Abstract
This paper reports on the development of HfB2 reinforced B4C composite prepared through reaction hot pressing of B4C and HfO2. These composites were characterized for phase composition, microstructure, mechanical and physical properties. Full dense composites were obtained by hot pressing at 1900°C and a pressure of 40MPa. HfB2 phase was identified as a reaction product in the composites by XRD analysis. Hardness of all the composites was measured to be in the range of 28–35GPa. High elastic modulus (525GPa) and shear modulus (196GPa) were measured for composite corresponding to 10wt.% HfO2. Fractography of the composites indicates transgranular mode of fracture. Fracture toughness of the composites was in the range of 4–7MPa.m1/2 which is higher than that of monolithic B4C (2.43MPa.m1/2). Microstructural observation of crack propagation patterns indicates the major toughening mechanism as crack deflection, crack arrest and crack bridging.
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