Microstructures and mechanical properties of high-performance nacre-inspired Al-Si/TiB2 composites prepared by freeze casting and pressure infiltration

The nacre-inspired Al-Si/TiB2 composites were successfully prepared by freeze casting and pressure infiltration. The microstructures and mechanical properties of nacre-inspired Al-Si/TiB2 composites were studied by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and mechanical testing. The results show that the high performance of Al-Si/TiB2 composites can be attributed to the clean interfaces between TiB2 and Al and several toughening mechanisms, such as crack blunting, crack branching, crack deflection, plastic deformation of Al layer, and bridging of the uncracked fracture process zone. Specifically, the compressive strength, three-point bending strength and K-IC of composites corresponding to LS were 640-710 MPa, 629 MPa, and 16.4 MPa m(1/2), respectively. The fracture behaviors of the Al-Si/TiB2 composites have been discussed in detail in this work. It was found that single cracks were accompanied by the propagation of multiple micro-cracks in the layered composites. The precipitation of Si particles at the TiB2/alpha-Al interface and the Al phases infiltrated in the TiB2 layers play a great role in the formation of single crack fractures and multiple micro-cracks fractures, respectively, in the nacre-inspired Al-Si/TiB2 composites.