Influence of Y2O3 contents on sintering and mechanical properties of B4C-Al2O3 multiphase ceramic composites

In this study, B4C-Al2O3 multiphase ceramic composites were prepared by spark plasma sintering (SPS) and Y2O3 was used as a sintering aid. Results show that in the range of 1350–1500°C, nearly full dense B4C-Al2O3 multiphase ceramic composites with a high densification rate (4×10−3/s) can be fabricated. Addition of Y2O3 can lead to reduce activation energy of densification and plastic flow mechanism during sintering of the ceramic composites. At the same time, Y2O3 can react with Al2O3 to form liquid Y3Al5O12, which can effectively reduce the densification temperature of the ceramic composites. With the increase of Y2O3 content, the temperature was lowered from 1500 °C to 1350 °C. When the Y2O3 content was 1.0 vol.%, relative density, hardness, fracture toughness, and flexural strength of the ceramic composites were 98.60%, 23.75 GPa, 4.89 MPa•m1/2, and 464.96 MPa, respectively. The toughening mechanism of the ceramic composites followed particle toughening and micro-crack toughening. The internal grains of the composites were tightly bonded, they were mainly fractured in the transgranular form and the cross section was relatively rough with a high bending strength of 450 MPa.