Microstructure and Mechanical Properties of Abow@Al2o3/Az91 Composites Regulated by In-Situ Abow

Abstract

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. The smaller dimension of ABOw increased the porosity of the ceramic skeleton, when the sintering temperature was low. 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, KIC and KJC at 700 °C increased by 25 %, 25 %, 37 % and 18 %, respectively.

Keywords: Aluminum borate, Freeze casting, Mechanical properties, Fracture mechanism