Chemical Reactions, Anisotropic Grain Growth and Sintering Mechanisms of Self‐Reinforced ZrB ₂ –SiC Doped with WC

Abstract

Transmission electron microscopy study of pressureless sintered ZrB 2 –20 vol% SiC composites with WC (5–10 vol%) additions was carried out in this work. Two independent chemical reactions in which the ZrO 2 impurities were removed from ZrB 2 grain surface were confirmed. Three new formed phases, (W, Zr) ss B, (Zr, W) ss C, and (W, Zr) ss Si 2 , apart from the plate‐like ZrB 2 and SiC grains, were identified in the samples. Microstructure observations strongly suggest that the liquid phases in terms of (W, Zr) ss B and (W, Zr) ss Si 2 , appear in this system during the sintering process below 2200°C, and the former could well wet the ZrB 2 grain boundaries. The mass transport process between ZrB 2 and (W, Zr) ss B was also confirmed by scanning‐transmission electron microscope analysis. The above results supports that the densification at 2200°C is assisted by liquid phase and the elongation of ZrB 2 platelets resulted from the Ostwald ripening during the dissolution–diffusion–precipitation process.