flexural strength loaded in the direction parallel to the ceramic layers was higher than that perpendicular to them, while the toughness exhibited an opposite trend. The main toughening mechanisms included crack blunting, crack deflection, plastic deformation of the metal layers and multiple cracking. This work offers a cost-effective and scalable method for the fabrication of laminated composites with exceptional damage tolerance.