Microstructure and mechanical properties of TiB₂-Al₂O₃ composites

Abstract

Effects of Al₂O₃ and Ni as the additives on the sinterability, microstructure and mechanical properties were systematic studied. The experimental results show that only a relative density about 96.2% of hot-pressing TiB₂-30%Al₂O₃ can be attained due to the plate-like TiB₂ particle and its random orientation and excessive Al₂O₃ grain growth. When sintering temperature is higher than 1 700 °C, TiB₂ grain growth can be found, which obvious improves flexural strength of TiB₂ matrix but decreases toughness. It seems that mechanical properties of TiB₂-Al₂O₃ composites are mainly depended on relative density besides grain growth. otherwise, they will be determined by relative density and TiB₂ matrix strength together. Anyway, Al₂O₃ addition can weaken the grain boundary and thus improve the toughness of the materials. A flexural strength of 529 MPa, Vickers hardness of 24.8 GPa and indentation toughness of 4.56 MPa·m^1/2 can be achieved inTiB₂-30vol% Al₂O₃.

Keywords

TiB₂-Al₂O₃ / pressureless sintering / microstructure / mechanical properties

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