Mechanical properties and microstructural evolution of pressureless sintered ceramics obtained from high-energy ball-milled TiB2–TiC powders

Abstract

A series of TiB2–TiC composites were successfully fabricated through one-step and two-step pressureless sintering using powders obtained by high-energy ball-milling. Effects of ball-milling time on crystal size and morphology of powders as well as microstructural evolution and mechanical properties of TiB2–TiC composites were investigated. The crystal size of TiB2–TiC powders decreases to 14.7 nm after ball milling for 30 h. Two-step pressureless sintering is beneficial to the densification process without obvious grain coarsening. The core-rim structure of carbides in TiB2–TiC composites is formed by nonuniform diffusion of W atoms from the outside to the interior of TiC grains. The phenomenon of selective solution of WC into TiC grains was carried out through experiments and verification of first-principles DFT calculations. An in-situ TiB2 plate toughened microstructure is developed for TiB2-40 wt %TiC composites two-step sintered at 1500 °C for 4 h and 2000 °C for 1 h with excellent comprehensive performances.