Preparation of a TiB2-ZrB2 composite assisted by mechanical alloying

A TiB2-ZrB2 composite was synthesized by 20-h mechanical alloying (MA) of a mixture of Zr, Ti, and B powders in a planetary ball mill (Zr:Ti:B molar ratio = 1:1:4; ball-to-powder weight ratio = 20:1). Milling was performed at 500 rpm in an argon atmosphere using a ZrO2 vial and balls and was followed by pressureless sintering at 1230 °C. The effect of milling time on MA-induced phase changes was investigated by X-ray diffraction, and the microstructure development of powder mixtures and the TiB2-ZrB2 composite was monitored by field emission scanning electron microscopy and transmission electron microscopy. MA reduced the activation energy for the transformation of the above powder mixture, allowing its complete conversion into TiB2 and ZrB2 at 1230 °C. Cold processing and sintering produced relatively dense TiB2-ZrB2 composites wherein ZrB2 was dispersed in the TiB2 matrix.