Microstructure and mechanical properties of ABOw@Al₂O₃/AZ91 composites regulated by in-situ ABOw

By adding the B₂O₃ into Al₂O₃, the morphology of in-situ Al₁₈B₄O₃₃w (ABOw) on the surface of Al₂O₃ was formed and controlled by sintering temperature. The ABOw@Al₂O₃/AZ91 lamellar composite were prepared based on the combination of freeze casting and pressure casting. The effect of in-situ ABOw dimension on the microstructure and mechanical properties of ABOw@Al₂O₃/AZ91 composites was researched. The results show that the larger ABOw formed a cross-interlocking structure, when the sintering temperature was high. The strength of the ceramic skeleton was improved, which helped to increase the compressive strength of the composite. At lower sintering temperatures, the reduced dimensions of ABOw resulted in increased porosity within the ceramic framework. The hard particles can be wrapped by the soft matrix, and the interface between the particles and the matrix was strengthened, which can alleviate the stress concentration and transfer load. This made the single crack propagation mode gradually changed into the multi-crack propagation mode, which dissipated more fracture energy and delayed the fracture of the composite. Compared with 1100 °C, the compressive strain, flexural strength, K_IC and K_JC at 700 °C increased by 25 %, 25 %, 37 % and 18 %, respectively.