Study on in-situ synthesis of ZrB_2 whiskers in ZrB_2-ZrC matrix powder for ceramic cutting tools

摘要

The composite powder of ZrB_2 whisker-toughened ZrB_2-ZrC matrix ceramic tool materials was synthesized by in-situ synthesis process combined with the carbothermal reduction method. The product contained ZrB_2 as the major phase and ZrC/Ni_2B as the minor phases. When increasing the synthesis temperature from 1400 °C to 1700 °C, the lattice parameters of ZrB_2 (a and c) decreased linearly, meanwhile, ZrC exhibited a non-stoichiometric property through the variation of the lattice parameter. The ZrB_2 whiskers showed an aspect ratio of 10-30 and a diameter of 1-3 μm. The agglomeration of the ZrB_2-ZrC matrix powder and the morphology of bonding particles in the whiskers were also observed. The solid-liquid-solid (S-L-S) mechanism and the anisotropic Ostwald ripening were found to govern the growth of the ZrB_2 whiskers during the in-situ synthesis process.