Effect of High-Energy Ball Milling of ZrB_2 Powder on the Microstructure and Mechanical Properties of ZrB_2-SiC Ceramics

摘要

The sinterability of ZrB2-20vol.% SiC ceramics by high-energy ball milling as well as introduction of Zr and Al as sintering additives. Densification process and microstructure of ZrB_2-SiC ceramics were investigated. After high-energy ball milling, the average particle size decreased to about 500 nm-2 um, and ZrB_2-SiC powder can be sintered to 98.92% theoretical density at 1800 °C, but a trace of amount of oxidation (ZrO_2) were detected in sintered sample. Introduction of Zr, Al and C combined with high-energy ball milling enhanced the densification of ZrB_2-SiC ceramics and reduced the particle sizes, and the relative density of obtained ceramic reached up to 99.49% at 1800 °C. The additions of Zr, Al and C can remove the oxide impurities of the surface of ZrB_2 particles and form a reaction between oxide impurities. The fracture toughness increased of the 40% when ZrB_2 powders were milled by high-energy ball milling, and increased to 4.77±0.18 MPa?m~(1/2). However, the attrition-milled composites had lower hardness and Young's modulus, which was attributed to the presence of a second phase in the grain boundaries.