Strong and tough 3D-(SiC–Si₃N₄)/Al co-continuous composite with enhanced interfaces

Materials with high specific strength and toughness are urgently needed in the fields of electronic packaging, armor, and aerospace. SiC/Al composites show good potential for these applications but the problem of mutual exclusion of strength and toughness still needs to be solved. Herein, we propose a new strategy to simultaneously enhance its strength and toughness from the perspective of structural optimization and interface enhancement. Inspired by the nacre structure, a 3D-(SiC–Si₃N₄)/Al co-continuous composite was prepared by freeze-casting combined with the pressure infiltration method. During the process, elongated Si₃N₄ grains were introduced into the ceramic framework to design the internal lamella wall structure and increase the contact area with the aluminum substrate. Moreover, a favorable interfacial bonding was designed between Si₃N₄ and Al to improve interface wettability. The reliable microstructure of porous 3D-(SiC–Si₃N₄) preform was tailored through the adjustment of initial solid loading and the α-Si₃N₄ component. The effects of initial solid loading and the α-Si₃N₄ component on the microstructure, interfacial wettability, and mechanical properties of the final composites were investigated. The results showed that the SiC–Si₃N₄/Al composites possess high flexural strength (769 MPa) and fracture toughness (15.1 MPa m^1/2), which is superior to data reported in general literature. Numerous elongated β-Si₃N₄ grains are produced on the ceramic skeleton, forming an interlocking structure with the aluminum matrix, which increases the contact area with the aluminum substrate. A chemical reaction layer was formed at the interface of the composite, greatly improving the interfacial bonding strength. This work provides a promising design guideline for developing and optimizing high-strength and tough composite.