Abstract
The B4C-YB4 composites with good comprehensive properties were prepared by in-situ hot pressing sintering under the conditions of sintering temperature 1950–2050 °C, pressure 20 MPa and holding time 15 min using B4C and Y2O3 as the raw materials. The phase composition, microstructure, mechanical properties of the composites fabricated with different contents of Y2O3 and different temperatures were studied, and the reaction mechanism, toughening and strengthing mechanism were explored. Y2O3 can react with B4C to form YB4, and 15B4C+7Y2O3 = 14YB4+2B2O3+15CO is the total reaction. With the increase of temperature, the mechanical properties of B4C-YB4 composites improve obviously, and the B4C-YB4 composites prepared with 3 wt% Y2O3 have the best performance. The relative density, hardness, flexural strength and fracture toughness of the B4C-YB4 composites fabricated at 2050 °C with 3 wt% Y2O3 are 97.00%, 34.84 GPa, 422.67 MPa and 4.92 MPa m1/2 respectively. The good comprehensive properties are attributed to the uniform distribution and small size of the second phase YB4, and the lower porosity. The coexistence of transgranular and intergranular fracture, and the phenomena such as crack bridging, deflection and microcracks contribute to the improvement of the toughness.
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